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February 3

Gravity in a bounded universe

The divergence of the gravitational field is equal to the mass density, which is non-negative everywhere and positive in some places. The net divergence in a bounded system must be zero. Doesn't this mean that the universe is unbounded, and thus the curvature must be non-positive? For that matter, even if it is, wouldn't an approximately even mass distribution result in an unbounded gravitational field?

My best guess is that the mass density of a vacuum is negative. Is this correct? — DanielLC 05:44, 3 February 2013 (UTC)

Your first statement is only correct within Newtonian gravity which is not applicable to the universe as a whole. Dauto (talk) 15:37, 3 February 2013 (UTC)

You are right that the mass density of vacuum is negative (in sense that it produces repulsion instead of attraction), while the energy density is positive. Ruslik_Zero 19:06, 3 February 2013 (UTC)

What does it mean for energy density to be positive? If you change the potential energy of every state under quantum physics, this does absolutely nothing. I've been told you need general relativity to find any sort of energy density of the vacuum. — DanielLC 23:21, 4 February 2013 (UTC)

while we're on the subject of turtle evolution

We've all seen the videos of the little turtle hatchlings crawling toward the sea as fast as they can while sea birds etc feast on them (also noted in our turtle article); why wouldn't evolution push them all to the point where they lay their eggs like 2 feet above high tide line? Particularly when I notice the aforesaid turtle article notes that turtle eggs kept moist do better than those kept drier? Gzuckier (talk) 06:49, 3 February 2013 (UTC)

Unless I'm missing something here, you have pretty much answered your own question. Above high tide line - less moist. At high tide line just moist enough. Richard Avery (talk) 08:00, 3 February 2013 (UTC)

This article suggests that predation is a likely controlling factor with the optimum nest position being close but not too close to the water's edge, I presume that by widening the strip within which nests may be located, the predator's job is made more difficult. Mikenorton (talk) 08:10, 3 February 2013 (UTC)

Also, predation can help eliminate defective genes, by removing the least fit individuals. StuRat (talk) 08:16, 3 February 2013 (UTC)

Another factor to consider is that nests which are placed too close to the high tide line run the risk of being drowned, and as noted in the "cape" episode of David Attenborough's Africa series, should the nest be flooded before the eggs hatch, they won't survive. douts (talk) 14:15, 3 February 2013 (UTC)

Light bulbs. halogen --> LED

I have 81 50-watt halogen downlighters GU10 ES50 which link to 240v - 12v transformers. Can I get something which will provide the same amount of light in one LED bulb? Kittybrewster ☎ 10:45, 3 February 2013 (UTC)

Assuming you mean to replace EACH 50 W halogen light with one LED fitting, the answer is yes. Have a look at this: http://www.siliconchip.com.au/Issue/2013/February/Replace+Your+Halogen+Down-lights+With+LEDs. Ratbone 124.182.26.251 (talk) 10:59, 3 February 2013 (UTC)

Yes. Good. Warm white, daylight or pure white? 2w 3w 4w or 5w? Is there a reference for these lights at a UK supplier?Do they need a 12w LED Driver Transformer for MR16-MR11-G4 LED Light Bulb by Long Life Lamp Company? Kittybrewster ☎ 15:19, 3 February 2013 (UTC)

I've replaced some GU10 12V halogens with LEDs. They run on 12V AC (IIRC, they have a built-in rectifier). For some reason they don't have the halogen-equivalent wattage marked. However, LEDs about about 3 times as efficient as halogens, so I'd go for about 15W. The lamps are marked as non-dimmable; if you want to dim them you might need to buy a ballast. CS Miller (talk) 20:02, 3 February 2013 (UTC)

The best answer is 'may be'. Presuming you don't mean to replace anything in the fitting, replacing 12V halogens with LED equivalents can be problematic. You can find many complaints from a simple search, some people recommend just replacing them with main voltage ones. The problem is in the transformer, the electronic transformers (switched mode power supply) commonly used may be designed for 50W bulbs and may not like the far lower voltage, some may not work at all. Even if they do work, you sometimes get flickering due to an interaction between the switch mode power supply on the bulb and the switch mode power supply in the fitting. The output from the SMPS is most likely not a simple 50 or 60 hz AC since it doesn't matter to the halogens. More reliable manufacturers often have long lists of transformer compatibility charts for their lights. In the unlikely event your bulb uses a simple transformer, I would guess you shouldn't have problems.

However although not commonly discussed, there is an advantage to the 12V namely safety. In fact I read about [1] [2] which shows even someone like Philips can screw up their design. I personally chose GX5.3 12V as opposed to GU10 240V despite the issues because I prefer cool white bulbs (at least 5000K and preferably higher) and it's not that easy to find high CCT bulbs from reliable manufacturer with a high CRI (even when it comes to the raw LEDs they're far rarer then low CCT high CRI). However I did encounter flickering from some of the bulbs I purchased from AliExpress using Sharp COBs. I believe the ones that flicker for me use a boost drive as the LED forward voltage is above 12V (some of the LED dies are series) which highlights I guess another unfortunate fact, a number of COBs and LED arrays do have a forward voltage above 12V because they're targeted at the line voltage market where it's an advantage since the buck driver doesn't have to reduce the supply so much. One intermediate option between going main voltage is to keep the fitting but replacing the transformer with one designed for LEDs (or better both LEDs and halogens) source from a reliable manufacturer. Of course you could replace the whole fitting with an LED one, I didn't do that here because what's available seems rather poor and limited, even before taking in to account my preferences but things may be better in the UK.

The other consideration is the design of your fitting. If the bulbs are enclosed or recessed in the wall, you're far more likely to have a problem since LEDs really don't like to get hot. For the same reason, 50W halogen equivalent is difficult for a bulb that sized. Some of the Philips GX5.3s (and I think GU10) even have a fan. (In my case I purposely overlighted the area so it doesn't matter if they aren't so bright.) This also depends on your requirements. If you want a high CRI low CCT light you'll need a more powerful bulb since both high CRI and low CCT generally means a lower luminous efficacy. Even when it comes to similar CRI and CCT, LEDs are still rapidly evolving so it depends significantly on the LED used. (As well of course on the efficiency of the driver.)

Nil Einne (talk) 05:31, 4 February 2013 (UTC)

P.S. From a quick search, one more problem you may have is I don't think GU10 12Vs are particularly common. AFAIK, GU10s are usually main voltage and GX5.3 are used for 12V in the MR16 world. Given the similarity, for Chinese manufacturers from AliEpxress you may be able to get them to make some GU10 12Vs easily if you're buying a decent quantity perhaps 10-20. For well known brands, you'll just have to use what's available. Nil Einne (talk) 05:51, 4 February 2013 (UTC)

Male vs female pain

I heard that females are more tolerant to pain than men, because men have more pain receptors. It's linked to the Y chromosome. Is this true?Dbjorck (talk) 08:30, 3 February 2013 (UTC) Copied from Talk:Nociception#Male vs female pain 10:54, 3 February 2013 (UTC)

In Sexual dimorphism it says generally females feel pain more than males. I believe I read somewhere this applies even to babies so it is not something that is just learnt. This makes sense really, males fight more and pain that distracted would be a disadvantage. Dmcq (talk) 14:07, 3 February 2013 (UTC)

This is like asking "is the sky brown?" Common sense should be more than enough to tell you it's blatantly false, and that women are far more sensitive to pain. In case you don't believe common sense, here is an article that quotes a scientific paper. Here is an article from Scientific American. "The reason for this is not known, Fillingim said. Past research suggests a number of factors contribute to perceptions of pain level, including hormones, genetics and psychological factors, which may vary between men and women, Fillingim said. It's also possible the pain systems work differently in men and women, or women experience more severe forms of disease than men, he said." --140.180.247.198 (talk) 17:56, 3 February 2013 (UTC)

Googling "number of pain receptors" returns some pages, amongst a lot of junk, that indicate both sexes have about the same number of pain receptors per unit area of skin. Since men are bigger and have more skin area than women, they have more pain receptors. However, this does not mean more sensitivity, nor less.

The study reported in Scientific American is deeply flawed, as reading the attached reader comments shows. To measure something, whether it is magnitude of pain, volts in an electric circuit, or the weight of a parcel, you need a measurement system that has appropiate resolution, and calibration. They measured by asking patients to rate their pain on a numerical scale, 0 = no pain, to 10 = worst pain imaginable. That's plenty of resolution, probably too much, but there is no calibration. Who is to say whether I can imagine a pain more severe than you? Perhaps I fell off a ladder, breaking my hip. Perhaps you were very sick with an intestinal blockage. Perhaps we both never before had any pain worst than childhood accidents. Perhaps I have a more vivid imagination. Perhaps I only think I do. A better question might be "What is the severity of your pain, 0 = no pain, 1 = I have pain, but I am happy to ignore it, 2 = the pain constantly intrudes on my consciousness, 3 = I cannot think or function at all with this level of pain 4 = I want to die" Since the brain has evolved over a very long period of time to prioritize what gets presented to consciousness with a well defined structure, this would give at least some calibration.

It should also be noted that we have more than one system for sensing pain. There is a specific nerve network ending in pain receptors in the skin. There is a quite separate system of nerves ending in pressure sensors in the digestive system. The brain interprets excess pressure as pain. It may well be that men are more sensitive than women for skin pain, and women more sensitive to gut pain. Or vice versa. Or some other combination. By not recording and accounting for this, the study repoted in Scientific American is futher flawed.

Not only is the preception of pain severity, and the degree which an individual reports it (two different issues confounded in the SA study) culturally influenced ("real men don't cry"), it depends on state of mind. It is well known that humans will put up with almost anything if they have the right state of mind, and/or they can see a light at the end of the tunnel. In World War 1, for example, General Monash was able to inspire troops to put up with hardships unimaginable to folk that have not served in a battle. After my wife had an operation, the nurse came around and asked her to rate her pain. On being told it was as bad as anything, the nurse gave her a narcotic and valium. A little later, my wife asked for more. But the nurse sized her up and said she could have a half dose of narcotic and no valium. My wife protested, saying the pain was again bad. The nurse replied, "You should expect some pain, you are obviously well aware of your surroundings now. If I keep giving you valium, you will become addicted." Whereupon my wife decided the pain was not so bad after all, and talked to me brightly about all the flowers and phone calls she had received from her work mates. — Preceding unsigned comment added by 124.178.53.46 (talk) 01:36, 4 February 2013 (UTC)

Wickwack 121.215.57.3 (talk) 01:03, 4 February 2013 (UTC)

Re calibration: Remembering my psych grad school daze, if people are provided with defined end points to a scale, they can be relied upon to scale stimuli very nicely (usually on a log scale) and repeatably, whereas in the absence of such defined end points the reported intensity wanders all over the scale between different subjects, or the same subject various times. Of course, we weren't paining people (that would be a creepy experiment; "Now, call this pain 10 out of 10" and then do ???), but the finding was so universal that I'd be really surprised if pain receptors were any different. As for the other factor, yeah, everybody who is familiar with dogs or kids has probably seen them smack into a wall full tilt or something when playing and laugh it off, while when they're looking for pity the teeniest scratch or bruise will cause copious agony. Gzuckier (talk) 02:49, 4 February 2013 (UTC)

True. I probably should have said the SA study had poor calibration at the top end, rather than saying there was no calibration. The top end calibration was poor because it requires imagining the most severe pain, and that depends on experience. Wickwack 60.228.245.239 (talk) 03:08, 4 February 2013 (UTC)

I admit the Scientific American article was not the greatest example. Nevertheless, there is abundant evidence that men have a greater pain tolerance than women, and none at all for the opposite viewpoint. This literature review, for example, describes studies that use brain imaging to measure human pain response. Differences in pain tolerance have been unambiguously found in both humans and animals. In humans, these differences appear in subjective questionnaires like the SA study, behavioral tests such as Lowery et al, and PET brain scans such as Paulson et al. In animals, the differences appear in behavioral observations and brain measurements, like measurements of stress-induced analgesia. By "differences", I mean that males have unambiguously higher pain tolerance than females, and not the other way round. This other review article claims that the results of brain imaging studies are mixed, but is nevertheless unambiguous in its conclusion: "Consistent with our previous reviews, current human findings regarding sex differences in experimental pain indicate greater pain sensitivity among females compared with males for most pain modalities, including more recently implemented clinically relevant pain models such as temporal summation of pain and intramuscular injection of algesic substances." Of course all of these studies, just like all of science, are limited or flawed in some way. Even so, they're much more trustworthy than WP:OR based on one anecdote about WWI and another anecdote about somebody's wife. --140.180.247.198 (talk) 02:58, 4 February 2013 (UTC)

The study quoted in our Pain threshold article is Sex Differences and Incentive Effects on Perceptual and Cardiovascular Responses to Cold Pressor Pain by Daniel Lowery, MA, Roger B. Fillingim, PhD and Rex A. Wright, PhD. Alansplodge (talk) 19:23, 4 February 2013 (UTC)

D'oh! Already linked above - sorry 140.180! Alansplodge (talk) 19:25, 4 February 2013 (UTC)

Wasn't there also some surprising finding, in the last few years, that certain painkillers were ineffective for women while being very effective for men? I recall it being taken as further evidence that the pain pathways and natural painkilling mechanisms were different in men and women. It also was taken as a cautionary tale of the dangers of narrow samples being used in drug trials and taken as representative of the wider population. Ring any bells for anyone? 86.163.209.18 (talk) 22:06, 4 February 2013 (UTC)

Black holes: Why the most complex objects in the universe?

