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May 13

While I know that it's a myth that you can stop a moving car...

...by shooting a .44 Magnum round though the engine block (did that belief come from a line in the film Taxi Driver, or was it one of the Dirty Harry movies - that people just picked up on?), is there any handgun cartridge at all that can actually do this? --95.150.167.241 (talk) 00:16, 13 May 2012 (UTC)[reply]

Technically, a .44 Magnum round could stop a car according to the law of conservation of momentum. However, a 1000 kg vehicle could only be going .0051 meters per second if the bullet was fired from exactly the opposite direction. Similar calculations could be done with other cartridges. Reaper Eternal (talk) 00:23, 13 May 2012 (UTC)[reply]

I guess it all depends on what you mean by "stop a car". If you mean stop it's forward movement immediately, it would be have to be going very slow, as noted above. If you mean to stop the engine, I don't think you're likely to cause much damage to the engine block. You could take out any number of critical components by chance, however. The fuel line, distributor, ECM, any number of wires, etc., could stop the engine almost immediately. However, this requires a lucky shot. If you are content to stop the car eventually, putting a hole in the radiator gives you a much bigger target. StuRat (talk) 02:17, 13 May 2012 (UTC)[reply]

Stopping a car with any speed would require a serious amount of force, enough to interrupt oil flow probably, or as mentioned above a very lucky shot. Puncturing the radiator, as mentioned, will lead to the engine eventually seizing, but will not be any sort of rapid stop. the largest production handgun in the world is the .500 S&W, which produces a stunning 2600 or more foot-pounds of force. This is nearly 700 Ft-lbs more than the puissant .454 Casull. If you were to assume that the round is similar to the indenter used in a Brinell scale test, then against a typical grey cast iron engine block, it would make an indent defined by: Brinell hardness = (2*force in Kgf) / ((pi * diameter) * (Diameter - Sqrt(Diameter^2 -Indentation^2))) in this case that would be 260 = (2 * 35946.2) / ((Pi * 12.7)(12.7- Sqrt(12.7 - D))). This simplifies to: 260 = 71892.4 / 39.8 * (12.7 - Sqrt(12.7 -d)). The simple answer is 12.55mm which is almost exactly 1/2 in. (one half inch is 12.7mm as seen above). Since the engine block is greater than .5 in. thick, it's unlikely the handgun bullet would penetrate. Since cast iron is fairly ductile it is unlikely to shatter, and it's unlikely to deform greatly from that impact. Keep in mind this is a best-case scenario with a full-caliber tungsten penetrator, like a military AP round.Ssscienccce (talk) 10:24, 13 May 2012 (UTC)[reply]

Don't count on a cast iron engine block (leaving aside that most are aluminium alloy these day) not shattering. I've seen more than one engine block with a dirty great hole in the side caused by a thrown conrod (caused by either incorrectly installed bigend bolts, or the conrod itself breaking). However, engines can continue to run under such conditions, if the driver can stand the horrible noise. And if you are shooting at him, he will. Keit120.145.7.207 (talk) 12:29, 13 May 2012 (UTC)[reply]

HominidMachinae (talk) 06:42, 13 May 2012 (UTC)[reply]

Your best bet would be having the engine destroy itself, since a turning engine has a lot more kinetic power than a bullet. Breaking the timing belt or a valve (if a bullet can reach there) would do serious damage. A bullet at the right spot can initiate catastrophic failure, I suspect. ::I would think that hitting the gearbox might well (though not always) cause immediate locking of the damaged gears and hence transmission, but you'd probably need quite advanced automotive experience to know where it was on your particular target, and whether or not it was effectively shielded from your position. {The poster formerly known as 87.81.230.195} 90.197.66.211 (talk) 11:31, 13 May 2012 (UTC)[reply]

Two words: smart bullet. Of course, when a bullet has the plans of every car coded inside it and decides where to hit in a few microseconds, the days of allowing the pathetic human behind it to have a say when it is fired will soon come to an end. Wnt (talk) 15:16, 13 May 2012 (UTC)[reply]

Mythbusters kinda hit on this one a while back. They were doing a myth about phonebooks making a car bulletproof... until Carrie put a .50 caliber round through the engine block(episode). So, I'd say no, a handgun won't be able to pull it off. — The Hand That Feeds You:^Bite 21:15, 13 May 2012 (UTC)[reply]

Like I said above, no handgun round could do it, even with military ammo. However a .50 BMG round from a rifle was BUILT to take out light armor would do it handily. Vehicles are tougher than a lot of people give them credit for. Anything capable of taking out a vehicle will be military-grade and probably a squad-level weapon (IE a Boys AT rifle is about the smallest they get, and that thing is 70 pounds). HominidMachinae (talk) 23:10, 13 May 2012 (UTC)[reply]

How's about a .50 BMG round fired from a pistol? I believe that .50 BMG pistols have been built before - though probably only in numbers amounting to single digits by people who want to see what holding and firing a .50 BMG pistol looks/feels like. --Kurt Shaped Box (talk) 19:19, 14 May 2012 (UTC)[reply]

The size of the round and powder charge is only part of the final end ballistic result, barrel length is also critical. a common pistol-length barrel firing a .50 BMG quite possibly would not have even burned all of its powder before said powder is flung from the barrel. a .500 S&W is about the upper end of "practical" pistol loads, though your definition of practicality may differ (the punishing recoil of the .500 S&W can break an inexpert user's wrist, or smash them in the face with their own weapon). If you put s shoulder-stock on the pistol you might fire a larger round, but then you're more properly talking about a carbine, and indeed that's what most rifle-round "pistols" like the .223 pistol are. HominidMachinae (talk) 04:36, 17 May 2012 (UTC)[reply]

Rusting after burning

Why is it that metal seems to rust much quicker after it's been burned in a fire? Or is this just confirmation bias on my part? Dismas|^(talk) 01:27, 13 May 2012 (UTC)[reply]

How is that you've observed the rusting of scorched metal often enough that you observed patterns in it?? If it is because you live in a city that was recently a battlefield, I sincerely feel for you, but otherwise, that is kind of strange. ike9898 (talk) 01:46, 13 May 2012 (UTC)[reply]

Upon reading the question I immediately thought of the old campers' dictum (now strongly discouraged) in my country, Australia, of what to do with empty cans - Burn, bash and bury. As Tin can tells us, "Tin cans are made of tinplate (tin-coated steel)", and the burning removed the thin protective tin coating, thus allowing the steel to rust more quickly. If this response has nothing to do with the question, just ignore me. HiLo48 (talk) 01:56, 13 May 2012 (UTC)[reply]

That seems like the proper explanation, although I doubt if the tin melts entirely. More likely there are just holes created in it. The plastic lining on the inside may burn away entirely, however, exposing the inside to the elements. Another factor to consider is that cans, once burnt, might be left in a fire pit, where they are far more exposed to the elements (water, changing temps, etc.), than the intact can was whilst in a cupboard. StuRat (talk) 02:06, 13 May 2012 (UTC)[reply]

My guess would be that it would have rusted before being exposed to high temperatures had there not been some coating on its surface preventing its exposure to oxygen and water. Paint serves this purpose but perhaps other clear substances, the presence of which one may not be aware of, could have been present before heating but removed or damaged by heat. Bus stop (talk) 02:29, 13 May 2012 (UTC)[reply]

No, I don't live in a war zone. And it occurred to me to ask after seeing the rubble from a house down the road that had recently burned down. Someone had made a pile of all the appliances and other large metal objects that were taken from the home. Every bit of it was rusted. Off the top of my head, I remember seeing a sink, a water heater, what appeared to be a washer or dryer, a stove, a few mattress springs, and what appeared to be possibly a table saw. Since the fire, it's been rather dry here with the exception being a couple days this past week and, of course more localized, the spray from the fire hoses. The items were all covered in rust. Dismas|^(talk) 03:34, 13 May 2012 (UTC)[reply]

Protective coatings burning off (like paint, oil on tools..) or damaged by impact, moisture for days, chemicals in the water, galvanic corrosion if touching other metals. Ssscienccce (talk) 10:51, 13 May 2012 (UTC)[reply]

You know what the difference between burning and rusting is? Speed. Apply oxygen to iron using water as a catalyst, and you get rust. Apply oxygen to iron using heat to speed up the reaction rate, and you get rust. The ingredients are the same, the underlying chemical reaction is the same, and the end product (iron oxide) is the same. --Carnildo (talk) 01:51, 16 May 2012 (UTC)[reply]

"Rusting" typically means the slow oxidation of iron, while "burning" can mean the rapid oxidation of anything (it also has other meanings), so there is so overlap, yes. StuRat (talk) 18:31, 18 May 2012 (UTC)[reply]

Autism

Autism is described as being on a spectrum. Presumably 'profound autism' is one end of that spectrum. What is the other end of the spectrum? 'Extrely Nuerotypical'? ike9898 (talk) 01:42, 13 May 2012 (UTC)[reply]

People who have abnormally good social skills. Count Iblis (talk) 02:08, 13 May 2012 (UTC)[reply]

Asperger's syndrome is a mild form of autism, and then there is PDD-NOS and high-functioning autism. StuRat (talk) 02:26, 13 May 2012 (UTC)[reply]

Stu is onto it. A basic definition of autism is the reduced ability to see another's point of view. But the range of Autism is not on a line - it is multidimensional. As with most mental/pschological "problems", a highly intelligent individual can overcome the "problem" by consciously thinking about it and correcting his behaviour. In doing so, the individual may make his autism seem different. I've put the word "problem" in quotes because to a high functioning autistic, it is a matter of opinion whether it is a problem. There are fields of employment where autism actually helps. Wickwack121.221.89.38 (talk) 03:08, 13 May 2012 (UTC)[reply]

'Stu is onto it' == 'Stu is on the autistic spectrum'? ~~ — Preceding unsigned comment added by OsmanRF34 (talk • contribs) 12:13, 13 May 2012 (UTC)[reply]

I'm sitting on a spectrum ? I can't feel it down there. I'd love to discuss this further, but it's 5:19, which means it's time for me to rip up pieces of paper for no apparent reason. :-) StuRat (talk) 05:19, 14 May 2012 (UTC) [reply]

Well, I wouldn't know, but as his posts are friendly, and he never attacks other posters, I doubt it. Note that I said "onto it", NOT "on it". The meaning is quite different. Wickwack58.164.226.214 (talk) 14:35, 13 May 2012 (UTC)[reply]

There is a hypothesis floating around by a Bernard J. Crespi that autism and schizophrenia are at opposite ends of a neurological spectrum. He's been going on about this since at least 2008. You can find lots and lots of papers [1][2][3][4][5] etc. about genes that affect both autism and schizophrenia. The problem is, it's hard to really categorize the effect as "same" or "different"; often one or the other is more what you'd call "altered". So some people paint it as two disorders based on the same mechanism, this fellow says they are opposite - in biology, there is little real distinction between synonyms and antonyms!

The most intriguing way to settle the issue would be to put some autistic kids on low-dose LSD - not enough to have obvious trippy effects, but maybe enough to revert autism to normality, if LSD is "psychotomimetic", and if that is some effect opposite to autism. But naturally many things could go wrong in such an experiment and some may question its ethics. ;) Wnt (talk) 04:38, 13 May 2012 (UTC)[reply]

You must be joking. Autism, neither the effects, not the cause, is well understood, but it is clear that it is caused by a lack of something - possibly a full set of functioning mirror neurons http://en.wikipedia.org/wiki/Mirror_neuron, maybe that and/or something else. You won't correct that with any sort of drug, any more than you could correct blindness, due say to genetically damaged retinas, with drugs. With enough LSD, you could maybe get the subject to think he has vision though... If you give LSD to autistic people, what you can only get is two problems instead of one - socially inept people who can't think straight, and if enough, socially inept people who halucinate and suffere from delusions. Hardly an improvement. Scientific American had a couple of good articles on autism, the mainstream professional view of it, and the role of mirror neurons, in the last year or so. Wickwack124.178.183.79 (talk) 11:07, 13 May 2012 (UTC)[reply]

I don't see the evidence that something is missing - while there are indeed large-scale and permanent variations in autistic brain (the location in the cortex where processing is done, the disruption of the inferior olive, AFAIR), it is often the case in biology that very visible alterations to an organ are less important than small and reversible regulatory changes. I'm not entirely serious in the sense that the low-dose LSD experiment I proposed probably wouldn't work and would very likely be regarded as unethical; nonetheless, I think there's a chance it would be beneficial. Wnt (talk) 15:11, 13 May 2012 (UTC)[reply]

In 2002 Simon Baron-Cohen put forward a theory that autism is an extreme form of the male brain, and there is a more recent article here about it. So one answer to the question could be "maleness" (or, depending on whether you see gender as a continuum, "femaleness").--TammyMoet (talk) 09:46, 13 May 2012 (UTC)[reply]

In the medical field generally, and the psycology field especially, you can always, if you look, find some wizzo professor who has very different and even bizare views about something. Here in Australia, we had a, otherwise quite well respected, medical professor who kept claiming that smoking had no role in lung cancer. He got in the news from time to time until he got lung cancer and died. However, TammyMoet's link is interesting. Wickwack124.178.183.79 (talk) 11:07, 13 May 2012 (UTC)[reply]

[OP] So, would it be safe to say that a spectrum is a bad analogy for the range of autism and related conditions?ike9898 (talk) 13:02, 13 May 2012 (UTC)[reply]

Not at all. "Spectrum" is a good word for it. Just as we talk about light having a spectrum, meaning a range of colours, autism is a spectrum, because it encompasses a range of conditions. Not only because you can be mildly, moderately, or severely autistic, but because not all autistic people, even if they are of the same severity, will display the same limitations or advantages. It is multidimensional in impact, as I said. (Not forgeting that autism can be a disadvantage or an advantage depending on the circumstances the autistic finds himself in). Wickwack58.164.226.214 (talk) 14:29, 13 May 2012 (UTC)[reply]

1 year.

Earth 2 forms a ring centered on the Sun, located on the circle* of old Earth's orbit. Earth 2 is stabilized by its rotational motion at old Earth's orbital speed. Your job is to find a way of having seasons on the ring. The idea for producing seasons is to allow Earth 2 to oscillate in the direction of its axis, perpendicular to the plane of its ring. Assume that a line from the Sun to Earth 2 oscillates through 46° of angle, with the mid-plane of the oscillation containing the Sun. What is period of the oscillations, in units of years?

If the Sun is a perpendicular distance $x$ from the ring, I worked out the magnitude of force acting on the ring to be ${\frac {Gm_{sun}m_{E2}x}{(r^{2}+x^{2})^{\frac {3}{2}}}}$ which is approximately ${\frac {Gm_{sun}m_{E2}x}{r^{3}}}$ since $r$ is surely much bigger than $x$ . It follows that the "spring constant" is ${\frac {Gm_{sun}m_{E2}}{r^{3}}}$ and the period of oscillation is therefore ${\frac {2\pi }{\sqrt {\frac {Gm_{sun}}{r^{3}}}}}$ . I look up the numbers and substitute and get a result of a single year. Since the result needs to be given in years, I am suspicious of this result and may have made a mistake. Does anyone agree/disagree with what I have done? --Widener (talk) 01:52, 13 May 2012 (UTC)[reply]

*By the way, I am aware that it is actually an ellipse.

Would not the "spring constant" be negative (which will not sustain oscillation)? Wickwack121.221.89.38 (talk) 02:41, 13 May 2012 (UTC)[reply]

That would be under the interpretation that

F=kx

rather than

F=-kx

. Widener (talk) 03:06, 13 May 2012 (UTC)[reply]

If I'm understanding the question correctly, is it not obvious that it will be a year? I don't see why you need to use any maths. Egg Centri c 02:43, 13 May 2012 (UTC)[reply]

Assuming I've understood his text etc correctly, he's visualising a donut/toriod shaped earth that supposedly oscillates up and down its rotation axis. The real earth has seasons because its rotation axis is at an angle away from perpendicular to its' orbital plane, forcing the seasons to be the same period as the orbital period. Such a thing is inapplicable to a donut surrounding the sun. So he needs to calculate the period of this "new" mode of oscillation, which is not locked to the orbital period. It will not actually oscillate though. Wickwack121.221.89.38 (talk) 02:50, 13 May 2012 (UTC)[reply]

I was going to say that the oscillation could be made any arbitary period (and therefore presumably a year) by altering the amplitude but then noticed the 46 degree thing... I see the problem

Egg Centri c 16:13, 13 May 2012 (UTC)[reply]

(So presumably you don't want to model it as a ring, just model it as a point mass with a centre of gravity which happens to pass through the sun during the oscillation, which means the equations will be very simple. Although it's a decade since I've done any mechanics, as this thought probably demonstrates) Egg Centri c 16:15, 13 May 2012 (UTC)[reply]

The statement that r is much bigger than x is not valid. It's bigger, but not enough bigger to make the approximation valid. The max value of x/r is tangent(23 degrees), which is about 0.42. Looie496 (talk) 03:07, 13 May 2012 (UTC)[reply]

I don't think this will actually work - the varying distance from the ring to the Sun means the idea of stabilising it by having it revolve at orbital speed doesn't work. The centripetal force from the Sun's gravity won't balance the centrifugal force from the revolution, since the revolution is constant and the relevant component of the Sun's gravity isn't. That means you're going to get internal forces within the ring, which will rip it apart (unless it is made of some hypothetical super-strong material). --Tango (talk) 19:32, 13 May 2012 (UTC)[reply]

I don't know what "stabilized" means here; rotation doesn't affect the tendency of a Ringworld to drift into the sun. —Tamfang (talk) 03:20, 14 May 2012 (UTC)[reply]

By the way, this sounds like a homework question to me, presumably for calculus class. Ah well, too late now. ;) Indeed, the Ringworld is unstable, but only small attitude jets are said to be necessary. The oscillation along the axis would be unrelated to its instability from side to side.

