Wikipedia:Reference desk/Archives/Science/2008 July 9

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July 9

Just thinking

Not sure if this is science or philosophy etc but posting here initially until told otherwise. Anyway I was just sitting here thinking, then I thought: Why is the human mind so damn inquisitive? —Preceding unsigned comment added by 79.76.144.199 (talk) 00:04, 9 July 2008 (UTC)

I suppose inquisitiveness has some evolutionary benefit, perhaps because it leads to the invention of tools and other ways of shaping the environment to suit our needs (agriculture, domestication of animals, etc.). It also leads to exploration, which allows populations to expand and new resources to be discovered. --Tango (talk) 00:58, 9 July 2008 (UTC)

I don't know, but if you find the answer, you'd be in a good position to improve this section: Curiosity#Causes. --Allen (talk) 05:10, 9 July 2008 (UTC)

Not only the human mind: most mammals (and possibly other animals) also exhibit curiosity. (Try lying down in a field full of cows - if you remain still, their curiosity overcomes their fear, and you will soon be surrounded by them!) Dbfirs 08:31, 9 July 2008 (UTC)

my BG sound

How 2 make my BG sound like upright DB? —Preceding unsigned comment added by 79.76.144.199 (talk) 01:30, 9 July 2008 (UTC)

You don't. Unfortunately (in this case) they're completely different. An acoustic BG would do better because you'd have a mic picking it up instead of a pickup. Other than getting a little mic from, like some kind of a headset or something and clipping it close to the strings where you're plucking them and getting the signal from there (which might actually almost work). I'd suggest lowering your pickups so they don't work quite as efficiently and you have to pluck a bit stronger like you'd do on a DB (no, lowering the volume won't have quite the same effect) and EQing the mid a bit stronger than high and low. No effects, obviously. If that doesn't work I can't imagine what else will. -LambaJan (talk) 02:54, 9 July 2008 (UTC)

Just for my benefit: what is BG and DB? Fribbler (talk) 11:06, 9 July 2008 (UTC)

bass guitar, double bass. 163.1.148.158 (talk) 11:09, 9 July 2008 (UTC)

Oh, another thought about EQing. Try turning the tone knob to cut the bass levels and let the high through. after that, if it's too tinny, back the high off a bit. I don't know what kinds of controls you have available but between the bass and the amp you can probably get a decent mix. The last thought I have is keeping your bass volume lower than normal and turning your amp volume a bit higher to compensate. It might be a total crap idea in practice but it makes sense in my head. -LambaJan (talk) 13:33, 9 July 2008 (UTC)

And buy a fretless bass. 80.229.160.127 (talk) 17:52, 9 July 2008 (UTC)

Megabats as “flying primates”?

Is there, at present, a dispute in the mainstream scientific community as to whether bats are monophyletic?

I ask because I am skeptical of this edit to the article Flying primates theory. It seems to me that as of 2008, the DNA evidence is pretty clear that all extant bats have a common ancestor not shared by any other extant mammal. Is that correct, and if so does the DNA evidence confirm the monophyly of bats, or is the DNA evidence just one part of the puzzle to be considered along with morphological evidence in the question of whether bats are monophyletic? --Mathew5000 (talk) 03:37, 9 July 2008 (UTC)

I don't know, but at a glance it looks like the edit you're pointing to was not good. The abstract of that Nature article doesn't just assert that bats are monophyletic; it asserts that there is consensus for that position, so it seems important for the article. Generally, I think DNA evidence is always just one part of the puzzle, in principle... genes and morphology, in a broad sense, are both just traits on which to base our phyletic inferences. But since genes are generally the cause of evolutionary changes in morphology, it makes sense to me that DNA-based phylogenies are often seen to trump those based on morphology. I like how the authors of this paper put it: "When molecular data produce a robust phylogeny that conflicts with morphology, we suggest a third approach: reevaluate the morphological evidence." --Allen (talk) 05:03, 9 July 2008 (UTC)

There was indeed quite a bit of controversy regarding bat monophyly prior to the existence of more advanced genetic sequence alignment software and such, up to about the mid 1990s. The more recent genetic comparisons found that some of the research supporting bat diphyly back in the 1980s wasn't exactly as solid as it had originally appeared (and it wasn't the most solid evidence in the first place). More recent phylogenies were recently confirmed by fossilized bat ancestors, which appear to have been previously undiscovered intermediate steps in bat evolution. These ancient bats shared some major similarities in ear structure with both older fossils and modern bats, for example. I have sources regarding this topic, but they unfortunately aren't accessible right now, so I'll post them later. --Several Times (talk) 17:27, 9 July 2008 (UTC)

Ah, here they are. This report, which unfortunately only offers the abstract for free, explains the confirmed bat phylogeny well. This paper by Eick et al may be a better one, as it is not only free, but examines some characteristics which make bats especially unique. --Several Times (talk) 23:32, 9 July 2008 (UTC)

Lice

If lice "spend their whole lives on their victim", why do they sometimes wait inside head clothing? 208.76.245.162 (talk) 03:53, 9 July 2008 (UTC)

