Wikipedia:Reference desk/Archives/Science/2010 July 28

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July 28

Phlebotomy Laws

Where would I look things up about Canadian Phlebotomy Laws. What about patient consent ?. Can the Dr. make me take blood fr om a patient, consenting? , or non-consenting? —Preceding unsigned comment added by Dean J Taylor (talk • contribs) 00:10, 28 July 2010 (UTC)

I don't know about Canadian law specifically, but I'm pretty sure it's the same as other similar legal systems in that sticking a needle in someone without their consent is an assault (or, maybe, a battery, depending on the terminology used in the jurisdiction in question). There are exceptions made for people trying to help someone who cannot consent (eg. they are unconscious, insane, a child, etc.). The exact details of those exceptions will depend on the jurisdiction and, as I say, I'm not familiar with Canadian law. --Tango (talk) 00:15, 28 July 2010 (UTC)

This document specific to Canada appears to confirm that adults generally have the right to refuse any medical treatment, even if the anticipated consequence of that refusal is death. Dragons flight (talk) 01:10, 28 July 2010 (UTC)

Of course taking blood from a a non-consenting person (in normal circumstances) is unlawful but I'm not sure the OP is asking about that. The question seems to imply that 'the doctor' is the employer and that the OP may be coerced into doing something he/she doesn't want to do. If taking blood is part of your job description then you may be obliged to carry out that duty. If this is a new task that the doctor is imposing on you then negotiation is in order. Do you have access to a local union? I am not an expert and this is not legal advice. Richard Avery (talk) 07:21, 28 July 2010 (UTC)

There would probably be a few other cases where medical treatment isn't really involved but consent isn't required to take blood, like a blood alcohol test compulsory under law (in many countries a police may be able to order a driver to undergo some test to determine their blood alcohol content) or a court ordered blood test for some other reason. Also someone who 'can't' consent may also include a suicidal person in quite a few countries where someone who is attempting/has attempted to commit suicide may be subject to suicide intervention and considered unable to refuse medical treatment. As per Richard Avery, if you are uncertain about what circumstances you may be required to take blood without the patient having given consent, you should consult a union or some other such authority who can hopefully advise you. Nil Einne (talk) 10:14, 28 July 2010 (UTC)

Your job description cannot oblige you to carry out an illegal act, though. If you think what the doctor is telling you to do is illegal, then you are legally obliged to disobey. --Tango (talk) 13:09, 28 July 2010 (UTC)

As for the needle, what about cases where intravenous injection is required for an unconscious patient? ~AH1^(TCU) 01:42, 2 August 2010 (UTC)

A question about Desmoplastic small round cell tumor question

is desmoplastic small round cell tumor in ewing sarcoma familiy of tumors? —Preceding unsigned comment added by 68.238.53.30 (talk) 00:58, 28 July 2010 (UTC)

From desmoplastic small round cell tumor: "Desmoplastic small round cell tumor shares characteristics with other small round cell cancers including Ewing's sarcoma, ...". Looie496 (talk) 01:48, 28 July 2010 (UTC)

I would interpret both the question and that response carefully. While both desmoplastic small round cell tumours and Ewing's sarcoma are examples of small blue round cell tumours (equivalently, just small round cell tumours), DSRCT and Ewing's are different members of that family. (Here's a free-access paper from Am. J. Clin. Pathol. describing an immunohistochemical approach to differentiating the two.) TenOfAllTrades(talk) 03:24, 28 July 2010 (UTC)

[I have modified the heading from "A question" to "Desmoplastic small round cell tumor question" to facilitate subject-matter searches. I believe this is in order, but apologies if I am in error.] 87.81.230.195 (talk) 10:21, 28 July 2010 (UTC)

It's good to do that, but you need to incorporate the words of the original heading when you do so. See Wikipedia:Reference desk/Guidelines#Don't_edit_others'_questions_or_answers Ariel. (talk) 16:20, 29 July 2010 (UTC)

Evolutionary adaption queuing problem

I’ve been thinking about a problem I see with current evolutionary theory (not that I’m a creationist). Sure, some genetic features for a given species in a given niche are better suited for survival and reproduction than other features. We constantly hear of examples of such features, like the giraffe’s neck. But in the case of the giraffe, and of all other species, each one has thousands of special adaptations, all of which presumably have been selected because of their efficiency. Now, my problem is that I can’t see how multiple features can be selected for at the same time, and yet I can’t see how they could be selected one at a time either. What if the member of some species has a beneficial trait and another member has a different beneficial trait? Now it would seem that if they are in competition, the traits themselves are in competition. But we never hear about this when the subject is being discussed. It’s always examples of beneficial traits discussed in isolation, as if the one being discussed is the only one at that time, in that species being propagated throughout their community. I’ve heard there is a name for this conundrum. Has it ever been discussed here? Eric155 (talk) 06:40, 28 July 2010 (UTC)

If you never hear of the traits evolving in competition and co-operation, then I can't think what advanced biology texts you're reading! Seriously though, that's pretty much the default way of thinking in modern evolutionary biology. The idea that traits evolve in isolation is responsible for people assuming irreducible complexity when they see things that must have evolved in tandem with other things. 86.164.66.83 (talk) 06:52, 28 July 2010 (UTC)

(ec) I'm not sure that there's necessarily a problem here. For simplicity's sake, let's assume that the original animal has traits a and b, each regulated by a single gene. It turns out that a mutation affecting a gives rise to dominant trait A, which confers a survival or reproductive advantage. An independent mutation in b gives rise to B, which also confers a survival advantage. The population now consists of a large number of individuals with the original genes ab, and a few with the beneficial new traits, Ab and aB. If A and B confer an advantage over a and b, the number of ab individuals will become depleted in the population as they are out-competed by the Ab and aB animals.

As you get more Ab and aB and fewer ab creatures, the likelihood is that there will be interbreeding between Ab and aB animals; some of whose offspring will now be AB. As the original ab animals disappear, the interesting competition becomes the one between the single-mutant Ab or aB animals, and the double-mutant AB animals. If AB in combination is more effective than (that is, confers a reproductive advantage over) the single mutants, it will gradually become more prevalent in the population. So I guess the short answer to your question is this — animals can acquire multiple beneficial traits because they interbreed, and because there is a pool of animals with a range of genotypes which survive each generation (it's not just one 'optimal' genotype which is cloned for all of the offspring of the next generation; there's significant mixing). TenOfAllTrades(talk) 07:04, 28 July 2010 (UTC)

I recommend Eric155 reads River Out of Eden by Richard Dawkins. This book is short in length and brilliantly suited to newcomers, like me, to the field of zoology and evolutionary biology. It is very readable and will answer Eric155's questions. Dolphin (t) 07:54, 28 July 2010 (UTC)

I have long had a similar problem to the OP's, and had been thinking of posing a similar question here along the lines:

given that in any population scores if not thousands of phenotypical traits (mostly at biochemical levels not evident to the eye) are presumably all evolving simultaneously, how is it that the advantageous and disadvantageous ones, proportionally represented in each individual of the population, do not cancel each other out? (To crudely oversimplify, a squonkbird won't pass on its advantageously longer wings if its unconnectedly and disadvantageously weaker heart leads to its death before it breeds.)

