Wikipedia:Reference desk/Archives/Science/2012 May 14

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May 14

Why is KCN basic but not KNO3?

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

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

Are the injuries sustained by Tony Stark at all possible?

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

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

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

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

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

Weight loss question

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

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

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

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

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

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

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

Thermodynamics of nuclear reactions

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

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

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

Help identifying swallowtail

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

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It doesn't look like all of our photos here have that white spot, if I understand what you're talking about - see File:Pandiyana_aristolochiae_polytes_helenus.png. In any case, this butterfly is subject to polyphenism between different forms, which means that there will be hybrid zones in which there are intermediate forms. Depending on the precise genetics, all sorts of funny things might turn up there. So the specifics become very important... it might help to get full text for PMID 20192689 . Your photo looks a lot like the stichius form - see [1] - though others called this in India have differing patterns [2][3][4][5]. Here's an illustration of the diversity in Vietnam. [6] And identifying mimetic butterflies from wing patterns can be chancy anyway! This might be the sort of thing where you have to be hardcore and base the ID on genitalia [7] - or, preferably, molecular genetics, which should give more certainty, and perhaps even some unexpected surprises. Wnt (talk) 07:20, 15 May 2012 (UTC)

Help Identifying another swallow tail

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

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

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

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

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

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

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

women

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

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

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

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

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

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

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

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

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

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

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

• Hypothesis for the Evolution of Human Breasts and Buttocks
• Evolutionary Perspectives on Permanent Breast Enlargement in Human Females

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

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

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

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

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

I should add that not only did Darwin pursue his well-known discussion of the reasons for male nipples in "The Descent of Man" - apparently even his grandfather had ideas about it. [8] Darwin wrote there that "Now if we suppose that during a former prolonged period male mammals aided the females in nursing their offspring, and that afterwards from some cause, as from a smaller number of young being produced, the males ceased giving this aid, disuse of the organs during maturity would lead to their becoming inactive; and from two well-known principles of inheritance this state of inactivity would probably be transmitted to the males at the corresponding age of maturity. But at all earlier ages these organs would be left unaffected, so that they would be equally well developed in the young of both sexes."^[9] It is curious to consider all of the ideas - sexual selection, "spandrels", modern-day male lactation - that he does not run through in this. Wnt (talk) 13:48, 15 May 2012 (UTC)

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Will Mira B explode?

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

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

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

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

glass in soil

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

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

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

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

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

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

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

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

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

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

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

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