I'm guessing that lice don't choose to be removed from their hosts, but that contact by headgear inevitably dislodges some individuals. Lice can only survive 24 hours when unattached to a host, according to http://www.healthcaresouth.com/pages/askthedoctor/headlice.htm. --Bowlhover (talk) 07:05, 9 July 2008 (UTC)

Lice 2

Can you catch lice from other animals? 208.76.245.162 (talk) 03:54, 9 July 2008 (UTC)

Not usually, no. Lice that feed on humans only feed on humans. But it must have happened at least once. --Allen (talk) 05:06, 9 July 2008 (UTC)

Mortice Locks

If you have a mortice lock in your door, but no key, can a locksmith make a key for it? I'm in the UK, if that makes a difference. 195.60.20.81 (talk) 09:43, 9 July 2008 (UTC)

Possibly a very skilled one.. but it would probably be easier to unscrew the lock, and replace it with a new one. Is the door open?87.102.86.73 (talk) 12:58, 9 July 2008 (UTC)

If you have a camera, our article on Mortise lock could really do with a picture. Plasticup ^T/C 14:14, 9 July 2008 (UTC)

As long as the locksmith can take apart the lock, no special skill is required in cutting a key for it. Each of the levers is so many millimetres wide, and the key cutting jig is set up to those measurements. However, it might indeed be cheaper to buy a new lock and keys. Note also that most locks can have the levers or tumblers changed so that they accept a specific key (of the same brand). Very useful if you want to cut down the number of keys you have to carry around.--Shantavira|^{feed me} 15:10, 9 July 2008 (UTC)

Many locksmiths and even hardware stores have an assortment of blank skeleton keys which can be cut to fit a given mortise lock. In a given brand of mortise lock, there were not that many different keys, and some manufacturers made a set for a given house numbered one through 6 or whatever, and supplied two keys per lock. If your front door was a number five, then your front door key would fit the house down the street which had a number five lock on the front door. Some locksmiths no longer will make a skeleton key to fit a customer's mortise lock, beause it takes a bit of expertise and customers do not want to pay the price required. The skeleton key blanks must have the correct central shaft size to fit the lock. New locks with new keys can be installed if you wish to maintain the appearance. Edison (talk) 03:29, 10 July 2008 (UTC)

I've actually done this myself with needle-files (years ago when I had the time and patience). It is not too difficult for a 3-lever lock (typically 150 different combinations), and remakably simple for the 1950s-style back-door mortice locks which were often identical, but it is a skilled task for a modern 5-lever lock (thousands of different keys), and would, in general, cost more than buying a new lock (£12 to £50 in UK depending on quality). Some locksmiths who stock that particular brand will be able to look at the levers and immediately set up their key-cutting jig to make a key to fit. Others will offer to replace just the levers complete with matching keys, but you will need to find specialist locksmiths for these options. Most key-cutters can only copy existing keys. Dbfirs 07:48, 10 July 2008 (UTC)

Minnesota Skid

What is a 'Minnesota Skid' and why should the tires not be locked up when performing one? 128.252.139.248 (talk) 13:19, 9 July 2008 (UTC)

--Anthonygiroux (talk) 14:13, 9 July 2008 (UTC)

Black people, poison ivy, lice

My black neighbor and her white husband both assert that black people are not susceptible to poison ivy; indeed, she walks right through the patch of it that separates our houses while he avoids it. My daughter's pediatrician asserted to me (on an occasion when my daughter had head lice) that she has never seen a case of them on a black child. These are credible sources, but I find the claims themselves questionable. I know about the malaria/sickle-cell connection, but is there any evidence that people of (fairly recent) African descent are immune to these ailments? --Sean 13:35, 9 July 2008 (UTC)

This would suggest that it is not true. Fribbler (talk) 13:43, 9 July 2008 (UTC)

Heh. That's the most informal text I have ever seen in PubMed.

From my observation, immunity to poison oak / poison ivy can be acquired. My father was allergic to it in his youth, until one day he had to cut through a field of the stuff. He came down with a terrible full-body rash, but after that, contact with the plant no longer affected him. ~Amatulić (talk) 14:03, 9 July 2008 (UTC)

My guess would be that the immunity to poison ivy is an individual thing, rather than all black people, and the lack of head lice cases is due to them being harder to spot on black person. That wouldn't result in no cases at all, but perhaps your paediatrician hadn't treated many black children, either due to being in a predominantly white area or simply being new to the job. --Tango (talk) 14:07, 9 July 2008 (UTC)

I am Koyukon Athabaskan and I am immune to poison/ivy/oak and so is my immediate family. I will ask my other relatives about this --Anthonygiroux (talk) 14:11, 9 July 2008 (UTC)

Also, my friend is half Athabaskan and half African-American and she is also immune to poison ivy/oak. Also, she said there was an outbreak of lice in her elementary school in California and she was the only one that wasn't affected. Go figure... --Anthonygiroux (talk) 14:13, 9 July 2008 (UTC)

In a quick scan of one of my patient databases, I found 272 patients labelled as "black" with an ICD9 code of 626.6 (Poison Ivy/Sumac). Also, I am white and I am completely immune to poison ivy (and all related "poison" plants). It may be that blacks are more likely to me immune, but all it takes is one case to prove that they are not all immune. -- kainaw™ 14:42, 9 July 2008 (UTC)