Andrew Strominger (and others) state that event horizons are governed by a strikingly simple set of quantum laws which implythat black holes are at once the simplest and most complex objects in the physical universe. I understand the first part, as they are defined by three parameters only - mass, electrical charge and angular momentum (however, this is derived from general relativity, not from quantum laws, isn't it?) But why are they the most complex objects? I understand it has to do with Black hole thermodynamics and the Black hole information paradox, but still fail to explain, not the least in confusion how the concepts entropy, information and complexity interact in this case. --KnightMove (talk) 13:09, 3 February 2013 (UTC)

Utter speculation on my part, but I'm guessing that if you tried to map the event horizon, you might end up with some ridiculously, fractally wiggly line, just like the Mandelbrot set, another surprisingly-complicated system with a surprisingly simple definition. —Steve Summit (talk) 13:41, 3 February 2013 (UTC)

It's probably because black holes have the largest physically possible entropy for an object their size (Bekenstein bound). -- BenRG (talk) 06:15, 4 February 2013 (UTC)

This article exactly demonstrates my confusion: This article uses the terms entropy and information as straight proportional almost-synonyms, while they are generally regarded as almost-opposites and an increase in entropy means a decrease in information. This leads to the next ??? when entropy is supposed to increase in the universe, while information supposedly cannot decrease... --KnightMove (talk) 10:53, 4 February 2013 (UTC)

Yes, the word information is used inconsistently. It means "the logarithm of the number of equiprobable states", but they may be talking about different states in different circumstances. If they're counting indistinguishable microstates, it's the same as entropy. If they're counting phase space volume, it's conserved. If they're counting distinguishable macrostates weighted by the number of indistinguishable microstates in each one, it's the sort of information you're thinking of. -- BenRG (talk) 17:16, 4 February 2013 (UTC)

antimatter

Is there any likelihood that there is a way to change matter to antimatter using a relatively small amount of energy so that you can use matter-antimatter interaction to gain energy? Bubba73 ^{You talkin' to me?} 14:17, 3 February 2013 (UTC)

What do you think, Bubba? Such a thing would make possible a perpertual motion machine, as no doubt you have realised. Floda 120.145.46.100 (talk) 14:46, 3 February 2013 (UTC)

How would you make a perpetual motion machine with this? What Bubba suggested converts matter into energy, so you would need to continually supply matter (fuel) to keep the machine running. - Lindert (talk) 14:54, 3 February 2013 (UTC)

(ec) No, it would not make a perpetual motion machine possible. What you gain in energy, you lose in annihilated matter and antimatter, via E=mc². There may be other reasons why this is impossible, but neither the first nor the second law of thermodynamics stands in the way. --Stephan Schulz (talk) 14:59, 3 February 2013 (UTC)

Erk! You are right. Floda 121.215.4.176 (talk) 16:13, 3 February 2013 (UTC)

My impression is that a very small black hole is just such a catalyst, but I don't know if that is actually true. Wnt (talk) 15:11, 3 February 2013 (UTC)

A very small black hole might conceptually be able to convert matter to energy efficiently - you feed the matter into the black hole at the same rate that it is dissipated in the form or Hawking radiation. However, this is highly unstable. The smaller the black hole becomes, the faster its rate of evaporation. So you need to feed it more matter to make it cool down. If the math at Hawking radiation holds up, a 200 ton black hole will produce 7 billion gigawatts. You need to feed the mass equivalent of that into the black hole to keep it stable, against that radiation pressure. And the major snag here is that we would need a good theory of quantum gravity - I doubt that general relativity scales down to quantum sizes. --Stephan Schulz (talk) 16:24, 3 February 2013 (UTC)

Well, the problem isn't really so much keeping it stable as getting over that hump to create a synthetic black hole in the first place; after that you can bulk it up until it converts energy at a sedate rate and is less likely to explode suddenly if the computer crashes. And yes, the question of what the smallest possible black hole looks like is of the greatest interest, since it is at once the greatest obstacle and, if it can actually be created, perhaps the greatest opportunity, to do the conversion at that step of creation only, never having a black hole that has any possibility of slipping away and eating the Earth. Wnt (talk) 17:07, 3 February 2013 (UTC)

If one had access to a smallish black hole (I'm not talking a furiously-Hawking-radiating size, necessarily, either, just conveniently smaller than a solar or planetary mass) it would be a dandy source of energy. Throw any old matter that you like into it, and you'll get a significant fraction – typically at least 10%, and possibly upwards of 40% depending on the circumstances – of the mass-equivalent energy radiated back out. (Frictional heating makes infalling matter hot. Like, really hot.) This isn't Hawking radiation, this is just plain old blackbody emission from still-outside-the-event-horizon matter making up the accretion disc. Black hole#Accretion of matter touches on this point. (Science fiction buffs may recognize this concept from Imperial Earth, in which Arthur C. Clarke used small black holes in this way to power interplanetary ships.) TenOfAllTrades(talk) 19:33, 3 February 2013 (UTC)

Guys, you seem to be missing the big picture here: the question is one step away from saying "Can we convert matter into energy according to e=mc^2, using a relatively small amount of energy"? If we do take the "logical" next step in the question (use the antimatter to gain energy), that's all this is equivalent to. In other words, using up matter directly, for its high theoretical energy yield, using relatively little energy. Is such a thing theoretically possible? Is it possible by the means suggested, of turning the matter into antimatter first, using relatively little enrgy? 178.48.114.143 (talk) 15:32, 3 February 2013 (UTC)

Well, that's what I described with the small black hole, but I suppose I should have clarified. If you make a very small black hole, smaller than a primordial black hole, then it will evaporate in a very short time by Hawking radiation. So in theory, if a black hole has only mass, charge, and spin that is, you can cram matter down its gullet (emphasis on the cram, as we're speaking of something the size of a subatomic particle, perhaps) and what comes out may be particle pairs, matter + antimatter, that can annihilate and produce light. But ... I don't know for sure myself, what with all the talk of some kind of conservation? of physical information in the Hawking radiation, whether there could be some sort of 'matter-ness' in the black hole you feed this way after all that would somehow foul the scheme. Wnt (talk) 16:16, 3 February 2013 (UTC)

I was talking to a friend who was wondering about getting energy from matter-antimatter interaction. I asked "where do you get the antimatter?". I said that it takes more energy to make antimatter than you would get out. He wondered if it was possible to convert regular matter to antimatter and use it, with a net gain in energy. I doubt it, but I don't know. Bubba73 ^{You talkin' to me?} 16:39, 3 February 2013 (UTC)

I don't think the question is one step away from saying "Can we convert matter into energy according to e=mc^2, using a relatively small amount of energy" ? The question is much more fundamental. Can you change the sign of the charge of a particle. Sean.hoyland - talk 16:48, 3 February 2013 (UTC)

Nay, it's not changing the charge. For example, if you dump only protons into a mini black hole, it will quickly take on a positive charge (one of the three properties they do have by all accounts) and repel taking up more; when a virtual pair becomes Hawking radiation it will be the negative one that drops in the event horizon and the positive one that goes away, most likely, until the balance of charge is restored. Wnt (talk) 17:03, 3 February 2013 (UTC)

The OP's question is "Is there any likelihood that there is a way to change matter to antimatter" Sean.hoyland - talk 17:08, 3 February 2013 (UTC)

Or "Is there any likelihood that there is a way to change matter to antimatter with using a minimal amount of energy", where minimal amount is << 2mc². ---- CS Miller (talk) 17:24, 3 February 2013 (UTC)

Right. And have it so that we can use it, e.g. not inside a black hole. Bubba73 ^{You talkin' to me?} 17:50, 3 February 2013 (UTC)

Wouldn't rotating matter in the fourth dimension make it into antimatter? μηδείς (talk) 21:24, 3 February 2013 (UTC)

Unless there's some exchange between different elemental particles, that would seem to violate Charge conservation, i.e. if an electron can be 'turned' into a positron through the fourth dimension without involving any positively charged matter, the net electric charge of the universe changes, which shouldn't happen. - Lindert (talk) 23:10, 3 February 2013 (UTC)

But charge alone isn't conserved, isn't it something like charge x mass x velocity that is conserved? You will have to forgive me, as I am totally ignorant here, but I seem to remember something like this. μηδείς (talk) 01:28, 4 February 2013 (UTC)

Charge is conserved, energy is conserved. Neither of these is necessarily violated by changing matter to antimatter, but doing that will violate conservation of baryon number. It's not clear whether conservation of baryon number is a fundamental law or just a general observation. Baryon asymmetry would suggest the latter. Someguy1221 (talk) 01:37, 4 February 2013 (UTC)

In the sense of "a black box that you push matter into, and antimatter (and some waste matter & energy) comes out" - yes, of course we can do that. Inside we'd have a fusion reactor which is converting matter into energy (and a lot of waste product) and something as described in Antimatter#Artificial_production using that energy to create antimatter. If you don't look inside the black box, it does what the OP wants - but the relatively small yield of the process means that you'd be better off just using the fusion reactor to do the work.

More directly, Antimatter#Positrons says that you can fire electrons at a small diameter gold target using a laser and get positrons out the other side - which is doing that conversion - but the amount of energy needed in the laser presumably exceeds the amount of energy you'd get by recombining positrons and electrons - or else I'd have something like that inside my electric car! So no free energy device here!

If there is a way to do this conversion cheaply, we don't know what it is because according to Antimatter#Cost, the current price to create antimatter is between $25 billion per gram (positrons) and $62.5 trillion per gram (antihydrogen). The cost of storing the stuff in any quantity would likely be off the charts!

However, the lower of those two numbers looks promising! One gram of antimatter can produce 2mc² = 18,000,000,000,000,000 Joules of energy. A KWh is 3.6MJ - so our gram of positrons makes 50,000,000,000 KWh. A KWh costs about $0.1 in the USA right now...so that's $5bn worth of electricity for a $25bn outlay...well, OK, nobody's getting rich on this anytime soon - but it's not that inefficient. A 20% efficiency would be economical for (for example) powering a car or an airplane. If you could find a way to reliably contain the stuff (and that's a huge "IF"!), you could easily store all of the energy your car would ever use in a box that might fit conveniently into the glove box and which could be installed into the car when it's manufactured! That kind of energy density would certainly be worth having.

SteveBaker (talk) 13:48, 4 February 2013 (UTC)

Assuming that such antimatter powered cars would have about the same efficiency as today's electric cars, and doing a quick back-of-an-envelope calculation (0.1-0.23 kW.h/km accroding to our article, and assuming a design life of 300,000 km), you would need about 100-200 GJ of energy, which is 25-50 tonnes of TNT. I'm not sure I want to be driving round with the equivalent of a small tactical nuclear weapon in the glove box, so the containment question is, as you say, a huge "IF". Apologies if I have made an order of magnitude error somewhere, I did the calculation rather quickly!

Equisetum (talk | contributions) 17:54, 4 February 2013 (UTC)

Yall might find Neutral particle oscillation interesting - a process by which neutral mesons do indeed (Spontaneously !) convert into their antimatter selves. Dauto (talk) 16:19, 4 February 2013 (UTC)

Basically, if there were any way of converting ordinary matter particles (protons, neutrons and electrons) into their antiparticles with a relatively small amount of energy input, it would happen spontaneously by quantum tunneling, and ordinary matter would decay into photons and neutrinos, and there would be no us. So no. -- BenRG (talk) 17:25, 4 February 2013 (UTC)

Chemistry after nuclear decay/transmutation

In most studies of nuclear decay, the atom's electron shell and what it is bound to is not considered. However, this is what I am interested in.

Consider a molecule of dimethylpropane (neopentane), that has been carefully crafted so that the central carbon is ¹⁴C, and then others are ¹²C, i.e. ¹⁴C(¹²CH₃)₄. It is observed until the central atom decays to ¹⁴N⁺, (assuming the electron ejected from the nucleus isn't captured by the shell). Thus we now have ¹⁴N⁺(¹²CH₃)₄.

My question is, is one of the methyl groups ejected by the nitrogen, to form N(CH₃)₃, (assuming that this molecule is stable)? CS Miller (talk) 16:40, 3 February 2013 (UTC)

Trimethylamine is a real and stable – though rather stinky – chemical compound. My first thought was that such a compound arising would be unlikely simply because radioactive decay is a relatively energetic process; one might expect the recoil of the newly-formed nitrogen-14 nucleus to rip it loose from any chemical compound to which it was attached. (For reference, the decay energy for carbon-14 is about 156 keV (156,000 eV), whereas typical covalent C-C and C-H bond-dissociation energies are on the order of 4 or 5 eV. While most of the beta decay energy gets carried off with the emitted beta particle and neutrino, some small fraction of it ends up with the N-14 nucleus.)

It turns out, though, that that isn't necessarily the case. Remarkably, carbon-14 decay is gentle enough (barely) that at least some of the expected derived N-14 compound may survive, under at least some circumstances. Way back in 1956, Wolfgang et al. actually did a similar experiment using C-14 labelled ethane (H₃C-CH₃), and found that 47% of the ethane molecules survived 'intact' post-decay to form the anticipated compound, methylamine: H₃C-NH₂. Whether or not this result generalizes well to the decay of neopentane, I wouldn't hazard a guess. TenOfAllTrades(talk) 17:55, 3 February 2013 (UTC)

Thank your for your speedy reply ToaT, unfortunately I don't have access to that paper. I didn't know that some of the decay energy ends up in the atom, rather than the ejected subatomic particles. Neopentane was just used as an example; I could have chosen any organic molecule. Assuming that the recoil doesn't rip the nuclide out of the molecule, am I correct to think, after the decay, the product nuclide will eject an attached group to retain a stable 8 octet?