Intellectually I agree they can't, because I fully accept that evolution is proven to proceed as extensively described, but intuitively it's hard to visualise. Can the total sub-set with each disadvantageous trait, and ditto for the advantageous ones, be validly considered as evolving separately, with the successful outcomes re-merging? I imagine that there might be some simple mathematical demonstration that the numbers really do work out, and if so I'd like to be able to point to it even if (as is likely) I can't myself understand it. (Hey, I'm willing to trust a mathematician! :-) ) 87.81.230.195 (talk) 10:45, 28 July 2010 (UTC)

Mutations tend not to be helpful. What would, for example, a wolf (or any other animal) with am extra-long neck have to give it an advantage. Its neck would be extremely hard to hold up unless it has more developed muscles and a strong heart to pump it up, along with extralong tissues of all kinds that are found in the neck. It also has to adapt to leaning down to drink water. All of these helpful mutations have to occur all at once, or the neck is utterly useless (i.e. the animal is a "freak animal"). If you take the mathematical probability of all of those helpful mutations occuring all at once, it is very low, definitely not able to occur in millions or even billions of years. (I am he in disguise). --98.221.179.18 (talk) 10:51, 28 July 2010 (UTC)

Most mutations are not things like "extra long neck." They are small changes to physiology. They do not have to happen "all at once." If you're actually interested in learning about what evolutionary theory says — and not just the bad parody of it that is given by the ID people — there are plenty of better explanations out there that you seem to have either missed or not understood. I am also not sure you can conceptualize how long a span of time 1 million years is, much less a billion years. --Mr.98 (talk) 12:15, 28 July 2010 (UTC)

The mistake being made in these questions is one of the most common misunderstandings about evolution - you can't approach evolution from a atomistic, particularistic viewpoint. evolution works by small advantages and small changes to entire organisms, not big advantages and big changes to parts of organisms. Let's take giraffes for an example. There was (by the theory) some paleontological period extending over millions of years in which having a longer neck was an advantage-niche that a species could occupy. the actual advantage is unknown, and probably constituted several advantages - e.g. a longer neck allowed for better detection of predators, better access to certain kinds of food, a more threatening, dominant posture (for purposes of breeding and defense). whatever that primal species was it had a normal but small distribution of neck sizes (just the way humans have have a normal but small distribution of heights), and the animals with longer necks where slightly more likely to survive to pass on their genes - they could see predators sooner, had better nutrition and thus better health, were less likely to be attacked and more likely to gain access to mates. Further, those of that species which did not have the internal biological structures needed to support a longer neck (stronger circulatory systems, exaggerated musculatures, etc) could not utilize the environmental advantages of having a longer neck, and would not gain any of the advantages. The entire system (longer neck and internal support structures) was required to take advantage of the niche.

you need to remember that this has nothing to do with the particular feature. sure, giraffes have long necks, but giraffes did not evolve long necks because it was advantageous to do so; giraffes evolved in a way that was advantageous in the environment, and that just happened to involve long necks. in a slightly different environmental context they might have evolved with very long legs and short necks. There's a strong tendency because of the way we think for us to use teleological reasoning - asserting that the effect we see in the world must have a specific cause that brought it about - when in fact this is less a specific effect than a by-product of other forces. --Ludwigs2 11:55, 28 July 2010 (UTC)

Increasingly tangential and heated discussion, collapsed by Brammers (talk/c) 17:25, 28 July 2010 (UTC)