As for the question, the Ringworld is simply a vertical wall to hold its bits in place. Mass cancels out and is irrelevant. A particle of the ring is accelerated toward the sun at G m_sun/sqrt(x²+r_earth²), but toward the midline at that multiplied by x/sqrt(x²+r_earth²). So you have to integrate dx/dt for G m_sun x/(x²+r_earth²), I think... And I don't think that you can assume x is much smaller than r_earth, or else you wouldn't get seasons from it. Besides, knowing/looking up/figuring out this integral is presumably the point of the assignment. ;) Wnt (talk) 04:30, 14 May 2012 (UTC)[reply]

Its not likely to be homework, becasue as such it would be a trick question - its not solvable because it is not oscillatory. In any case, its ok, because this OP showed us he had a go at working it out. Wickwack124.178.138.77 (talk) 06:02, 14 May 2012 (UTC)[reply]

If it doesn't oscillate, what does it do? It's not an escape trajectory (you can imagine it starting at rest at one of the mid-winter/mid-summer positions, so the total energy must be negative), and there isn't enough going on for it to be on a bounded but non-periodic trajectory (it essentially boils down to a two-body problem). It's not quite simple harmonic motion (the restoring force is inverse square, rather than a simple linear force) but it's still an oscillation. --Tango (talk) 18:24, 14 May 2012 (UTC)[reply]

It is an escape trajectory, as the "restoring force" for oscillation perpendicular to the rotation axis is negative. Unless I've mis-understood the OP's question. Please re-read the original question, my third post (begins "assuming I've understood....". and then tell us what you think. Your previous posts (and possible EggCentric's) are sort of/partly consistent with a different interpretation - that of a toriod (or bottomless & topless thin drum) with its centre of gravity in eliptic orbit about the sun. That will give seasons, but is not consistent with the OP's explanatory words to his question. Wickwack120.145.187.143 (talk) 00:54, 15 May 2012 (UTC)[reply]

I agree with Tango that you have misunderstood the question. The idea is that you have a ring, with the sun at the center, then you give it an "upward" push. It slows down until the angle of the face of the ring and the sun is 23 degrees, then accelerates back "downwards" until it reaches the ecliptic again and starts decelerating, then at -23 degrees it accelerates "upward" again. I think you've gotten lost in the equations, because it's simple to see that it will be an oscillator if you look at the problem practically :)

And to the OP: As a rough check of your calculations, you could take the freefall time of a point mass with the same mass as the ring at an equivalent distance directly above the sun, then quadruple it to get the time for a full oscillation. Too lazy to do the calculations myself, but a quick back-of-the-envelope calculation tells me the oscillation period should be on the order of hours-days, not years. -RunningOnBrains^(talk) 03:53, 15 May 2012 (UTC)[reply]

Agreed. I think Wickwack is reliving the glory days of (Larry Niven says, MIT students chanting "The Ringworld is unstable". But here the Ringworld is being pushed perpendicular to the direction it was moving in Ringworld Engineers. Wnt (talk) 19:39, 15 May 2012 (UTC)[reply]

Unfortunately no glory days. I've had another think, prompted by Runningonbrains's method, and decided that it will oscillate after all. Wickwack124.178.42.68 (talk) 01:03, 16 May 2012 (UTC)[reply]

Why is CO not the anhydride of formic acid?

The acid's article does not describe why formic acid behaves differently from carbonic acid, which I viewed as simply a higher oxyacid of carbon.--Jasper Deng (talk) 03:30, 13 May 2012 (UTC)[reply]

I think you might be mis-reading how carbonic acid behaves when it dehydates: its reaction is O=C(OH)₂→O=C=O, which is a standard gem-diol dehydration to form a carbonyl (lose an H from the OH, O remains attached). Formic acid doesn't have a gem-diol, and forming CO from it would involve loss of H from the C itself. It's pretty difficult to envision losing H and OH from the same position and getting anything close to a stable structure in general: dehydrohalogenation from a single atom (R₂C(H)(X)→R₂C analogous to your O=C(H)(OH) proposal) gives a carbene, which is generally extremely unstable unless there is something special about the R groups.

On the other hand, carbon monoxide is an anhydride of formic acid (see our formic anhydride article for details about CO formation in this sense). The carbene-like structure for O=C: in particular is just a resonance form of carbon monoxide, and the lone-pair on the "carbonyl oxygen" is exactly special to fix the octet instability of this carbene. DMacks (talk) 03:48, 13 May 2012 (UTC)[reply]

My conclusion stemmed from the fact that CO itself does not seem to hydrolyze in a reaction like CO(g) + H₂O(l)→ H₂CO₂ analogous to carbonic acid.--Jasper Deng (talk) 03:56, 13 May 2012 (UTC)[reply]

Carbon monoxide does react with water, just not in the way your intuition thinks it does. See Water gas shift reaction. --Jayron32 04:11, 13 May 2012 (UTC)[reply]

I knew about that particular one... I guess that there's little reason for my previous predicted reaction? -Jasper Deng (talk) 04:13, 13 May 2012 (UTC)[reply]

(edit conflict) Formic acid is the first of a homologous series known as the carboxylic acids, and those form dimeric anhydrides. If you look at formic acid like acetic acid and propionic acid, you'll see the pattern. The oxidation state of carbon in all three of those is the same, whereas in the carbonate ion, the electronics are quite different. Another way to think of formic acid as quite different than carbonic acid: formic acid has one of its hydrogens bonded directly to carbon, whereas all of the hydrogens in carbonic acid are oxygen bound. Any of these ways of thinking of it will lead you to the more correct conclusions than you reached. --Jayron32 03:50, 13 May 2012 (UTC)[reply]

Sorta the same reason that phosphorous acid is diprotic while phosphoric acid is triprotic, I guess...--Jasper Deng (talk) 03:56, 13 May 2012 (UTC)[reply]

Have you looked at carbonous acid and methanediol? Plasmic Physics (talk) 07:03, 13 May 2012 (UTC)[reply]

Formic acid was once made at a large scale by dissolving CO in hot NaOH solution under pressure. So you could consider it to have some anhydride properties (stoichiometrically) Staticd (talk) 12:17, 13 May 2012 (UTC)[reply]

Are there any traits (genetic traits) that are only inherited from one parent?(mom or dad)

Like the mitochondrial DNA that is inherited only from mothers?--2.147.67.209 (talk) 06:43, 13 May 2012 (UTC)[reply]

Anything on the Y chromosome is inherited from the father. Boys only, of course. — kwami (talk) 07:53, 13 May 2012 (UTC)[reply]

Colour-blindness in boys comes via the mothers. There are others, but I can't remember them right now. HiLo48 (talk) 08:29, 13 May 2012 (UTC)[reply]

Yes, the mitochondrial DNA is only inherited from the mother. Since virtually everything inside that DNA is directly related to the function of mitochondria, you don't really see anything but diseases being passed in it (i.e. when it works, you don't notice, except that you're not sick/dead). See Mitochondrial disease for a list of potentially inherited traits. As mentioned above, the Y chromosome is only inherited from the father. Explaining what HiLo said, boys inherit their X chromosome only from their mother. Sex linkage lists a variety of diseases that are linked to the X chromosome. There is also the case of genomic imprinting, in which case you inherit the DNA from both parents, but the DNA from only one parent is active and determines the phenotype. There are maybe 90 such genes, spread out across the chromosomes. Someguy1221 (talk) 08:46, 13 May 2012 (UTC)[reply]

Greenland as three islands

There's been a problem with an unref'd or poorly ref'd assertion at Greenland for several years now. The common understanding is that Greenland is really three islands connected by ice. A look at a topographic map shows that's not true: the center is below sea level, but the rim is unbroken. However, AFAIK that's not where the story came from. If the ice sheet were to melt completely, the sea level would rise 6–7 m, and then Greenland would be three islands; conversely, it's thought that glaciation united what had been three islands (at a higher sea level than now). I can't find a decent ref, though. Does anyone know of one, or am I remembering it wrong? (I can find lots of maps of what Florida would look like if the Greenland icecap were to melt, just not what Greenland would look like.) — kwami (talk) 07:52, 13 May 2012 (UTC)[reply]

Another theory is that as the icecaps melt, the weight removed would allow the land to rise, so none of Greenland without icecap may be below sea level. HiLo48 (talk) 08:27, 13 May 2012 (UTC)[reply]

Not a "theory" but a well-known phenomenon. It's pretty slow, though. Short Brigade Harvester Boris (talk) 21:24, 13 May 2012 (UTC)[reply]

I traced the assertion back to 1951 - see the reference I added to the article. However, the original discoverers said nothing about sea level rise so I deleted that bit. --Heron (talk) 09:56, 13 May 2012 (UTC)[reply]

check out greenland geology map 186.151.67.249 (talk) 11:18, 13 May 2012 (UTC)[reply]

OK, you write the article and then we'll check it out. -- ♬ Jack of Oz ♬ ^{[your turn]} 21:39, 13 May 2012 (UTC)[reply]

Canada & the northern US are still rebounding from the retreat of the glaciers 11 ka, so I think it might be a while before the same happens to Greenland.

Without a rise in sea level, it looks as though Greenland would be a single island with a giant lake in the middle. But that's not realistic: all that water has to go somewhere. The 1951 claim may not have addressed that, but it's been done since. — kwami (talk) 03:01, 14 May 2012 (UTC)[reply]

And to further complicate matters, consider that the warmer conditions needed to melt the Greenland ice cap would also melt the ice shelves off Antarctica, some mainland Antarctic glaciers, and some other smaller glaciers. So, should that extra sea level rise also be taken into account ? If so, perhaps Greenland would be fully submerged. StuRat (talk) 04:51, 14 May 2012 (UTC)[reply]

No, that would not happen even if the entire planet were ice-free. But correlations with Antarctica are speculative, and you could at least hypothesize that only the northern hemisphere would be affected, as a minimal model. Not likely, but if Greenland melts, the sea level must rise by at least the amount of melt water from Greenland, so that's the theoretical lower bound. — kwami (talk) 11:09, 14 May 2012 (UTC)[reply]

I have a hard time imagining and scenario where only the Northern Hemisphere warms up. StuRat (talk) 23:33, 14 May 2012 (UTC)[reply]

Some kind of giant hat, perhaps? FiggyBee (talk) 13:27, 15 May 2012 (UTC)[reply]

I suppose if Greenland drifted south that might have the same effect, although the tens of millions of years for this to happen by continental drift is vastly longer than the glaciation cycles, which are on the order of tens of thousands of years. StuRat (talk) 17:02, 15 May 2012 (UTC)[reply]

Well yeah, but again, it's the bare minimum: if Greenland is icefree, the sea-level rise will be 7m plus whatever from Antarctica, so 7+m. The amount of the "+" is unknown, really, so I was going with 7m. But it's not enough. Got a data set from the NSIDC and mapped Greenland for various sea-level rises. In order to get the inland basin to connect at all, you have to raise sea levels almost 50m. That opens up the northwest channel (or channels, really: there are two of them). To get a second channel for Greenland to break up, you need close to the 68.3m estimated rise from both Greenland and Antarctica, and even then it's a rather narrow channel. Thermal expansion would push that up, but unless that's a big difference, the northeast channel would not open, so at most Greenland would be two big islands. — kwami (talk) 23:31, 17 May 2012 (UTC)[reply]

The Nature of Jupiter's Metallic Hydrogen Interior

The wikipedia article of Jupiter says that most of the interior is Metallic hydrogen a kind of degenerate matter. What I'm not clear on is how solid this state of matter would be. Does the metallic hydrogen act more like a liquid or a solid or a gas? Ignoring the gravitational effects, could a spaceship fly through it? I've always been under the impression that Jupiter was mostly a cloud of gas and now need to revise my incorrect ideas. Thanks for any help. --CGPGrey (talk) 10:15, 13 May 2012 (UTC)[reply]

It says that in the Jupiter article that there is liquid metallic hydrogen; a spaceship cannot fly through the centre of Jupiter; it is not simply a cloud of gas. Plasmic Physics (talk) 10:31, 13 May 2012 (UTC)[reply]

It is a planet with a ferrosilicate core, with a mantle of liquid metallic hydrogen, overlaid with a deep ocean of super-critical molecular hydrogen, topped off with a thick atmosphere of various gasses. Plasmic Physics (talk) 10:45, 13 May 2012 (UTC)[reply]

To get hydrogen solid, it would need to be below the triple point temperature, which is only 13.84 K. Not very likely within a large planet. Keit120.145.7.207 (talk) 12:21, 13 May 2012 (UTC)[reply]

But as the pressure on the hydrogen increases, so does its melting point. Conceivably, the pressure inside Jupiter could be high enough for solid metallic hydrogen to exist near the core. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 12:40, 13 May 2012 (UTC)[reply]

The triple point is where all three phases can exist. Maybe you mean the critical point. But that's thepoint where there's no more difference betweengas and liquid. Higher pressure may still make it a solid. Ssscienccce (talk) 12:55, 13 May 2012 (UTC)[reply]

I meant the triple point. Whoop whoop could be correct if the melt line, which begins at the triple point, "leans" significantly towards higher temperatures at higher pressures. From memory, there's not a lot of lean in the hydrogen melt line, but I don't have a phase diagram for hydrogen to hand. Keit120.145.7.207 (talk) 14:21, 13 May 2012 (UTC)[reply]

There are some conflicting statements in the metalic hydrogen article imo:

The initial prediction about the amount of pressure needed was eventually proven to be too low.
Because previous predictions of the nature of those interiors had taken for granted metallization at a higher pressure than the one at which we now know it to happen, those predictions must now be adjusted.
at 345 GPa, hydrogen is still not a true alkali metal
at 140 GPa ... the hydrogen might be considered metallic.
The lead mentions solid metallic hydrogen but the rest of the article seems to talk about liquid only. It's a bit confusing Ssscienccce (talk) 12:55, 13 May 2012 (UTC)[reply]

Even if it's a gas, that doesn't mean a spaceship could fly through it. The density would be enormous, which means the resistance would be enormous too. It would take lots of energy to move the spaceship and all that energy would go into generating heat, so the spaceship would either not move or it would burn up. --Tango (talk) 20:03, 13 May 2012 (UTC)[reply]

There is a possibility that metallic hydrogen could be metastable at low pressures. Then if a giant Jupiter like planet is destroyed in a collison, there could be small fragments containing metastable metallic hydrogen, which could give rise to strange meteorites, see here. Count Iblis (talk) 20:54, 13 May 2012 (UTC)[reply]

Interesting idea, what would happen if such a meteorite, composed of solid metallic hydrogen, entered Earth's atmosphere? Could it perhaps be a candidate for the Tunguska event? Plasmic Physics (talk) 00:43, 14 May 2012 (UTC)[reply]

Maybe a reson why it could descend so far into the atmosphere, could be that the hydrogen centre was thermally insulated by another frozen gas such carbon dioxide (not likely). Plasmic Physics (talk) 00:48, 14 May 2012 (UTC)[reply]

I don't think you can have metallic hydrogen at any temperature if the pressure is not something "astronomical" - and by that I mean more astronomical than a meteorite. ;) Besides, I think if you work it out you'll find a meteorite contains more energy in its motion than it would have in chemical energy even if it were hydrogen ... but I don't know for sure. Anyone up for an exercise? ;) Wnt (talk) 19:37, 15 May 2012 (UTC)[reply]

Stronger superacids than fluoroantimonic acid

Since gold pentafluoride and bismuth pentafluoride are both stronger fluoride-ion acceptors than antimony pentafluoride, shouldn't hexafluoroauric acid, HAuF₆, and hexafluorobismuthic acid, HBiF₆, be even stronger superacids than fluoroantimonic acid? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 12:15, 13 May 2012 (UTC)[reply]

I think these superacids are in the Brønsted–Lowry sense, so acidity is "how strongly does the metal–F complex hold the H" not "how strongly does the metal hold the F?". AuF₅ might be the strongest Lewis acid, since that deals with electron-acceptor modes of the metal center. But adding HF to AuF₅ causes the whole thing to decompose--due to that acidity--and liberate fluorine and gold(III) fluoride (see [[doi:10.1002/1521-3773(20011001)40:19<3690::AID-ANIE3690>3.0.CO;2-5]]) rather than forming a [AuF₆]^– cluster. I know this exact question has been asked on WP before but I can't find it right now. DMacks (talk) 15:47, 13 May 2012 (UTC)[reply]

Heh...was my talk-page. See User talk:DMacks/Archive 13#Need help from the smarter where I had found some refs and related ideas. DMacks (talk) 20:40, 13 May 2012 (UTC)[reply]

Steel laptop and electroshock

How do they isolate the steel of those new laptops so you don't get a shock? OsmanRF34 (talk) 12:51, 13 May 2012 (UTC)[reply]

I don't think there are any steel laptops, although some are made from aluminium or titanium alloys. They are isolated in the same way as any other electricity-using equipment with metal part (washing machines, cars, stereos, toasters...), namely by making sure that there is no electrical contact from power carrying circuits to the frame of the device. If you want more details, iFixit has an article on disassembling a unibody MacBook Pro with pictures showing how the components are mounted on plastic circuit boards mounted inside the metal unibody enclosure. --Stephan Schulz (talk) 13:42, 13 May 2012 (UTC)[reply]

In countries following European standards, and countries that have their own standards more or less in harmony with European standards, laptops and any other appliance mus conform to one or two choices. With Choice 1, any and all exposed meatl work must be electrically earthed. The 'third pin' (the one that is different to the other two, or is aligned different to the other two) on the power plug carries the earth connection. Should any fault occur which would otherwise make the exposed metal live, the current is carried away via the earth connection, so you can't get a shock. With Choice 2, the laptop or appliance must conform to the standard commonly known as "double insulated", and must display the double insulated symbol (two squares, one inside the other). In double insulated equipment, it is designed in such a way that no concievable fault can, on is own, cause the exposed metal work to become live. This may be achieved by simply providing two insulating barriers, or by other technically acceptable methods. Choice 1 is the most common choice for personal computers & laptops. As a general rule, countries that have only 2-pin wall outlets (eg Japan) historically had lower electrical standards. However, these days, as manufacturing is for world markets, equipment is made to conform to European standards. Keit120.145.7.207 (talk) 14:12, 13 May 2012 (UTC)[reply]