There was an episode of Mythbusters where they tested a bunch of vodka myths, one of which was that application of vodka helps with poison oak rash. (It didn't.) I recall that they actually had a bit of a problem with that one, because it turned out that they had a lot of trouble finding someone from their staff who was allergic to the stuff -- they had to go through four or five people before they found one who actually reacted to it. I think all of them, with the exception of Grant Imahara, where white. I also seem to recall they said that 90% of the people weren't immune to it; they just happened to have a small statistical bump there... Anyway, your neighbor's wife apparently is one of the lucky 10%, but that certainly doesn't mean that all black people are. -- Captain Disdain (talk) 14:56, 9 July 2008 (UTC)

Thanks to all that answered. I suspect that she had heard this myth, and then suffered confirmation bias when she found herself to indeed be immune. --Sean 15:30, 9 July 2008 (UTC)

According to this page, because of their specific hair type (curly), African-Americans are less likely to have head lice infestations, but they are not "immune". (I would also suspect the prevalence of very short hair amongst African-American men to play a factor in that as well). According to this page, people of African descendent not in the US do get head lice infestations more frequently, because the local lice in said areas have adapted to their specific hair types. --98.217.8.46 (talk) 18:22, 9 July 2008 (UTC)

Sensitivity to poison ivy can also show up later in life. As a youth I walked through the stuff on several occasions and had no reaction of any kind. Later, in high-school, I was helping to plant some trees and unknowingly came into contact with some ivy "spikes" and got a beautiful rash. Matt Deres (talk) 14:48, 10 July 2008 (UTC)

primates

Why no primates in parts of North/South America? Surely they could make it along the coast and settle in new hampshire?87.102.86.73 (talk)

Isn't that an image of where primates are native to, rather than where they are present? — CycloneNimrod  ^Talk? 14:36, 9 July 2008 (UTC)

I'm not aware of chimp colonies in conneticut...87.102.86.73 (talk) 14:40, 9 July 2008 (UTC)

(try again) Why are no primates native in parts of North/South America? Surely they could have made it along the coast and settled in new hampshire?87.102.86.73 (talk) 14:57, 9 July 2008 (UTC)

There are plenty of primates in New Hampshire.-Wafulz (talk) 15:06, 9 July 2008 (UTC)

(try again) Why are no non-human primates native in parts of North/South America? Surely they could have made it along the coast and settled in new hampshire?87.102.86.73 (talk) 14:57, 9 July 2008 (UTC)

From the looks of the distribution map, the primate range ends at the south side of a large expanse of desert in Mexico and this would be a formidable barrier to transit northward. I believe author Jared Diamond gave this as a reason for a lot of differences between North and Central America. Franamax (talk) 15:43, 9 July 2008 (UTC)

This image seems to show a subtropical dry forest link along the east coast, maybe it's not accurate enough. would this be a barrier (lemurs live in subtropical dry forest in madagascar..)?87.102.86.73 (talk) 16:02, 9 July 2008 (UTC)

Actually if you blow up the primate map, it shows a little tongue in just that part, apparently ending at the Rio Grande. So I guess they made it as far as the river and then either couldn't or didn't cross. Funny, it looks so easy when Clint Eastwood does it. :) I'm not sure how wide the river is in the last stretches before the mouth. Franamax (talk) 16:54, 9 July 2008 (UTC)

Nowadays we take so much water out of the Rio Grande that some years it never reaches the ocean - so that would be zero width. Rmhermen (talk) 17:38, 9 July 2008 (UTC)

A more intriguing question is, why are there any non-human primates native to the Americas, considering that monkeys evolved well after Africa and South America were separated by ocean. The article New World monkey is brief and unsourced on this point; it suggests that some monkeys came to South America on a raft of vegetation. But could enough monkeys have made it that way to form a viable population? --Mathew5000 (talk) 17:36, 9 July 2008 (UTC)

((The previous question title Wikipedia:Reference_desk/Science#Megabats_as_"flying_primates"?? seems to suggest one possible theory... (joke) ))87.102.86.73 (talk) 17:50, 9 July 2008 (UTC) (or maybe not a joke - I've no idea actually)87.102.86.73 (talk) 18:04, 9 July 2008 (UTC)

This question is as old as theories of evolution itself. But yes, the current theory is that they floated on across one way or another, though it is still considered a pretty open question. This chapter from an anthro textbook sums up the major theories about it, and their respective deficits. There are some who theorize that they might have made it around Asia and North America, but that is controversial as well. --98.217.8.46 (talk) 21:32, 9 July 2008 (UTC)

• The probable reason why there are no primates in North America is there is no good habitat linking New Hampshire with Mexico. New World Monkeys are exclusively arboreal, unlike the Old World monkeys which have some terrestrial species such as macaques and baboons. The temperate species of Old world monkeys are the species most able to adapt to a wide range of diets and foraging strategies, including the ground. American monkeys are excluded from North America by three factors - there is no continuous dense forest between South Mexico and the US, the forest that is there is unable to sustain primates without them traveling to the ground (which American monkeys don't - yet), and the two million years since the Ithmus of Panama formed hasn't apparently been long enough for primates to move northwards that far. Sabine's Sunbird talk 02:41, 10 July 2008 (UTC)

Thanks, that's a good answer. Though it seems from the links above that there once were (tiny) primates in north america (the article mentions the mississipi) - those must have just died out then? (ps I had no idea the Isthmus of Panama was 'new'; thanks for telling me.)87.102.86.73 (talk) 10:04, 10 July 2008 (UTC)

Engine slows you down?