wwwwait! TenOfAllTrades you said about the mutations of genes. mutations ,which are very rare, are 99.9% of the time failures and make the animal, insect,etc. worse. Some are even deadly. And that statement is proven by experimenting; an example of mutation is two-headed snakes and albino squirrels which, as you obviously see, isn't better than the original creature. so, sorry, mutation doesn't make things better.--Horseluv10 12:05, 28 July 2010 (UTC) —Preceding unsigned comment added by Horseluv10 (talk • contribs) "99.9%" is just a made up, fake statistic, along with your false "experimenting" snake example. It's true that there are a lot of non-beneficial mutations, but that's not the problem. Mutation rates just provide a background rate of variability for which natural selection can then act upon. Most mutations are small physiological changes that can add up over time. There is a lot of real scientific work on this, with precise understandings of gene flow and mutation rates and the mechanism of mutation and so on — not just hand-waving bad Creationism. If you want to have a conversation about how this really works and what the scientific arguments really are, that's fine, but this is not a general discussion forum where ignorant trolling (from any side) is really tolerated. --Mr.98 (talk) 12:15, 28 July 2010 (UTC) Horseluv10 appears to be using the notion that mutations must be either good or bad - no random mixture is contemplated. Horseluv10 has cited examples like two-headed snakes and concluded Voila, mutations are bad - all of them! That is nonsense. Mutations are entirely random. We must expect that many of them, perhaps most of them, will be bad but all it takes is for one or two of them to be beneficial and those one or two will be retained in the gene pool whereas the disadvantageous ones will eventually disappear. Dolphin (t) 12:32, 28 July 2010 (UTC) Advantageous mutations are really harmful to the creature and result in a lower rate of selection. You can see how many advantageous mutations have occurred in man's history or any animal's history. Mutations generally are corrected or result in cancer or do not affect the creature at all. Mutation is disorder, and it cannot produce order except for the occasional good mutation which is buried under countless bad mutations. If all of those mutations happened to a creature and it impossibly remained alive, then that creature would be unrecognizable. Dolphin51, your statement seems to me to be bordering on ID. How can the good changes be saved and the bad changes be deleted if nature, with its bad mutation-causing sunlight and bad mutation-causing chemicals and other bad stimuli, generally leans to the bad and decaying side? Animals die; they do not become more healthy as they get old, which shows that helpful mutations are practically nonexistent. If you have one real dollar bill buried in a huge pile of counterfeit ones (or whatever your currency is), that whole pile is practically useless monetarily, even though it does contain a dollar bill. But suppose Nature (represented by a windstorm) came and blew away all counterfeit dollar bills, leaving just the real one. That would be evolution in action. If such a thing could be observed, it would prove natural selection is capable of discarding bad mutations and keeping good ones. --Chemicalinterest (talk) 12:57, 28 July 2010 (UTC) Dear Chemicalinterest. Please provide some references for your bullshit. And while you're at it, although it'd be hard to make it factually correct, at least try to make your argument logically and linguistically followable. Aaadddaaammm (talk) 13:47, 28 July 2010 (UTC) aaadddaaammm I write in a "stream of consciousness" techique. Whatever I think of I write. --Chemicalinterest (talk) 15:19, 28 July 2010 (UTC) (EC with above) Your analogy is silly but let's go with it. Let's say I'm so evil dictator and I have millions of slaves. I want that real dollar bill, perhaps it has sentimental value. I send my slaves to each get a bill from the pile. If they come back with a counterfeit I shoot them in the head. (If they come back with nothing I also shoot them in the head). Guess which of my slaves will be alive at the end? The one who found the dollar bill. Let's use a less extreme analogy. This time I'm not quite so evil. I don't kill my slaves. I do require each one of them to pick up a dollar bill. For the one who finds it, I let them spend that dollar bill however and whenever they want. One of my slaves is going to find that dollar bill and they now have some small advantage over their fellow slaves since they have this dollar bill to spend when they want. Nil Einne (talk) 14:03, 28 July 2010 (UTC) (more ec) To keep with the analogy: This happens all the time. There is a mountain of rocks mixed with gold, and yet we select the gold out from the mountain. There is a mountain chain of rocks on the rock, and we still manage to pick out the Carrara marble. And while there are plenty of mutations, of course only those in the germ line affect evolution - if I remember correctly, there are on average about 4.6 mutations in the genome of each human. Many of those are neutral, some are advantageous in certain situations, and some are disadvantageous. Of course, the bad ones are selected out fairly quickly, leaving the "good" ones. --Stephan Schulz (talk) 14:09, 28 July 2010 (UTC) I would hesitate to use those analogies, simply because they invoke an intelligent agent (a human being) to apply the fitness criteria. In truth, the problem is that the original 'pile of money' analogy is a crappy analogy that is divorced too far from reality to be the basis for drawing meaningful conclusions. An analogy that would be better – though still not good – would be one that involved dollar bills that could reproduce. (Ultimately, reproductive success is the basis for natural selection.) Suppose we take a million one-dollar bills, and impose a different mutation on each. All but one of the mutations is deleterious, preventing those bills from reproducing and passing on their defective (or 'counterfeit') gene. For simplicity's sake, we assume that the gestation time of a healthy dollar bill is one day, and that each healthy bill is able to produce one offspring per gestational period. Today I'll have 999 999 unsuccessful bills, and 1 viable one. Tomorrow, I'll still have the same 999 999 counterfeits, but I'll have 2 live ones. That sounds pretty unsatisfying — the pile is still mostly junk. Something remarkable happens by the time I get out to about three weeks, however, when I'll have roughly equal numbers of unsuccessful bills and viable ones. By the end of a month, I'll have about a billion live dollar bills; only one in one thousand notes in the pile will be counterfeit. That's the power of natural selection over multiple generations. Note that this process still works even if it isn't a stark alive-dead or fertile-barren choice. Even small advantages add up over sufficient generations. Let's say that a particular mutation confers a very small advantage: on average, a 1% greater number of offspring in each generation. After ten generations, the population with the mutation will have expanded by about 10% more than the population without. After a hundred generations, that 1% advantage turns into 2.7 times as many offspring. After a thousand generations, that tiny little 1% advantage will be parlayed into twenty-one thousand times as many offspring — the original, slightly less advantageous version of the gene will be nearly invisible in the population. TenOfAllTrades(talk) 14:33, 28 July 2010 (UTC) That analogy relies on the theory that good mutations are naturally selected, while bad ones are thrown away. It is not the case. Very rarely do cancers disappear (harmful mutations) or "good" mutations such as photographic memory get selected until everyone has photographic memory. --Chemicalinterest (talk) 15:04, 28 July 2010 (UTC) Actually, successful mutations are selected in cancer. With loss of checkpoints in replication and increasing genomic instability, the rate of mutation tends to increase within a malignant tumor. Mutations which confer resistance to apoptosis, resistance to immune system attack, tolerance for hypoxia, more rapid cell division, and (after treatment begins) resistance to chemotherapeutic agents are all selected for (and observed in real tumors). As in populations of animals, the tumor cells that develop survival-impairing mutations do die off (or become a smaller fraction of the tumor mass) — but the death of individual cells doesn't eradicate the entire tumor. In real life, late-stage tumors tend to grow faster than early-stage ones; they've accumulated more 'beneficial' mutations. Natural selection isn't some supernatural ethical judgement; there isn't a magical preference for anything that humans would deem 'good'. Look, it would probably be helpful if you just gave us a link to whatever creationist (or crypto-creationist 'intelligent design') website you're getting your material from so that we can hook you up with one of the many competent, clearly-written rebuttals of these terrible analogies. Better yet, read intelligent design and evolution, and let us know which concepts you're still confused by. TenOfAllTrades(talk) 15:23, 28 July 2010 (UTC) Yes, the mutation is beneficial to the cell but not to the organism, which causes cancerous organisms to be ejected from the gene pool. --Chemicalinterest (talk) 15:47, 28 July 2010 (UTC) All of this, while emotional, does not actually advance your argument one bit. Having a spontaneously mutating tumor in your organism is not the same as being a mutant yourself.--91.148.159.4 (talk) 16:38, 28 July 2010 (UTC) I said above that I am not getting this from any website. It is just what I logically think when I observe the world. --Chemicalinterest (talk) 15:47, 28 July 2010 (UTC) What is the evolutionary cost of a photographic memory? Does it get you laid more? Do people with photographic memory have more children? When they mate, their children probably won't have a photographic memory. Such is the highly chaotic nature of personality. Also, it doesn't suit most species to be immortal. It's actually a bad thing for the species -- you get tons of people with "old genes" and adaptation slows down. People usually get cancer after they have children. Evolution is a little cruel sometimes -- it doesn't care what happens to the parents so much after they reproduce. John Riemann Soong (talk) 15:29, 28 July 2010 (UTC) There wouldn't be so much variety. If one type of animal was most suited to its area for reproduction, it would dominate and all other animals that are less adapted would be blown away by natural selection. The multitude of types shows that God create the world and enjoyed having large varieties of animals. The lack of missing links (and their very name) shows that animals do not change. --Chemicalinterest (talk) 15:47, 28 July 2010 (UTC) Ever heard of ecological niches? I'm sure your god enjoyed making parasitic intestinal worms, and the sound of excellently designed carnivore teeth piercing the necks of small lambs fills him with inexpressible joy. I'm glad I don't know him, though knowing his friends is bad enough.--91.148.159.4 (talk) 16:38, 28 July 2010 (UTC) There is no solid evidence for "photographic memory" in the usual sense to begin with. In humans, memory is very much trainable, indicating that genetic variation is at best one factor. And humans have indeed evolved to have outstanding memory over time. --Stephan Schulz (talk) 15:34, 28 July 2010 (UTC) nearly insurmountable barriers Don't forget group selection and sexual selection guys. They massively accelerate evolution and it really becomes less of a "mutation because of chance" and more of "reassortment and recombination of traits". In fact, there are "insurmountable" barriers that evolution doesn't like to cross. Take for example, the electron transport pathway. In high school they tell you it gives you 32-34 ATP or whatever per glucose molecule, but IIRC a lot of energy is still wasted in that transition from cytochrome c oxidase to oxygen -- that final jump is huuuuge compared to all the previous jumps, and ATP synthase utilises only a fraction of that final redox reaction. The rest is wasted as heat. It would really give all eukaryotes (and all aerobic bacteria) more useable energy to develop a "cytochrome V complex" in between....but you see, the electron transport chain is such a fundamental pillar of cell life that nature usually punishes any mutant cells that mess around with it. (Not to mention, it is probably hidden away in a protected area in most genomes, to prevent damage to these critical genes). The same goes for why plants don't simply avoid photorespiration by modifying RuBisCO by only allowing carboxylation and not oxygenation (both are Lewis acid'ish reactions) -- they work around the inefficiency of this enzyme by using C4 carbon fixation or Crassulacean acid metabolism on top of RuBisCO. Once complex multicellular organisms get ... complex, they usually refrain from tinkering with their fundamental machinery. The changes would just be too big. Evolution takes the path of least resistance. High selective pressures can cause massive changes within a few dozen generations. John Riemann Soong (talk) 15:15, 28 July 2010 (UTC) Do we get to archive/delete this thread as the unholy lovechild of trolling and soapboxing yet? Aaadddaaammm (talk) 15:59, 28 July 2010 (UTC) Wait several more days and then you will get the wish of your heart. --Chemicalinterest (talk) 16:29, 28 July 2010 (UTC) Since Chemicalinterest seems to be uninterested in reading the relevant articles on the topic (evolution, intelligent design, or even missing link, which he seems unaware is a misnomer), preferring instead to argue pointlessly, I don't intend to continue responding in this thread. I encourage other editors (who are interested in keeping this a Science Reference Desk) to do the same. TenOfAllTrades(talk) 16:52, 28 July 2010 (UTC)