Further to the above valid replies, all the laptops that I have ~~ever~~ seen in the last fifteen years run from a low voltage (usually 19v) fed from a "power brick" (Switched-mode power supply) which conforms to the EU double-insulation standards in isolating the whole of the laptop from any high voltages. Dbfirs 15:08, 13 May 2012 (UTC)[reply]

I think Dbfirs' answer is actually the most relevant one here. It is the power adapter that will have to comply to the mains standard, not the laptop, the laptop runs on relatively low voltage DC. The metal on the laptop does not need to be earthed externally as it is not a shock hazard. Vespine (talk) 22:53, 13 May 2012 (UTC)[reply]

Not all laptops have external power units. All the laptops (Toshibas mostly) they issued us with at work had internal power supplies. Wickwack121.215.40.247 (talk) 00:42, 14 May 2012 (UTC)[reply]

Ah, I wondered if they existed. I was trying to remember whether my first work laptop (heavy and bought in the 1980s) had an internal supply. I assume they conform to the same double-insulation regulations, rather than have all metal earthed. Dbfirs 07:23, 14 May 2012 (UTC)[reply]

Nope. Those Toshiba laptops were earthed via the third pin, the same as a desktop PC. Wickwack60.230.232.194 (talk) 07:52, 14 May 2012 (UTC)[reply]

Was this perhaps a few years ago? I first looked at the available models at the Toshiba site, but had to expand my search a bit to find one: a Toshiba t5200 from 1988, 8.5 kg, with built-in power supply. Who would have thought that the first laptops didn't run on batteries... Ssscienccce (talk) 11:20, 14 May 2012 (UTC)[reply]

Promiscuity and inbreeding

Would a fully promiscuous mating system reduce the minimum starting population needed to avoid problems related to inbreeding? Assuming equal gender ratios in the starting population. Horselover Frost (talk · edits) 16:31, 13 May 2012 (UTC)[reply]

As compared to a monogamous mating system, I mean. Horselover Frost (talk · edits) 16:32, 13 May 2012 (UTC)[reply]

A fully promiscuous mating system would make the problem worse, not better, since it would imply some level of mating between close relatives. But if you didn't really mean that, then I think the answer is that it would not make any difference, since every child has precisely two parents regardless of how promiscuous the mating is. Looie496 (talk) 18:21, 13 May 2012 (UTC)[reply]

a system of non-random mate choice for dissimilar individuals would be the best defence against inbreeding in a small population. (rats can smell out close relatives and some plants reject closely related pollen from fertilizing their eggs). Here are my calculations for a random mate choice system -

monogamy with random partner: If an individual has 'n' offspring, probability of all n being inbred = probability of picking a close relative (p)
promiscous mating with random partners: probability of all n being inbred = probability of picking a close relative n times = pⁿ < p for n > 1.

So yes, by my rough calculations for a toy model promiscuity is better than monogamy for inbreeding.Staticd (talk) 19:09, 13 May 2012 (UTC)[reply]

What do you mean by "problems related to inbreeding", or "fully promiscuous"? There are many separate issues at play in inbreeding, and not all of them are necessarily detrimental to the population. In the meantime, you may be interested in founder effects, and assortative mating. SemanticMantis (talk) 19:51, 13 May 2012 (UTC)[reply]

Lead poisoning and weight gain

Could children's bodies react to lead poisoning with weight gain--to sequester the harmful lead in fat tissue?Rich (talk) 19:54, 13 May 2012 (UTC)[reply]

I doubt it, since the article mentions as classic signs and symptoms in children: loss of appetite, abdominal pain, vomiting, weight loss. Ssscienccce (talk) 21:35, 13 May 2012 (UTC)[reply]

What you're talking about is an evolutionary response. Those only occur in response to problems which remain a serious threat to the species for thousands of generations. Thus, we have evolved a starvation response to keep us alive during famines. However, toxic lead exposure is rare today, and almost unheard of throughout most of human history. That's just not enough of a threat to the species to cause such an evolutionary response. StuRat (talk) 04:57, 14 May 2012 (UTC)[reply]

Stu, if by "toxic lead exposure", you mean exposure high enough to produce obvious symptoms, then its true that such exposure isn't common. However, lead is toxic, meaning degradation in rational behavior and measurable degradation in intelligence, down to very low levels. In response to another question, somebody posted a link to a study that showed that blood levels in US children had dropped in recent years. However, in western countries generally, lead is ubiquitous in the environment, resulting in blood levels around 30 to 100 ug/L. The USA has set an arbitary limit of 100 ug/L as safe, but that is not universally accepted - some experts think that is too high. Even so, a significant fraction of childen are above the US limit. It only takes a few industrial incidents or lead-using industry not complying with requirments, or some developer turning old industrial estates into residential, and you get children way over 100 ug/L. Here in Australia, lead poisoning of children gets reported in the media from time to time. See example report http://www.esperanceport.com.au/downloads/inquiry/Leadissueupdate2.pdf Wickwack124.178.138.77 (talk) 05:55, 14 May 2012 (UTC)[reply]

But evolution doesn't care about low-level exposure (please, no comments on my anthropomorphization of evolution). It would only care if a large percentage of people were prevented from reproduction, due to lead exposure. StuRat (talk) 23:30, 14 May 2012 (UTC)[reply]

Correct. Low level exposure to lead reduces your intelligence, but it doesn't take much brains to get a girl pregnant. Wickwack120.145.187.143 (talk) 01:02, 15 May 2012 (UTC)[reply]

I dunno about "toxic lead exposure is [...] almost unheard of throughout most of human history". Lead has a long history of all kinds of uses in western civilization, and it has been suggested (controversially) that sapa made in lead pots was a contributing factor in the decline of the Roman empire. Better documented, back to ancient Greece, is illness among miners, plumbers and potters who worked with lead. In the medieval and early modern period there were frequent outbreaks of illness caused by alcoholic drinks made with lead equipment or sweetened with lead (Devon colic). Of course, I agree with the rest of your assessment. :) FiggyBee (talk) 22:47, 14 May 2012 (UTC)[reply]

thd

what total harmonic analyzer measures? — Preceding unsigned comment added by Vivekmishra1988 (talk • contribs) 20:05, 13 May 2012 (UTC)[reply]

Total harmonic distortion. Tevildo (talk) 20:12, 13 May 2012 (UTC)[reply]

And THD analyzer. Red Act (talk) 20:17, 13 May 2012 (UTC)[reply]

How does myopia work?

I'm wondering how shortsightedness can work: apparently it is usually due to the eyeball being too long, but the point as I see it is that the lens focuses the image so that it will land on the retina. I can't see why we treat it as a focal-length mismatch between the eye and the lens, when the lens is adjustable. It does not have a fixed focal length, so what is the problem? Why can't it just compensate?

Another question: why do people's eyes so frequently get worse? Why don't they spontaneously get better? Assuming the eye is fixed in size and shape from one's early years, what is actually changing to make shortsightedness worsen, and why does it not improve? Thanks in advance, IBE (talk) 20:24, 13 May 2012 (UTC)[reply]

It does compensate, which is why they can still see things that are nearby. There is a limit to the range of focal lengths the lens can produce, though. Normally, that limit allows objects at distances from a few centimetres to infinity to be in focus. For shortsighted people, the range doesn't go all the way to infinity. For longsighted people, it starts further away. Some people (particularly the elderly) have both, so end up with a very short range - this can be corrected with bifocals. --Tango (talk) 20:45, 13 May 2012 (UTC)[reply]

The lens and the cornea, in combination, focus the light to a particular point. If you have normal vision, the image lands in the right place on the retina. If the eyeball is slightly misshapen, the focused image does not land in the right place. As Tango says, your eyes can adjust, but only so much - and their ability to adjust decreases with age. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:10, 13 May 2012 (UTC)[reply]

I think the reason why eyes get worse with age is that our ability to change the focus decreases, as a normal part of aging. There is sometimes an improvement in vision, such as in middle age, when people tend to go from having myopia to presbyopia. This can result in a short window when vision is improved. Eye exercises might also improve vision, at least temporarily. StuRat (talk) 05:04, 14 May 2012 (UTC)[reply]

Presbyopia unfortunately cannot help myopia: myopia occurs when the longest focal length is too short (principally a function of the cornea and eye length), and presbyopia is the lengthening of the shortest focal length without affecting the longest (because it is the ability of the crystalline lens to shorten the focal length of the cornea that is reduced). Put differently, presbyopia reduces a sort of depth of field of the eye, rendering some distances impossible to focus on without granting any other focusable distances in exchange. --Tardis (talk) 01:22, 16 May 2012 (UTC)[reply]

Myopia may be caused partly by doing to much near work, or for example children that read a lot and keep the book close to their face. The ciliary muscle is a ring of smooth muscle around the lens. When the muscle s relaxed, the lens is stretched (flattened) by the zonule fibers that connect to the ciliary muscle. When the muscle contracts, the ring gets smaller, there's less stretching so the lens becomes more spherical. How this would explain myopia is not certain, it seems there are several theories. Some researchers suggest myopic people use reading glasses (+ dioptry) for near work. Now the opposite usually happens, children get perscription glasses when they can't read the blackboard in class, and they keep them on when reading and writing. To focus correctly, the ciliary muscle will have to contract even more in that situation. But we don't know for sure. It's not clear why myopia doesn't worsen as rapidly with contact lenses as with glasses for example. Ssscienccce (talk) 12:29, 14 May 2012 (UTC)[reply]

what is cally disease

got it off of a mate and has same symtoms — Preceding unsigned comment added by Errrrrrcally (talk • contribs) 20:54, 13 May 2012 (UTC)[reply]

See a doctor. ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:04, 13 May 2012 (UTC)[reply]

Cally disease is a disease from the planet Auron, in the TV fiction Blake's 7. Has someone pulled your leg or are you pulling ours? Wickwack121.215.40.247 (talk) 00:37, 14 May 2012 (UTC)[reply]

Maybe that's what his unstated symptom is: A pulled leg. ←Baseball Bugs ^{What's up, Doc?} carrots→ 11:22, 14 May 2012 (UTC)[reply]

May 14

Why is KCN basic but not KNO3?

KCN is basic because $CN^{-}+H_{2}O\leftrightharpoons HCN+OH^{-}$ . Why doesn't this happen for KNO3? $NO_{3}^{-}+H_{2}O\leftrightharpoons HNO_{3}+OH^{-}$ ? --130.56.90.101 (talk) 01:06, 14 May 2012 (UTC)[reply]

Because HNO₃ is a strong acid, which means that the NO₃^- ion will not take an H⁺ from water. HCN is a weak acid, which by definitions means that CN^- will take H⁺ from water. The reasoning is the strength of the relative bonds. In this case, the H-O bond in HNO₃ is much weaker than the H-O bond in water, so there is no impetus for the H⁺ to leave water and join with the NO₃^- ion. With the cyanide ion, the H-C bond in HCN is considerably stronger than the H-O bond in water, so the transfer is exothermic, and the water readily gives up its hydrogen to the cyanide. --Jayron32 01:16, 14 May 2012 (UTC)[reply]

Are the injuries sustained by Tony Stark at all possible?

I'm re-watching Iron Man (2008 film), and shortly after the start Tony Stark is injured during a fire-fight and discovers when he wakes up that there are pieces of shrapnel stuck in his chest which are impossible to remove but which if unchecked will penetrate his heart killing him. It is mentioned by another character that this injury is not uncommon in 'his village', and hence he knows the solution is to rig an electromagnet onto Stark's chest to stop the shrapnel moving any further. Now the final part sounds to me like clear fantasy, and I doubt anyone could actually ever be saved from any known injury by sticking a large magnet on their chest. How about the rest though? Have people ever sustained chest injuries from shrapnel that haven't been killed immediately but have died later from the shrapnel finally reaching vital organs? And if not, is it a reasonably plausible injury to occur in the right circumstances? Or is the entire thing just a story to explain the premise, and has no basis in fact at all? Thanks in advance. 130.88.172.34 (talk) 02:01, 14 May 2012 (UTC)[reply]

Yes, people have been killed by delayed effects of shrapnel, but absolutely the last thing you would ever do with somebody with dangerous shrapnel inside them is to bring them into the vicinity of a strong magnet. Looie496 (talk) 02:12, 14 May 2012 (UTC)[reply]

I seem to recall a story of a US Civil War soldier, wounded near the heart. The doctors concluded that the shrapnel/bullet (I forget which) was best left in, as trying to remove it would likely be fatal. The soldier then lived out his life, and died, in old age. The autopsy showed that his aorta (or maybe vena cava), now weakened with old age, had been torn by the metal fragments. So, he was, in a sense, the last Civil War victim. StuRat (talk) 05:10, 14 May 2012 (UTC)[reply]

Interesting stuff, thanks both of you. 130.88.172.34 (talk) 09:40, 14 May 2012 (UTC)[reply]

You're welcome, may we mark this Q resolved ? StuRat (talk) 16:38, 15 May 2012 (UTC)[reply]

Weight loss question

According to Weight_loss#Intentional_weight_loss, "Weight loss occurs when an individual is in a state of negative thermodynamic flux: when the body is exerting more energy (i.e. in work and metabolism) than it is consuming (i.e. from food or other nutritional supplements), it will use stored reserves from fat or muscle, gradually leading to weight loss." The article does not make it clear exactly what stored reserve is used: fat or muscle? So in a state of negative thermodynamic flux, will a person loose fat or muscle? --NGC 2736 (talk) 04:07, 14 May 2012 (UTC)[reply]

Both. The object is to lose more fat than muscle, of course, and exercise helps with that. Also, that weight loss summary seems to neglect the possibility of retaining water. In that case, losing weight merely means losing water, which has nothing to do with "thermodynamic flux". StuRat (talk) 05:12, 14 May 2012 (UTC)[reply]

Thanks. I was searching the Wikipedia articles on this topic and just found Dieting#Fat_loss_versus_muscle_loss. It has an uncited claim "If the diet plan includes a daily caloric intake greater than the basal metabolic rate (BMR), the person will most likely lose fat. In contrast, if the person follows a diet that includes a lower caloric intake than the BMR, this person will lose fat but also a higher percentage of muscle." Although there is a citation tag there, just wondering whether it is true? --NGC 2736 (talk) 05:28, 14 May 2012 (UTC)[reply]

I think the logic there is that fat can only be converted to energy so fast, and if that doesn't provide enough energy, muscle will also be burnt. I don't see how the BMR rate is a magic dividing line, though. I would expect it to be more of a continuum, with muscle loss increasing as the rate of weight loss increases. Something else that can happen, of course, is that virtually all of the fat can be gone, say in starvation victims, in which case only muscle remains to burn.

Another factor is that, as you lose weight, less muscle is required to do normal activities. Less leg muscle mass is required to walk, less heart mass to pump less blood a shorter distance, etc. So, unless you increase your exercise rate to compensate, your body will naturally lose muscle mass, as we are designed to use the minimum amount of energy required, and excess muscles "waste energy". StuRat (talk) 05:34, 14 May 2012 (UTC)[reply]

Thanks for the explanation. It was helpful. --NGC 2736 (talk) 01:32, 15 May 2012 (UTC)[reply]

You're welcome. Can I mark this Q resolved ? StuRat (talk) 05:59, 15 May 2012 (UTC)[reply]

Thermodynamics of nuclear reactions

Do thermodynamic concepts like thermodynamic free energy apply to nuclear reactions analogously to the way they are applied to chemical reactions?--82.137.12.211 (talk) 11:14, 14 May 2012 (UTC)[reply]

If yes, how is the formalism adapted to nuclear reactions?--82.137.12.211 (talk) 11:21, 14 May 2012 (UTC)[reply]

Yes, provided there rate of nuclear reactions are fast enough to maintain thermal equilibrium. In the early universe, nuclear reactions were occuring at a fast enough rate to maintain thermal equilibrium between e.g. neutrons and protons. But as the universe expanded and cooled the reaction rate dropped, and the ratio between neutrons and protons became "frozen" at exp[(mp - mn)c^2/(k T)] where T is the temperature at that freezout time. The neutrons ended up in deuterium and helium. This ratio can be calculated quite accurately, and this leads to a prediction for the helium abundance in the universe consistent with observations. Count Iblis (talk) 16:27, 14 May 2012 (UTC)[reply]

Help identifying swallowtail

These used to grow on some citrus plants (lime/lemon/sweet lime/orange not sure what was planted) and on curry trees (Murraya koenigii) in Mangalore, coastal southern India. They look like Papilio_polytes but the wing pattern seems to be missing one white spot in the center. Once I have these Identified, I can rename the and describe the good ones (the pupa and prepupal larva) for further use in wikipedia.

It doesn't look like all of our photos here have that white spot, if I understand what you're talking about - see File:Pandiyana_aristolochiae_polytes_helenus.png. In any case, this butterfly is subject to polyphenism between different forms, which means that there will be hybrid zones in which there are intermediate forms. Depending on the precise genetics, all sorts of funny things might turn up there. So the specifics become very important... it might help to get full text for PMID 20192689 . Your photo looks a lot like the stichius form - see [6] - though others called this in India have differing patterns [7][8][9][10]. Here's an illustration of the diversity in Vietnam. [11] And identifying mimetic butterflies from wing patterns can be chancy anyway! This might be the sort of thing where you have to be hardcore and base the ID on genitalia [12] - or, preferably, molecular genetics, which should give more certainty, and perhaps even some unexpected surprises. Wnt (talk) 07:20, 15 May 2012 (UTC)[reply]

Help Identifying another swallow tail

Found this pupa on a Caryota fish tail palm leaf in mangalore.