People sometimes talk of using the engine/gears of their car to slow them down instead of the brakes. My question is; where does the kinetic energy of the car go when you use this method of slowing down? —Preceding unsigned comment added by 79.76.156.19 (talk) 14:45, 9 July 2008 (UTC)

friction in part, as well as rotational energy, additional energy can be lost in having to compress the gases in the cylinders of an engine that lacks sufficient fuel input to operate at the current speed.87.102.86.73 (talk) 14:48, 9 July 2008 (UTC)

Yep. The article isn't great, but engine braking explains this a little bit. Friday (talk) 14:58, 9 July 2008 (UTC)

Ok. You are traveling at 60 mph in top gear. You then slam it into second gear with your foot off the accelerator. Youll slow down alright, but the engine rpm cannot suddenly increase to the required rate demanded by the road speed and gearbox. So I ask again: where does all that KE go? —Preceding unsigned comment added by 79.76.156.19 (talk) 15:21, 9 July 2008 (UTC)

HINT people don't usually 'engine brake' by changing gear, but by gradually taking their foot of the throttle Doing what you describe may damage the clutch, the gearbox and your head as it slams into the steering wheel/windscreen (see also whiplash) - always wear a seatbelt.87.102.86.73 (talk) 16:57, 9 July 2008 (UTC)

Hmm? I downshift for engine braking quite frequently- I don't imagine this is uncommon at all. Friday (talk) 17:50, 9 July 2008 (UTC)

Do you slam it into second gear with your foot off the accelerator at 60mphr?87.102.86.73 (talk) 18:01, 9 July 2008 (UTC)

You just answered it.. the engine rpm would have to increase - this would mean an increase in rotational energy... -direct analogy: flywheel 87.102.86.73 (talk) 15:24, 9 July 2008 (UTC)

Engines have a certain amount of moment of inertia (and a flywheel). You cannot instantaneously increase the rotational energy of anything with non zero moment of inertia. So when you suddenly let your clutch in, what happens to the excess energy whilst the engine is getting up to the required rpm? —Preceding unsigned comment added by 79.76.156.19 (talk) 16:00, 9 July 2008 (UTC)

The clutch slips. Franamax (talk) 16:04, 9 July 2008 (UTC)

OR.(edit conflict) It would be the same as suddenly connecting to a flywheel - in one case the wheels would skid. Also note that because the gas in the engine is compressable it acts as a torque converter - (ie like an 'elastic band')87.102.86.73 (talk) 16:05, 9 July 2008 (UTC)

Aha! so its not your engine that dissipates the energy: its your clutch or your skidding tyres, right? —Preceding unsigned comment added by 79.76.156.19 (talk) 16:12, 9 July 2008 (UTC)

Until the engine is fully revved up to speed, yes (partly). As the engine revs up, it is increasing its kinetic energy and dissipating energy through the vacuum effect, and the clutch is slipping at the same time. Possibly the tires too, I've never dumped a clutch that hard. Once the engine is revved up, the clutch locks and it is only the engine slowing things down after that. Franamax (talk) 16:26, 9 July 2008 (UTC)

I'm not sure the clutch slipping dissipates much energy, it just allows the energy to be transferred from the kinetic energy of the car to the rotational energy of the engine gradually. It's the engine that finally dissipates the energy. The clutch probably does get warm in the process, so some energy will be lost that way, but probably not much. A better option would be to lift the clutch gradually, I would expect. --Tango (talk) 16:36, 9 July 2008 (UTC)

I always feather out the clutch when downshifting in engine braking. Dumping it and letting the engine rev up that fast is awfully hard on things (IMO). Franamax (talk) 16:43, 9 July 2008 (UTC)

I suspect that some energy is eventually transferred to the engine because its been speeded up. Also some energy must be lost in the clutch. Question is, what proportion of energy is stored in the engine (as angular momentum) and what proportion lost in the clutch as heat? I propose its half and half, but is there a proof?