The proof that giraffe needed more than one genetic change in order to look the way they do is that their necks are long because their legs are long. A short-necked giraffe would be unable to reach the ground in order to drink - so the long neck and the long legs had to evolve together. If the giraffe had first evolved a long neck - then the long legs would be unnecessary - so they must have started getting longer legs and needed to evolve longer necks in order to reach the ground! There is much more than that going on though - their hearts are stupendously powerful in order to pump blood all the way up those long necks. Read Giraffe#Circulatory_system to see the huge range of problems that long neck causes for the animal. It's heart is two feet long - it's blood pressure is twice that of other mammals - it has special valves in the arteries around the brain so that when it leans down to drink, the extra pressure doesn't cause it to black out! The legs have a specially built blood supply to prevent the huge pressures from exploding the veins and arteries. There is a lot more to the Giraffe than a longer neck!

So evolution had to change multiple aspects of the giraffe more or less at once. Because of the implausibility of genetic change for long legs, long neck, big heart, neck valves, etc all happening at once in one individual, the changes had to have been gradual. A few centimeters of extra leg length making it easier to reach higher branches, a few centimeters of neck length allow the animals to drink from shallower pools, a little extra heart capacity allowing for longer life and increased breeding success as pumping the blood higher put more of a strain on the organ. Round and round that cycle for 20 million years - and you go from a fairly normal-looking, deer-like Climacoceras to a modern giraffe - one centimeter at a time.

I used to live for a while in Kenya as a child - and on frequent occasions we'd go to the Nairobi game reserve and watch giraffes. It's really noticeable that the umbrella-shaped trees in the park were precisely high enough that the local giraffes could JUST reach them by stretching as far as their legs, neck, snout and tongue could reach. As tall as those animals are - they looked like they were standing on tippy-toes to reach the leaves! A giraffe with just a few inches of extra reach would have no trouble finding food...one that's just a few inches shorter would have a much harder time of things. It's not just the legs and neck - the snout and even the tongue is long. Conversely, trees that are shorter lose most of their leaves - they need more water and nutrients to produce leaves that do them no good because the giraffe get them - leaving them less food and energy for reproduction. A tree that grows just a few inches taller than the tallest animal can avoid the worst of the ravages of the Giraffe. Clearly the trees and the giraffe are locked in an evolutionary arms race.

SteveBaker (talk) 03:15, 29 July 2010 (UTC)

Steve: without disagreeing (because I think what you said is reasonably accurate), be careful of the 'had to' language. saying 'had to' implies all sorts of misleading things (that 'evolution' is a particular thing, that giraffes are somehow a necessary result, even that the modern giraffe is somehow implicitly present in all of its evolutionary ancestors). A few million years ago there were creatures which were distinctly not giraffes; environmental pressures turned them into modern giraffes over time, but environmental pressures could have turned them into a wide assortment of creatures. there is no particular 'thing' called 'evolution' that 'does things' to change creatures; 'evolution' is just a code-word to point to the numerous processes by which species consistently change in response to a consistently changing world. --Ludwigs2 12:38, 29 July 2010 (UTC)

Consider the weather. A myriad of factors are involved in myriads of locations, yet clear patterns emerge. 67.243.7.245 (talk) 18:58, 29 July 2010 (UTC)

OP eric155 back. Thanks all for an invigorating discussion. I still feel at sea on this question though I will read more. I'm thinking of the various references to giraffes above. I've long thought that the traditional evolutionary example of the giraffe is hackneyed and a red herring. Everyone sees the long neck, to the exclusion of all else. As Steve and others pointed out, that long neck needs a strong back to support it, and that back needs special legs to support it, and they all need a specially powerful heart to keep them fuelled and so on. It means that the neck has ancillary phenome traits which from the head right down to the toes, probably hundreds of them. I guess my question was how does nature select when so many traits need to work together to effect a functional organism. So, what's the point of a longer neck if the giraffe strains its back from the effort.