Well, a swallow doesn't make a summer, nor a swallow tail a swallowtail. ;) Note that this butterfly has only four visible legs, with the others being, at least, much reduced. This, and also the general appearance of the wing veins, puts it in Nymphalidae, the brush-footed butterflies, not Papilionidae, the swallowtails. The same wing vein lengthened in the swallowtails can also be lengthened in daggerwings like this and this. Haven't figured out this one yet though... Wnt (talk) 17:04, 14 May 2012 (UTC) OK, I'm looking at Elymnias hypermnestra. It came up when I searched for "Caryota hostplants Nymphalidae". here's another image. I'm not sure this is the precise species, mind you, but I definitely smell a wumpus. Wnt (talk) 17:24, 14 May 2012 (UTC)[reply]

You might be better off asking at http://www.whatsthatbug.com/ SmartSE (talk) 17:25, 14 May 2012 (UTC)[reply]

Is it possible (however unlikely) for quantum fluctuations to violate conservation of energy?

Could a stable electron-positron pair just pop into existence out of nothing without annihilating afterwards? Goodbye Galaxy (talk) 14:51, 14 May 2012 (UTC)[reply]

Even if the entire Universe is the result of a random quantum fluctuation, the answer could still be no. As there seems to be just enough negative potential energy to cancel out all the rest. Hcobb (talk) 15:02, 14 May 2012 (UTC)[reply]

No. Energy (defined by the Hamiltonian) is always conserved in any quantum theory. -- BenRG (talk) 19:12, 14 May 2012 (UTC)[reply]

women

Why do women have titties all their lives when they only need them when they have a baby, and might not even have a baby for many years? Why couldn't they grow during pregnancy? — Preceding unsigned comment added by 95.26.220.146 (talk) 18:36, 14 May 2012 (UTC)[reply]

Well, they do grow during and after pregnancy, and they only "operate" during the period of nursing, that is the milk glands only produce milk during that time period. During the rest of a woman's adult life, the serve a more recreational purpose. --Jayron32 19:58, 14 May 2012 (UTC)[reply]

See also Secondary_sex_characteristic#In_humans. Basically, the processes involved start in utero, and there has been no strong selective pressure to change this state of affairs. Also, using the word "titties" in a science question makes you sound like a troll. SemanticMantis (talk) 20:03, 14 May 2012 (UTC)[reply]

Since I have found swimming with breasts quite a different experience to swimming without them (your bouyancy is very different, you can swim along on your front without using your arms while still keeping your face out of the water, etc), and given the Aquatic Ape Hypothesis, I have occasionally pondered whether this was a factor. But, even if true, I don't see how it could be shown conclusively in my lifetime. Short of a trip in the Tardis.... 86.161.213.137 (talk) 22:03, 14 May 2012 (UTC)[reply]

Men also have "titties", some more pronounced than others, and they have no practical application at any time. Bielle (talk) 20:02, 14 May 2012 (UTC)[reply]

Well, the nipples serve no purpose in men, but the fat, just like fat everywhere else, serves as a reserve energy source. StuRat (talk) 20:20, 14 May 2012 (UTC)[reply]

I'd beg to differ with you that nipples serve no purpose in men. They serve no milk in men, but are quite useful in other, more recreational, aspects of the human condition. --Jayron32 20:24, 14 May 2012 (UTC)[reply]

On an odder note, male lactation... ;) Wnt (talk) 20:32, 14 May 2012 (UTC)[reply]

Sexual selection is the primary reason for their permanance in human females. That human females have hidden ovulation and constant sexual display leads to conditions that ensure pregnancy in individuals that may have otherwise wished to avoid this biological process that might kill them when giving birth due to complications caused by the human infant's large cranium. Also human infants are dependant on parental care for a long time and prior to permanent human settlements it would have been routine for offspring to feed off mothers milk for several years until they became more independant and able to help with the foraging. SkyMachine ⁽⁺⁺⁾ 22:02, 14 May 2012 (UTC)[reply]

This guy from the Game of Thrones tv show has the most impressive man boobs I've seen for a while. Vespine (talk) 22:29, 14 May 2012 (UTC)[reply]

The evolutionary perspective is necessary here. Women's breasts are large because Homo sapiens is sexually dimorphic and sexual attractants play vital role in sexual selection. Breasts function as sexual attractants without which it will be difficult for women to find mates which is prerequisite for reproduction and continuation of the species. Read the followings:

If you are seriously interested in the evolutionary purpose of women's breasts, I'll suggest go through the book The Naked Woman by Desmond Morris. --NGC 2736 (talk) 00:52, 15 May 2012 (UTC)[reply]

Humans walk upright, which means falling over is possible and has the potential to damage the front of the chest in ways quite unlikely in mammals that walk on all fours - in fact it is very difficult to get a 4-legged animal to trip or fall over in any case. Also, in less advanced societies, fights amongst females may have occurred from time to time. Most of the volume of women's breasts is fat and not milk-producing tissue, even when lactating. This fat protects the milk producing tissue. There was evolutionary pressure to increase the amount of protecting fat - Before the invention of formula milk, damage, even minor bruising, to the milk producing tissue could mean the death of your baby - one you have now, and possibly one you have later. And of course breasts make girls attractive to boys. Wickwack120.145.187.143 (talk) 01:19, 15 May 2012 (UTC)[reply]

Desmond Morris has some interesting ideas, but they are basically Just-so stories. I encourage anyone reading his works to put on their skeptical and critical hats! SemanticMantis (talk) 16:00, 15 May 2012 (UTC)[reply]

Attractive to boys ... girls, men and women, oh yes, and babies. Bielle (talk) 03:38, 15 May 2012 (UTC)[reply]

Another thing to remember is that birth control is not actually part of the standard design - evolution tends to keep women pregnant and children fighting for survival. I imagine that in some of our less enjoyable societies those breasts are still in near-constant use.

I should add that not only did Darwin pursue his well-known discussion of the reasons for male nipples in "The Descent of Man" - apparently even his grandfather had ideas about it. [13] Darwin wrote there that "Now if we suppose that during a former prolonged period male mammals aided the females in nursing their offspring, and that afterwards from some cause, as from a smaller number of young being produced, the males ceased giving this aid, disuse of the organs during maturity would lead to their becoming inactive; and from two well-known principles of inheritance this state of inactivity would probably be transmitted to the males at the corresponding age of maturity. But at all earlier ages these organs would be left unaffected, so that they would be equally well developed in the young of both sexes."^[14] It is curious to consider all of the ideas - sexual selection, "spandrels", modern-day male lactation - that he does not run through in this. Wnt (talk) 13:48, 15 May 2012 (UTC)[reply]

"birth control is not actually part of the standard design - evolution tends to keep women pregnant" - Hmm. So what are you saying, feminism is in conflict with evolution? --NGC 2736 (talk) 14:02, 15 May 2012 (UTC)[reply]

Peace of any kind is in conflict with evolution, except as a short-term tactic, and indeed evolution is one of rape's most ardent supporters. Most of the development of human culture can be cast as a struggle between the loyalty of the human body and instinct to the genome and its propagation, versus the loyalty of the human mind and spirit to itself in all its incarnations as a new and fundamental force of nature. Wnt (talk) 15:34, 15 May 2012 (UTC)[reply]

Surely you've heard of evolution of altruism? It is also very shortsighted to say "evolution is one of rape's most ardent supporters." Evolution can act on social structures just fine (e.g. pair bonding), and offspring of rape may well be less likely to successfully procreate. SemanticMantis (talk) 16:00, 15 May 2012 (UTC)[reply]

Nevertheless, what possible explanation in evolutionary terms can there be for the occurrence of rape other than it must have reproductive advantages in some cases? - Lindert (talk) 16:38, 15 May 2012 (UTC)[reply]

? What possible explanation in evolutionary terms can there be for the occurence of men getting drunk and punching other people in the face, other than that it must have reproductive advantages in some cases? What about pedophilia? What about getting turned on by being hurt, or by hurting others? What about body dysmorphia? What about daring each other to do pointless dangerous things until you're seriously injured? What about abusing your children, even to the point of death? When you're talking about something carried out by less than 5% of the population, you can find all sorts of behaviours and tendencies that don't improve reproductive success. 86.161.213.137 (talk) 16:54, 15 May 2012 (UTC)[reply]

For many of the things you mention there are possible advantages, e.g. punching each other, daring to dangerous activities, hurting others etc. can kill weak individuals or eliminate competition. A pedophile may occasionally impregnate a girl other men are not interested in, thus outsmarting the competition. Otherwise, if these things are always detrimental and they continue to exist, that is a problem for evolution, because natural selection should cause detrimental traits to die out. Btw in some animal species rape is very common, or even the norm. Note that I am in no ways encouraging the aforementioned actions, morals should not be based on reproductive advantages. - Lindert (talk) 18:35, 15 May 2012 (UTC)[reply]

LOL, okay, I think you need to step out of the Just-so story realm. Seriously, look at your pedophilia thing. Do you really think that is going to give an advantage over just having sex with a grown partner, the small chance that the child will actually conceive, survive the pregnancy and childbirth, and the baby will be raised to successfully breed itself? There is a tendency among people who have learnt just enough evolutionary theory, but not quite enough, to attribute everything as 'just how evolution made it', exactly fit for purpose. But it is obvious that some aspects of humanity exist as aberrations, such as someone who seeks a doctor to sever their spinal cord because they feel they are 'supposed' to be wheelchair bound, or severe alcoholism, or someone who cannot control their anger and alienates other people, or a pedophile, or a rapist. It is true that more moderate versions of some of the traits that produce this aberrant behaviour can be advantageous: it is easy to see how someone being more aggressive about meeting their own needs, over the needs of others, and perhaps a desire to have more sex than normal, could be a successful strategy in some circumstances, especially if they have the ability to temper it as needed. And it is also easy to see how an extreme version of that trait might contribute to somebody deciding to rape little old ladies. But that is far and away from saying that rape itself is favoured by evolution. 86.161.213.137 (talk) 19:48, 15 May 2012 (UTC)[reply]

You misunderstand what I'm saying. I'm not saying that pedophilia or rape in general is advantageous. But in the case of someone who has no other options, i.e. no woman will take him, he's unable to compete in the struggle to reproduce, then as a desperate measure it is always better for the purpose of reproduction to resort to rape and/or pedophilia than to remain without a sexual partner. - Lindert (talk) 20:11, 15 May 2012 (UTC)[reply]

Not true. Lactation itself suppresses the menstrual cycle, making conception less likely. This means a breastfeeding mother is less likely to fall pregnant again. This is a form of natural birth control, with the evolutionary drive being that falling pregnant again so quickly is dangerous for the mother and child. This is natural birth control, which evolution favours. Births about a year apart tend to arise in cultures that do not view breastmilk as the best food for babies.

On top of that, when bodyfat falls below a certain percentage, the menstrual cycle stops. This is rare in modern developed countries except for in anorexics, athletes and models, but historically common. This is also a form of natural birth control, preventing conception when the mother is malnourished.

Your view of human nature red in tooth and claw sadly neglects that humans are intensely social creatures, who tend to naturally form societies. Forming societies, and raising their young within them, is one of the ways humans have historically survived and prospered.

Also, if rape were actually about anything like passing on genes, we would find that women of childbearing age were disproportionately targetted. In fact, we find the opposite: vulnerable women are disproportionately targetting, especially children and the elderly. The younger the rapist, the more likely they are to rape an old woman. It has nothing to do with passing on genes, and cannot be so excused. The actual strategy which has some success, is the serial cuckold, who has sex with willing women and then doesn't stay to raise the children. This allows for a greater initial quantity, but doesn't spend energy of ensuring the children survive and breed. This contrasts with the strategy of staying and investing time and energy is raising the children, which gives each child a better chance of survival and breeding, but risks raising someone else's child. Both strategies are clearly evolutionarily significant, as can be seen by studies that look at what male character women find most attractive at various times in their menstrual cycle. Note that neither strategy involves rape. Human societies tend to punish rape, even if they don't all agree on what counts. We evolved alongside our culture. 86.161.213.137 (talk) 16:10, 15 May 2012 (UTC)[reply]

Well, if you consider a situation like German camp brothels in World War II or Rape in the Bosnian War, rapists have no objection at all to women of the right age and characteristics for effective breeding. Wnt (talk) 19:33, 15 May 2012 (UTC)[reply]

Did I say they did? No, I said that the general pattern of rape does not suggest that it aims to increase offspring, since the general pattern of rape targets the vulnerable rather than the fertile. 86.161.213.137 (talk) 19:48, 15 May 2012 (UTC)[reply]

And that is simply a flawed argument. Just because the individuals targeted are no ideal opportunities for reproduction does not in the least imply that that is not the aim. Compare a lioness targeting mostly old, sick and young zebras. Does that mean the lioness does not aim for the best possible meal? A healthy adult zebra would provide much more food for the lioness and her family. It's just a matter of taking the easiest route instead of accepting a high risk of failure. The same goes for the rapist. - Lindert (talk) 11:48, 16 May 2012 (UTC)[reply]

Many primative cultures had birth control, some were very efficient. For example, initiation ceremonies of male Australian aborigines often involved cutting the penis so that almost all semen was discharged and not injected into the woman. When children were specifically desired, the fingers were used to close the hole and thereby cause all semen to be injected into the woman. They had been doing that for at least 40,000 years, long enough for other evolutionary pressures on breast size to act. But breast size in Australian aborigines is no different to that of Europeans. In some cultures, it is believed that women had their own secret methods. Also, evolution does not act to keep females pregnant. When times are tough and food scarce, too many children consume too many resources, and can actually reduce group survival. Wickwack124.182.184.54 (talk) 15:02, 15 May 2012 (UTC)[reply]

Sounds amazing. Is there a good source for that initiation story? HiLo48 (talk) 11:57, 16 May 2012 (UTC)[reply]

Oh my God, there are still weird things in the world of which I have no inkling. Penile subincision. While I had a vague appreciation that human genetic diversity shouldn't be shoehorned into a hierarchy by the judgmental, I had no concept that some cultures would actually view something akin to hypospadias as the normal/desirable condition. But interesting as that is, 40,000 years is not much time by evolutionary standards. Wnt (talk) 15:40, 15 May 2012 (UTC)[reply]

Will Mira B explode?

How close is Mira B to the Chandrasekhar limit? Hcobb (talk) 18:44, 14 May 2012 (UTC)[reply]

As the article you linked to says, Mira B appears to be a main sequence star, not a white dwarf, so the Chandrasekhar limit isn't relevant. --Tango (talk) 23:57, 14 May 2012 (UTC)[reply]

Wasn't every white dwarf formerly on the main sequence? —Tamfang (talk) 06:12, 15 May 2012 (UTC)[reply]

The article says recent measurements indicate it is a white dwarf of 0.7 solar mass, half the limit. —Tamfang (talk) 06:12, 15 May 2012 (UTC)[reply]

glass in soil

I purchased some soil from Home Depot to put on my garden. After I spread it on my garden I noticed when the light hits it it looks like it has little tiny pieces of broken glass in it. I'm assuming they added this for decorative reasons. Is this possible? I'm surprised the government would let them do that--Wrk678 (talk) 22:27, 14 May 2012 (UTC)[reply]

Probably not for decorative reasons, nor is it broken glass. A better bet would be the presence of small rock bits in your soil, which possibly may have been polished to that state by the amount of agitation its processing involves. It could also be a supplement material for certain required elements, like magnesium. Just musing.--Jasper Deng (talk) 22:31, 14 May 2012 (UTC)[reply]

I don't think so because it is clear--Wrk678 (talk) 23:03, 14 May 2012 (UTC)[reply]

Unless it's in shards, it's most likely just quartz sand. I doubt if it was added intentionally. StuRat (talk) 23:20, 14 May 2012 (UTC)[reply]

I've seen some batches of soil from those stores with bits that look a lot like mica. DMacks (talk) 00:44, 15 May 2012 (UTC)[reply]

Is it possible you're looking at vermiculite? (Which according to the article might actually be more disturbing....) Wnt (talk) 01:14, 15 May 2012 (UTC)[reply]

expanded vermiculite is used in soil. It's also the substrate of choice for growing magic mushrooms :-) Ssscienccce (talk) 11:45, 15 May 2012 (UTC)[reply]

whatever it is, I think it was added intentionally because I also found it in some cow manure fertilizer I purchased--Wrk678 (talk) 01:56, 15 May 2012 (UTC)[reply]

I believe that they add sand to improve drainage. StuRat's answer sounds likely to me (we're agreeing again!). Alansplodge (talk) 09:50, 15 May 2012 (UTC)[reply]

Mica and perlite are also common ingredients in soil mixes and soil additives. Mica especially can occur in clear, glassy flakes. SemanticMantis (talk) 11:11, 15 May 2012 (UTC)[reply]

It could well be glass. When glass recyclers round here get small fragments of glass they just crush them very small and mix it into potting mix. This is because it is too hard to separate the different colours when the glass is broken into small bits. Graeme Bartlett (talk) 13:03, 15 May 2012 (UTC)[reply]

why would they add Mica to cow manure fertilizer?--Wrk678 (talk) 23:00, 16 May 2012 (UTC)[reply]

May 15

Surfactants

Which have the best cleaning property : anionic surfactant, cationic surfactant or nonionic surfactant? — Preceding unsigned comment added by 113.162.202.31 (talk) 02:59, 15 May 2012 (UTC)[reply]

I guess that would depend on what you are trying to emulsify. I assume you know the difference between the three types? (I do.) Plasmic Physics (talk) 06:22, 15 May 2012 (UTC)[reply]

There's no right answer, it depends on what you try to clean, and there's loads of products of each type, varying in strength but also in price, toxicity, temperature ratings,... Your choice would likely depend more on availability and price, given that the "strongest" cleaner may not be on the market. The use of phosphates in laundry and dish detergent has been banned in EU and some other countries, replaced by more expensive, less effective alternatives. Not only were they biodegradable, they even caused eutrophication (from Greek "healthy, adequate nutrition, development"). But it seems that water plants, algae and jellyfish are considered inferior forms of life. Ssscienccce (talk) 21:05, 17 May 2012 (UTC)[reply]

Proper Dimensions for Mortality Rates

Compare these two statements:

"XXXXX syndrome has a mortality rate of 8%."

and

"XXXXX syndrome has a mortality rate of 8% per annum."