I have no proof, but in practical terms, you either blip the throttle a bit to get the revs up and/or feather out the clutch when you downshift in engine braking. The aim is to dissipate as little energy as possible in the clutch - once you can smell it, you know you did it wrong. Also note to the above, if you release the clutch fast enough to lock the wheels and skid, you've 1) put maximum stress on the entire driveline; and 2) lost control of your vehicle. Nice theoretical exercise, but do it with someone else's car, and do it on a test track. Franamax (talk) 08:53, 10 July 2008 (UTC)

When a throttled engine, like most gasoline engines, is operated at closed throttle, the engine acts as a positive displacement vacuum pump, moving (rarefied) air from the low-pressure intake manifold to the atmospheric-pressure (or so) exhaust manifold, against a pressure gradient. This requires energy. See manifold vacuum, which I think covers engine braking better than engine braking. -- Coneslayer (talk) 15:44, 9 July 2008 (UTC)

Muscles

My biology teacher said muscles can only contract, never relax on their own, and need an opposing muscle to contract otherwise your arm would be stuck in the same position. I don't believe this. If I lift my arm it'll drop if I stop contracting the top arm muscle without the bottom muscle doing anything. Is my teacher right or they full of crap? User:Rhodopsin drinker (talk • contribs) 15:23, 9 July 2008 (UTC)

Gravity may be causing this.87.102.86.73 (talk) 15:29, 9 July 2008 (UTC)

Muscles can relax, but that won't move the body part back to where it was, you need something to move it back. That could be another muscle, or gravity, or someone pushing your arm, or whatever. Muscles come in pairs to move limbs, or whatever, in different directions - bicep and tricep, for example. --Tango (talk) 15:47, 9 July 2008 (UTC)

What your teacher was probably trying to hint at is they can contract and relax but only in one direction. This is why you require an adjacent muscle to move it back. — CycloneNimrod  ^Talk? 15:59, 9 July 2008 (UTC)

Yes, if you are standing and try to let your arm follow its own course, it will fall down because of gravity. But if you are lying on a bed and then try to do same thing, or in other words if you try to stretch your arm in the horizontal direction, you will need the tricep muscles to do that. Biceps are to move your wrist towards your face, triceps are to do the opposite. DSachan (talk) 03:39, 10 July 2008 (UTC)

Tendons are like ropes. Muscles are like ropes that can contract themselves. If you've ever been on a sailboat, you'll know that, in order to move something back and forth with ropes, you need either two ropes pulling in opposite directions or one rope and something else (gravity, wind, a spring, etc.) pulling against it: you can pull on a rope, but you can't push on it. —Ilmari Karonen (talk) 19:49, 13 July 2008 (UTC)

some naive hypothesis at odds with basis of physic- what wrong with them ?

I- In nature exist an unique particle where all kind of energies have the same value,where each physic law fit precisely.in this particle the matter is concentrated "in extreme" inside of " tiniest" portion of space.The concentration is so dense that is no room to accept the tiniest increment of matter and the gravity is so strong that do not permit any decrease of matter. This mean that the unique particle do not interact with common particles known by science and evidently is undetectable by whatsoever phenomenon known till now. Is it a black hole? It is not a hole . It is matter with it constituents: electric charge and charge of gravity.It is the brick in the structure of each common particle. The only variable in structure is radius of space occupied by par of unique particles. —Preceding unsigned comment added by 70.133.175.56 (talk) 15:49, 9 July 2008 (UTC)

I think you need to give a reason why such particles of opposite charge would not just clump together.. Otherwise your description sounds very similar to something like protons and electrons.87.102.86.73 (talk) 16:08, 9 July 2008 (UTC)

• "...where all kind of energies have the same value..."

I have no idea what that's supposed to mean.

• "in this particle the matter is concentrated 'in extreme' inside of 'tiniest' portion of space. The concentration is so dense that is no room to accept the tiniest increment of matter."

If it's a particle, it has no volume.

• "...and the gravity is so strong that do not permit any decrease of matter."

A black hole is anything with so much gravity that nothing can leave it, though Hawking radiation will appear right next to the event horizon, leave, and take some of the black hole's mass with it. I think quantum physics prevents anything smaller than a Planck mass (about the size of a small flea) form a black hole, so if it is a particle, it's very heavy.

• "This mean that the unique particle do not interact with common particles known by science and evidently is undetectable by whatsoever phenomenon known till now."

Force carriers are among the Hawking radiation, so it does interact with common particles.

• "Is it a black hole? It is not a hole ."

Thanks to Hawking radiation, it's not black, either. "Back hole" is a misnomer.

• "It is matter with it constituents: electric charge and charge of gravity.It is the brick in the structure of each common particle."

I have no Idea what any of that is supposed to mean.

• "The only variable in structure is radius of space occupied by par of unique particles."

Assuming it is a black hole, the no hair theorem, which may or may not be true, states that the only variables are mass (which can be calculated by volume), charge, and angular momentum. I'm not sure that's what you meant, though. — DanielLC 17:48, 9 July 2008 (UTC)

Did you actually see the title "...naive hypothesis..."??87.102.86.73 (talk) 17:53, 9 July 2008 (UTC)

Self-replication in open thermodynamics??