A follow up question. If the the groups are different (say the 3rd carbon in 3-methylhexane decays), is it possible to predict what will be ejected? CS Miller (talk) 19:28, 3 February 2013 (UTC)

Tetramethylammonium, or even more complex Quaternary ammonium cations, isn't so unstable that it would be likely to fall apart (you probably have bottles of them in your shower and laundry!). It still does have a stable octet, it just also (now) has a charge. DMacks (talk) 21:32, 3 February 2013 (UTC)

Uh, tetramethylammonium is toxic and is not normally used in household detergents. Most household detergents use alkyl sulfonates, which are more effective in this application in any case. 24.23.196.85 (talk) 04:54, 4 February 2013 (UTC)

Quat-ammonium compounds are commonly found in many products for many reasons (obviously less-toxic ones often suffice). I encourage you to read our article about them to see many applications (including subarticles such as shampoo the common polyquaternium class of ingredients among others). The question was about stability vs flying apart: even the tetramethyl article's studies on toxicity are predicated on it being stable enough to study. DMacks (talk) 12:33, 4 February 2013 (UTC)

What is this crinkly wood - and why is it so?

Split wood showing crinkly grain (approximately circumferential split face uppermost, radial split face on right)

The pictured wood is from the UK, is lightweight and easily split in either plane. It is mainly pale yellow with some red streaks and is very crinkly throughout available samples. The wavelength of the crinkles is 6-7mm and their polarization is circumferential to the tree, so that the surface of radial splits is highly corrugated. No bark remains on the sample.

What is it? and why is it so?

Thanks --catslash (talk) 23:24, 3 February 2013 (UTC)

It's hard to say with certainty without knowing more about its source, but it seems to be a form of burlwood. E.g.:[3], from:[4] ~:74.60.29.141 (talk) 00:41, 4 February 2013 (UTC)

Is it perhaps from a Dutch elm diseased tree? Is Crinkley Wood near Crinkley Bottom? See also Noel's House Party --Senra (talk) 04:19, 4 February 2013 (UTC)

No, Dutch Elm disease affects the bark and the structures immediately below, the woody trunk is unaffected, apart from the fact that it becomes part of a dead tree. Elm is notoriously slow to rot, Old London Bridge sat on elm piles for 650 years. I'm old enough to remember trying to burn the damned stuff; "Elmwood burns with a churchyard mould, E’en the very flames are cold..."[5]. Alansplodge (talk) 13:12, 4 February 2013 (UTC)

'Walter' here has a theory about it. I have seen it in mature oak and olive wood. A real nuisance when you're splitting logs. Richard Avery (talk) 08:20, 4 February 2013 (UTC)

I like the "reaction wood" explanation - and (of course) we have an article about that: Reaction wood. SteveBaker (talk) 13:11, 4 February 2013 (UTC)

Perhaps that photo→   would make a good addition to the article (which could also use a citation to the certified arborist @Wavy Wood - Explained) - However, would this be WP:OR or perhaps wp:synthesis?   ~:74.60.29.141 (talk) 17:56, 4 February 2013 (UTC)

Eventually found it on the web. It would have been easy to find if only I had known that it was called a curly figure. This looks very similar to mine in every particular. Apparently the cause is not known, or at least not agreed. Thanks for the suggestions though. --catslash (talk) 01:10, 7 February 2013 (UTC)

February 4

Acupunture for Cerebral Venous Thrombosis

request for medical advice
The following discussion has been closed. Please do not modify it.
Dear Sir, I was diagnosed for Cerebral Venous Thrombosis, bilateral papilloedema, left VI nerve palsy, Neck Supple, Plantar↓. I have been under conventional medication for the past 2 years and there are no signs of reducing my drug dosage. I started having side effects and when I spoke to my Neuro Physician about the side effects. I was told it is to be expected due to drug effects. For a holistic approach for my medical condition, I started taking Acupunture for the past 3 weeks. I feel lot of relief. But I need to know if there is any document on positive relief for CVT. I am unable to locate any document, article on effects of Acupunture treatment for CVT. Can you please guide me on the topic.Marhabha (talk) 06:59, 4 February 2013 (UTC) We cannot give any medical advice. Articles may be at acupuncture and Cerebral venous thrombosis. Graeme Bartlett (talk) 08:32, 4 February 2013 (UTC) Graeme is right; we cannot give medical advice. Talk to your physician again and ask him the specific question you asked here. Typing the name of the medication in the Wikipedia search box may lead you to other relevant Wikipedia pages. --Guy Macon (talk) 10:02, 4 February 2013 (UTC)

freezing insect eggs?

Various sources suggest putting insect prone food (oatmeal, rice, etc.) in the freezer to kill the eggs; but I'm dubious. Does that really kill the eggs, or just keep them from hatching while it's actually in the freezer? Because if it does kill the eggs, why don't they treat the food at the plant before selling it? Gzuckier (talk) 07:34, 4 February 2013 (UTC)

The ability to reliably survive freezing is a rare trait in insects. I think you can be confident the eggs really do die. No clue why they're not so treated before hand if its a real concern. My guesses would be that either some of in the insect contamination is post-shipping, or they are being cheap. Someguy1221 (talk) 07:42, 4 February 2013 (UTC)

This is pure anecdote but you can take what you want from it. I found a superb local baker but unfortunately his flour has flour moth and after a couple of weeks I had some flying out of my bread box. I bought in batches of a dozen loaves, putting most in the deep freezer until needed. This action had no effect on the viability of the eggs, they survived the freezer for up to 3 weeks. I now reheat the loaves in a hot oven for 5 minutes. No moths. Richard Avery (talk) 08:04, 4 February 2013 (UTC)

woah dude, I'd be looking for a different baker myself ---- _nonsense ferret 13:14, 4 February 2013 (UTC)

For good bread I go the extra mile! Richard Avery (talk) 14:07, 4 February 2013 (UTC)

We have our very own baker for that. He may be a bit off your beaten track, Richard. You may have to go the extra 5,000 miles. -- Jack of Oz ^[Talk] 08:07, 5 February 2013 (UTC)

Different insects have different amount of resistance to freezing[6][7] and even different basic strategies.[8] One surprising aspect of this is that many insects are better at surviving freezing if they have experienced winter weather in the previousmonth[9] -- insects generally do not maintain their cold protective systems when their environment remains relatively warm. --Guy Macon (talk) 10:28, 4 February 2013 (UTC)

It is doubtful that the moths came from eggs in the baker's flour; they wouldn't survive the bread baking process (note your 5-minute re-heat). I had this problem until I lined my pantry with "Spanish cedar" (which is neither Spanish nor cedar). ~:74.60.29.141 (talk) 18:17, 4 February 2013 (UTC)

I agree, there is no way the moths came from the baked loaves. They probably simply live in your house and are attracted to the crumbs left over in the bread box. So your experiment of freezing them did not determine anything. If reheating them does anything, you are simply killing eggs that are laid, in your house, on the outside of the loaf. As a practical suggestion buy a pheromone sticky trap made for pantry moths. Ariel. (talk) 18:42, 4 February 2013 (UTC)

It sounds like freezer temperatures should kill any stage of Ephestia kuehniella [10] [11] (99% of eggs in 5 hours). But the other one... would you believe somebody wrote a book about it? But no freeview. Still, [12] says that eggs are the hardiest stage and 99% of them die in 6 hours. Then again, I don't know the species for sure. Wnt (talk) 19:14, 4 February 2013 (UTC)

As it happens I had a detailed conversation with the baker and they are aware of the problem and are embarking on a new pheromone based capture strategy. They flour the baked loaves with unbaked flour and this is the source of the eggs, so there we are - I came to offer some personal advice not seek comments about my eating habits. I'm not complaining, they bake the best bread I've ever eaten. Richard Avery (talk) 19:22, 4 February 2013 (UTC)

Thanks for the encouraging advice; particularly since I could potentially stash stuff outside in winter for a bit.... but anyway, in regard to the tangent re contamination in said baker's place; the reason I asked is because I'm getting so many products contaminated. I did at first think perhaps they were getting contaminated by a domestic infestation, although why certain products would or wouldn't get infested is a question, so I started stashing each item I bought in a tupperware or similar container as soon as it got home, but that didn't improve things, so I assume they're getting imported in the food. Not just the usual stuff you'd expect like flour or rice, but processed stuff like spaghetti, hot cocoa mix, etc. Of course, FDA regulations are always grosser than the layperson expects. Gzuckier (talk) 19:41, 4 February 2013 (UTC)

Why would they flour the baked loaves with unbaked flour? It's normal to use some flour as a release agent, but that flour gets baked. Why add unbaked flour after? Ariel. (talk) 19:54, 4 February 2013 (UTC)

Are you saying that bread, flour, rice, spaghetti and hot cocoa mix all have the same insects even when stored in Tupperware? So what is common to all? Same store? Same warehouse feeding multiple stores? Could it be something weird like always leaving the food on the same rug or in the same auto trunk for a while or maybe all your Tupperware has loose lids? (Not that I believe that any of those could be the common factor, just asking what all the foods have in common) --Guy Macon (talk) 20:26, 4 February 2013 (UTC)

Looks to me like the same guys; they never get past the larvae stage, those little beige guys with dark heads. I've wondered the same thing. For stuff like spaghetti in the usual box, I can see that the parents could get in anywhere along the line, but the cocoa baffled me. (Individual single serving foil packages in the box). Only some foil packs had bugs, and you could tell a priori because they had little holes in the foil; i'm convinced those were the larvae chewing from inside out, rather than outside in because 1) it was only some of the foil packs, not all 2) there was no evidence of insects outside the foil, despite the holes 3) logically, how would the eggs hatch and grow into larvae that could chew through the foil outside the pack without anything for them to eat? And some brands had the problem, some didn't, which may be just random sample variation. So i'm somewhat baffled. If I ever find holes chewed in tin cans, I'm going to panic. Gzuckier (talk) 16:49, 5 February 2013 (UTC)

Sounds like weevils, which are known to infest pantries and then be found in all your starch boxes. When I was little and we moved from the US South to the North we brought them with us and they took keeping everything in tins or the freezer finally to get rid of. μηδείς (talk) 01:10, 6 February 2013 (UTC)

Evolutionary purpose of non-reproductive sex

From the perspective of evolution, the purpose of sexual intercourse is reproduction, and the purpose of reproduction is species continuation. But some species such as bonobos, dolphins and humans have non-reproductive sex. From the perspective of evolutionary biology, what is the purpose of non-reproductive sex? Even from an evolutionary perspective, non-reproductive sex may be harmful to a species as it will create continuous sexual competition and resulting injuries and death. So does it provide any evolutionary benefit? --PlanetEditor (talk) 17:51, 4 February 2013 (UTC)

We have an article Animal sexual behaviour which despite its flaws, goes in to this in a variety of ways. Our article Bonobo#Sexual social behavior also discusses it as specific to bonobos (notably it appears to function somewhat the opposite of what you're suggesting). We have a large number of articles like Human sexuality covering sex among humans and related topics (Concealed ovulation for example may be of interest) although if you're old enough you may have ample knowledge that sex can serve many purposes among humans many of which will have a variety of possible evolutionary benefits. Nil Einne (talk) 18:56, 4 February 2013 (UTC)

Pair bonding - "sex for pleasure" keeps the male close enough to the female to contribute (directly or indirecty) more than just his gametes to raising offspring. Roger (talk) 19:06, 4 February 2013 (UTC)

• It's a fallacy, selectionism, to assume that every aspect of biological organisms has to be seen as serving some evolutionary purpose. μηδείς (talk) 20:30, 4 February 2013 (UTC)

  Gould was a known anti-sociobiology writer. You need to find a neutral source. It is absolutely possible to explain each and every physiological and behavioral feature of a species, including humans, in evolutionary terms. --PlanetEditor (talk) 05:13, 5 February 2013 (UTC)

Absolutely. And if we accept the suggestion that there's competitive advantage in making reproductive sex pleasurable, the pleasure in non-reproductive sex appears to come as a trivial side-effect. AlexTiefling (talk) 22:50, 4 February 2013 (UTC)

Take a look at Why Is Sex Fun?, which gives many evolutionary arguments for why it is so. Shadowjams (talk) 01:05, 5 February 2013 (UTC)

Non-reproductice sex exists because sex conveys an evolutionary advantage, and prevention of non-reproductive sex doesn’t. - Nunh-huh 02:37, 5 February 2013 (UTC)

That's a non-answer, it just restates the question in different terms. What the OP is asking about is what the evolutionary advantage is. --Jayron32 04:56, 5 February 2013 (UTC)

Actually, Nunh-huh's answer is correct if you add the premise that non-reproductive "side effects" arise from successful reproductive ones. If females being attracted to males is a well successful strategy, but it results in certain males also being attracted to other males, it will exist because the first is a very successful strategy and the second doesn't matter. Evolution doesn't care about the homosexuality of the male in that circumstance so long as his mother and sisters are successful. μηδείς (talk) 05:19, 5 February 2013 (UTC)

You could add any number of sentences to Nunh-huh's answer to make it correct. He didn't add any such sentences. What he wrote, however, is neither correct nor incorrect, merely a redundant restatement of what evolution is. --Jayron32 05:30, 5 February 2013 (UTC)

Obviously you can't just add any old sentence to his claim and make it true. The logical premise that "non-reproductive "side effects" arise from successful reproductive ones" is very specific, and seems quite likely what Nunh Huh meant--I simply made it explicit--I didn't make it or any old sentence up from scratch. μηδείς (talk) 01:53, 7 February 2013 (UTC)

OP, you say that some species have non-reproductive sex, and you mention bonobos, dolphins and humans as examples. I prefer to believe that pretty much all species engage in this behaviour. Can you show me a single species where conception occurs every time they have sex? Or that the participants could care less either way? (other than humans; we seem to be the only species for whom this is an issue) They enjoy getting their rocks off as much as we humans do. -- Jack of Oz ^[Talk] 05:23, 5 February 2013 (UTC)

Evolution isn't trying to weed out those traits that do not contribute to survival and reproduction. Evolution describes how small advantages in survival and reproduction tend to be perpetuated in succeeding generations. Non-contributory traits, as long as they are not too disadvantageous or are merely neutral vis-a-vis survival and reproduction, tend to be perpetuated as well. Bus stop (talk) 05:54, 5 February 2013 (UTC)