Is it usual to express mortality rate per unit of time, e.g., "8% of people with this syndrome are likely to die within a year"

Or WITHOUT a dimension of time, e.g., "8% of people who develop this syndrome are likely to die from it eventually."

Thanks, Wanderer57 (talk) 04:19, 15 May 2012 (UTC)[reply]

Mortality rates for non-permanent conditions are often offered without a dimension of time. But if you actually dig into the literature used to cite the statement, you will always find time measurements or additional caveats buried in the methods of measurement, even they're not presented as part of the short conclusion. Someguy1221 (talk) 04:26, 15 May 2012 (UTC)[reply]

Agreed. For something like influenza, it's likely to either kill you, or not, in short order, while with a disease like diabetes, you might live with it for years before it finally kills you (or something else does). So, flu mortality doesn't need to be broken up by year, while diabetes does (although the total mortality rate from diabetes is also useful). StuRat (talk) 05:57, 15 May 2012 (UTC)[reply]

how much farther does a giraffe see

Hi,

how much farther does giraffe see? I mean due to vantage. --80.99.254.208 (talk) 10:59, 15 May 2012 (UTC)[reply]

The article Horizon contains various methods to calculate the distance, but first you need to measure your giraffe! Roger (talk) 11:16, 15 May 2012 (UTC)[reply]

Right, I just popped out and held down a giraffe long enough to measure it. Turns out they're between 5 & 6 metres tall. Assuming an average of 5.5m, using the calculation from the Horizon article we get a 'distance to the horizon' for the average giraffe of 8.37 km. That's 3.67 km further than the average human (4.37km at an average height of 1.7 m), a little less than twice as far. - Cucumber Mike (talk) 11:42, 15 May 2012 (UTC)[reply]

Wow, that's dramatic. Like, "If I have seen farther than those who came before me, then it is because I am a giraffe." — Preceding unsigned comment added by 188.6.70.25 (talk) 12:34, 15 May 2012 (UTC)[reply]

...or stood on the shoulders of the giraffes before you. :-) StuRat (talk) 16:22, 15 May 2012 (UTC) [reply]

Maybe it's giraffes all the way down. Gandalf61 (talk) 16:25, 15 May 2012 (UTC)[reply]

Note that this assumes a perfectly flat (actually spherical) surface with no trees or other objects in the way. And, since giraffes are that tall to reach leaves on even higher trees, we can assume that there frequently are trees blocking the view. StuRat (talk) 16:24, 15 May 2012 (UTC)[reply]

You also have to make an appointment for your giraffe to see an optometrist, because he might not actually be capable of seeing clearly all the way to the horizon anyway. Roger (talk) 16:30, 15 May 2012 (UTC)[reply]

Apparently giraffes do have excellent vision. As for the question, why do giraffes have long necks, the answer is that they have smelly feet. (*rolling tumbleweed* .... but my inner child is rolling in the aisles) FlowerpotmaN·(t) 16:56, 15 May 2012 (UTC)[reply]

You mean hooves. — Preceding unsigned comment added by 165.212.189.187 (talk) 14:02, 16 May 2012 (UTC)[reply]

Magnetic moment of a neutron

How does the quark structure of a neutron acount for its magnetic moment?--188.26.22.131 (talk) 11:35, 15 May 2012 (UTC)[reply]

There is a Neutron magnetic moment article, but unfortunately it's not much more than a stub. Red Act (talk) 19:21, 15 May 2012 (UTC)[reply]

The individual quarks within a neutron generate their own magnetic fields. And so the neutron will have its own magnetic field that is the superposition of the fields of its constituent quarks, resulting in a measurable magnetic moment even though it has no net charge. This is similar to how an electric dipole can have an electric field even though it need not have any net charge. And that's as much as I can tell you, for I don't know how to calculate magnetic fields/moments in quantum physics, much less how to superimpose the fields within a baryon. Someguy1221 (talk) 01:28, 16 May 2012 (UTC)[reply]

Lemonade (Citrus limon × reticulata)

How do I germinate lemonade seeds, what do I need to do to produce healthy seedlings? I have decided to use a paste made from crushed wheat biscuts mixed with water as a growth medium. The seeds have already been dried, naturally of course. Plasmic Physics (talk) 11:44, 15 May 2012 (UTC)[reply]

I found citrus seedlings are quite hardy when they are planted/germinated in sandy well drained loam (buried around 2cm deep). Once they grow a bit, they can be transplanted into their final destination. Will need the advice of someone better at horticulture for this though. (BTW, why are you trying to use that particular growth medium? I would expect that It to just help bacteria and fungi grow causing it to sour and form a film on the roots. Also I am not sure how much extra benefit the seeds would gain from the medium as the seeds are quite big. Again, just OR and speculation) Staticd (talk) 12:38, 15 May 2012 (UTC)[reply]

Staticd's instructions on medium and depth are good. I see that you are in the UK. It is probably not warm/ bright enough there right now to get fast results outdoors (e.g. not enough degree days), but it should work, given that you don't let it get moldy or drop below 40 F. If you are less patient, you could sprout it indoors, and provide supplemental lighting. It is important to not let it dry out, but also not to keep it sodden. "Evenly moist" is what you're going for. Lastly, your choice of medium does indeed seem bizarre, and likely to end in a moldy mess. Did someone suggest it to you, or did you read about it somewhere? Even if you don't want to buy peat pots, or potting soil, sandy loam is a far superior sprouting medium than crushed biscuits. Good luck! SemanticMantis (talk) 13:22, 15 May 2012 (UTC)[reply]

I'm actually posting from New Zealand, I live in a multistory appartment building; I'm growing it indoors for now. Thanks, I'll try and find some sandy loam. Plasmic Physics (talk) 15:00, 15 May 2012 (UTC)[reply]

Growth media are better suited for bacteria, fungi or cell cultures. Germination is what you wantSsscienccce (talk) 13:37, 15 May 2012 (UTC)[reply]

Is my idea then completely unsuitable, or will it just impede their development? Plasmic Physics (talk) 15:00, 15 May 2012 (UTC)[reply]

I feel that it will impede their growth quite dreadfully (going by my experience with pots having insufficient drainage and attempts at fermenting foods to get microscopy samples) so please don't try this unless you have a good source or you want to experiment. (Please do tell us the results if you do try it, I'm quite curious). Citrus plants need a lot of sun, but florescent light should do just fine. (They use them in the growth chambers at my research lab. Staticd (talk) 15:21, 15 May 2012 (UTC)[reply]

It contains a lot of nutrients your plant cannot use, but molds can. Plants mainly get water and inorganic nutrients from the soil. I doubt they can absorb carbohydrates, they get their carbon from CO2. A seed normally contains enough energy to grow the seed leaves, and then photosynthesis takes over. I'm not saying it's impossible to grow in such a medium but they have to compete against molds for which this is the perfect substrate, and there's lots of spores floating around. That's why substrate for growing mushrooms is sterilised in a pressure cooker first. Ssscienccce (talk) 17:17, 15 May 2012 (UTC)[reply]

It's amazing what mould can do. I remember saving bread end-crusts, before throwing them on the lawn when I get the chance. I forgot about a particular collection, and when I finally remembered, I found that mould had completely turned it into green dust. I made the mistake of opening the bag it used to be in, it sent a stiffling, noxious green cloud into the air. I also noticed that bread kept in a bag and chilled, and then returned to room temperature, will mould faster than a bagged bread kept at constant room temperature. I think it has to do with the reduced vapour pressure, which caused liquid water to condense on the bread. Plasmic Physics (talk) 03:01, 16 May 2012 (UTC)[reply]

Please send us photos when those lemonade seeds grow. I'd like to see what type of carton they sprout: Wax paper? Plastic? ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:45, 16 May 2012 (UTC)[reply]

I'm using a disposable plastic catering tray. Plasmic Physics (talk) 03:01, 16 May 2012 (UTC)[reply]

And another one bites the dust, eh Bugs? I liked it though. Richard Avery (talk) 07:25, 16 May 2012 (UTC)[reply]

Personal experience alert: about ten years ago, I managed to germinate three lemon seeds from a supermarket lemon by using a two-litre lemonade bottle. Cut it in half, fill about two-thirds of the bottom half with soil and/or compost (we have a fairly heavy clay soil where I live in the UK, but it didn't do any harm; I suspect sandy loam would be better), then plant your seeds in and wedge the top back on. Put it in a warm, sunny place for the seeds to germinate. If they need extra water, dribble some in through the top of the bottle. Eventually I planted mine in pots and kept them in a warm lean-to on the side of our house; they lived until they got too big to move around between summer and winter. Have fun, Brammers (talk/c) 10:08, 16 May 2012 (UTC)[reply]

Thanks.

Another question: are lemonades grown outside of australasia? Plasmic Physics (talk) 12:01, 16 May 2012 (UTC)[reply]

To be clear, "Citrus limon x reticulata" is one possible composition of the Meyer lemon. Is this the fruit being discussed here? And have some people in NZ started calling them "lemonades"? (Note as explained in the article, "Meyer" was the guy who introduced the original Chinese hybrid into the U.S., so I doubt our term applies there, at least) But this has a poster saying that lemonades are much sweeter than Meyer lemons. And this says limon x reticulata is more like a lime! NCBI delivers nothing of note about Meyer lemons, but Google Scholar yields a source talking about a Citrus meyerii[15] But ARS-GRIN calls lemonade a "hybrid of unknown parentage" [16] The joking above reflects that in the U.S. "lemonade" is strictly a drink and is never used to name a type of fruit. Clearly it would be much appreciated if some taxonomists would do a little molecular biology here! Wnt (talk) 15:28, 16 May 2012 (UTC)[reply]

Here's the definition of the "-ade" suffix.[17] Lemonade or orangeade or anything-ade is a product of the fruit, typically a juice product. Calling the fruit itself something-ade seems rather weird. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:04, 17 May 2012 (UTC)[reply]

No, I'm not talking about the 'Meyer lemon'. The 'Lemonade' is a ligitimate name used by plant nurseries. From what I know, it was created a few decades ago in Australia. I've never had lemonade drink, I've had lemonade flavoured drinks before though, Lemonades taste like lemonade. Unlike ordiniary lemons, the Lemonade can be eaten as is by most people. (not that I don't enjoy a good lemon). Plasmic Physics (talk) 01:53, 17 May 2012 (UTC)[reply]

Help identifying moths

Found this hawk moth/hornworm on some sort of colocasia.

Found this pupa on a ficus(?) like shrub that grows wild around coastal India. A leaf is visible in the second pic. The moth never had any wings and I can tell that It was a female as it laid a whole lot of eggs a few days later.

Found this pupa on the same species as the previous moth.

Thanks. Hope to make at least some of each set useful for articles once they have been Identified. Staticd (talk) 12:28, 15 May 2012 (UTC)[reply]

These appear to be the Theretra clotho [18], the wingless female Orgyia antiqua perhaps?, and the Glyphodes bivitralis.[19] (Disclaimer: I am not a lepidopterist! But I do like these bugs. :-))--Modocc (talk) 06:41, 16 May 2012 (UTC)[reply]

relationship between telomere length and cancer risk

Hello,

I am writing a biology paper on inhibiting telomerase to fight cancer, and I'd appreciate some help in interpreting the literature that's out there thus far. I'm not a biology student, but I did this research for a general education biology course at my college.

My literature review is focusing on this study published by Terry earlier this year, which stated that there is no clear relationship between telomere length and cancer risk. However, that seems to contradict the findings of Martinez-Delgado and others, who did find that shorter telomeres could present a risk factor for cancer. Indeed, my lit review has found that scientists have hoped to develop cancer therapies that focus on telomerase inhibition as a way to target malignant cells, and such methods rely on a strong association between telomere length and cancer risk. I know that it's not unusual for scientists to arrive at different conclusions, but what bothers me is that I can't find any articles online that attempt to reconcile these divergent findings. For example, I couldn't find any reactions to the Terry study, which seems to have overturned much of the previous literature. Am I looking at the wrong websites or databases, or am I approaching this paper in the wrong way? 128.135.100.102 (talk) 15:57, 15 May 2012 (UTC)[reply]

Not an answer, but have those considering such a treatment considered the side effects ? The telomere length is important for all cells, not just cancer cells, after all. While cancer cells reproduce more often, and thus will suffer from short telomeres sooner, all the cells in the body eventually will (except perhaps nerve cells which don't reproduce). StuRat (talk) 16:29, 15 May 2012 (UTC) [reply]

(aside to Stu:) Nerve cells do regenerate, in a few different ways. See Nerve_regeneration, Neuron#Nerve_regeneration, and Neurogenesis. The idea that they don't is just another incorrect "fact" they taught us in highschool ;) SemanticMantis (talk) 18:43, 15 May 2012 (UTC)[reply]

The lede in your first link says "...the central nervous system is, for the most part, incapable of self-repair and regeneration". StuRat (talk) 18:50, 15 May 2012 (UTC) [reply]

Sure it does. It then goes on to discuss a few different forms of regeneration that do occur. My last link says "Adult neurogenesis is an example of a long-held scientific theory being overturned." That's all I really wanted to point out. SemanticMantis (talk) 19:18, 15 May 2012 (UTC) [reply]

I was initially looking at the wrong study.. Anyway, the main or only difference I can see is that Martinez talks about age adjusted telomere length. The effect she found decreased with age, the highest OR was in women under 30. The ovarian cancer article gives a median age at diagnosis of 63, with 4.7% in women under 34. Maybe that explains part of the discrepancy, that the effect Martinez found would be smaller in Terry's study who grouped the subjects by telomere length instead of age? I believe some data could even support both conclusions, see Simpson's paradox. I also noticed that mutations in BRCA1 and BRCA2 genes were linked with an increased risk, and in the BRCA1 article there's a list of specific mutations depending on nationality; Is it possible that the relationship between telomere length and cancer risk would be related in some mutations, but not in others? Ssscienccce (talk) 19:30, 15 May 2012 (UTC)[reply]

The papers are just simply too new to have received any responses yet, I think. Note that the Martinez-Delgado paper cites the Terry paper. Looie496 (talk) 18:22, 15 May 2012 (UTC)[reply]

Even taking both papers at face value, they are not contradictory, as they deal with different cell types. A critical tumor suppressor in one tissue may be completely dispensable in another. Someguy1221 (talk) 19:07, 15 May 2012 (UTC) Sorry, I think I read the abstracts too fast. Someguy1221 (talk) 20:08, 15 May 2012 (UTC)[reply]

It looks like both consider correlations between peripheral blood leucocytes and ovarian cancer. As is too often the case, it looks like the smaller study had the significant (p<0.001) result, and the larger found no correlation. But I wouldn't want to simply discount the role of telomeres, because the larger study found that variation in TERT. We'd have to get the full papers, pick over every detail of who was chosen for each study, consider the second author's discussion very carefully ... and even then, this is the sort of thing that might have to be resolved over the phone, if at all. Some questions in my mind would be if they were able to control in any way for the effect of cigarette smoking, obesity and so forth [20] and if there were any technical differences in how the studies did it. The problem is, I doubt it's the shortening of the telomeres per se that will cause cancer; it's probably what happens when a short telomere is found, or when there's no telomere at all. So my gut feeling is that the length of the telomere is the distraction and those polymorphisms in TERT are closer to what you should be interested in. It seems conceivable to me that you could make a drug that would affect TERT and have no effect on telomere length at all, yet affect the risk of cancer e.g. by affecting cellular senescence mechanisms. Wnt (talk) 19:16, 15 May 2012 (UTC)
Here's a numeric example that would give opposite conclusions: 10 young women with short trlomere's: 8 of them have cancer (80%). with long telomeres 30 out of 40 have cancer (75%). The numbers for old women are: short telomers: 60/100 (60%) long: 15/30 (50%) For both groups long telomers give a lower percentage. If you take the totals: short telomers: 68/110 (61%) long telomers: 45/70 (68%). So Martinez would find that short telomers increase the risk for young (80% to 75%) and for old women (60% to 50%) , while Terry would conclude that short telomers decrease the risk (61% to 68%). Ssscienccce (talk) 20:21, 15 May 2012 (UTC)[reply]

Grasshopper in Zion National Park

I was looking for a page similar to de:Wikipedia:Redaktion Biologie/Bestimmung, but it seems that there is none. Anyway, I hope is the right place for my question.
I took a photo of a comely grasshopper and uploaded it to Commons. However, since neither me nor editors from de.wikipedia were able to identify the species, it is not very useful. I hope a biologist from the Southwestern United States may help.
Place: Zion National Park; time: August. --Leyo 21:23, 15 May 2012 (UTC)[reply]

I'm not a biologist, but it looks a lot like Melanoplus femurrubrum to me. Cf. this image, for instance. Deor (talk) 23:03, 15 May 2012 (UTC)[reply]

I'm no entomologist, or more specifically, I'm no orthopterologist, but that looks like a very good match to me. ;) Vespine (talk) 23:47, 15 May 2012 (UTC)[reply]

:-)

Deor, you seem to have hit the bull's eye. Thank you. --Leyo 07:32, 16 May 2012 (UTC)[reply]

May 16

Non-ethanol effects of alcoholic beverages

Can anyone find any information about why different alcoholic drinks have different effects independent of the volume of ethanol consumed? The effects of champagne, red wine, whisky, rum, gin and beer are all subtly different, yet I've never read anything to explain why. The volume of water has some effect with beer, but the hops have others; presumably the herbs used in gin make a difference too, as do the flavonoids in red wine. Are there are secondary metabolites that brewers yeast produces during fermentation that are bioactive in humans? SmartSE (talk) 01:00, 16 May 2012 (UTC)[reply]

Whilst we're at it, can anyone improve on the first sentence of Ethanol#Pharmacology? SmartSE (talk) 01:06, 16 May 2012 (UTC)[reply]