One of the most distinctive and apparently retrograde features of evolutionary adaptation, is that any beneficial mutation must have IMMEDIATE beneficial effect, otherwise it is just a bad or neutral mutation, and will not be selected for. That caveat is to many people the most puzzling aspect of the process, especially because human life is so much a planned affair where we forgo immediate benefits in order to achieve advantageous long-term goals. How nature can work without recourse to any teleological vision and yet end up with organisms of infinite and wondrous complexity is often baffling. It would mean that potential traits of immense power are obliviously ignored just because they do not have an immediate effect.

Part of the answer seems to be that the environment selects via the structure of the whole organism, not via single genes. I believe that Dawkins makes this point somewhere. But to me it raises the further question then of how a complex trait, one which includes many sub-traits, such as the giraffe's neck combined with its back, legs, heart etc can be propagated via the genome, which would have to select for multiple traits all across the genome. And of course the kernel of my question is this, briefly: If beneficial mutations are rare, then how much rarer would it be for an organism to have, by sheer happenstance, a multiple of these mutations? Allied to this problem is another one I also have, and that is simply how a beneficial mutation, a mere blip in the organism's history manages to survive. Don't forget that most individuals of a species die before they can reproduce. In many species only 1 or 2 percent make it. Now, the forces leading to extinction are so massive, I keep thinking that they would make some small new "beneficial" mutation nothing more than a tiny noise, inundated by far more powerful forces. It's like saying that having the beneficial mutation of eyebrows will make a difference when your village is attacked by marauders or a volcano explodes. How many millions of beneficial mutations disappear in the face of these vast destructive forces? Eric155 (talk) 07:59, 30 July 2010 (UTC)

That is actually an important point that often gets overlooked in simplified explanations: many potentially beneficial mutations will not survive following exactly that sort of situation, and neutral mutations will propagate simply because the organisms with them happened to survive and reproduce better. This effect is more pronounced in small populations, where genetic drift is more significant as a result. In large populations, it averages out a bit more, since a potentially beneficial mutation, or a beneficial combination of traits, will be more likely to arise several times, making it more likely that some individuals with it will survive long enough to reproduce. 86.164.66.83 (talk) 14:36, 30 July 2010 (UTC)

Do blackholes tear holes in space-time?

According to General Relativity mass create "dents" in space-time. But can a gravity well be so strong that it rips the fabric of space-time? 148.168.127.10 (talk) 13:52, 28 July 2010 (UTC)

You can interpret the singularity and the centre of a black hole to be a hole in space-time, I suppose. In reality, we don't know what happens there. The maths goes crazy, which is a very clear sign that we've made a mistake somewhere in our theory. --Tango (talk) 14:36, 28 July 2010 (UTC)

It is worth noting that singularities (at least as predicted in general relativity) have literally zero size. Qualitatively, I don't think I would generally refer to a zero-size object as a "hole", since that generally tends to suggest a space large enough to fit something through. Dragons flight (talk) 15:55, 28 July 2010 (UTC)

What makes more sense is that "black holes" force out all empty space from the event horizon in. That empty space as we now know has an energy and volume that cannot be ignored. this is how gravity works: it is the vacuum energy created by the condensation of extra empty space around the surface of matter trying to displace the matter or get "back in" to where it once was. Something that virtually all physics laws have taken for granted is that empty space is uniform throughout spacetimud. that is why we can't figure out black holes, we are using archaic laws of physics that have the empty space or as I like to call it aether "built in" to the equasions. Basically, we will never be able to understand "black holes" if we keep forcing the current laws of physics down the throats of black holes. it is similar to trying to both locate and measure an electron. the tools we use to do those things inherently prevent us from achieving the goals. —Preceding unsigned comment added by 165.212.189.187 (talk) 13:47, 29 July 2010 (UTC)

Ring singularities are thought to allow "swallowed" objects to pass through the black hole into a white hole, causing the development of parallel universes. ~AH1^(TCU) 01:37, 2 August 2010 (UTC)

That's a really bad description of a black hole. It seems to be attempting to explain a black hole as being purely a spatial anomaly, ignoring the crucial role that the nature of time plays in black holes. For a much more accurate description of a black hole, read black hole. Red Act (talk) 21:20, 4 February 2011 (UTC)

DEVELOPMENT!????

how many people have drifted off to space irrevocably while on moonwalks

how many people have died a cold and lonely death after drifting off to space from one of their moonwalks and not being able to get back to their ship? 92.229.14.166 (talk) 13:56, 28 July 2010 (UTC)

None? Don't you think you would have heard of it? See also Space accidents and incidents which I found from a simple search Nil Einne (talk) 14:04, 28 July 2010 (UTC)

"Don't you think you would have heard of it" - I'm an artist, I don't see why I'm supposed to follow space-news. 92.229.14.166 (talk) 15:20, 28 July 2010 (UTC)

You seriously never heard of the Challenger disaster then? These things are big news. I don't follow space news myself much but these things are big enough news that most people do hear them, whoever they are. This one would be even more so since it would have been the first time it happened (that we know of), and 'lost in space' or 'earth's latest satellite' also makes a great headline (even if in reality the body probably would burn up in the atmosphere before long so would join everyone else on earth). Nil Einne (talk) 07:33, 29 July 2010 (UTC)

No-one has died during a moonwalk or spacewalk (although Leonov got dangerously stuck during his Voskhod 2 walk). Almost all spaceflight casualties have all arisen during either launch or reentry (the scary energetic bits of flight); only Soyuz 11 happened on orbit. It is impossible to float away from the moon - lunar escape velocity is 2.4km/s, vastly more than the speed a person could attain by jumping. - Finlay McWalter • Talk 14:06, 28 July 2010 (UTC)

Even the Soyuz 11 disaster happened during re-entry, it was just early on in re-entry so it was still "in space". It wasn't in orbit, though: it was after they fired the retrorockets. --Tango (talk) 14:44, 28 July 2010 (UTC)

I assume you mean "space walk" not "moon walk"? If not, you should know that there's gravity on the moon. You weigh less on the moon (about 1/6), but you certainly don't weigh zero. You couldn't "drift away" from the moon any more than your could on Earth.

You'd be hard pressed to drift away on a space walk, too. Usually they're tethered. They used to occasionally use thruster backpacks instead, but they don't do that anymore for whatever reason.