One more question. Are only the animals with menstrual cycle exhibit non-reproductive sex? --PlanetEditor (talk) 06:48, 5 February 2013 (UTC)

No. Many types of birds pair up for life, or at least long periods of time, and enjoy sex for bonding purposes. Birds do not menstruate. Wickwack 121.221.92.200 (talk) 06:57, 5 February 2013 (UTC)

I remember reading a book titled "Hung Like and Argentine Duck" which provided a rather interesting overview to the evolution of sexual intimacy (as the author termed it). As I recall, the author provided several examples where non-procreative sexual behaviors carried distinct benefits for the individual. For example, 'homosexual' behaviors in male garter snakes led to them being warmer than their counterparts and therefore more attractive to females. In species with social structures increased cooperation also increased the likelihood of one individual in that group being able to pass on their genes, or for a close relative to do so. So it may be possible that some of these these behaviors may have actually been positively selected for. 130.102.158.16 (talk) 02:49, 6 February 2013 (UTC)

Coffee

How many typical styrofoam cups of caffeinated coffee, filled approximately 3/4 of the way, does an average person needs to drink consecutively in order to be killed by caffeine overdose? 140.254.121.34 (talk) 19:28, 4 February 2013 (UTC)

This is perhaps a trick question. Ignoring the size of a "cup" for now, the article caffeine says 80 to 100 cups of coffee have a 50% chance of doing the trick. But if a cup is indeed a cup, then this is 40 pints, 20 quarts, five gallons of water, and water intoxication would probably set in sooner than that. Therefore, you should not be able to die of caffeine overdose because something else would kill you first. :) But ... differences in cup size, and the length of time required to clear water versus caffeine from the system, might undermine that. Funny, I just can't interest myself in doing this math, though I feel like for some reason differences in cup size should normally be more interesting. :)Wnt (talk) 19:41, 4 February 2013 (UTC)

It takes quite a large amount of caffeine to be dangerous. Caffeine can start causing problems once you consume more than 1 gram of the substance and be lethal at 10 grams, so doctors like [Cleveland Clinic cardiac surgeon] Gillinov recommend that people don't consume more than 400 to 500 milligrams a day. For comparison, he said an average cup of tea has about 40 miligrams while a tall cup of Starbucks coffee (12 ounces) has about 260 milligrams of caffeine, though other brands average about 100 milligrams for a regular sized cup.   —Castillo, Michelle (October 24, 2012). "Can you overdose on caffeinated drinks?". CBS News. CBS Interactive, Inc.     ~:74.60.29.141 (talk) 19:53, 4 February 2013 (UTC)

Great! Now you have me craving coffee! Thanks. μηδείς (talk) 20:25, 4 February 2013 (UTC)

It might also be worth noting that there are adverse health effects other than caffeine poisoning, such as increased risk of kidney stones, from consuming too much caffeine.202.155.85.18 (talk) 08:00, 8 February 2013 (UTC)

I think you might have that backwards. --Srleffler (talk) 18:49, 8 February 2013 (UTC)

Twin fingerprints

Are identical twins born with identical fingerprints, and then the prints diverge later as they grow, or are they born with different fingerprints? RNealK (talk) 22:54, 4 February 2013 (UTC)

Different fingerprints. Uncle Cecil says so. Identical twins are only identical genetically. They will develop in non-identical environments, and as a result will have subtle differences, including fingerprints. This NYT column briefly explains the effect of subtle environmental difference, and itself links to more in depth documents. --Jayron32 23:17, 4 February 2013 (UTC)

Thanks. RNealK (talk) 23:22, 4 February 2013 (UTC)

February 5

Yellow rain

In December 2012 Sri Lankan towns such as Mineragala and Southern provinces experienced Red rain and towns of Polonnaruwa and Kantale experienced Yellow rain. But the article about yellow rain totally differs from this rain. So natural yellow rain should be also included here. Sri Lanka based researches reveal that this colouration of monsoon rains was due to remains of meteorites. So what is the difference between natural and artificial ones? Source:

• [13]
• [14]
• Rupavahini broadcasting (government's official broadcasting channel)

--G.Kiruthikan (talk) 07:06, 5 February 2013 (UTC)

I fixed the dead links above. Sean.hoyland - talk 07:38, 5 February 2013 (UTC)

Both the red rain and the natural form of yellow rain are actually varieties of blood rain, which is caused by large quantities of dust and pollen in the air (the meteor hypothesis, BTW, has been disproved). "Artificial" yellow rain, however (I put it in quotes because its very existence is unproven) is a hypothetical Soviet chemical weapon allegedly used against South Vietnam by the Vietcong in 1975, which may be composed of various mycotoxins, mustard gas, etc. FWiW 24.23.196.85 (talk) 08:53, 5 February 2013 (UTC)

Law of excluded middle, null hypothesis, and disproof of god

Ok so let's say that the statement "god doesn't exist" is the null hypothesis and "god exists" is the alternative hypothesis. So the null hypothesis can not be proven and is the default position, that directly implies that the claim "god doesn't exist" can not be proven. Let's define god as the being that is described in The Book of Genesis. Since this being has been described as creating humans, that is a demonstrable claim that can be falsified. Evolution has falsified creationism, and therefore the god described in The Book of Genesis has been disproven. According to the Law of excluded middle, two contradictory propositions (i.e. where one proposition is the negation of the other) one must be true. Since the alternative hypothesis has been disproven, it stands to reason that the null hypothesis must be true according to the Law of excluded middle. So my question is, can something be true, without it being proven (using this logic)? ScienceApe (talk) 02:00, 5 February 2013 (UTC)

This is the reference desk. Can you rephrase that as a specific request for research help, rather than a long invitation to debate? μηδείς (talk) 02:13, 5 February 2013 (UTC)

A statement can be assumed true, and thus require no proof. This is the essence of the method by which most religious persons justify their convictions. 72.128.82.131 (talk) 02:38, 5 February 2013 (UTC)

Your argument utilizes the strawman argument and is not a proof; and "using this logic" [sic] one can prove anything. ~:74.60.29.141 (talk) 02:44, 5 February 2013 (UTC):~

Or disprove anything. No believer has ever come up with any evidence that would convince a scientist there is a god, and no scientist has ever been able to cause a believer to doubt there is a god. Then there are scientists who teach evolution but privately are strong believers in the God who created the universe ab initio. Work that out. -- Jack of Oz ^[Talk] 02:53, 5 February 2013 (UTC)

Not to mention that God and evolution are not mutually-exclusive. [I didn't mention that] ~:74.60.29.141 (talk) 03:48, 5 February 2013 (UTC):~

The flaw here is in this line: "Since this being has been described as creating humans, that is a demonstrable claim that can be falsified."...Sadly, that is not the case. God is described as being "omniscient" and "omnipotent" - and that's a major problem for any disproof of his existence. If this is true, then he can do absolutely anything. For example: He could create humans (per Genesis), then completely falsify all of the evidence (planting fake fossils, adding appropriate junk DNA, etc) to make it look to scientists like we evolved from pond-slime...or he could warp the minds of scientists who investigate evolution to make them believe it to be true and to ignore contradictory evidence. Heck, it might be that not one single person in the world believes in evolution but God decided to warp your mind to make you think that it's widely accepted as true. Maybe he allowed evolution to do the work and then faked the creation of the book of Genesis. An omnipotent being has literally no limits...that's why the non-existence of God is unfalsifiable - even by complicated arguments like yours. Of course my claim that there are omnipotent, green, piano-playing aardvarks living on the dark side of the moon is also unfalsifiable - and so are an infinite number of other possibilities. The "God hypothesis" therefore has a statistically infinitesimal (but not zero) probability of being true...so rational beings may ignore that possibility. SteveBaker (talk) 16:17, 5 February 2013 (UTC)

Your final sentence does not logically follow. The premise that there are is an infinite number of possible omnipotent beings does not lead to the conclusion that the probability for each of those possibilities is infinitesimally small, because that requires the unstated (and unproven) assumption that each of those possibilities is equally probable. - Lindert (talk) 16:36, 5 February 2013 (UTC)

Yeah - that's true to a degree - but since these are unfalsifiable hypotheses and none of them (including the "God hypothesis") has any solid evidence to prove them, our best guess has to be that they are equally probable. SteveBaker (talk) 20:41, 5 February 2013 (UTC)

The trick here is that you are defining "god" very narrowly here, as being not merely the god of Genesis but a particular interpretation of that god which is one whose work must leave evidence demonstrably contradictory to evolution. So your proof of "god not existing" is equally narrow. You have not, for example, disproved that there could be a God who created the world as in Genesis, but who subsequently covered up his prior work by some miraculous means to leave only evidence of the natural history implied by our current laws of physics; or who did the creation in a parallel universe and copied and refined it in this one; or who did the work in some sort of Platonic realm of archetypes; etc. Wnt (talk) 05:12, 5 February 2013 (UTC)

I am not personally very interested in not the god-vs-no-god debate - at least, not at face value. I feel that this debate has been rehashed by many intelligent people, and many many more unintelligent people, for many centuries, and in many languages. What I am interested in is the Kolmogorov complexity of their debate, and more importantly, the marginal contribution to that complexity of any new individual's argument. I fear that we are reaching a plateau, where the complexity no longer increases, because the exact same arguments for each side are made, over and over and over again, by people who have chosen not to invest the time to read the earlier parts of the "thread." Now, it's a heck of a lot of effort to expect every Tom, Dick, and Harry to start off with Plato and Thomas Aquinas and Sartre; but by golly, if somebody's interested in the subject, then they really ought to invest the time to read all the prior arguments so that we can make forward progress in the discussion, instead of repeating the same string-literal arguments, without adding to the complexity. (And yes, I posit that in five centuries of English, and five decades of digital texts, somebody has written almost exactly the same string of text as your brilliant idea to prove, or disprove, anything). If only there were a free repository of great classic literature, and short encyclopedic summaries to help guide the interested reader through the denser parts of the prose... I bet each person could expend a little effort to ramp up on "prior art," and there would be much less repetition of the elementary tenets of formal logic, theology, and the general theory of human knowledge. And more to the point, we could then process this digital corpus to estimate the Kolmogorov complexity of the god-vs-no-god debate, giving us an upper-bound of the importance of it, as measured in bits-of-entropy. We could then compare that to the bits of entropy in other observed phenomena. Nimur (talk) 05:28, 5 February 2013 (UTC)

While what you say is valid in many arenas, basic-level questions should be welcome here - we don't tell people to read Schroedinger when they ask about quantum teleportation, for example. Also there may be an argument that in modern society, our unspoken assumptions about God have changed so dramatically that the same arguments may not lead to the same conclusions, because our generalizations may not accurately reflect our actual feelings and the range of potential philosophy under which we might evaluate them. Wnt (talk) 15:24, 6 February 2013 (UTC)

This is not a place for religious debates. Why don't we just hat the whole thing? 24.23.196.85 (talk) 05:39, 5 February 2013 (UTC)

Malala, the girl who survived the Taliban's assassination attempt, today called her survival a gift from God. And there's not a soul on earth who can prove her wrong. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:47, 5 February 2013 (UTC)

Being nearly assassinated and surviving? I think I'll pass on gifts from God then thank you very much. Dmcq (talk) 10:30, 5 February 2013 (UTC)

The assassination attempt was a "gift" from evil people. If you would prefer not to survive an assassination attempt, that's up to you. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:46, 5 February 2013 (UTC)

That's the old argument from The God Delusion - why did Our Lady of Fatima not guide the bullet another 20cm that way? Or, more generally, why is there evil in the world? If you assign all evil in the world to "evil people", and all good to god, what stops me from doing the same with communism, or Thor, or the Beach Boys? --Stephan Schulz (talk) 21:47, 5 February 2013 (UTC)

Right, the assassination attempt was by humans because it was evil, whereas the recovery was by God because it was good. Teams of dedicated doctors, sophisticated medical devices, and generous donors obviously had nothing to do with it. Apparently, a 14 year old girl with zero scientific training and minimal scientific knowledge is now the world's sole scientific authority. --140.180.247.198 (talk) 15:51, 5 February 2013 (UTC)

more for us165.212.189.187 (talk) 13:58, 5 February 2013 (UTC)

I would guess the Taleban think they follow God's teaching and British surgeons are in general misguided infidels even, dare I mention it?, atheists and evil has triumphed for the moment in this case by saving her life. Dmcq (talk) 17:10, 5 February 2013 (UTC)

As (it seems to me) usual in these debates, it all hinges on each individual's definition of "God"; and (it seems to me) any such concrete definition can be disproved, the more concrete and specific the easier to disprove. In this case, God defined as the God of the first portion of Genesis. This doesn't lead to any ending, however, if one's definition of God includes transcendence over concrete definition by the human intellect. See Neti neti and Apophatic theology. Gzuckier (talk) 18:09, 5 February 2013 (UTC)

(I have un-hatted this discussion. While some responses have gone off the rails, the question is a valid one and there have been several valid answers.) SteveBaker (talk) 14:14, 6 February 2013 (UTC)

feeling "surreal" or like the world is a fabrication or a simulation

Is this a known symptom of psychosis? This is not a medical question, I just wonder if there are lots of people in society with undiagnosed schizotypal disorders, thanks. 71.207.151.227 (talk) 11:44, 5 February 2013 (UTC)

This is not about the philosophical belief, more like the emotional feeling that people have, i.e. it is a very visceral feeling. 71.207.151.227 (talk) 11:44, 5 February 2013 (UTC)

see Derealization, the reference desk cannot provide a medical opinion or speculation ---- _nonsense ferret 13:00, 5 February 2013 (UTC)

And yes it stands to reason that there are lots of people in society with undiagnosed mental illness. The NIMH found that half of all cases of mental illness begin by age 14, and that " there are long delays — sometimes decades — between first onset of symptoms and when people seek and receive treatment". --TammyMoet (talk) 13:04, 5 February 2013 (UTC)

Why do questions like this make me feel like wikipedia is a potentially endlessly recursive computer platform? μηδείς (talk) 20:44, 5 February 2013 (UTC)

Ask somebody to kick you in the shins, and then get back to us about whether it seemed "real" or not. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:28, 5 February 2013 (UTC)

Whenever I suggest that people accuse me of being cruel! μηδείς (talk) 23:32, 5 February 2013 (UTC)

I might call it the Three Stooges Experiment. If it's real, it hurts. If not, it doesn't. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:40, 6 February 2013 (UTC)

Zycosoil

Please help me by telling me what is the generic name for Zycosoil — Preceding unsigned comment added by 188.245.230.38 (talk) 12:35, 5 February 2013 (UTC)

A Google search shows it is a waterproofing agent. --PlanetEditor (talk) 12:57, 5 February 2013 (UTC)

I need to know what is the generic name for Zycosoil that is manufactured in India.