Conway's Game of Life was named as such only because the patterns are "life-like" in their complexity, and not because GOL represents a simulation of actual organisms. John von Neuman's self-replicating cellular automata was actually designed by hand, not discovered. <link rel="stylesheet" type="text/css" href="http://en.wikipedia.org/w/index.php?title=User:Lupin/navpop.css&action=raw&ctype=text/css&dontcountme=s"><link rel="stylesheet" type="text/css" href="http://en.wikipedia.org/w/index.php?title=User:MarkS/XEB/live.css&action=raw&ctype=text/css&dontcountme=s"> We know that open (dissipative) thermodynamical systems give rise to spontaneous order, and the reason is because effective dissipaters of gradients are "fed more" by the source for logical reasons. This is why funnel clouds are self-sustaining in a tornado storm. It is also the reason that Benard Cells form in boiling water. Does there exist any such thermodynamic simulation in which self-replication is the "order" that arises spontaneously? I hope I am not the first person on earth to have asked this question! paros (talk) 00:48, 10 July 2008 (UTC)

You're certainly not the first to suggest it, but the first I've heard of it without reference to the thermodynamic objection to evolution. That said, many would say that the origin of life is the ultimate example of what you're asking. If you're specifically asking about something that has actually been observed, the only thing I can think of are protein-coacervates, which are capable of spontaneously forming from solvated proteins of a suitable nature, accreting more of them, and splitting upon reaching a critical size. Someguy1221 (talk) 03:49, 10 July 2008 (UTC)

Why does the temperature decrease with increasing altitude?

Gidip (talk) 16:46, 9 July 2008 (UTC) :This should answer your question pretty well. Per the below comment, disregard my link :) — CycloneNimrod  ^Talk? 17:09, 9 July 2008 (UTC)

I very much dislike the explanations given in the above link, and would point to the Lapse rate article and the explanation given in this section. Also, it's not always true that temperature decreases with increasing altitude.—eric 16:59, 9 July 2008 (UTC)

Agree, the explanation in the external link looks terrible to me. Volcanos? Franamax (talk) 17:12, 9 July 2008 (UTC)

Check out Earth's atmosphere for a description of the temperature changes due to increasing altitude (it doesn't just go down) and a discussion of some of the reasons. PhySusie (talk) 18:55, 9 July 2008 (UTC)

Thanks everyone. Gidip (talk) 19:05, 9 July 2008 (UTC)

"cynical but open minded" etc

On a programme "revealing" an illustionist I heard mention of a list of statements which most people thought applied to themselves more than to the general population. These are used by spoof mind readers etc. I have tried on WP psychology articles and google etc. Can anyone point me to such a list? --BozMo talk 17:29, 9 July 2008 (UTC)

The Forer effect and cold reading articles list some, but it sounds like you may have read those already. --Bennybp (talk) 17:41, 9 July 2008 (UTC)

No, I hadn't. Thanks for the steer. --BozMo talk 19:14, 9 July 2008 (UTC)

Formula to determine water flow rates and temperatures to maintain tank temperature.

I am looking for a formula or to be pointed in the right direction.

I have a tank of water.
I withdraw water from the tank at a constant rate, use it to cool a manufacturing process, and then return the water to the tank.
At the same time, I withdraw water from the tank at a constant rate, push it through a heat exchanger to extract heat from the water, and then return the water to the tank.
What temperature can I expect to maintain in the tank or what will be the rate of temperature change in the tank?

Assume:
Clean soft water.
Tank size: 500 gallons
Tank starting temperature: 75°F
Heat absorbed from the manufacturing process: 50 kW
Process flow: 16 gpm
Water temperature from the heat exchanger: 45°F
Flow rate from the heat exchanger: 30 gpm

The values above are likely to change, so I am looking for help on the formula.

Thank you for your assistance.
--Mikewbum (talk) 17:36, 9 July 2008 (UTC)

Mmmh 'gpm' as flow rate, does that mean 'grammes per minute'? (if it does it looks like your water will boil..) Sorry gpm is gallons per minute right?

Also you need more information (I think) to calculate how much energy is transfered per second in the heat exchanger.. that would depend on its design - ie how long the 'pipe' is that goes throught the water at 45F, and how good a conductor the exchanger is made of..

If you can supply a figure in watts for the heat exchanger, either as maximum or as a function of 'water in temperature', that would make it very easy.87.102.86.73 (talk) 17:58, 9 July 2008 (UTC)

In SI units it is incredibly easy but I don't use imperial. Roughly cooling 1 litre 1 degree Kelvin takes 4.2kJ so cooling 30 gallons=135 litres (imperial galloons?) by X F=Xx5/9 K takes Xx135x4.2x5/9 If X was 30 it gives roughly 10,000kJ a minute or 166kW say. But you only need to sink a third of this so the temp diff will fall to about 10F. Someone can correct the conversion and maths but that's the idea. --BozMo talk 19:25, 9 July 2008 (UTC)

To answer your q for clarification: taking 30F gives a heat transfer of 166kW but you only needed a heat transfer of 50kW to balance flow out with the 50kW in (that's the sink a third of that bit). So since the heat transfer is linear on the temp difference the stable temp diff would be about 10F. The important thing in the calc is to think in terms of "litre-degrees" of water as an energy unit. Then you work out how many litres how many degrees per minute and convert it to kW. --BozMo talk 20:41, 9 July 2008 (UTC)

If 50 kW out of the original 166 kW is used to cancel the 50 kW input of energy, shouldn't the remaining 166-50=116 kW cool the water by 20 degrees, which is two-thirds of 30 degrees? --Bowlhover (talk) 07:38, 10 July 2008 (UTC)

Except I think you want 30 U.S. gallons = 113.5 L so only 8F. Rmhermen (talk) 22:09, 9 July 2008 (UTC)