If you did somehow unhook your tether and drift away you'd probably still be OK. They never leave the ship (or station) completely unattended. If you drifted away from the space shuttle they could track you on radar and follow you. I'm not sure what the procedure is for dealing with an astronaut that somehow drifted away from the space station, but I suspect that they could jump in their Soyuz capsule and go pick you up that way. I'm not sure how fast they can suit up and get that thing ready for launch, though. APL (talk) 16:06, 28 July 2010 (UTC)

APL is referring to the manned maneuvering unit ("rocket backpack"). The "whatever" reason they no longer use it was a massive overhaul and reassessment of all hazards, risks, and safety considerations, following the Challenger disaster (as described in our MMU article). Though not in any way related to the Challenger incident, the MMU was one of a number of "risky" things that were eliminated from the American manned space program as part of a massive risk reduction campaign. Nimur (talk) 05:05, 30 July 2010 (UTC)

They still have a smaller version of it, but they don't use it regularly: it's just for emergency purposes. --131.188.3.21 (talk) 09:42, 30 July 2010 (UTC)

Oh, Just remembered, you may be interested in the legends of the Lost Cosmonauts. The story goes that some number of cosmonauts were lost, but Russia went to great lengths to erase them from history. Almost certainly nonsense, but just plausible enough that it makes a great campfire story. APL (talk) 16:10, 28 July 2010 (UTC)

You wouldn't drift away very fast (unless you pushed off quite hard, which you just wouldn't do), so they would have until your suit runs out of air/power (whichever comes first, I'm not sure which it is) to come and get you. The Soyuz has an airlock, so the pilot doesn't need to suit up, the drifting astronaut can enter the airlock without decompressing the rest of the Soyuz. Also, spacewalks on the ISS are always done in pairs, so the partner would already be suited up. Whether they could easily get to the Soyuz, I don't know (it would depend on which station airlock they were using, I guess). --Tango (talk) 16:18, 28 July 2010 (UTC)

Also, they have things like the Simplified Aid for EVA Rescue so they can manoeuvre back to the station on their own. --Tango (talk) 16:24, 28 July 2010 (UTC)

Also, and I'm REALLY surprised no one has mentioned the bleeding obvious, the astronaut is TETHERED to the space craft. An obvious precaution, and one of minimal cost and inconvenience. So space walks are really very safe, as the only thing that could hurt you, that is, drifting away, has been negated. Your big risks in space travel are your space ship blowing up, crashlanding, or losing its way. The dangers of getting out on a rope for a brief waddle in space is so harmless it will be a special kid's treat when Branson's Virgin Space Ship enterprises get operational. I wonder about some posters sometimes. I kinda imagine that if one of them was asked to go on a space walk, the first thing they would say is "Can I get a rope to secure me to the ship?" But not on Wikipedia. They may go on space walks in pairs on the ISS, but prior to this, most space walks, on MIR and the American ones, were by lone astronauts, all tethered of course. One of the scenes in Kubrick's 2001 : a space odyssey that had me wondering was that one in which Frank dies after he is thrown off course during his space walk by the deranged computer HAL. Why did Frank and Dave make those long space walks without any kind of harness? Just asking for trouble. Eric155 (talk) 05:15, 31 July 2010 (UTC)

An unexpected solar flare, collision with micrometeorites or even a gamma ray burst could potentially pose a risk to astronauts on a spacewalk, however. ~AH1^(TCU) 01:26, 2 August 2010 (UTC)

Also, if someone were to drift off during a spacewalk, they might burn up in the Van Allen Belt or the thermosphere instead of colliding with the Earth's lower atmosphere while they are above the Kármán line. ~AH1^(TCU) 01:35, 2 August 2010 (UTC)

explanation on weather precip chance

Ok, so I have noticed on weather.com there is an hourly forecast that includes precipitation percent. For the past couple of days, as an example, I have seen it say over an 8 hour period, 10am - 20%, 11am - 20%, 12pm - 20%, 1pm - 30%, 2pm - 30%, 3pm - 30%, 4pm - 30%, 5pm - 30%. Now statistically, that would say to me that there is only a 8.6% chance ((0.8^3)*(0.7^5)) that it will not rain at some point during that 8 hour span, but my experience shows that it does not frequently rain during that 8 hour time. So is there a special meteorological method that one is supposed to use to interpret these precipitation chance %s? Googlemeister (talk) 15:20, 28 July 2010 (UTC)

I don't think that is a proper calculation. The chance would be found by averaging all of the percents. --Chemicalinterest (talk) 15:50, 28 July 2010 (UTC)

I have wondered about those percentages as well. You often see the daily chance at around the same figure as the hourly chances, which doesn't seem to make sense. --Tango (talk) 15:55, 28 July 2010 (UTC)

I don't think the chances are probability. --Chemicalinterest (talk) 15:58, 28 July 2010 (UTC)

Your calculation is assuming that the hourly chance of precipitation can be interpreted as uncorrelated, independent events. In reality, the chance it rains at 1 PM is highly correlated with the chance it rains at 3 PM, etc. Consider the following example. I tell you that I will give you a dollar at a random time tomorrow. Then the probability you get a dollar between 1 PM and 2 PM is 1/24. Treating those hourly probabilities as independent you might then conclude you have a 1 - (23/24)^24 = 64% chance of getting a dollar tomorrow, but that is false since I have guaranteed you a 100% chance. In the limit of totally dependent events, one might predict the probability that it rains tomorrow is equal to the max of the hourly probabilities (i.e. 30% in your example). Much of the time weather forecasts seem roughly consistent with an assumption like this in that they predict a daily chance of rain not much different from the max of the hourly chance. In general, we would usually expect that the true probability of rain tomorrow is intermediate between the max value and the value calculated via your method, but it is not possible to predict an actual value without additional knowledge of how the hourly predictions relate to each other. Dragons flight (talk) 16:21, 28 July 2010 (UTC)

See also Probability of Precipitation--it's not quite as simple as the plain-language meaning the chance that it will rain in the city. DMacks (talk) 16:57, 28 July 2010 (UTC)

The forecast probabilities on weather.com are bogus -- they've annoyed me for years. You can safely assume that a higher "probability" means a greater likelihood of rain, but the actual numbers are pretty much meaningless as far as I can see. The only probabilities you can rely on in my experience are 0% and 100%. Looie496 (talk) 20:40, 28 July 2010 (UTC)

To those posting here who are, I'm guessing, mostly Americans - be aware that many weather services around the world do not provide percentage chance of rain forecasts. The one I know well is Australia's Bureau of Meteorology. One argument against that I have heard from some of its staff is that a percentage chance of rain forecasts is a cop out. It cannot be wrong. If it rains, they can say "We said it might" and if it doesn't, they can say "We said it was a low probability". HiLo48 (talk) 22:27, 28 July 2010 (UTC)

I've tried asking a question about adding up POP values, and it simply did not work out. I'm not sure how to calculate probabilities in this way within a general context anyway, but the POP is the probability that it will rain during a day or time period, not the percentage of the time it will rain. I'd say that the chance of rain during that 8-hour period does not exceed 30%, but in real-life circumstances it can rain when the probability is 0% and it can not rain when it's 100%. ~AH1^(TCU) 01:22, 2 August 2010 (UTC)

safety procedures

Are these situations worrisome enough to warrant attention?