188.245.230.38 (talk) 13:13, 5 February 2013 (UTC)

It seems to be a fairly unusual product and I'm not sure that there is an agreed generic term for it. It is used to protect soil from water erosion so it could be called a 'soil protective' or an 'erosion preventer', You might find this link useful as it has a video demonstrating the action of Zycosoil. This may be a Language Desk question. Richard Avery (talk) 14:32, 5 February 2013 (UTC)

• Organosilicon compound — See also: [15]   ~:74.60.29.141 (talk) 17:05, 5 February 2013 (UTC):~

Chelating?

Has chelating have any other practicle purposes other than medical? Would the removal of rust be called this . . . or has it another name? — Preceding unsigned comment added by Cousin Bruce (talk • contribs) 13:34, 5 February 2013 (UTC)

Our article suggests it has other uses than medical Zzubnik (talk) 13:46, 5 February 2013 (UTC)

One application they missed is hydrometallurgy: for example, chelating agents can be used to extract boron from seawater, or plutonium from a nitric acid solution of spent nuclear fuel (among many other things)... 24.23.196.85 (talk) 05:22, 6 February 2013 (UTC)

Vacuum of space

does the vacuum of space exert a negative energy on objects in an outward and perpendicular direction to the surface of the objects?165.212.189.187 (talk) 14:06, 5 February 2013 (UTC)

That's sort of a backwards way to look at it. Any object in space, let's say a human who forget his space suit, has some internal pressure (blood pressure is one form of this). On Earth this is countered by atmospheric pressure. Without this, in space, there is an unbalanced outward pressure which causes the person to swell up. StuRat (talk) 14:23, 5 February 2013 (UTC)

Wikipedia says negative energy is "A plot device in fiction" Zzubnik (talk) 14:24, 5 February 2013 (UTC)

OK a positive energy from the negative mass density of space. so the vacuum of space is not exerting outward pressure on the earth? that only applies to objects with inertial outward pressure, (which the earth does not have)?165.212.189.187 (talk) 14:31, 5 February 2013 (UTC)

"Things" have internal pressure. Vacuum of space does not exert a force at this scale. Zzubnik (talk) 14:39, 5 February 2013 (UTC)

So the gravity of earth prevents its internal pressure from exploding like the human without the suit?165.212.189.187 (talk) 15:26, 5 February 2013 (UTC)

Yes, gravity holds it all together. There's also the effect of the solar wind, which tends to blow off lighter elements at the top of the atmosphere, explaining why there is so little free hydrogen and helium in the air, despite those being the most common elements in the universe. BTW, a human in space doesn't explode, he just swells up. StuRat (talk) 15:48, 5 February 2013 (UTC)

Also, the use of the word "Energy" in the question is completely incorrect. Force would've been a much better choice. Energy doesn't have a direction in space and cannot point outward or be perpendicular. Neither does pressure. Dauto (talk) 16:14, 5 February 2013 (UTC)

Thanks for clarifying. Why doesnt gravity hold the human together the same way?165.212.189.187 (talk) 16:52, 5 February 2013 (UTC)

Gravity doesn't by itself help with holding humans together; a man on the moon experiences gravity, but because the lunar atmosphere is practically nonexistent, he'd swell up as if he were in a vacuum. Launch him back into space inside a spaceship, and he'll be safe because of the air inside the spaceship, even though he's experiencing no gravity. It's simply that Earth's gravity holds the atmosphere that prevents us from swelling up. Humans have their own gravity, simply because all matter does, but we're far far too tiny for that gravity to have any practical effect. Nyttend (talk) 17:23, 5 February 2013 (UTC)

But that doesn't explain why the human will swell and the earth doesn't. Also if the swell is an action in the outward direction then what is responsible for stopping the swell. ...object in motion will stay in motion, no?165.212.189.187 (talk) 19:00, 5 February 2013 (UTC)

The same thing which keeps a balloon from exploding when you inflate it. The membranes are strong enough to withhold a certain amount of pressure, but too much pressure would, indeed, cause both to explode. StuRat (talk) 20:00, 5 February 2013 (UTC)

Gravitational forces are proportional to the mass of the object producing it. A person's gravity is simply to week to hold an atmosphere. Dauto (talk) 01:56, 6 February 2013 (UTC)

We should also state that there are other forces which can cause small clumps of matter to stick together in space. There can be chemical bonds, for example. StuRat (talk) 16:50, 6 February 2013 (UTC)

Intermezzo (zolpidem tartrate)

In the past, medications avoided English words as their names, presumably so the pharmaceutical company could protect the trademark copyright more easily. So, why does this med have an English name ? Has something changed ? StuRat (talk) 15:09, 5 February 2013 (UTC)

Hmmm, is that more English than Allegra? Wnt (talk) 15:37, 5 February 2013 (UTC)

I don't speak Italian, yet know what "intermezzo" means. So, to me, that means it has now become an English word, like "pizza". StuRat (talk) 15:51, 5 February 2013 (UTC)

If they thought that avoiding English words as drug names helps to protect trademarks (note: not the same thing as copyrights - there are no one-word copyrighted works) then they don't understand trademark law. Apple (the computer), Genesis (the band) and Mercury (the car) have no trouble protecting their trademarks. Mostly the name choices reflect style. You can look at the drug names "Dr. Bateman's Pectoral Drops" and "Lipitor" and figure out roughly when they were introduced. --Guy Macon (talk) 18:54, 5 February 2013 (UTC)

Who are "they"? The medications? --Trovatore (talk) 03:13, 6 February 2013 (UTC)

Yes. --Guy Macon (talk) 11:25, 6 February 2013 (UTC)

microbiology

Principles of pregenancy test — Preceding unsigned comment added by 93.186.23.89 (talk) 15:21, 5 February 2013 (UTC)

Information about different types of pregnancy tests and the principles by which they operate can be found in the Wikipedia article pregnancy test. TenOfAllTrades(talk) 15:29, 5 February 2013 (UTC)

Live double-headed eagles

Has a live double-headed eagle (or the body of a dead one) ever been recorded, as far as Reference Deskers know? I know that conjoined twins have been found in multiple non-human mammalian species, and I'm pretty sure that I've read about them in other chordates (amphibians, perhaps?), so I don't imagine that it would be completely impossible for the same phenomenon to appear in birds. Google gave exactly eight results, and they were either "I'll buy you a live double-headed eagle for your birthday!" or lists in which "live" happened to be right before "double" etc. Nyttend (talk) 17:18, 5 February 2013 (UTC)

Gah. I'm sure I saw an exhibit of a double-headed eagle at the Odditorium in Blackpool when I was a child. However, I don't think you can search the "Believe It Or Not" website to try and find it. Maybe someone more computer savvy than I can find it. Anyway, thanks for getting me to a site I'd been meaning to find for some time. I may be some time! --TammyMoet (talk) 18:26, 5 February 2013 (UTC)

A huge number of those kinds of things are faked by clever taxidermists. I don't think "having seen one" really tells us much either way here. SteveBaker (talk) 20:32, 5 February 2013 (UTC)

There are a number of images of two headed birds on the internet which may or may not be genuine. This one looks kosher though. Richerman (talk) 20:45, 5 February 2013 (UTC)

Double-headed eagle is a very well known symbol in European heraldry. It's been on the coats of arms of numerous countries, and is currently on the national flags of Albania, Serbia and Montenegro. Countries tend not to have mythical animals in their symbology, so I'm assuming it had some real basis. -- Jack of Oz ^[Talk] 22:00, 5 February 2013 (UTC)

Unicorns, dragons and phoenixes have all been used in European heraldry. I take it the OP is referencing double-headed snakes? CS Miller (talk) 22:32, 5 February 2013 (UTC)

Huh? I'm looking for members of the family Accipitridae (I suppose I'd accept non-eagles from that family) with two heads, in part because I'd already looked at the article Jack links, and I observed that it doesn't discuss the existence or nonexistence of individual members of this family that appeared to have two heads. Snakes hadn't even come to mind; I can't remember ever hearing of a two-headed snake. Nyttend (talk) 23:00, 5 February 2013 (UTC)

See polycephaly and here. I remember reading or hearing that two-headed carnivores usually attack each other, which would explain the lack of such birds. μηδείς (talk) 23:40, 5 February 2013 (UTC)

Two headed carnivores usually attack each other? - you can't be serious! Richerman (talk) 00:40, 6 February 2013 (UTC)

I certainly can be serious that I remember hearing, I think it was about turtles, that they would bite each other. If I had a reference (probably one of those 10 most craziest critters shows) I'd give it but it's not the sort of thing I keep files on, sorry. Lol. μηδείς (talk) 01:05, 6 February 2013 (UTC)

Hmmm - my fault for editing when I've been to the pub I suppose. However, a lot of people believe nonsense like that - you should make it clear with that sort of comment that it's a joke. Richerman (talk) 06:37, 6 February 2013 (UTC)

No, it wasn't a joke. The heads supposedly peck at each other. Did you think I meant various two-headed carnivores seek out other two-headed carnivores to battle? μηδείς (talk) 17:57, 6 February 2013 (UTC)

No, I thought that "it would explain the lack of such birds" meant that the two heads always fight to the death, which sounds rather like something from an ancient Greek myth. Richerman (talk) 18:49, 6 February 2013 (UTC)

That only happens in WWE. μηδείς (talk) 03:49, 7 February 2013 (UTC)

Black sky at night

Given that there are "billions and billions" of stars and that light (obviously) travels at the speed of light, why do we see so much "black" in the night sky rather than filled with starlight? Thank you. Rdhartwell (talk) 21:04, 5 February 2013 (UTC)

Black#Why the night sky and space are black - Olbers′ Paradox --Guy Macon (talk) 21:12, 5 February 2013 (UTC)

More to the point, Olbers' paradox. --Jayron32 21:25, 5 February 2013 (UTC)

The universe is finite and expanding, which explains why it is not infinitely bright in all directions, but it does glow in all directions, see cosmic background radiation. μηδείς (talk) 23:42, 5 February 2013 (UTC)

The universe is not in fact known to be finite. See shape of the universe. (The observable universe is finite, but that's different.) --Trovatore (talk) 03:04, 6 February 2013 (UTC)

Yes, and neither is the Flying Spaghetti Monster not known to exist. There's no evidence its infinite, nor even any coherent way of formulating claims about an infinite universe. μηδείς (talk) 17:51, 6 February 2013 (UTC)

Medeis, that's just completely wrong. There are definitely coherent ways of formulating claims about an infinite universe. In Riemannian geometry, it's no more difficult to talk about an infinite universe than a finite one.

As for evidence: The simplest models having nonpositive curvature are infinite, and there definitely is evidence of nonpositive curvature. Whether that evidence is compelling or not at the current time, I can't speak to, as I'm not really up to date on that. But evidence certainly exists.

Now, there are models with nonpositive curvature that live on a compact manifold (that is, finite universe), but they're weird. They're things like a solid dodecahedron with opposite faces identified. Why the universe should have that topology would be more in need of explanation than why it should be infinite. --Trovatore (talk) 21:09, 6 February 2013 (UTC)

I am quite aware there are models which use infinity as a factor. None of them has a real or concrete interpretation. If the universe is "infinite", then however big it actually is, it is even bigger than it actually is. Among other things that means atoms have no size or charge in relation to the universe. That's fine if you want to play such linguistic games, but there's no evidence for it. μηδείς (talk) 00:27, 7 February 2013 (UTC)

You're not making any sense, Medeis. However big it actually is, it's even bigger than that??? What's that even supposed to mean? If the size of an atom is not as large as any finite submultiple of the size of the universe, then why is that bad? Mathematics is perfectly capable of handling infinities as first-class objects, and it is perfectly plausible that the universe could be an example of such. As for evidence, I already addressed that, and you haven't responded to my specific points. --Trovatore (talk) 01:21, 7 February 2013 (UTC)

Medeis is definitely wrong here. In standard cosmology, the universe is qualitatively different if its total energy density is above, equal to, or below a critical threshold. If it's above the threshold, the universe has positive curvature, and must be finite. If it's at the threshold, the universe has 0 curvature and is flat--that is, its geometry is very nearly Euclidean--which implies an infinite universe If it's larger, the universe has negative curvature and must be infinite. This model holds as long as we assume that the universe is nearly uniform at large scales (the cosmological principle). It is indeed nearly uniform within our observable universe, but whether it's uniform elsewhere is not a testable question. As for how an infinite universe can expand, imagine the set of natural numbers: 1, 2, 3, 4... This set is infinite. Now multiply every element by 2, and you can 2, 4, 6, 8... The set has expanded by a factor of 2, and is still trivial to describe. As another example, imagine a large sheet of rubber that's being stretched in all directions. The distance between any two points on the sheet will increase with time, and even if the sheet were infinite, the expansion would still be perfectly well-defined.