Thanks but its the other way round. Less water higher temp diff so 12F... --BozMo talk 22:27, 9 July 2008 (UTC)

Name of hard cardboard-like stuff

Hi all,

What's the name of that really stiff cardboard with tiny dimples/holes in it (dimples look like they were made with a needle)? This stuff is thinner than chipboard, yet stiffer and less papery than paperboard or corrugated cardboard. Any thoughts? Thanks! — Sam 19:18, 9 July 2008 (UTC)

Pegboard? APL (talk) 20:57, 9 July 2008 (UTC)

Ryvita? —Preceding unsigned comment added by 79.76.156.19 (talk) 21:20, 9 July 2008 (UTC)

Coroplast? --Sean 22:56, 9 July 2008 (UTC)

Hardboard, or one of its fiberboard kin. -- Finlay McWalter | Talk 23:00, 9 July 2008 (UTC)

Oriented strand board? Try looking through Category:Engineered wood. Dar-Ape 01:17, 10 July 2008 (UTC)

Hmmm... none of those, I'm afraid, and I had looked through all the categories. I guess I'll just go find it at my hardware store and ask there. Thanks! — Sam 13:52, 10 July 2008 (UTC) —Preceding unsigned comment added by 63.138.152.238 (talk)

Be sure to post the answer here. --Bowlhover (talk) 05:07, 11 July 2008 (UTC)

Perfluorocarbon

Do the Perfluorocarbons make suitable refrigerants? Mimus polyglottos (talk) 19:57, 9 July 2008 (UTC)

The article says they are used as such (see the Other Applications section). Fribbler (talk) 20:05, 9 July 2008 (UTC)

Pakistani President Pervez Musharraf and his glasses.

Pervez Musharraf has glasses and I heard on T.V he cannot see without them. What's this illness? 190.49.95.195 (talk) 20:39, 9 July 2008 (UTC)

Eyeglasses are commonly worn by people who have one or more of the the following : Myopia, Astigmatism (eye) , Hyperopia, Presbyopia; however none of these are commonly referred to as an "illness." --LarryMac | Talk 20:46, 9 July 2008 (UTC)

I think this is really an English usage question, not a science question. When we say that someone "cannot see without his glasses", we just mean that he sees very badly without them. For example, maybe he has a severe case of myopia, astigmatism, or some such condition. --Anonymous, 04:55 UTC, July 10, 2008.

Penises

Today I read that 82% of men in the world have not been circumcised, and that outside the US erectile dysfunction is less common or to a lesser degree. Can this be verified? Mac Davis (talk) 20:50, 9 July 2008 (UTC)

I'm relatively sure, but with no citation, that 82% is an incorrect percentage. I'll have a look tomorrow when i've slightly more time. — CycloneNimrod  ^Talk? 22:31, 9 July 2008 (UTC)

We have an article, Prevalence of circumcision, with a lot of references in it. As for ED, I guess that could be related to obesity rates. Fribbler (talk) 22:35, 9 July 2008 (UTC)

Remember that correlation does not imply causation. Drownings increase in the summer, and so do ice cream sales, but ice cream doesn't cause drownings. --98.217.8.46 (talk) 01:15, 10 July 2008 (UTC)

Perhaps drownings increase ice cream sales ?

Pallbearer: "This sure is hot work, hold up for a sec while I get a nice triple scoop with sprinkles for my free hand." StuRat (talk) 03:46, 10 July 2008 (UTC)

I'd say the higher incidence of "ED" (or "LD", as I like to call it) in the US is because pharmaceutical companies in the US just love to call a normal part of aging a disease (so they can get people and/or insurance companies to fork out billions to buy their drugs). StuRat (talk) 03:43, 10 July 2008 (UTC)

(What's LD ? laser disk? lingam??)87.102.86.73 (talk) 10:38, 10 July 2008 (UTC)

LD = "limp ....". :-) StuRat (talk) 13:53, 10 July 2008 (UTC)

It may be a normal part of ageing, but that doesn't mean it's desirable. I was reading an interesting article from a doctor just the other day which discussed how frustrating it used to be when impotent men came asking for help, as there wasn't really anything they could do. Of course, mostly these men pretended to be asking about something else and only added the impotency as a 'hand on the doorknob, just leaving' thing, but it was why they were really there. Viagra, as a genuine treatment for much erectile dysfunction (which as a much easier term for men to ask a doctor about, apparently), has transformed this and men are much happier visiting the doctor about this problem these days. So men who would previously not have been recorded as having this problem now are because it's less embarrassing, and they can solve it. Not all changes have been bad... 79.66.67.219 (talk) 04:40, 13 July 2008 (UTC)

I'm really looking for an answer other than "carefully" here...