• Perchloric acid and nitric acid being stored next to organic solvents
• Bottles of acids like TFA, HF and sulfuric acid being stored in rusty metal containers-- is the rust a sign of a leak problem? (Don't worry the HF is stored in polyurethane).
• A nurse storing a bottle of NaF next to the clinical trial medications in a research unit?

John Riemann Soong (talk) 16:02, 28 July 2010 (UTC)

In the order that you pose the questions.

• This is bad laboratory practice. Of course, everything will be fine until you have a major fire in the lab, in which case the laziness will make the fire much worse and much more dangerous to try to extinguish. In most labs, it is really easy to design a storage system which keeps strong oxidizing agents away from flammable organic solvents, and putting such a system in place is a good reminder that you should try to envisage the worst case scenarios when thinking about safety measures.
• This is fairly normal laboratory practice (in virtually every lab I've worked in). The rust is not necessarily a sign of a leak problem from the bottle inside, the atmosphere in chemical storerooms is often propicious for corrosion (because of drips on the outside of bottles that evaporate, or humidity levels, or condensation). The metal container provides a small amount of shock protection, and also a small amount of containment if the bottle breaks, but that's not the main reason. Simply, the label on the metal container is often easier to read than the label on the bottle!
• I wouldn't do it, because it seems like a needless risk; on the other hand, you have to ask yourself where else the nurse would have to store it. In a lab, you can usually find an appropriate place to store something, but "storage resources" can be more limited in a clinical context. If you know that it's NaF, then at least the labeling is adequate!

Physchim62 (talk) 16:45, 28 July 2010 (UTC)

Also, is it normal for bottles of sulfuric acid, etc. to become really sticky? I didn't notice this before -- it was the first time I was rummaging without gloves (was looking for H2O2). John Riemann Soong (talk) 16:17, 28 July 2010 (UTC)

In my opinion, this question is asking for the kind of personal professional advice that we aren't really capable of giving. We can't really tell you what is safe or reasonable without knowing both the details of what you are doing and the legal / professional standards that apply to your particular workspace. You would probably be much better off discussing the issues with your colleagues and/or a local safety officer. Dragons flight (talk) 16:28, 28 July 2010 (UTC)

We can't give professional advice, but we can (and often do) reply to general queries like this. JRS is only an undergraduate (as he has made clear in his many previous posts), so has no power to change anything! Physchim62 (talk) 16:33, 28 July 2010 (UTC)

When someone asks for specific safety advice about their work environment I see that as less a general query and more analogous to looking for personal medical advice. If our advice is good, then there is no harm, but bad safety has the potential to cause personal harm in a way that is very analogous to bad medical advice. In addition, since none of us can see his personal work area, it is very possible that us strangers on the internet might be unaware of factors that change the situation significantly. For example, rusty metal containers might be innocuous 98% of the time, but 2% of the time an inspection might notice that the rust is caused by vapors from an improperly stored strongly oxidizing chemical (e.g. NaClO). Also, there are situations where subpar practices might be tolerated (even routine) in one lab environment while the same practices would be illegal and/or grounds for firing in another lab. We don't and can't have a complete picture, and hence I still think it is much better for JRS to discuss safety concerns with a more senior colleague than to rely on the advice of people on the internet. Dragons flight (talk) 17:54, 28 July 2010 (UTC)

Well if it's safe to begin with, I don't really want to make a fool of myself. John Riemann Soong (talk) 16:30, 28 July 2010 (UTC)

Jugs of strong acids (2.5 L concentrated sulfuric, etc.) often are coated with a thin layer of rubber/plastic, and that is what seems to become sticky. I assumed it was either swelling or decomposing a bit in the lab atmosphere (organic vapors in an orgo lab and/or acid vapors in an acid storage cabinet), plus picking up misc dirt in the stickiness. The test would be to remove part of this coating on a new bottle and see what happens over time. DMacks (talk) 16:52, 28 July 2010 (UTC)

In my experience, the problem is particularly bad with sulfuric acid bottles; with nitric acid, you tend to get the plastic coating hardening rather than softening, especially around the top. I guess its just that university research labs keep these bottles around far longer than the chemical suppliers would like ;) Physchim62 (talk) 16:59, 28 July 2010 (UTC)

If you have the slightest concerns or questions about safety, I encourage you to ask the person who organizes the lab storage about them. Ordinarily such people are delighted to see that people in the lab are thinking about safety -- usually their problems go in the other direction. Looie496 (talk) 20:33, 28 July 2010 (UTC)

Seconded. It is never foolish to seek to improve your knowledge of factors affecting Health & Safety. Any professional workplace (including academic or research establishments) should have a Health & Safety Department or at minimum a properly qualified person to consult, and clear procedures should be in place, training be given, and advice be available on request: if the ethos is one where concern for safety is thought foolish, I for one wouldn't care to work there at all (and yes, I have worked on sites involving laboratory, and mechanical & electrical engineering, facilities). You, JRS, are clearly well educated and intelligent, so if you're unsure about something's safety you either haven't been properly/fully instructed regarding your workplace's H&S by those who should have done so, or there is genuine cause for investigation and reassurance - or correction. 87.81.230.195 (talk) 23:27, 28 July 2010 (UTC)

It's not just my lab. Fellow interns in other labs describe a lot of the same things - clogged/disorganised fume hoods where the hoods are treated as storage areas. I mean, in training we were told to look out for these things, but I'm not sure in practice if it matters? If it does, it's the sort of thing I'd want to fix quietly since I've had a lot of favours done for me and I don't want to cause too much trouble.