Trovatore is not correct in saying there's evidence of nonpositive curvature. Our best value for the curvature is 0, to within 0.4% (see shape of the universe). The fact that the universe is so remarkably flat, along with a few other problems, inspired inflation theory, which current cosmological experiments are trying to test for. --140.180.247.198 (talk) 03:30, 7 February 2013 (UTC)

My understanding is that there are some surveys that come up with a positive number and others with a negative number, isn't that so? In that case, there is evidence of nonpositive curvature (namely the studies that show the negative number). I never asserted that it was the current best hypothesis that the curvature is nonpositive; I don't need to assert that, because Medeis was claiming there was no evidence the universe is infinite, which is not so. --Trovatore (talk) 03:38, 7 February 2013 (UTC)

Oh, and by the way, zero is nonpositive :-) --Trovatore (talk) 03:48, 7 February 2013 (UTC)

The best available measurements indicate the curvature is 0, to within a small margin of error. That means there's roughly 50% chance of the actual curvature being positive, and 50% of it being negative. Whether you call that "50% evidence that the curvature is negative" or "100% evidence that we don't yet know" is a matter of semantics. --140.180.247.198 (talk) 04:42, 7 February 2013 (UTC)

Yes, but semantics are important, especially in this sort of case. There's a big difference between "there's no evidence that proposition A is true" and "the evidence that proposition A is true, and that it's false, is roughly balanced". --Trovatore (talk) 04:46, 7 February 2013 (UTC)

Yeah - Olbers' paradox is the answer here. It goes something like this:

• The light from a distant object attenuates as the square of the distance between us...a star at distance 2X is four times dimmer than a star at distance X.
• The number of stars (galaxies, whatever) within a distance X is (on average) four times smaller than the number at distance 2X.

So this growth in the number of stars over distance is exactly compensated for by the reduction in light over that distance...but...

• The amount of dust and gasses attenuating that light is (on average) proportional to the distance to the star ('X') - and therefore the amount of light they absorb is also proportional to X. So the further you get away from here - the less light there is (in total) coming from the stars at that range.

That sounds like it solves the problem...but sadly, no. Things are more complicated than that...

• Those intervening dust and gas clouds are heated by the incoming light - and will eventually heat up and glow - emitting the same amount of energy that they absorb. So, again, we should have an infinitely bright sky.

The resolution of this problem relates to redshift. The universe is expanding - so the frequency of light from distant objects has longer and longer wavelengths - so visible light is converted into microwaves and longer wavelengths. The "cosmic background radiation" is where that light ends up - and the sky is indeed filled with that radiation (although, interestingly, it's kinda patchy).

Stars that are sufficiently far away are retreating from us at faster than the speed of light (because of the expansion of the universe) - so their light can never catch up with us anyway.

SteveBaker (talk) 14:10, 6 February 2013 (UTC)

Steve, you were just fine until your last sentence. Light just doesn't work that way. Even if it was possible for anything to travel faster than light (it isn't in our current understanding of the universe), if you had a flashlight moving away from you at twice the speed of light, it's radiation would still reach you, because the speed of light in a uniform medium is constant. Of course, as you mentioned, it would be very redshifted so your eyes couldn't see it, but it would still be moving at the speed of light. Another example: the light from the headlamp of a speeding train isn't moving any faster than the light from your computer screen, or any other light traveling through air on Earth. —Rutebega (talk) 03:48, 7 February 2013 (UTC)

You're thinking in special-relativistic terms. Light that originates from beyond the horizon of the observable universe, from our point of view, will indeed never reach us. In any local inertial frame containing those photons, sure, they're moving at c, but it doesn't matter because such an inertial frame cannot be extended out to our position. --Trovatore (talk) 04:13, 7 February 2013 (UTC)

First, it's not true that things with a recession velocity larger than c are invisible. The recession velocity of the CMBR is about 3c and we can see it. Second, dust does absorb starlight in the real world. Only in a steady-state universe would it have to be in equilibrium with the starlight (although arguably everything would have to be in equilibrium - I'm not sure how steady-state cosmologies solved that problem).

The size of the observable universe increases with time. If not for the accelerating expansion, light from arbitrarily far away would eventually reach us. In the accelerating universe there is a genuine horizon beyond which nothing is ever visible. However it's far from certain that that model is correct; the universe could still recollapse. -- BenRG (talk) 05:01, 7 February 2013 (UTC)

OK, fair enough. There seem to be two roughly complementary notions that, at least naively, could be called "the observable universe", and I'm probably using the wrong one (i.e. the one not standardly called by that name). --Trovatore (talk) 06:14, 7 February 2013 (UTC)

Economic growth , what curve?

We are constantly told that economic growth is brilliant for us (I think it's to do with GDP?)

However what kind of growth are they implying? Linear? Exponential? Does it head towards a limiting value?

(edit) Also if it IS Exponential won't that be completely unsustainable and almost a joke that economic growth is even talked about as a fact?

Ap-uk (talk) 21:35, 5 February 2013 (UTC)AP

If you get "X" number of economists to answer this question, you're likely to get "X+1" different answers. If economists knew what drove the world economy towards a positive outcome with any certainty, we'd have been there yesterday. --Jayron32 21:37, 5 February 2013 (UTC)

(from op) If it is exponential and say 3% growth I see a problem with sustaining it now as the Wikipedia article sites 1830 as a start date [[16]] . At 3% we would get doubling every 23 years and it's the old wheat on a chessboard problem [[17]] as we now are getting onto the second row where the next 23years growth must equal the sum of all that has gone before in order to grow.

Except it's not a problem, because 1) nobody's saying exponential growth can continue forever, and 2) due to inflation, you have to distinguish between growth in real and nominal terms. If the inflation rate is 2%, that means all money in the country will be worth 2% less next year. Even if the economy produces exactly the same amount of goods and services next year, its nominal growth rate will still be 2%, even though real growth is 0%. --140.180.247.198 (talk) 23:52, 5 February 2013 (UTC)

Can exponential economic growth (which of course refers to real GDP) continue forever? The answer is unknown, but here are some considerations. Malthusianism was the idea that population grew exponentially while food supply grew just arithmetically, so soon there would be mass starvation that would prevent the population from continuing to grow exponentially. The reason that was wrong (at least up to and including the present) is that it ignored technological change -- the amount of food that we know how to get out of a given amount of land itself grows exponentially. This reality of technological progress applies more generally to our ability to produce the variety of things that go into GDP -- this ability has grown exponentially. The question is whether that can be sustained even in a world with finite resources. The answer to resources running out has so far been to figure out different ways of sustaining and exponentially increasing production by shifting away from the declining resources and into currently plentiful resources. A key example right now has to do with energy: the petroleum is going to run out at some point (though predicting when is enormously difficult), but we are in the process of learning how to use solar, hydrogen fusion, etc.

The question of whether resource constraints will ultimately put a cap on world-wide output is up in the air. But never assume that human ingenuity is going to run out -- it has given us a trend of long-term exponential growth so far, and so far the optimists have been right. Duoduoduo (talk) 15:49, 6 February 2013 (UTC)

An interesting question... I won't pretend I have an answer. I wonder, for example, if there is some kind of "social entropy" that increases over time, so that the GDP can increase despite no real increase in resources. (i.e. Year 1 you own cows, the next year you own cows and iron on the same land with the same resources ... eventually you add shares in a radio station, copyright on a song, a set of collectible trading cards, a digital telephone, a paint-spattered canvas that art appraisers say is worth something, some Bitcoins, an audience of 30,000 following your blog, etc. Yet it's the same land and you still eat the same amount) Wnt (talk) 19:57, 6 February 2013 (UTC)

All of this is assuming humans stay on Earth. Remember that for all practical purposes, the universe has infinite resources, and starlight is a source of infinite energy. --140.180.247.198 (talk) 00:26, 7 February 2013 (UTC)

Burnt stew

I have a 32 quart stainless steel stock pot in which I made some stew from chicken, potatoes, onions, green beans, baby carrots, corn, dried beans, etc. I filled it almost to the top, and boiled it vigorously over an open flame. I left it uncovered, since this prevents boiling over and I don't mind the heat and humidity in winter. Everything went well the first day, and the pot was still half full by night (maybe 1/4 boiled off and 1/4th was eaten). So, I covered it and left it to cool. Early the next morning, it was still warm, and I turned the flame back on. Then I detected a burning smell. So, since the pot was still half full, something must have adhered to the bottom and started to burn. Is there any way to prevent this, other than constant stirring ? Would it have helped if I oiled the pot before using it ? Should I have left the dried beans out ? StuRat (talk) 23:17, 5 February 2013 (UTC)

How does leaving it uncovered keep it from boiling over? ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:22, 5 February 2013 (UTC)

Covering a pot retains the heat that would otherwise be lost as the water vapor leaves the pot, allowing heat to build to a point where it boils over, right after knocking the lid askew. Leaving it uncovered prevents this (of course, an uncovered pot still can boil over, but this requires a significantly higher flame). StuRat (talk) 23:32, 5 February 2013 (UTC)

Put a saucepan nearly full of water on a burner of your stove, turn on the heat, watch it boil, and tell me that it doesn't boil over. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:30, 6 February 2013 (UTC)

As I said above, there is some level of flame which will cause even an uncovered pot to boil over. It being filled near to the top makes this worse. But, an uncovered pot has a wider range of thermal equilibrium, where more flame leads to more heat being lost from the top, thus keeping the temperature in check.

Incidentally, I have another stock pot, filled with water near the top, which is heated on low flame, uncovered, as a way to add humidity to the house. It has never boiled over (or boiled at all), but likely would have had I covered it. StuRat (talk) 16:41, 6 February 2013 (UTC)

My guess is that after you removed the heat and left it overnight, the ingredients compacted on the bottom and more and more as time went on, with the moisture at the layer touching the bottom of the pot reducing. In the morning when you turned the flame back on you were essentially heating rather dry ingredients which promptly burned. If you had given the pot one thorough stir (as opposed to constant stirring) before turning the flame I think you might have avoided the problem.--Fuhghettaboutit (talk) 23:42, 5 February 2013 (UTC)

Yes, one stir on reheating was all that was necessary. μηδείς (talk) 23:44, 5 February 2013 (UTC)

OK, I'll try that tomorrow. StuRat (talk) 00:15, 6 February 2013 (UTC)

I can confirm the phenomenon that leaving a pot uncovered prevents it boiling over. I always thought this was due to the pressure-cooker effect where higher pressure leads to higher temperature thus faster boiling. (Rhetorically) where do you live? That stew really sounds nice from here!

Detroit. I'll leave a bowl on the porch for you. :-) StuRat (talk) 16:43, 6 February 2013 (UTC)

There is another possible effect of leaving the lid off that would prevent boiling over: reducing the lifetime of bubbles. This is very easy to observe when boiling pasta; with the lid on, the water vapor is retained, keeping the humidity high. The bubbles formed when a protein solution is boiled last longer in a high humidity environment. When you take the lid off, the local (absolute) humidity drops to nearly the same as the room, the bubbles pop much sooner and the foamy layer shrinks. --Wcoole (talk) 22:12, 6 February 2013 (UTC)

Yes, a question of the partial pressure of the water vapor. μηδείς (talk) 00:20, 7 February 2013 (UTC)

Agreed. When you take the lid off a boiling pot of pasta full of foam, the foam collapses immediately. StuRat (talk) 00:23, 7 February 2013 (UTC)

February 6

Law of excluded middle, null hypothesis redux

I have to ask this question again because it wasn't answered and was actually side tracked by a discussion I didn't intend. Long story short, can something be true, without it being proven? ScienceApe (talk) 01:34, 6 February 2013 (UTC)

How would you prove that it hurt if I kicked you? Can you prove that existence exists without referring to anything which exists? There are axioms, and perceptions, neither of which can be proven true, but both of which are assumed veridical. The law of the excluded middle is also axiomatic--it is the basis for any proof, but cannot itself be proven without assuming its own truth. μηδείς (talk) 01:43, 6 February 2013 (UTC)

(ec) :If you believe in philosophical realism, you pretty much have to believe that the answer is yes. --Trovatore (talk) 01:44, 6 February 2013 (UTC)

You might also look at foundationalism and coherentism, both of which are true. Whereas skepticism is a self-refuting idea. μηδείς (talk) 01:48, 6 February 2013 (UTC)

Additional concepts to consider: [David] Hume's Law (a.k.a.: Is–ought problem derived from: Fact–value distinction. For an in-depth exploration of proof vs. truth as it relates to logical constructs and string theory, (etc.) - look into Gödel's In/Completeness theorem. ~Eric _the Read 74.60.29.141 (talk) 02:01, 6 February 2013 (UTC)

Should we treat Hume's theory as true? μηδείς (talk) 02:07, 6 February 2013 (UTC)

Maybe you ought to. ~E:74.60.29.141 (talk) 02:35, 6 February 2013 (UTC)

:) ---- _nonsense ferret 03:03, 6 February 2013 (UTC)

(edit conflict)    I believe the bottom line of this discussion will depend on the definition of "truth", and the answer will be "yes/no". Can truth apply to itself? 74.60.29.141 (talk) 03:14, 6 February 2013 (UTC)

Define "prove". ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:28, 6 February 2013 (UTC)

The question is nonsense as are the "answers". If there's no such thing as truth, it isn't true there's no such thing as truth. If there's no such thing as proof, there's no proof there's no such thing as proof. This thread is ready to destroy itself. μηδείς (talk) 03:35, 6 February 2013 (UTC)

Such is the nature of Existence theorem: An existence theorem may be called pure if the proof given of it doesn't also indicate a construction of whatever kind of object the existence of which is asserted. (see also: Existential instantiation) ^>poof!< _{74.60.29.141 (talk) 03:48, 6 February 2013 (UTC)}

If you say "I'm thinking of ___", and if you're really thinking of that, it's true, but there's no way to prove it. Quite obviously the answer is yes. Nyttend (talk) 04:05, 6 February 2013 (UTC)

Unfortunately, that's not a very defensible example, because once the question is asked, you are thinking of   "thinking of ____" - and you can immediately see the problem of recursive self-reference. -Thus the answer is both "yes" and "no" simultaneously. 74.60.29.141 (talk) 04:26, 6 February 2013 (UTC)

Very well to be pedantic about it; what about "I was thinking about __ two minutes ago", or what if you're in out in the woods by yourself (no cameras around) and see a leaf fall; you can't prove that you saw it fall, but it still fell. Nyttend (talk) 04:35, 6 February 2013 (UTC)

By the definition of "that which conforms to reality", it would indeed be true that the leaf fell (assuming that it actually did, which it didn't, since you just made-up that example).  ;) ~:74.60.29.141 (talk) 05:06, 6 February 2013 (UTC):~

I said that the hypothetical you is claiming to have seen it fall; since I live in the woods by myself, I'm frequently able to see things happen, and it's easy to prove that they happened, but impossible to prove that I was watching when they happened. It's simply common sense, just like denying the paradoxical nature of the first two of Zeno's paradoxes that we list; we need not make an answer more complicated that the one given (according to the paradoxes article) by Diogenes the Cynic. Nyttend (talk) 05:26, 6 February 2013 (UTC)

(edit conflict) ~ If you define truth on a case-by-case basis such that there are an infinite number of definitions and an infinite number of proofs (e.g.: the leaf proved to you that it fell) - then the answer is "yes". ~:74.60.29.141 (talk) 05:31, 6 February 2013 (UTC):~

• "All I know is that I don't know nothing" --Jayron32 06:00, 6 February 2013 (UTC)

(edit conflict) ←again ~:74.60.29.141 (talk) 06:07, 6 February 2013 (UTC):~   ~ Before I wrap my brain around a cup of hot chocolate with peppermint schnaps and head off to the realm of dreams where nothing and everything is true...