I'm guessing this is mostly observer bias. Someguy1221 (talk) 01:11, 16 May 2012 (UTC)[reply]

Someguy is probably close to the answer. There have been numerous studies which show that a large portion of drunkeness is psychological, and not directly related to the ethanol itself. I have seen countless studies and demonstrations which show the placebo effect on drunkenness; people who are given non-alcoholic beverages and told they are alcoholic show signs of intoxication. It is quite likely that different types of drinks make you feel certain ways, not for their chemical composition, but for the social implications of what they represent (champagne or fine wine feels sophisticated, big fruity drinks seem fun, etc. etc.) so your internal feelings likely represent something of that beyond the mere chemical effects of the drink. That's my guess, anyways. --Jayron32 01:47, 16 May 2012 (UTC)[reply]

There's a few other possible factors at play as well: Many people can have an adverse reaction to sulphites found in certain drinks, especially wine. Anecdotal evidence suggests that drinks high in sugar can result in a worse hangover, but I have yet to find a reliable source for this. Also, if you have had a bad experience with a certain liquor (as in, you end the evening worshiping the porcelain gods), it is more likely to make you feel ill in the future: see Taste aversion. -RunningOnBrains^(talk) 01:54, 16 May 2012 (UTC)[reply]

fusel oils are supposed to worsen hangovers. Staticd (talk) 07:15, 16 May 2012 (UTC)[reply]

I would personally expect drinks high in sugar to result in a worse hangover for the simple reason that eating and drinking a lot of sugar can give you many of the same symptoms as a hangover, in my experience. Presumably for similar reasons (dehydration). 86.161.213.137 (talk) 09:14, 17 May 2012 (UTC)[reply]

Ripping someone a new one

In among all the -ostomies and -plasties and whatnot, there's got to be a medical term describing the forcible creation of a new asshole. What would it be? --Carnildo (talk) 01:56, 16 May 2012 (UTC)[reply]

Giving someone a new asshole is actually a necessary medical procedure following certain types of rectal cancer. I see various articles calling this "rectal reconstruction", but I haven't seen anyone apply a fancy name to it. Someguy1221 (talk) 02:02, 16 May 2012 (UTC)[reply]

Ok, that actually made me laugh... I guess if we take the lead from tracheotomy, it would make it a rectumotomy, not sure if that sounds quite right, maybe rectotomy might need someone with some latin skills to figure out the correct spelling.. This reminds me of defenestration, the technical word for throwing someone (or something) out a window. Vespine (talk) 02:51, 16 May 2012 (UTC)[reply]

Newborns also can have an imperforate anus, which, as you can imagine, needs to be fixed fairly quickly. StuRat (talk) 03:18, 16 May 2012 (UTC)[reply]

What about colostomy which is quite a common procedure for people with advanced colonic cancer where removal of the colon is necessary. The exit is usually placed on the lower left or right front abdomen for the obvious reason that anastomosing the colon to the anus is difficult and likely to give poor control. Richard Avery (talk) 07:17, 16 May 2012 (UTC)[reply]

As proctology is the branch of medicine dealing with the rectum and anus, would it be proctostomy? As an aside, the proctologist at my local hospital is Mr Shatwell. Prime example of nominative determinism. --TammyMoet (talk) 08:44, 16 May 2012 (UTC)[reply]

Wouldn't a proctostomy be the removal of a proctologist impacted in your nether regions ? StuRat (talk) 16:15, 16 May 2012 (UTC) [reply]

The imperforate anus article mentions a "perineal anoplasty". --Sean 20:15, 16 May 2012 (UTC)[reply]

List of Self Limiting diseases?

I'm trying to find this list. It appears that wikipedia does not have such a category. Many definitions I've found will list a few, but so far I've got gastroenteritis, hepatits, the common cold, dyptheria, tonsillitis, llaryngitis. I imagine an exhaustive list would be huge, but can anyone find (or has seen) a list of the most common 20 or so? Vespine (talk) 02:43, 16 May 2012 (UTC)[reply]

I don't think many of those qualify as "self-limiting" as they are limited by our immune response. A truly self-limiting organism would control it's own population, say with waste which is toxic to itself in sufficient quantities. StuRat (talk) 03:13, 16 May 2012 (UTC)[reply]

Self limiting in medicine has a slightly diffent meaning to that of general biology. From the article: the term may imply that the condition would run its course without the need of external influence, especially any medical treatment. Vespine (talk) 04:16, 16 May 2012 (UTC)[reply]

Don't all diseases run their course with or without medical treatment? 112.215.36.183 (talk) 10:16, 16 May 2012 (UTC)[reply]

If you count "death" as an allowable outcome, then yes. I presume, however, the OP is asking about diseases that don't normally result in death if left untreated. If that is the case, then I'd remove diphtheria from that list. --TammyMoet (talk) 11:06, 16 May 2012 (UTC)[reply]

If you search wikipedia for articles containing self limiting, you get 2464 results. The description usually has enough info to know if it is a self-limiting disease. Examples: Scheuermann's disease, Scleredema, Vernal keratoconjunctivitis, Transient synovitis, Epiploic appendagitis, idiopathic scoliosis, Mondor's disease, Acute posterior multifocal placoid pigment epitheliopathy, Pityriasis alba, Cricopharyngeal spasm, Necrotizing sialometaplasia... For a list of the most common ones, I guess the best way would be taking a list of the say 50 most common diseases and check which ones are self-limiting. Problem is finding such a list, I can't even find two sources that agree on the nr 1 (gum disease according to one tabloid), even found a list that had sociopathic personality disorder in the top five. Ssscienccce (talk) 16:55, 16 May 2012 (UTC)[reply]

I thought there might have been a strict medical meaning but it seems there might not be.. Diptheria says it has a fatality rate of 5%-10%, lol, ok, I just searched for the source of the claim that diptheria is self-limiting back to Herbert_M._Shelton. Not exactly a reliable source.. But Ssscienccce has given me a great start. Thanks. Vespine (talk) 22:51, 16 May 2012 (UTC)[reply]

red giant's maximum diameter

How big is red giant at the maximum diameter. Can some red giant be as big as Mars orbit. How we know how big will our red giant be? Does some red giant get as big as 2 AU or as big as 3 AU? What is the size range of red giant from the smallest to the biggest?--69.228.133.188 (talk) 02:44, 16 May 2012 (UTC)[reply]

Does red giant answer any of this ? Note that the "size" is usually given as mass, which tends to be fairly constant, versus volume or radius, which can change dramatically. They list 0.5 Suns to 10 Suns as the range, with any stars more massive than that called red supergiants. (The illustration in that last article answers your Mars question.) As for how they know what the Sun will do, that's based on it's mass. StuRat (talk) 03:02, 16 May 2012 (UTC)[reply]

If your question was specifically "What is the biggest star?", see VY Canis Majoris. Its radius is estimated to be between 8.4 and 9.8 astronomical units, which is almost out to the orbit of Saturn. You may also be interested in our List of largest known stars. As far as our sun, it is estimated its radius will only be about 1.2 AU at its maximum, so the Earth will likely escape destruction due to its increased orbital radius by then (not that any of us will be around to care). -RunningOnBrains^(talk) 03:26, 16 May 2012 (UTC)[reply]

1.2AU isn't the maximum, it continues to say that it will eventually grow to 2AU. Vespine (talk) 04:14, 16 May 2012 (UTC)[reply]

My question was the biggest red giant in size, not the red supergiant or biggest star. I am asking for largest red giant only.--69.228.133.188 (talk) 05:34, 16 May 2012 (UTC)[reply]

Well then the answer is about 200 solar radii (2AU); the cutoff between red giant and red supergiant is quite fuzzy, if not arbitrary. For instance, Epsilon Aurigae at 135 solar radii is described as a red supergiant, while Rho Persei at 164 solar radii is considered merely a Asymptotic giant branch star (i.e., red giant).RunningOnBrains^(talk) 05:50, 16 May 2012 (UTC)[reply]

An inquiry into the nature of solenoids

The equation $B_{z}={\frac {\mu _{0}}{4\pi }}{\frac {2\pi IN}{L}}\left[{\frac {d+L/2}{\sqrt {(d+L/2)^{2}+R^{2}}}}-{\frac {d-L/2}{\sqrt {(d-L/2)^{2}+R^{2}}}}\right]$ gives the axial magnetic field strength $B_{z}$ in a solenoid. This is true for the case where every turn of conductor in the solenoid has the same radius $R$ . Would you expect the magnetic field strength measured in a coil consisting of many layers of turns, each with a slightly different radius, to be higher or lower in magnitude than that predicted by this equation using the inner radius of the solenoid? --130.56.84.118 (talk) 02:53, 16 May 2012 (UTC)[reply]

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our policy here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Anonymous.translator (talk) 03:23, 16 May 2012 (UTC)[reply]

GRRROOOAAAANANNNN. My line of reasoning was that the answer is higher because the many layers reinforce each other. Is this right? --150.203.114.37 (talk) 03:42, 16 May 2012 (UTC)[reply]

We actually can't answer your question because you didn't tell us enough about the multi-layered solenoid. Are you taking a solenoid with the same number of turns and simply altering the radii of the turns? Are you wrapping an additional solenoid around the original? Are you scrunching the solenoid up so that it's shorter and fatter? What is the distribution of radii with respect to the original radius? If you make the total circuit length longer, are you changing the total voltage to keep the current constant, or are you dropping the current to keep the total power output constant? Someguy1221 (talk) 04:08, 16 May 2012 (UTC)[reply]

I don't suspect this is a homework question, as it is more a test of algebra skills than magnetic understanding, and a generic math teacher is not likely to set such an applied question. On the other hand, electronics technicians and radio hams often ask this - they tend to only find the single layer formula in books etc.

Assuming you want to know what happens if you have the same total number of turns in a multilayer solenoid as in a single layer solenoid, with the current, wire gauge, and everything else the same, for comparison, the asnwer is simple: Apply the formula to each layer separately. The total axial field strength is the sum of the fields contributed by each layer. As the layer radius is lower (denominator) terms in the calculation, the layers are progressively less effective moving out from the inner layer. Therefore the total axial field strength in a multi-layer solenoid is less than that for a single layer coil of the same turns, and less than that estimated by taking the inner layer radius. However, if wire gauge is reduced so that the radial distance occupied by the turns is the same, you'll get near enough the same field. This is because the improved contribution of the inner layers is balanced by the reduced contribution of the outer layers. Keit120.145.9.168 (talk) —Preceding undated comment added 04:40, 16 May 2012 (UTC).[reply]

There seems to be some laziness in presenting an equation which contains 2 pi in the numerator and 4 pi in the denominator. Please simplify and ask again. Is it correct to infer that mu nought is the permeability of free space, I is current in amperes, and L is inductance in ohms? Is R in meters or centimeters? (My education included physics textbooks using both units of distance). Edison (talk) 05:34, 16 May 2012 (UTC)[reply]

You made me look at his formula again. It doesn't look right - for a start the Ln (natural log) symbol is missing. However, L in this case is not inductance (& inductance is not measured in ohms), but the length of the coil. Keit124.178.152.203 (talk) 07:18, 16 May 2012 (UTC)[reply]

Looks right to me, L being the length, and d the distance from the center (between -L/2 and L/2). If I understand the question correctly, it's whether using this formula for a multilayer solenoid, with R equal to the inner radius, would underestimate or overestimate the field strength? Assuming we're still talking about a solenoid of length L with N turns, I'd say the measured field strength would be lower, since the real radius is larger. Ssscienccce (talk) 17:44, 16 May 2012 (UTC)[reply]

Orbital Chainsaw

The Orbital Chainsaw would consist of thousands of small "teeth" satellites in Low Earth orbit. Each such tooth would have a reasonable sized solid state laser that was powered by ultracaps that were then refilled by solar power during the 99% of the orbit when that tooth wasn't over a useful target.

Each tooth is only over a target area for a short period of time, so only needs enough power storage to cover lasing for that short period of time.

The Orbital Chainsaw would have a thousand and one uses. From laser propulsion for laser powered aircraft and satellite launches (to fill in more teeth satellites), to weapons uses such as shooting down hostile ICBMs or satellite launches and dealing with gatherings of terrorists or other dissidents.

So why hasn't this been implemented yet? (What exactly is the flaw in this brilliant (pun intended) scheme of global domination?) Hcobb (talk) 10:58, 16 May 2012 (UTC)[reply]

You would need literally millions of satellites. Not very practical. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 11:09, 16 May 2012 (UTC)[reply]

Expensive. Plasmic Physics (talk) 11:10, 16 May 2012 (UTC)[reply]

Very—it would require more money than the entire U.S. gross national product. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 11:12, 16 May 2012 (UTC)[reply]

I don't know about the number but I agree cost seems to be a big factor. Consider say the cost of Iridium satellite constellation (which only involves 66 active satellites) or Globalstar or Orbcomm involving communications satellites. For example if we take Iridium, scale up the cost for your fancy laser satellites, times it by 50 for your proposal involving thousands of satellites (with some discount for the large number) and you probably end up with something more then the entire Military budget of the United States. Also while probably not banned by the Outer Space Treaty, I think it's clear such an extreme Militarisation of space is unlikely to be popular. The Strategic Defense Initiative was rather unpopular, and considering the existing ability of the US to nuke the entire planet many times over, the advantages seem slim considering the cost and unpopularity of such a move, mutually assured destruction is generally considered to remain a powerful deterence to any large enemy. In terms of 'rogue states', the US already have their Missile Defense Agency allegedly for that purpose. And smart bombs and UAVs to deal with gatherings of people they don't like. I think many would question how achievable most of your stated goals are anyway (using them from satellite launches sounds like wishful thinking to me). Nil Einne (talk) 11:37, 16 May 2012 (UTC)[reply]

Just compare the cost of the system against what is spent on commercial jet airliner fuel every year and it pays for itself in no time.

As for the number needed, assuming a reach of 200 km, fewer than 5000 satellites are needed to cover the entire Earth. Hcobb (talk) 12:05, 16 May 2012 (UTC)[reply]

Unlikely. Assuming this implausible amount, you would require 6332.573979 satellites. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 12:13, 16 May 2012 (UTC)[reply]

Exactly who is going to pay to get them up there? Plasmic Physics (talk) 12:19, 16 May 2012 (UTC)[reply]

Yeah. It is much easier to get citizens to pay for things to move them places than it is to get anyone to pay for orbital weapons already racked with other problems. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 12:46, 16 May 2012 (UTC)[reply]

And capacitors to store power collected in one orbit (1 hour) would have to store megawatts of energy. These would be big and heavy. Graeme Bartlett (talk) 12:39, 16 May 2012 (UTC)[reply]

And that would give complete 100% global coverage at all times (die penguin scum!). A few dozen would be sufficient for satellite launches. (At which point the launch costs go way down.) Hcobb (talk) 12:22, 16 May 2012 (UTC)[reply]

"And that would give complete 100% global coverage at all times." Wrong. Because circles do not tesselate, you would need at least twice that number. And practically, you would need twice that, to provide redundancy and allow for failures. Which comes out to over 25,000 satellites. And a number of satellites this large would be extremely difficult to keep from occulting each other, colliding with each other, dragging each other out of orbit etc. Dyson sphere#Dyson swarm lists the problems with such a large swarm of satellites. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 12:33, 16 May 2012 (UTC)[reply]

They only have to worry about occulting each other if they block a significant fraction of the sunshine striking the Earth. Given a a few meter diameter satellite every hundred km, this isn't much of a problem. As for energy storage the satellite would only be in a position to fire for an average of 200 km (not the full diameter of 400 km, because passing directly overhead is rare) and since it is traveling at 7 km/s it only fires for half a minute. Given a solid state laser of 100 kw, this is only three megajoules of power storage or 30 kg of ultracaps. Hcobb (talk) 12:59, 16 May 2012 (UTC)[reply]

Were the satellites light enough to be significantly helped to orbit by each others' lasers, then whenever one of the satellites fired its laser, the recoil would be enough to throw it into a higher orbit, possibly causing it to tumble as well, and forcing EITHER the launch of a replacement satellite, in which case the satellites would be literally one-use-only, necessitating replacement whenever fired, which would VASTLY increase the costs, OR the expenditure of large amounts of fuel to bring it back down to its rightful orbit.

Also, for attacks on ground-based targets, atmospheric attenuation might be a problem for objects near the satellite's horizon.