How do hedgehogs, porcupines, enchiladas, pangolins and any other type of spiny/razor-coated mammal that I haven't thought of actually mate without injuring each other? --Kurt Shaped Box (talk) 21:11, 9 July 2008 (UTC)

They flatten their spines (a bit like we do really :)) —Preceding unsigned comment added by 79.76.156.19 (talk) 21:15, 9 July 2008 (UTC)

See [1] for a description of porcupine mating. Dragons flight (talk) 21:17, 9 July 2008 (UTC)

In short, "very carefully" :-) --Carnildo (talk) 22:11, 9 July 2008 (UTC)

Hedgehogs do not have to be very careful. First of all, the spines are not that sharp. I regularly handle them with my bare hands. Only the babies have sharp quills (because they are so small). Second, the female has the ability to protrude her vagina well behind her spines. Her tail is very short and when curled upwards, the anus and vagina move behind it. Third, the male's penis is almost halfway up his abdomen. For reference, consider if yours was a few inches above your belly button. So, the male doesn't have to fully mount the female. he just slide up behind her a bit. His only real risk is having the female turn and bite if she's not in the mood. -- kainaw™ 22:28, 9 July 2008 (UTC)

Mindtrap

One of the question in the game "Mindtrap" is similar to this:

A guy who weighs 99kg wants to cross a bridge, but the maximum capacity is 100kg and he's carrying three 1kg gold balls.

He crosses it by constantly juggling all three in the air.

Is this legit? —Preceding unsigned comment added by 65.110.174.74 (talk) 23:48, 9 July 2008 (UTC)

No, he can't even cross the bridge juggling one ball, let alone three. The force required to slow the ball down while he's catching it will take the bridge load over 100kg. Of course, footsteps would have the same effect, so he probably wouldn't make it with zero balls. -- Tim Starling (talk) 00:14, 10 July 2008 (UTC)

But of course the Engineers who designed the bridge would have included a large factor of safety, so he should be fine ;-) Fribbler (talk) 00:19, 10 July 2008 (UTC)

And, of course, in the traditional manner of juggling three objects, two are frequently in the juggler's two hands at the same time. Deor (talk) 02:46, 10 July 2008 (UTC)

According to Newton's third law, every force has a corresponding force that is equal in magnitude and opposite in direction. For the man to send a ball upwards, his hands must apply a force greater than the gravitational force pulling the ball down. The ball in turn applies a pressure downwards, so the bridge experiences three forces:

(1) the force of gravity on the man (99 kg)

(2) the force needed to stop the downwards acceleration of the ball, which is equal to the weight of the ball (1 kg)

(3) the force needed to accelerate the ball upwards, thereby reversing its downward motion (a positive value)

Even juggling one ball would inevitably collapse the bridge. (Technically, kg is a measure of weight and not force, but I'm using the unit for convenience.) --Bowlhover (talk) 03:23, 10 July 2008 (UTC)

Just to be pedantic - kg is a measure of mass, not force. Weight is a type of force (force due to gravity). --Tango (talk) 14:07, 10 July 2008 (UTC)

I suggest he toss the three balls across first then walk very gingerly across the bridge. StuRat (talk) 03:39, 10 July 2008 (UTC)

He could also just take the balls across one at a time, or roll them across :p --Shaggorama (talk) 06:09, 10 July 2008 (UTC)

If the man's planning to carry his balls across, he'd better not lift his feet. Since the bridge can only withstand the force equivalent to the gravity on a 100 kg object, if his feet ever hit the deck, the additional force delivered would collapse the bridge. --Bowlhover (talk) 06:40, 10 July 2008 (UTC)

Gold is running >US$900/oz...surely with 3kg, he could shave off a little and just pay some lighter dude to carry the stuff across or a personal trainer to help him lose slightly more than 2kg of flab and carry them all himself. DMacks (talk) 12:25, 10 July 2008 (UTC)

Some interesting and good ideas but I personally wouldn't trust some lighter dude to take my 3kg of gold balls across a bridge which I potentially couldn't cross. Heck even if I could cross the bridge I'm not sure I'm going to trust some lighter dude. 3 kg won't weigh the dude down that much and he/she's going to have a head start of the length of the bridge at the very least. Nil Einne (talk) 18:05, 10 July 2008 (UTC)

What kind of bridge is that? Is it made out of bottlecaps and cardboard? He's either really fat or really muscular. Either way, that bridge shouldn't exist, and if he values his gold that much he can go take a different bridge. Unless he's crossing the moat from his castle (well he is carrying his money as gold balls) there's always a bank around that you don't need to risk your life on a ridiculous bridge to get to. Maybe he can use the money to find a competent engineer. -LambaJan (talk) 20:25, 10 July 2008 (UTC)

Or maybe he could hire a lawyer to sue the bridge-builder for negligence. That would certainly help lighten the load of those pesky balls of gold :) OTOH if he won the case, he'd get to keep the gold, plus get the bottlecaps and the cardboard too! Franamax (talk) 07:23, 11 July 2008 (UTC)

Nah, he needs a 1kg scooter. Roll or throw the balls across first, then give himself one big push off the bank to scoot across the bridge without once touching it. Or he could shave some gold off the balls and use it to buy appropriate resources to build his own temporary bridge. 79.66.67.219 (talk) 04:33, 13 July 2008 (UTC)

"One of the question in the game "Mindtrap"....Is this legit?" In general, the answer to that will be 'no': a great many of the questions in that game are very poorly-thought out. Olaf Davis | Talk 10:49, 17 July 2008 (UTC)