"Believe those who are seeking the truth. Doubt those who find it." ~André Gide^[18]

Now that one I like. It's going into my list of quotes and anti-quotes. -- Jack of Oz ^[Talk] 06:51, 6 February 2013 (UTC)

Suppose we constrain the question to only axiom-based formal logic systems, such as mathematics, where "truth" and "prove" can be concretely defined using the structure of the system. Then according to Godel's incompleteness theorem, it is generally the case that one can write true statements using the logic of the system that nonetheless can never be proven to be true using the axioms and methods provided by the logic system. In this sense, in most logical systems (including mathematics) there exists statements which are true or false, and yet can not be proven to be true or false. The truth of such statements is essentially unknowable. So, if you model your worldview after formal logic, then it is generally the case that there will be things that are true (or false) and yet which can never be proven to be true or false. I think this comes as close to answering the original question as possible without going off and fretting about poorly defined subjective philosophies. Dragons flight (talk) 06:17, 6 February 2013 (UTC)

The incompleteness theorems certainly make it more difficult to sustain the notion of truth-equals-provability in mathematics specifically. There are those who make the effort; intuitionists, for example, identify truth with provability, but they do so by disidentifying provability with provability in any specific formal system.

I would be cautious, though, about generalizing that observation to more quotidian sorts of truth and provability. The Goedel theorems are specific to a particular sort of proof, namely proof in first-order logic from a computably enumerable collection of axioms strong enough to interpret Robinson arithmetic there are extensions to other sorts of deductive system, but that would take us rather far afield. So while I agree that a statement doesn't have to be proved in order to be true, I don't think the Goedel theorems are the best argument to make in non-mathematical situations. --Trovatore (talk) 08:43, 6 February 2013 (UTC)

There are problems like the Halting problem which says that you cannot (in general) produce a procedure that will reliably prove whether a particular computer program will or will not eventually finish running. Whether a particular program will eventually halt is a simply boolean fact - it's true or false - but no algorithm that a Turing machine (a computer, in other words) can execute will tell us which it is. This is similar to Godel's incompleteness theorem - where there are theorems in mathematics that mathematical thinking can neither prove nor disprove.

Now...the critical question is whether a computational engine that's (logically) more sophisticated than a Turing machine could (perhaps) solve the halting problem - or whether some form of logical thinking that's outside the realms of the mathematics that Godel's theorem addresses could resolve the truth or falsehood of all mathematical theorems. As far as we know, there are no such ways of thinking. It appears that human brains are turing machines - and the "Church-Turing" theorem says that all turing engines are logically equivalent. So we're doomed to being unable to resolve the halting problem - and (in all likelyhood) unable to escape Godel's incompleteness trap.

Is it possible that some higher realms of logic/computation might exist? Maybe - but Godel and the Turing engine argument says that humans can never possibly find or comprehend it.

So the answer to ScienceApe's original question is "Yes!"

SteveBaker (talk) 13:49, 6 February 2013 (UTC)

I guess the opposite is true too, some things can be proved and yet not be true, or at least lots of people think they have proved them but I of course know they are untrue. ;-) Dmcq (talk) 14:41, 6 February 2013 (UTC)

That's just a matter of error though. The thing can obviously be untrue even though there is an erroneous proof out there that (incorrectly) said it was true. But for a correct proof with all of the i's dotted and t's crossed, then there obviously can't be something that's proven to be true that really isn't because that belies the very definition of the word "proof" - meaning "absolute certainty". SteveBaker (talk) 17:56, 6 February 2013 (UTC)

You can certainly have a valid proof of a false statement, if you start with false axioms. (And yes, axioms can certainly be false. For example the axiom of determinacy is false, though useful.)

The halting problem has a somewhat different set of issues from the Goedel theorems (which I discussed above; did you read it?) as a reason to accept that truth is different from provability. What the undecidability of the halting problem says is that there is no fixed algorithm that can correctly decide the halting or non-halting of all Turing machines. It doesn't say assert, for any specific Turing machine, that there is no way of knowing whether it halts. --Trovatore (talk) 20:09, 6 February 2013 (UTC)

Touch one part of your body, feel it elsewhere

I was going through the Allochiria article and it made me wonder if this is similar to touching one part of your body and then feeling it elsewhere. I've seen this discussed elsewhere, like on this forum. Ok, so two questions: is there an actual word for that phenomenon (touch/scratch/whatever one area of the body and feel it elsewhere)? There is a reverse phenomenon that someone mentions at the bottom of that forum, which is, you feel an itch in one area, but scratching it doesn't relieve it because the itch is actually elsewhere.

Okay, second question is, is this the same thing used in the children's trick where Person A closes their eyes and holds their arm out. Person B slowly tickles their arm from the wrist up toward the elbow (the inside bendy part — cubital fossa). Person A is supposed to point out when Person B's reached the center of their elbow, but Person B won't have... sort of like an "optical illusion" for touch. Hopefully that makes sense. Reflectionsinglass (talk) 05:53, 6 February 2013 (UTC)

I'm not sure if there's a term for general touch, but there is a concept known as Referred pain which is very similar to your first question. --Jayron32 05:59, 6 February 2013 (UTC)

Somewhat related is when somebody has a phantom limb. That is, they still feel pain or itchiness or other sensations coming from a limb which is no longer present. The nerves continue to fire even though they no longer extend all the way to their original locations. StuRat (talk) 06:01, 6 February 2013 (UTC)

Hmmm... I would add to the examples a sore gum by the second molar that creates a pain along the rim of the ear, and an unpleasant sensation from the navel that can affect the tip of the penis. These match the Straight Dope examples in terms of target, but seem outside or at least poorly specified by the classic dermatomes --- I wonder if someone has totted up enough anecdotes to tell whether there are certain specific regions of the brain that "attract stray nerves" or something...? Wnt (talk) 15:17, 6 February 2013 (UTC)

Only slightly related but I've noticed that occasionally, based on factors I can't figure out, the actual and perceived place a mosquito pierces my skin are not quite the same place. They can be several centimetres apart. No idea what is going on there but it struck me that it would be a useful risk reduction technique for a mosquito to have evolved. Sean.hoyland - talk 17:26, 6 February 2013 (UTC)

I think that's just due to having few nerves in those areas (as opposed to fingertips, your tongue, etc.). With larger objects, which trigger multiple nerves, it's not a problem. However, a small object that triggers a single nerve could be anywhere in the area that nerve covers. StuRat (talk) 17:37, 6 February 2013 (UTC)

The problem there is that I've only observed it for mosquitoes. None of the many other small biting and stinging insects, some of which are tiny, seem to produce the same effect, although admittedly they don't have the precision of the mosquito. Sean.hoyland - talk 18:06, 6 February 2013 (UTC)

There's an experiment where you close your eyes, and have a friend poke you with either one or two pins, and you tell them if it's one or two. They try at different locations and with different distances between the two. It turns out that the distance at which you can't tell two pins from one is much greater in areas like the arms, where there are fewer nerve endings. StuRat (talk) 21:10, 6 February 2013 (UTC)

• ghost limb. μηδείς (talk) 21:06, 6 February 2013 (UTC)
  • A Henny Youngman classic: "Guy goes to a doctor. Says, 'Everywhere I touch it hurts!' Doctor says, 'Your finger's broken!'" ←Baseball Bugs ^{What's up, Doc?} carrots→ 22:48, 6 February 2013 (UTC)

Thanks all for the replies! I'm not thinking of phantom/ghost limbs for sure. My own experience with this (hopefully without turning this into a medical issue) is that if I tickle the inside of my right elbow, the back of the inside of my right tongue tickles like you wouldn't believe (have to trill my tongue forever to get it to itch). I have other examples too. Someone once told me that's how acupuncture works (and incidentally that's mentioned in the forum I linked to above). That article doesn't go into it, unfortunately (because it's unknown?). Jayron32's "referred pain" may be the closest relevant answer so far: and its "the mechanism of referred pain is unknown" quote leaves me to think that may be the same thing here. I'll keep checking back for any other replies! Reflectionsinglass (talk) 09:08, 7 February 2013 (UTC)

single slit - interference in a slit

If you hold your index finger and ring finger close together and look through the little slit between them at some light, you see dark lines parallel, you can see dark lines parallel to the sides of your fingers. Undoubtedly this has something to do with the wave nature of light, interfering with itself. But this is a single slit - not a double slit. Why do you see the dark lines? Bubba73 ^{You talkin' to me?} 06:19, 6 February 2013 (UTC)

Diffraction#Single-slit diffraction. --Jayron32 06:20, 6 February 2013 (UTC)

I'm skeptical that diffraction comes into play here -- but I don't really understand the description of the phenomenon. Where are those dark lines? Looie496 (talk) 06:36, 6 February 2013 (UTC)

I agree; diffraction/interference is not a very plausible explanation, as the patterns would be on the order of thousands of wavelengths, and the light source is neither spatially nor chromatically coherent. But so then what *is* the explanation? I'm curious too. --Trovatore (talk) 06:51, 6 February 2013 (UTC)

It sounds like you are describing the Black drop effect.

Here is a paper with a far better picture of it our article has: http://metaresearch.org/home/viewpoint/blackdrop.asp

Here is a video demonstrating it with fingers: http://www.youtube.com/watch?v=wylnvUor4Z0

Here is another paper on it: http://www.rasc.ca/sites/default/files/DuvalBlackDrop.pdf

Here is a 1922 paper that shows the parallel lines that you describe (figures 14 through 18): http://www.bo.astro.it/~biblio/Horn/Blackdrop.htm

If you look at the above links and the links in Black drop effect, you will not only see an explanation, you will see several mutually contradictory explanations! Who could ask for more?

--Guy Macon (talk) 07:32, 6 February 2013 (UTC)

Nicely sourced explanation, @Guy Macon. Related question: how many Wikipedia editors monocularly occluded their own vision today reproducing this two-fingered effect? — Preceding unsigned comment added by Senra (talk • contribs) 14:35, 6 February 2013 (UTC)

Also interesting; do the same thing against a dark background with a bright light illuminating your fingers. --Guy Macon (talk) 18:56, 6 February 2013 (UTC)

I estimate that the width of the slit between my fingers is less than 0.001 meter and there are several of the lines visible. So I estimate that the lines are about 10^-4 meters apart - on the order of 200 times the wavelength of visible light. I'm not sire about the Black Drop explanation since it connects things and these lines are discrete. Bubba73 ^{You talkin' to me?} 18:18, 6 February 2013 (UTC)

Did you look at figures 14 through 18 of the 1922 paper? --Guy Macon (talk) 18:56, 6 February 2013 (UTC)

Yes, I did, but there is only one line in there whereas there multiple lines (ten or so) in the finger slit. In the figures it looks like that line is in the process of making the black drop. I can see the black drop effect in the finger slip, and these lines don't seem to have anything to do with it. Bubba73 ^{You talkin' to me?}

More like 20 or so lines. Bubba73 ^{You talkin' to me?} 02:34, 7 February 2013 (UTC)

Let me describe what I see: When I hold two fingers in parallel, try to make the slit as thin as possible, and look at a lamp shade (bright but not blinding), I see many fine parallel dark lines in the opening, parallel to the slit. As I move the fingers apart, the lines seem to get thinner until they fade away. As I move my fingers closer together, the lines get thicker, until at some point there is no transparent lines between them and the block the light. Because my fingers are not perfectly straight, some part of the slit gets blocked first in what looks to me exactly like the black drop effect. When I do the same with the tips of my thumb and index finger I see one "line" that looks like the figures in the 1922 paper.

All of the above are through the top of my bifocal glasses, meaning that the fingers are out of focus. When I look through the lower lenses, the many-lines effect vanishes and I can get the fingers much closer before I see a classic black drop with no lines. If I move my fingers far enough away that the lower lenses can't focus, I think I see lines, but it s hard to make out -- I need longer arms.