Firing the laser against property of another nation would be an act of war. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 13:04, 16 May 2012 (UTC)[reply]

It is also doubtful whether another space-faring nation would allow the development of such a system without deploying its own laser-armed killer satellites. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 13:11, 16 May 2012 (UTC)[reply]

Because of the energy conversion issues, the Solar sail effect of the solar cells would be much greater than the laser recoil and almost, but not quite, vanishing small. It still makes a tiny bit of sense to be able to tilt the solar cell wings to (very very slowly) bleed off excess rotational momentum from the stabilization reaction wheels. One imagines that any country able to achieve Prompt Global Strike against any target on or near the Earth within one second of locating that target wouldn't care very much about what other countries thought about it. Hcobb (talk) 13:21, 16 May 2012 (UTC)[reply]

See my post above about enemy killer satellites. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 13:24, 16 May 2012 (UTC)[reply]

Also, the force exerted by the laser on another satellite would be exactly equal to the force exerted on the satellite firing its laser. Have you any knowledge of Newton's third law of motion or the law of conservation of momentum? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 13:30, 16 May 2012 (UTC)[reply]

See Space-based solar power. I'm afraid you're golfing pretty far into the woods this time. There are limits on how precisely you can focus a laser from orbit. And using light defeats much of the purpose of space-based power since it gets absorbed in the atmosphere anyway. And a geosynchronous array loses only 75 minutes of sunlight to the Earth's shadow twice a year. And the satellites can be useful for power generation without being military assets. Wnt (talk) 14:54, 16 May 2012 (UTC)[reply]

Whether it is practical or not, I can't see why it would be useful. You can cover the whole Earth's surface with just a handful of geosynchronous satellites, so why bother building thousands of LEO ones? --Tango (talk) 23:06, 16 May 2012 (UTC)[reply]

In LEO the laser beam would have a much smaller spot on the ground. So it could be more concentrated, causing less damage outside its target area. Also from your geostationary orbit fixed location you may get a building in the way of your target. Graeme Bartlett (talk) 21:40, 17 May 2012 (UTC)[reply]

Compatibility (mechanics)

Can someone explain to me in ver simple terms what compatibility in mechanics is? I've read the article on Wikipedia & many books but they all confuse me. Thanks.Clover345 (talk) 13:50, 16 May 2012 (UTC)[reply]

It means that a certain kind of parts can be used with ("are compatible with") a certain device. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 13:54, 16 May 2012 (UTC)[reply]

Well, I've read the Wikipedia article http://en.wikipedia.org/wiki/Compatibility_(mechanics), and I'm none the wiser. But it has nothing whatever to do with what Whoop whoop said. The word "compatibility" is apparently used in the sense that certain conditions must be satisfied for the math theory of deforming/bending a solid by distributed force to be valid, such as not tearing. The article needs to be re-written, or at least a preamble added, in ordinary language, so us ordinary mortals can figure out what possible use it might be. The wiki article was written by some math nut who likes the sound of his own gibberish, and thinks that links to other math nut stuff means something. Wickwack120.145.133.138 (talk) 15:30, 16 May 2012 (UTC)[reply]

It's unusual to see an article entirely written by one editor, but no, it's not total gibberish. You might like to read our article on Finite strain theory first, but unless you are "into" tensors, that might not make much sense either. I agree that the lead needs to be written for non-specialist readers. Dbfirs 16:04, 16 May 2012 (UTC)[reply]

I think it has to do with: 1) the deformation must be continuous, ie a curve or surface must still be a curve or surface after the deformation, and 2) the formulas or matrix representing the distortion have more unknowns than there are independent variables, so you'll have additional constraints, which are the compatibility equations. Edit: just found the Continuum mechanics article. Ssscienccce (talk) 19:05, 16 May 2012 (UTC)[reply]

Whether I saw the moon.

I saw a thin white cresent, perhaps waxing, not far above the horizon, roughly in the east, from London at 9:00 this morning. Was it the moon? 82.31.133.165 (talk) 14:01, 16 May 2012 (UTC)[reply]

Very likely yes. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 14:06, 16 May 2012 (UTC)[reply]

The Moon is in its waning crescent phase right now, and would appear as a thin crescent near the eastern horizon (and not too far from the sun) in the mornings. Also, there just isn't anything else that looks like a crescent moon in the sky, really, ever. TenOfAllTrades(talk) 14:10, 16 May 2012 (UTC)[reply]

Actually, the crescent was indeed waning. I confused waxing and waning. Thanks. 82.31.133.165 (talk) 19:20, 16 May 2012 (UTC)[reply]

Definitely waning; it needs to be a new moon soon so we can have this weekend's eclipse. You can always tell waxing vs waning by if the moon is visible at sunset or sunrise: visible at sunset means it's waxing, visible at sunrise means it's waning. -RunningOnBrains^(talk) 20:37, 16 May 2012 (UTC)[reply]

Or remember the word DOC, D for waxing, O for obviously full moon, C for waning, note the curve of the letters. Richard Avery (talk) 22:06, 16 May 2012 (UTC)[reply]

Maybe I'm missing something, but that doesn't seem like a very helpful mnemonic. Won't it depend on what direction you're facing? Also how do you keep track of which is waxing and which is waning? -RunningOnBrains^(talk) 22:13, 16 May 2012 (UTC)[reply]

Won't it depend on what direction you're facing? - Technically yes, but only if you can get yourself to somewhere beyond the far side of the Moon to be able to observe it from that side. From the Earth, which is where most of us live most of the time, it appears the same everywhere, at least in terms of general shape and orientation. -- ♬ Jack of Oz ♬ ^{[your turn]} 22:29, 16 May 2012 (UTC)[reply]

I agree DOC does not seem useful, DOC seems to refer to crescent or gibbous but the moon goes throug each phase both waxing and waning: Lunar phase. Waxing or waning indicates whether the moon is going towards full or away from full (towards new), which you can not easily tell from casual observation, except to note whether it is morning or evening, as Running on Brains pointed out. Vespine (talk) 22:41, 16 May 2012 (UTC)[reply]

Doesn't a moon with a crescent on the right side appear to have the crescent on the left side when the viewer is upside down ? And, being an Aussie, you must be aware that you are upside down from the civilized world. :-) StuRat (talk) 22:41, 16 May 2012 (UTC)[reply]

(edit conflict)If I'm facing south and the moon is curved like a "C", then when I turn and face north the moon will look like a "D". I know I'm not mistaken... -RunningOnBrains^(talk) 22:40, 16 May 2012 (UTC)[reply]

Thank you guys, I'm really glad I'm not crazy :) -RunningOnBrains^(talk) 23:03, 16 May 2012 (UTC)[reply]

If you're facing south and looking at the moon and then turn and face north, then you can't see the moon any more because it's behind you... --Tango (talk) 23:13, 16 May 2012 (UTC)[reply]

And, if what you say is true, the HOLLYWOOD sign would read DOOWYLLOH from the front, depending on which way you're facing the sign. Is that your actual experience? If so, I suggest a good optician or even a psychiatrist. -- ♬ Jack of Oz ♬ ^{[your turn]} 23:33, 16 May 2012 (UTC)[reply]

Okay, but does the Hollywood sign move across the sky and rotate over the course of the night? When the moon is near the horizon, it is neither a C or a D, it is a U (the spines of a crescent always point up from the horizon). When it is directly above, it could be any of these, depending on what direction your body is facing as you look up. I'm not trolling, I'm legitimately trying to point out that this method just doesn't work. -RunningOnBrains^(talk) 00:45, 17 May 2012 (UTC)[reply]

And when I say "always" points up, I'm talking seeing the moon at night. I assume you can't see a small crescent while the sun's up (although I've admittedly never tried to look for it). -RunningOnBrains^(talk) 00:51, 17 May 2012 (UTC)[reply]

What is the connection between the letter D and the word waxing? Or the letter C and the word waning? Even if you are restricting yourself to one hemisphere (as StuRat says, the moon is the other way around in the opposite hemisphere), I don't see how the word DOC helps you remember anything. --Tango (talk) 23:13, 16 May 2012 (UTC)[reply]

I'm not sure I get what Jack is saying, the moon DOES look upside down when viewed from the other hemisphere. You'd have to flip Hollywood along the horizontal axis too to get the correct picture, but since a C and a D are symmetrical along that axis, you don't notice it as much with the moon. That's why Orion and most of the other constellations are upside down when viewed from Australia, because northerners made them up. Australian Aboriginal constellations like the emu will look upside down from the north. Vespine (talk) 23:52, 16 May 2012 (UTC)[reply]

Actually, I might be wrong about the emu because I think even us southerners look south at emu, you'd probably have to be on the south pole to look north at it. Vespine (talk) 23:58, 16 May 2012 (UTC)[reply]

Forget this D and C stuff. "Waxing" means "getting bigger" and "waning" means "getting smaller" - as in the size of the illuminated portion of the moon as seen from earth. Next time, class, I'll explain what "gibbous" means. :) ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:59, 16 May 2012 (UTC)[reply]

Resembling a gibbon ? :-) But seriously, why do we use such an archaic term as "waxing" instead of "growing" ? What would it be like if we used "waxing" for anything else ? "Hey mom, can you measure me ? I want to know how much I waxed today !" :-) StuRat (talk) 00:06, 17 May 2012 (UTC)[reply]

My interest in this topic is waning. ;) Vespine (talk) 00:25, 17 May 2012 (UTC)[reply]

Except for this bit "it appears the same everywhere, at least in terms of general shape and orientation." That's definitely wrong, even the Moon phases article points out that the moon looks different from the northern and southern hemispheres. Vespine (talk) 00:27, 17 May 2012 (UTC)[reply]

OK, I overstated my argument. I'm trying to get to the bottom of what Runningonbrains said: If I'm facing south and the moon is curved like a "C", then when I turn and face north the moon will look like a "D". If there are 30 people standing in a circle out in a moon-lit field, and they all look up at the Moon, ALL of them will report seeing a C-shaped object, or ALL of them will report seeing a reverse C-shaped object, or ALL of them will report seeing a (roughly) circular object. Is this not true? I cannot get my head around the claim that it will appear C-shaped to some but the reverse orientation to others in exactly the same place at exactly the same time, depending on which why they happen to be standing on the ground. That would be true of an object that is MUCH, MUCH closer, such as a photo of the crescent Moon stuck on your bedroom ceiling. But the actual, real Moon is WAY further away than that and it simply does not change its orientation in a matter of seconds as the observer changes their attitude to it. -- ♬ Jack of Oz ♬ ^{[your turn]} 22:06, 17 May 2012 (UTC)[reply]

So if the dean is waxing wroth, he's getting bigger, Bugs? That will certainly make it harder for Roth to wax the dean when it's his turn. Deor (talk) 00:37, 17 May 2012 (UTC)[reply]

EO is way ahead of you on that one.[21] :) "Waxing wroth" is an obscure way of saying "growing angry". As to the verb form of "wax", which appears to have nothing to do with the noun form, my old Webster's indicates the word is cognate with Latin and Greek terms that are also the basis for the term "augment". So instead of a "waxing crescent", we could have an "augmenting crescent". But that doesn't alliterate with "waning" very well. :( As regards the moon looking "upside down", the "tilt" of the crescent is going to vary depending on your latitude, just like the sun's angle will vary - however, the "midpoint" of the crescent moon is always going to be "aimed" at the rising or setting sun. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:35, 17 May 2012 (UTC)[reply]

If you google [waxing] you'll see other relatively common uses of that old-fashioned term. "Waxing poetic" seems the most obvious, along with alliterative pair, "waxing and waning", which can refer to most anything, like "ebb and flow". ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:41, 17 May 2012 (UTC)[reply]

One other thing: On the night of May 5th we had that "super" full moon, so it stands to reason that it would be in waning crescent phase 11 days later. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:48, 17 May 2012 (UTC)[reply]

There's actually heaps of sites that explain this if you google "does the moon look upside down", but I can't find any that have a clear illustration showing why. I might try to make one later. Vespine (talk) 00:40, 17 May 2012 (UTC)[reply]

Indeed, just thinking outer-spatially about it, the moon is going to appear 180 degrees different from the north pole to the south pole. -RunningOnBrains^(talk) 00:49, 17 May 2012 (UTC)[reply]

Controversy on Gravitational Singularities

If the universe had begun from a single point of zero volume and infinite density and mass, then why is the present universe so imperfect? — Preceding unsigned comment added by 205.178.233.168 (talk) 14:04, 16 May 2012 (UTC)[reply]

"Imperfect" in what way? If you mean the uneven (yet still highly homogeneous and isotropic) distribution of matter, our article on cosmological inflation gives credit to quantum fluctuations magnified to large scales during that period, and further references the galaxy formation and evolution and structure formation articles. — Lomn 14:15, 16 May 2012 (UTC)[reply]

So far as I know - correct me if I'm wrong - this "point" never really existed, not even in theory. To quote our article, "This singularity signals the breakdown of general relativity. How closely we can extrapolate towards the singularity is debated—certainly no closer than the end of the Planck epoch." Given how much stuff is said to have happened in the first second after the Big Bang - see Chronology of the universe - it is hard to think of any part of the process as "actually" being "instantaneous" in any meaningful sense. It is simply absurdly fast and absurdly small by our yardsticks - by the vibrations of cesium atoms, for example. But in the philosophical sense - the sense abused by some as described in Religious interpretations of the Big Bang theory - I think it would make more sense to view our universe as infinitely "old" (in the sense of a logarithmic time), but "receding to the horizon" as we look backward to ages where different properties of matter predominated. So there is no need to explain this contradiction - indeed, if we extrapolate from any time we can actually observe, the hypothetical first point, if it existed, would be an imperfect point. Wnt (talk) 14:44, 16 May 2012 (UTC)[reply]

Yes, since things tend to happen much more quickly, and in a much smaller area, at higher energies, it's reasonable to take this logarithmic view of the early universe. Still, the laws of physics presumably bottom out somewhere, so there would still be a beginning in traditional big bang cosmology, though it wouldn't be a singularity.

The other issue is that inflationary cosmology explicitly replaces the early universe, including the supposed singularity, with something quite different, which has no obvious beginning. So in a sense we're back where we used to be, with a universe that has existed for an unknown time, perhaps forever, with the details seemingly beyond the reach of present-day experiment. -- BenRG (talk) 20:17, 16 May 2012 (UTC)[reply]

Spontaneous symmetry breaking Hcobb (talk) 16:52, 16 May 2012 (UTC)[reply]

Beryllium barrier

What would be happened if beryllium-8 were a stable isotope? --84.61.181.19 (talk) 17:09, 16 May 2012 (UTC)[reply]

The entire universe would scream in horror. Looie496 (talk) 17:32, 16 May 2012 (UTC)[reply]

Big bang nucleosynthesis#Heavy elements briefly discusses one consequence. I'm not sure how much sense it makes to discuss this happening in isolation though - would it be possible to change physics in such a way that this isotope becomes stable, but nothing else is affected? 81.98.43.107 (talk) 18:00, 16 May 2012 (UTC)[reply]

If beryllium-8 were 10 eV lighter, it would be stable. --84.61.181.19 (talk) 19:20, 16 May 2012 (UTC)[reply]

Yes, but in order to achieve this you would have to change fundamental laws of physics, which would likely have dire consequences for life as we know it. -RunningOnBrains^(talk) 19:59, 16 May 2012 (UTC)[reply]

10 eV or 100 keV? --84.61.181.19 (talk) 20:28, 16 May 2012 (UTC)[reply]

Irish Great whites

If global warming is going to make the sea levels rise and warm up a bit does this mean that sharks like the great white might end up appearing in irish coastal waters. — Preceding unsigned comment added by 86.41.81.98 (talk) 21:20, 16 May 2012 (UTC)[reply]

Actually, quite possibly the opposite effect would happen in Ireland. The Gulf Stream, which brings warm tropical water to the coast of Ireland, is driven by a complex circulation in the North Atlantic. Melting northern polar ice is, in many models, predicted to disrupt this process, actually interrupting the flow of the Gulf Stream, causing the water (and likely the climate) of Ireland and other parts of Western Europe, to actually get colder. That's because, while the term is "GLOBAL" warming (that is the average temperatures of the entire world, averaged together) are getting warmer, the effects of those changes are complex, and can result in some local areas getting colder. That's why the preferred term is "climate change" as it captures the more complicated nature of what melting ice and overall warming will be. See Shutdown of thermohaline circulation which explains in some more detail how global warming can have a cooling effect on Ireland, which is named specifically. --Jayron32 21:30, 16 May 2012 (UTC)[reply]

I prefer the term "global weirding". StuRat (talk) 21:50, 16 May 2012 (UTC)[reply]

I have always had a problem with the "Gulf Stream Shutdown" theory, mainly because it's not purely a thermohaline circulation; it is also a dynamically-driven western boundary current. Seems like an incredibly unlikely scenario to me. Computer models seem to agree with me too, from the lede of the "shutdown" article: "In coupled Atmosphere-Ocean General Circulation Models the THC tends to weaken somewhat rather than stop, and the warming effects outweigh the cooling, even over Europe" -RunningOnBrains^(talk) 23:08, 16 May 2012 (UTC)[reply]

Indeed, the Gulf Stream itself will continue as long as the Earth continues to rotate at roughly its present rate and the Atlantic Ocean is not ice covered. Short Brigade Harvester Boris (talk) 00:26, 17 May 2012 (UTC)[reply]

Probably. The question becomes whether the nature of the Gulf Stream, such as the specific direction it travels, the temperature and salinity of the water it caries, and the way it affects the climate of Europe, which is in question. It is a complex situation, and does not have a simple answer, or even necessarily a known one. That's part of the major issue with climate change: If its effects were well understood, they could be prepared for. --Jayron32 00:29, 17 May 2012 (UTC)[reply]

There's no "probably" about the continuation of the Gulf Stream, or its direction, just basic fluid dynamics. See western boundary current. You're right about questions of thermal transport, salinity, and thus effects on climate of Europe (though in strict terms the latter are attributable to extensions of the Gulf Stream such as the North Atlantic Drift, rather than the Gulf Stream proper). Short Brigade Harvester Boris (talk) 01:45, 17 May 2012 (UTC)[reply]

I wouldn't call it "basic" fluid dynamics! That'd imply that it's the sort of thing we could use a simple equation for. Or, that it's the sort of topic that gets covered in an introductory textbook on fluid motion! The hydraulic equation is basic fluid mechanics. Bernoulli's law is basic fluid dynamics. The statistical dynamics of an ideal gas flowing in a perfectly thermally isolated closed box is fairly intermediate or advanced fluid dynamics. But climate and oceanic currents? That's some serious world's-largest-supercomputer kind of cutting-edge theoretical physics research. We have fairly sparse coverage in Wikipedia. One day I intend to work on improving our articles on global circulation models, but it's really dense stuff. Nimur (talk) 03:42, 17 May 2012 (UTC)[reply]

The equations which lead to a western boundary current are simple... or as simple as you get on the scale of fluid dynamics, anyway. They are laid out here quite nicely. Western boundary currents are unavoidable even in extremely simplified models of large bodies of water on a rotating sphere. -RunningOnBrains^(talk) 03:51, 17 May 2012 (UTC)[reply]

Urgent Antihistamine Question

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

If you have a question about the effects, uses, or dosage of medication, consult a medical professional. --Jayron32 23:14, 16 May 2012 (UTC)[reply]

Fair does. However, since "the deed is done" and I am genuinely not asking about my situation any more I will repost what I believe to be a compliant version just in case it interests people:

Antihistamine and general drug dosage question

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

If you have a question about the effects, uses, or dosage of medication, consult a medical professional. --Jayron32 23:14, 16 May 2012 (UTC)[reply]