It looks like an interference pattern to me. Given the fact that I am using a "camera" made out of jelly, I'm surprised that it works as well as it does. --Guy Macon (talk) 03:31, 7 February 2013 (UTC)

I agree with your description (including the thumb and index finger) and it is the same with different types of indoor lighting. If it is interference, what causes it - perhaps reflections off both of the two fingers? The black drop article says that the effect is due to the atmosphere and optics, but that doesn't seem to be what is going on here. Bubba73 ^{You talkin' to me?} 04:55, 7 February 2013 (UTC)

My best guess is that I am seeing a combination of black drop effect, which isn't very well understood, and an interference pattern. My theory about the interference pattern is that the slightly out-of-focus fingers have a region where the blurry edges of the fingers overlap, thus allowing an interference pattern. A good experiment for investigating this would be to use a high-quality digital camera to take a picture of the finger slit, with the fingers in sharp focus and out of focus. --Guy Macon (talk) 06:08, 7 February 2013 (UTC)

It might take some work to photograph it. When I hold my hand at arm's length, the fingers are in focus but I can still see some lines. Bubba73 ^{You talkin' to me?} 06:13, 7 February 2013 (UTC)

POM application for ethanol

Is POM compatible to 30% ethanol mixed Fuels. — Preceding unsigned comment added by 115.254.23.116 (talk) 07:10, 6 February 2013 (UTC)

What's POM? 24.23.196.85 (talk) 07:13, 6 February 2013 (UTC)

http://www.broadlandmemories.co.uk/blog/wp-content/uploads/2010/10/pomadvert_1949.jpg --Guy Macon (talk) 07:39, 6 February 2013 (UTC)

From POM and a quick search, I'm guessing Polyoxymethylene [19] Nil Einne (talk) 07:51, 6 February 2013 (UTC)

In that case, it should be compatible with ethanol at any concentration. 24.23.196.85 (talk) 08:54, 6 February 2013 (UTC)

pKa-value in the medicine substance articles?

Hi,

what do you think about putting systematically pKa-values in the articles of medicine substances?

For example into the table that contains all the basic information (formula, mol. mass...)

194.100.75.169 (talk) 12:58, 6 February 2013 (UTC)

This is an article editing question that should be proposed somewhere else - you might start with the talk page of the specific compound that you have in mind, and the WP:navigational template that it uses. Of course, many medical compounds are acids and have pKa values, but there could be other components of the pill (inert excipients); they may not be pure chemicals. If they are pure chemicals, likely the article has a Template:Chembox or the like that can be filled in. Wnt (talk) 14:59, 6 February 2013 (UTC)

It should be noted that every compound with a hydrogen has a putative pKa value... --Jayron32 17:00, 6 February 2013 (UTC)

Hmmm, what's the pKa of lithium hydride? :) Wnt (talk) 19:50, 6 February 2013 (UTC)

Fair enough, but only because there are no known "lithides" to compare to. There are known examples of other Alkalides, so one could calculate the putative pKa of any other alkali-hydride compound. That doesn't mean that lithium hydride doesn't have a pKa, if lithides were known we could get numbers to calculate the putative pKa from that; the methods exist to do so, we just lack the numbers yet. The other alkalides have only been known for 40 years or so. --Jayron32 20:03, 6 February 2013 (UTC)

Ab initio prediction of pKa is reasonable for some types of structures. There's less data about alkalides to use for validation, but LiH is such a simple molecule that one could do quite advanced calculations for it in reasonable time. DMacks (talk) 20:12, 6 February 2013 (UTC)

Tests on a newborn baby

When a baby is born (in the United States), I assume that the hospital staff does a battery of tests on the baby to assess his health. Do they test if the baby is blind and/or deaf? (I assume that they do.) If so, how exactly would they test for those conditions in a newborn? Thanks. Joseph A. Spadaro (talk) 20:17, 6 February 2013 (UTC)

We have a fairly detailed article about the various newborn screening tests, which includes a section on hearing but does not appear to mention vision. DMacks (talk)

For blindness, I expect that such a test is sufficiently elementary that it doesn't necessarily rate a mention -- specifically, does the baby react to bright light? Contrast this with the hearing screening described above, or any of the other disorders noted, which require specialized procedures and equipment. — Lomn 20:34, 6 February 2013 (UTC)

Newborns can't focus, so sight tests would be unhelpful. A search on sight in newborns here gets you to the article on the disgusting, perverse, and evil movie, human centipede. But not to sight in newborns. μηδείς (talk) 21:05, 6 February 2013 (UTC)

"Newborns can't focus, so sight tests would be unhelpful" -- the former does not imply the latter. Response to stimulus is a basic means of testing that does not necessarily require comprehension or cooperation on the part of the patient. Now, that said, any sort of infant vision screening will necessarily have limitations, as the results aren't much more detailed than "nothing" or "something" until the child is old enough to provide more detailed feedback. — Lomn 21:28, 6 February 2013 (UTC)

In the UK, "Newborn babies are usually screened for any potential hearing problems using two quick and painless tests. They are the: Automated Otoacoustic Emissions test (AOE), and Automated Auditory Brainstem Response test (AABR)." The AOE test consists of "A tiny earpiece is placed in the baby's ear and quiet clicking sounds will be played through it. If the baby's ear is working normally, reaction sounds (echoes) should be produced in the cochlea. A computer is used to record and analyse the reaction sounds." In the AABR test; "three small sensors will be placed on the baby's head and neck. Soft headphones will be put over the baby’s ears and quiet clicking sounds will be played through them. A computer will then be used to analyse how well the baby’s ears respond to the sound."

A newborn baby's eyes are "checked for any obvious physical defects, including squints (where the eyes look in different directions), cloudiness (a possible sign of childhood cataracts) and redness." There are other tests including; "The pupil reflex test" (shining a light in the eyes to see if the pupil constricts), "The red reflex test" (using an ophthalmoscope to look for a red reflection from the retina, a lack of which could be an indication of a cataract) and "Attention to visual objects" (whether a newborn baby pays attention to visual objects). See National Health Service: Hearing and vision tests for children - How they are performed. I suspect that there is similar screening in other developed countries. Alansplodge (talk)

There is no routine screening for vision other than the discharging doctor assessing eye contact, which is an imperfect method. If eye contact is obviously poor, eyes are visibly abnormal, or moving abnormally (nystagmus)the child is likely to be referred to a pediatric ophthalmologist to examine the optic nerve. Many congenital defects of vision are only detected as parents begin to realize the eye contact is poor in the first months of life. One of the reasons vision screening is not done routinely is that there are no conditions which are treatable at birth but not at a few months of age, so there is little benefit from detection at 2 days as opposed to 2 months. Does this cover your concerns? alteripse (talk) 22:41, 6 February 2013 (UTC)

Yes, once again, babies don't track or focus at birth, and they may react to light even if they are blind, but it is good to know that doctors slaving for the civilized national health get credit for performing non-diagnostic tests on newborns. Good for them. μηδείς (talk) 23:01, 6 February 2013 (UTC)

It's not non-diagnostic, and pupillary response has nothing to do with the ability to focus the eyes. Blindness caused by damage to the optic nerve will result in no change in the pupil upon exposure to light, so confirming pupillary response in newborns at least rules out some (most?) types of blindness. I don't know much about the signs of nystagmus mentioned above, but I seriously doubt they would be in common use if they were not effective in establising vision problems. Evanh2008 ^{(talk|contribs)} 23:29, 6 February 2013 (UTC)

Yes, certain types of absolute blindness, not all, that can't be treated, and will be discovered by the time of the first pediatrician's visit, can be discovered at extra expense at birth. I don't think that was denied. μηδείς (talk) 00:19, 7 February 2013 (UTC)

The "at extra expense" part is silly, but other than that, it's a reasonable summary. — Lomn 01:45, 7 February 2013 (UTC)

You have obviously never seen an $80 charge for a tylenol on a hospital bill (I have). These things even get accounted for by the NH, although you may not see them. :) μηδείς (talk) 01:49, 7 February 2013 (UTC)

I can promise you it wasnt the doctor who put the $80 Tylenol charge on your bill. alteripse (talk) 02:23, 7 February 2013 (UTC)

By NH I assume you mean the British NHS. We hear a lot about the problems and deficiencies of the NHS, but if it gives you itemised bills such that you know what drugs and services you got, that's pretty good. The equivalent in Australia, Medicare, has some disadvantages. After a hospital stay and operation, you get a cacophony of invoices continuing for months afterwood. Each invoice is a standardised form, listing the date of service (which may be a survical procedure, hospital bed charge, anesthetic drug, or whatever), provider's name, the provider's Medicare registered ID number, the Medicare registered service code number, and the price. There is no text description of the service, just code numbers. In principle, you pay on the invoice and get a reciept that looks identical except it has the word "Paid" on it. You take the reciept to Medicare or your private insurere, as appropriate, and they give you a percentage (usually around 70 to 80%) back as cash. In practice, it is automated to varing degrees, depending on the service provider and what consents you have signed. Money just comes and goes from you bank account, if you agree to it. Just as you think it's been a few weeks, it's settled now, a bit more of your money suddenly dissappears.

When my wife was operated on for intestinal cancer, I got an invoice a week or so later from the hospital, with several codes listed (bed use code, theater use code, bandages and materials used, etc) totalling a few $K. No problem - it was expected. Also got an invoice from the surgeon (around several $100's) and the anesthetist. No problem - they were expected as well. Then an invoice from another doctor we had never heard of. Checked up - he was another surgeon assisting - should have expected that I suppose. Then, over the next month or two, several invoices from more names we had never heard of. I checked their names in the phone book - turns out some were thousands of kilometres away in other States. I phoned our medical insurer about it - they said "don't worry about it - if the codes are valid, and of course they will be, we'll pay you." I decided to check up on it all anyway. It turns out they were all pathologists. When the surgeon (and his assistant) cut cancerous bits out of patients, they send the bits off to labs for analysis and reports, so they know a) whether or not they got it all, and b) what the consequences are if they haven't. Some lab tests are highly specialised, and not done in all cities. So the bits of you get frozen, specially packaged up, and airfreighted to a lab that does whatever is wanted. I'm impressed that it all works so well and seemlessly, but the potential for rip-offs is significant.

Wickwack 124.178.141.64 (talk) 03:07, 7 February 2013 (UTC)

I brought it up because when I was hospitalized for major abdominal surgery, I ended up (luckfully) getting a case of the shingles so minor I literally thought it was a bugbite. I ended up being placed in isolation, but the only treatment I was given was acetominophen, for which pills I was charged $80+. I could have got them on the street for about $2.95. My private employer's private insurance paid for it, and several hundred thousand dollars in other charges which I didn't necessarily audit line by line. μηδείς (talk) 03:46, 7 February 2013 (UTC)

Why (broadly) was there charges to the extent of "several hundred thousand dollars"? We hear that the USA is the most expensive in terms of medical costs. However, my wife's operation (in Australia) for intestinal cancer was as complex as any, state of the art, and took the surgical team about 6 hours. Her entire time in hospital was about 8 days (she was off work for several weeks). The total cost for that, 3 months chemotherapy, and some radiotherapy was, as invoiced, about $28,000. That is not the full story though. All drugs prescibed, which were current standard for USA and other advanced countries, were subsidised by the government. We found out one of the drugs, for which 6 doses were required, cost ex-factory $2,500 per dose! We paid about $5 for each dose. All up, after Medicare and private insurance payouts, we were out of pocket about $2400 - we cannot complain about that. Wickwack 120.145.203.87 (talk) 06:40, 7 February 2013 (UTC)

Not defending the present US system, but one aspect is that hospitals, unlike any other private business, are not allowed to turn people away because they cannot pay. That money has to come from somewhere, and that somewhere is charging more to those who do pay. In addition, medical insurance companies, unlike any other private business, get to decide how much they are willing to pay after the service has been devivered. Add a thick layer of government regulations and you get things like $2,500 per-dose drugs. --Guy Macon (talk) 06:55, 7 February 2013 (UTC)

We can't forget the bilirubin test, which results in babies occasionally named Billy Rueben. StuRat (talk) 07:03, 7 February 2013 (UTC)

February 7

New Horizons photos of Pluto

The most recent photograph of Pluto taken by New Horizons that I've been able to find is this one, from September 2006. Since the probe is now at a little over 5 AU from the dwarf planet, I'm wondering why I've not been able to find more recent pictures. New Horizons took many photographs of Jupiter and its moons during a flyby in 2006, so it seems that they would have also planned to photograph Pluto and Charon during the approach, and not just during flyby in 2015. I've not done the math to calculate what kind of angular diameter Pluto would have from New Horizons' current location, but I have to imagine that any image taken from the probe right now would provide better detail than the embarrasingly-blurry Hubble composite (though I admittedly know little about the technical specs of the cameras on board). Evanh2008 ^{(talk|contribs)} 00:08, 7 February 2013 (UTC)

Here's a photo of Pluto, taken by LORRI, released from January 24, 2008. There's no need to remain in the dark: the science payload description contains detailed descriptions of each camera on board. Right now, the spacecraft is in the interplanetary cruise phase, so it isn't actively taking photos very often. It's pretty easy to know what the photos would look like: LORRI, the highest-spatial-resolution camera, has a 20.8 cm aperture, so you can trivially compute the farthest distance before Pluto will resolve to anything more than a single pixel. (About 500 million miles from Pluto, which is ... still a little ways to go). Space is very big! Nimur (talk) 00:20, 7 February 2013 (UTC)

Using a camera entails risks of damage, so taking lots of low-res pics is a bad risk-versus-reward option. They might take a pic occasionally, just to ensure that the camera is still working, but that's it, 'til they get closer. StuRat (talk) 00:27, 7 February 2013 (UTC)

A single pixel? According to my research (which consists of watching detective shows on network TV), you can expand a single pixel into a high-resolution picture. Just tell the technician "enhance!"... (Note to the humor impaired: no, I am not being serious) --Guy Macon (talk) 06:14, 7 February 2013 (UTC)