Since you made your intent known in the previous version, people here cannot unremember the past. It is best to just drop this line of questioning, and ask a doctor if it is of concern to you. Or use the Wikipedia or Google or WebMD search function where no one will try to stop you. --Jayron32 23:35, 16 May 2012 (UTC)[reply]

I appreciate that but I'm not at all asking about the medicine as it relates to me, or tbh that medicine at all. I'm genuinely interested in the theoretical question. Although as the actual medicine is starting to kick in now, I will just ask tomorrow at some time when it is obvious it's just for interest, then we can all rest easy

Egg Centri c 23:40, 16 May 2012 (UTC)[reply]

Talk to someone who's qualified to answer, such as your doctor or maybe your pharmacist. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:50, 16 May 2012 (UTC)[reply]

One suspects that the complainants here must be associated with the medical profession, as once they have branded the defendant as "sick" and permanently denied him the rights other people would have on this basis, their work is done! Wnt (talk) 04:35, 17 May 2012 (UTC)[reply]

We can't answer any questions on specific medical matters, it doesn't figure into that how hypothetical it might be. It's a moral and a legal issue, if someone reads the archives or the thread here and makes an assumption they could become seriously hurt. It's not just because of the original question-asker, but anyone who might read the advice and be tempted to follow it rather than the guidance of a certified medical professional. HominidMachinae (talk) 04:39, 17 May 2012 (UTC)[reply]

No, I think you've misunderstood. We can't offer medical advice. We can indeed answer questions about medicine. --Trovatore (talk) 05:29, 17 May 2012 (UTC)[reply]

Physicians can bluster about the importance of following medical advice, but unless the person can pay them their shakedown, even the most medically necessary medicine will be banned from the patient by law, even though it is otherwise affordable - just as their advice on this would be limited to paying customers. I am wearied of their ethics. Wnt (talk) 04:53, 17 May 2012 (UTC)[reply]

Some of us are fortunate enough to live in a country where medical advice is free at the point of use. Here in the UK, if I need medical advice of the sort that's often asked for here on WP, I can go and ask my GP, or a pharmacist, and pay nothing for the privilege. (I've already paid for it in my taxes, but I'll complain about tax spending on aircraft carriers or unimplemented national databases before I complain about tax spending on keeping me and everyone else healthy.) AlexTiefling (talk) 08:15, 17 May 2012 (UTC)[reply]

Wnt apparently would stake his very life on the free (and worth the price) advice from strangers on the internet, rather than pay a trained professional. That's up to him. And if he suddenly stops editing one day, we'll know what happened. But wikipedia has rules against giving medical advice, and if Wnt doesn't like that rule? Too bad, too sad. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:27, 17 May 2012 (UTC)[reply]

Yeah, well, here in the U.S. they just closed down the local hospital, one which had stood for decades, in a sensible business decision reflecting that there is just not that much demand for medical care in the Third World. The prisons for people who sell allopurinol without a prescription, of course, well, those received a perky plus with all the money the state saved cutting the education budget. Wnt (talk) 21:32, 17 May 2012 (UTC)[reply]

What has that got to do with wikipedia's rules against giving medical advice? ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:04, 17 May 2012 (UTC)[reply]

May 17

What is the formal definition of a chromosome, or is there one?

I cannot seem to find a definition anywhere, Wikipedia contains conflicting information across different pages, as do Google results. Hoping someone here with a genetics background can enlighten me. Chromosome says that it is DNA complexed with protein, but I've read elsewhere that it is DNA complexed specifically with chromatin. The latter definition would exclude prokaryote circular DNA from being classed as chromosomes then.

Also, in regards to karyotype, I've heard at various times both a chromatid and a pair of homologous chromosomes being referred to as a chromosome in the singular. Humans have 23 pairs of chromosomes, right? So 46 different (heterozygous?) chromosomes in a normal interphase cell? Sorry if I have overcomplicated this, I just can't get my head round it at the moment. Thanks for any clarification in advance -Zynwyx (talk) 09:30, 17 May 2012 (UTC)[reply]

Metal loses its magnetic properties when in a liquid state?

I was just reading this, http://en.wikipedia.org/wiki/Electromagnetic_projectile_devices_%28fiction%29#Literature

And it stated that "Later it was shown that molten metal cannot be accelerated by a magnetic field as metal loses its magnetic properties in a molten state, and Clarke admitted his error gracefully." Is that true? In a railgun however, a piece of metal need only be conductive, not magnetic. Would molten lead or an eutectic of lead and bismuth still remain electrically conductive? ScienceApe (talk) 15:28, 17 May 2012 (UTC)[reply]

Mercury (element) is a metal in it's liquid state at room temperature, and, I believe, retains electrical conductivity. Perhaps what they mean is that, if significantly perturbed, the liquid will then break into droplets, making it more difficult for an electric charge to pass between them. StuRat (talk) 16:25, 17 May 2012 (UTC)[reply]

Mercury is absolutely conductive in its liquid state, see mercury switch for a common electrical use of mercury. --Jayron32 17:23, 17 May 2012 (UTC)[reply]

It must be possible because you can buy one. This link is to the Permanent Magnetic Pump (PMP), but the data sheet also mentions an Electromagnetic Pump (EMP). --Heron (talk) 18:35, 17 May 2012 (UTC)[reply]

A railgun uses an electric current to generate a magnetic field in the projectile, accelerating it through simple magnetic repulsion, and can use any projectile material that remains conductive during acceleration. A coilgun is essentially a linear motor that accelerates a magnetized projectile, and so requires that the projectile be able to remain magnetic during acceleration. You can (theoretically) fire a liquid metal from a railgun, but not from a coilgun. --Carnildo (talk) 23:04, 17 May 2012 (UTC)[reply]

If a nail is heated red hot, as with a propane torch, it reaches its Curie temperature and is no longer attracted by a magnet. Other ferromagnetic metals have varying Curie temperatures. Iron would still be electrically conductive when heated red hot, though its resistance would change.Molten iron and steel would still be conductive, since an electric arc furnace relies of current flow from an electrode to molten metal in the crucible. Metals typically have an increase of resistivity of 1.5 to 2.5 in the liquid form compared to the solid form at the melting point per [22]. Edison (talk) 23:54, 17 May 2012 (UTC)[reply]

Space radiation

Lets say you are in outerspace and you are protected from everything (pressure, you have oxygen, temperature, etc) except radiation. About how long would it take before you die from radiation? ScienceApe (talk) 15:46, 17 May 2012 (UTC)[reply]

- which part of outer space? Some parts are full of radiation, and you'd die immediately. Some parts have very little, and you'd die of old age. 91.125.207.125 (talk) —Preceding undated comment added 16:03, 17 May 2012 (UTC).[reply]

I don't think there's enough radiation, near the Earth, to kill from radiation sickness. There is enough, however, to cause genetic damage and cancer. But these things aren't always fatal, so there would be a decreased life expectancy, not certain death. If you were closer to the Sun, the radiation damage might be more severe.

Note that I'm assuming that you are excluding UV light. If that is included, I'd expect bare skin in space (if somehow protected from the cold and vacuum) to quickly burn, crack, and bleed. Death might occur within hours or days, from dehydration and infection. StuRat (talk) 16:04, 17 May 2012 (UTC)[reply]

The article Health threat from cosmic rays may be of interest to you. LukeSurl^{t c} 18:46, 17 May 2012 (UTC)[reply]

Define "radiation". What portions of the electromagnetic spectrum are you including, and what portions are you excluding? --Carnildo (talk) 23:05, 17 May 2012 (UTC)[reply]

Mario Rabinowitz

I was reading through the Ball lightning article, and it has some stuff about black holes by someone named Mario Rabinowitz. At a first look the Mario Rabinowitz article makes him out to be someone very impressive, but I can only see links to ArXive papers, and I can't see any affiliation with physicists I've actually heard of, or a position at a university or laboratory. Looking at the article's history, it looks like almost all of it was added to wikipedia by people who haven't done other things. So I'm a bit suspicious. I can't find anything worthwhile about this person by searching Google (I find facebook and patents and whitepages and stuff, and copies of the papers). So I'm concerned that a] this person doesn't really exist at all (that the article is a hoax) or b] that this person does exist, but isn't a physicist anyone has heard about (and so maybe should't be on wikipedia). Or is he really a famous physics guy who I've just failed to hear anything about? 91.125.207.125 (talk) —Preceding undated comment added 15:59, 17 May 2012 (UTC).[reply]

He's a real person,[23] but it sure looks to me like he's a non-notable person who wrote an article about himself as an autobiography, and the article should be deleted. But WP:AFD would be the place to bring that up, not here. Red Act (talk) 19:29, 17 May 2012 (UTC)[reply]

Cooperative lightning? Intelligent grass?

I'm sure this is a very dumb question, but assuming that what this website says is true: When lightning begins to travel downward from a cloud, many objects that have built up a charge emit streamers. This could come from anything such as a blade of grass or a power pole. The first streamer to make contact with the bolt defines the final path the lightning will take. - then how do the ground objects "know" when it's time to start emitting streamers? A simple answer please, for this admittedly ignorant non-scientist. Textorus (talk) 16:03, 17 May 2012 (UTC)[reply]

See our article on lightning. Fundamentally, though, positive streamers from the ground emerge for the same reason that negative streamers from the cloud (i.e. the formative lightning strike) emerge -- there's a large electric charge differential present. — Lomn 16:11, 17 May 2012 (UTC)[reply]

You might also want to know how gravity works. That is, how does the Earth "know" there is a star 93 million miles away which it should orbit ? Some rather non-intuitive explanations emerge, such as space being curved, or the even weirder gauge boson theory. StuRat (talk) 16:20, 17 May 2012 (UTC)[reply]

Now that you mention it, that is a fascinating question, but I'll save that one for another time. (The aether gets knotted up into a rope, maybe, like a yo-yo string?) Textorus (talk) 18:01, 17 May 2012 (UTC)[reply]

Lightning is a very complicated electrodynamic phenomenon. In addition to the visible incandescent stream of hot gas that you see, there are also wide-band electromagnetic waves (radio waves), preceding the lightning strike, occurring in tandem with the lightning strike, and coupling with the complicated streams of moving ions and electrons. The radio signals from a lightning strike are often called "sferics." Like all other radio waves, they travel approximately at the speed of light. The actual event of a lightning "striking" may be preceded by a very quick burst of radio-energy; and then as the streamer forms, all sorts of electromagnetic effects start happening and interacting with each other chaotically. The gas gets hot and incandesces, releasing visible light (incandescent light); but the gas is also ionizing and forming an electrically conductive stream, providing a current path, releasing more radio-wave emissions; and of course, the radio-waves emitted will affect air surrounding the lightning streamer. Here's a fairly advanced science web-site: Lightning Modeling, that reviews some of the physics necessary to accurately describe what's happening during a lightning strike. Nimur (talk) 17:10, 17 May 2012 (UTC)[reply]

The website is above my pay grade, but it makes sense that there must be some connecting force linking earth and sky. So when conditions are right for a storm, you're saying there's already a lot of ions and electrons moving between the two, invisible to our eyes? (I'm sure I must have learned that in Physics 101 but that was a l-o-n-g time ago.) Textorus (talk) 18:01, 17 May 2012 (UTC)[reply]

I think this is actually a very interesting question. The electricity clearly finds a quite specific path. My suspicion is that even in the absence of thunderstorms we are surrounded by an amazing display of static electricity which is simply, most often, too weak for us to see. Certainly I know that during a thunderstorm I can feel frequent little shocks from a mattress if it contains metal springs - sort of the sensation of being first bitten by a mosquito, but of course without the mosquito or subsequent irritation. Sometimes I've ever observed sparks from a window screen though lightning was not nearby. Has anyone ever sought to visualize the wider web of static electricity, or is it simply impossible, or indeed, am I deluded? Wnt (talk) 18:04, 17 May 2012 (UTC)[reply]

HAIL Project sought to visualize the wider web of electrodynamics in the atmosphere on massive geographic scales. By monitoring perturbations in the continuous background of electromagnetic signals (specifically, several LORAN transmitters), data was collected to drive a complete realtime model of the ionization and the electromagnetic environment for the continental US. Nimur (talk) 20:58, 17 May 2012 (UTC)[reply]

A former colleague of mine attempted to measuring electric fields near clouds by photographing polarization changes through an optical telescope. This is called the Kerr effect, and refers to the change in optical properties of certain materials (like atmospheric air) when exposed to very strong electrostatic fields. I recall thinking the idea was crazy (the signal should be well buried in the noise); but that's why it's research... Nimur (talk) 21:02, 17 May 2012 (UTC)[reply]

I can't search videos online at work, but I encourage you to find the ultra slow motion videos of lightning, it's frikken awesome! The "streamers" they talk about are a LOT slower then the speed of light and there are videos of them propegating though the sky, once they "contact" eachother, the lightning bolt actually fires like a flash. It's one of the most incredible natural phenomena on earth I think. Vespine (talk) 22:56, 17 May 2012 (UTC)[reply]

And of course, the fine folks in Gainesville, shoot off rockets trailing metal wires. Nimur (talk) 00:33, 18 May 2012 (UTC)[reply]

Where can drugs get in your body? What barriers are there?

I'm aware of the blood-brain barrier but presumably there are plenty of other barriers. Where can orally or intra-venously taken drugs get in your body? Presumably anywhere blood can get, but where is that? Can drugs get inside cells? What about bones? What about your eye lenses? What effects whether they DO get there?

I think that's enough questions for now... although I've got a lot more.

What would be a good place to start looking for the basics of this stuff?

Egg Centri c 19:50, 17 May 2012 (UTC)[reply]

Hair analysis shows that detectable levels of many drugs can be found in your hair. Long-haired drug users effectively carry a timeline of their drug consumption imprinted in every hair of their head. --Jayron32 20:31, 17 May 2012 (UTC)[reply]

An oral drug should get into a cell at least once, in the intestinal epithelium, in order to enter the body. These and many other drugs usually have their effects inside a cell. Sort of an exception are antibiotics, which act inside a cell, but not one of yours! ;) There are exceptions, though - any drug which blocks a cellular receptor, for example. So far as I know any injected drug (well, "biologic") with a name ending in "-mab" (monoclonal antibody) will not get into a cell for meaningful purposes (it might get endocytosed with a receptor and have a trip to the lysosome, but that hardly counts). Vaccines don't get into cells, at least not the old fashioned kind available on the market. There's nothing quite like the blood-brain barrier and even that allows some things to pass. Certainly bones are visited by Fosamax and its ilk. The lens of the eye is a curious case, as it receives sustenance from the aqueous humor from the ciliary body; thus drugs must go by this indirect route; nonetheless they can arrive. For example, acetaminophen overdose can form cataracts in experimental animals receiving the drug systemically;[24] however, this occurs after it is first processed by the liver to form a more toxic metabolite. [25] Wnt (talk) 21:28, 17 May 2012 (UTC)[reply]

The place to look for basic information is any introductory pharmacology textbook. Generally speaking in order to get into cells a chemical needs to be lipophilic, meaning capable of dissolving in fats or oils. That's basically the same thing required for a drug to cross the blood-brain barrier. The exception is substances that are transported by active uptake mechanisms. Looie496 (talk) 23:47, 17 May 2012 (UTC)[reply]

sun become a red giant 5 or 7.5 billion years?

Wait, I am a little confused here. said sun enter red giant about 5 billion years from now. Dr. Schroeder and Smith's website said tip of RGB is 7.59 billion years from now. Does it take 2.69 billion years for the sun to become a red giant, or sun last of red giant for 2.69 billion years. So when sun leaves main sequence in 5 billion years, it becomes a yellow subgiant first, and it slowly work the way to red giant by gradual increase of size/luminosity, or once it branches off main sequence it goes directly to red giant by large increase of size/luminosity. Is the end of red giant alot larger in diameter and luminosity then the beginning of red giant?--69.233.254.22 (talk) 01:32, 18 May 2012 (UTC)[reply]

Revision as of 01:32, 18 May 2012 edit 69.233.254.22 (talk) →‎sun become a red giant 5 or 7.5 billion years?: new section ← Previous edit		Revision as of 01:38, 18 May 2012 edit undo 69.233.254.22 (talk) →‎sun become a red giant 5 or 7.5 billion years? Next edit →
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	== sun become a red giant 5 or 7.5 billion years? ==		== sun become a red giant 5 or 7.5 billion years? ==

	Wait, I am a little confused here. [http://books.google.com/books?id=Qxva-lg9_5cC said sun] enter red giant about 5 billion years from now. Dr. Schroeder and Smith's website said tip of RGB is 7.59 billion years from now. Does it take 2.69 billion years for the sun to become a red giant, or sun last of red giant for 2.69 billion years. So when sun leaves main sequence in 5 billion years, it becomes a yellow subgiant first, and it slowly work the way to red giant by gradual increase of size/luminosity, or once it branches off main sequence it goes directly to red giant by large increase of size/luminosity. Is the end of red giant alot larger in diameter then the beginning of red giant?--[[Special:Contributions/69.233.254.22\|69.233.254.22]] ([[User talk:69.233.254.22\|talk]]) 01:32, 18 May 2012 (UTC)		Wait, I am a little confused here. [http://books.google.com/books?id=Qxva-lg9_5cC said sun] enter red giant about 5 billion years from now. Dr. Schroeder and Smith's website said tip of RGB is 7.59 billion years from now. Does it take 2.69 billion years for the sun to become a red giant, or sun last of red giant for 2.69 billion years. So when sun leaves main sequence in 5 billion years, it becomes a yellow subgiant first, and it slowly work the way to red giant by gradual increase of size/luminosity, or once it branches off main sequence it goes directly to red giant by large increase of size/luminosity. Is the end of red giant alot larger in diameter and luminosity then the beginning of red giant?--[[Special:Contributions/69.233.254.22\|69.233.254.22]] ([[User talk:69.233.254.22\|talk]]) 01:32, 18 May 2012 (UTC)