Btw, can lab vapors cause that much rust? The containers are thoroughly corroded. Should HF be stored out in the open? With its translucent plastic container I almost thought it was just another bottle of alcohol -- I freaked out for a bit after I touched it and realised what it was, lol. John Riemann Soong (talk) 00:06, 29 July 2010 (UTC)

A volatile strong oxidizer (of which NaClO is perhaps the most common example) can thoroughly rust all available iron pieces after less than 24 hours if you leave a bottle open in an enclosed space. So it is certainly possible, and will depend on what is available. When not immediately in use volatile corrosive compounds should always be kept in closed containers. After all, if the vapor can eat iron it is generally likely to be bad for other lab equipment as well as the skin of young researchers. Dragons flight (talk) 03:07, 29 July 2010 (UTC)

JRS, only you can be fully aware of your own circumstances and constraints, but if I were in your position and seeing the things you are describing, and finding they were representative and not isolated, I would be investigating opportunities to transfer to a better-run establishment, and should I succeed in transferring I would consider passing my observations, perhaps anonymously, to whatever government authority has legal jurisdiction over Health & Safety in the locality concerned, in order to prompt an official inspection. In the UK that authority would be the Health & Safety Executive. Some might feel that it would be better to make representations to a senior level in the establishment or its parent organisation, if any, but in my experience standards are set from top management on down, and if things are that bad, the top isn't caring.

You say " . . . I'm not sure in practice if it matters?" H&S rules are never dreamed up for the sake of inconveniencing everyone for no good reason (though they can be inappropriately applied). Where H&S rules are flouted, it may not appear to matter for long periods of time without incident, right up to the moment when someone is maimed or killed. 87.81.230.195 (talk) 17:42, 29 July 2010 (UTC)

woodpecker question

This is an uncited and questionable excerpt from the Red-headed woodpecker article. "Like all woodpeckers, this species's tongue is actually one-half to two-thirds longer than the length which the bird uses for feeding. The extra length is wrapped longitudinally around the brain, between the brain and the skull, to provide added padding for the bird's head's repeated decelerations against wood. The tongue thus helps in preventing the brain from bouncing against the skull, which would cause brain damage." This sounds extremely suspect to me, but I am far from expert in the anatomy of these creatures, so could someone enlighten me as to if the tongue fact is true or not? Googlemeister (talk) 16:07, 28 July 2010 (UTC)

it's true. 92.229.14.166 (talk) 16:19, 28 July 2010 (UTC)

It is partially true. First, it is not true of "all" woodpeckers. Some have evolved different means of storing their long tongues. Second, the reason could be just for storage. It may have nothing to do with protecting their brain. -- kainaw™ 16:27, 28 July 2010 (UTC)

It hardly seems to have anything to do with "protecting the brain", otherwise there would also be structures at the front of the head. The line in the article is wrong. Physchim62 (talk) 17:20, 28 July 2010 (UTC)

on an "evolutionary" note, I find it completely implausible that this arrangement could have "evolved" in five generations. this would be like having your grandkid's grandkids suddenly all sprouting penises that go all the way around their butts to give them a cushion to sit on in school and at their desks. evolutionary biologists just have absolutely no proposed mechanisms that could account for this development in five generations. 92.229.14.166 (talk) 16:45, 28 July 2010 (UTC)

Nor should they have to give explanations for such ridiculous conjectuures! Physchim62 (talk) 17:20, 28 July 2010 (UTC)

No - it's totally impossible for 5 generations to do it. The population of these birds is declining - not increasing - so the average number of baby woodpeckers raised to maturity by a breeding pair over their lifespans MUST be less than two. So if some mutation happened - all at once (meaning, probably a single gene changed) in a particular bird - and if it's offspring out-bred birds without the gene 4:1 (so birds with the gene had, on average, 8 successful offspring rather than the more usual 2) and if the gene were passed perfectly onto 50% of the next generation then there could be 4x4x4x4x4 birds with the mutant tongue gene today. Sadly, that's only just over 1000 birds. So even with such crazily optimistic assumptions, there is no way that the entire species could have gotten this change in just 5 generations! Changes like this require many, many changes to the genome - each making a small difference to the survival of the birds (a few percent improvement, maybe, per gene change) - the spreading of that gene is slow - it's gotta take hundreds of generations. Worse still, you have to ask yourself - how are the birds that DON'T have the gene surviving without smashing their brains out? Since the species has been around for a long time - they would already have evolved an adequate means to avoid problems. Only some kind of a change of habitat (like maybe the trees that they inhabit are getting harder) could explain this. SteveBaker (talk) 19:34, 28 July 2010 (UTC)

Where is this "five generation" thing coming from? I see nothing that claims the tongues on anything evolved in five generations. -- kainaw™ 17:39, 28 July 2010 (UTC)

If you mean that it evolved in the some one hundred million years birds have been around, well, that's a lot more credible now, isn't it? 92.229.14.166 (talk) 18:44, 28 July 2010 (UTC)

It would be after then, analysing woodpeckers with this feature and closely related birds without this sort of feature and trying to determine how old the last common ancestor is would give some clue. As with Kainaw, I have no idea where this five generations thing came from, and you were the one to bring it up. Even for a young earth creationist, it makes little sense since five generations of woodpeckers is probably like 10? years ago. If it evolved in five generations and didn't exist 10 years ago we wouldn't even be discussing this since it would be another example of evolution creationists like to ignore. Nil Einne (talk) 19:26, 28 July 2010 (UTC)

Yes. Yes, it is more credible. So ... Was this some ham-fisted attempt to say "If something is ridiculous in ten years then it must also be ridiculous in ten million years?", I hope not, not only because that is seriously flawed thinking, (Try applying it to continental drift, erosion, or building the great wall of china.) but because it means you were intentionally trying to muck up someone's question with a debate. APL (talk) 20:18, 28 July 2010 (UTC)

I now realise 98.229 is not Chemicalinterest or one of his/her sisters which I had initially thought so is perhaps not a YEC although I still don't understand where the 5 generations thing came in to it from. BTW SB is right that it's impossible for it to happen in 5 generations, I didn't mean to suggest it was possible, just that suggesting it happened in 5 generations makes little sense no matter how unusual your world view. Nil Einne (talk) 07:35, 29 July 2010 (UTC)

What do you mean by your first comment, Nil Einne? --Chemicalinterest (talk) 12:18, 29 July 2010 (UTC)

When I first responded I mistakenly thought 98.229 was you or one of your sisters (and therefore a young earth creationist) as the IP looked similar to your IP and their comments sounded a bit like what you would say in a topic you've been active in recently. Nil Einne (talk) 16:47, 29 July 2010 (UTC)

Please note that the IP is 92.229 not 98. --Chemicalinterest (talk) 18:10, 29 July 2010 (UTC)

I don't understand part of General Relativity

General_relativity#Relativistic_generalization

I don't understand this section at all. What is it saying? 148.168.127.10 (talk) 16:22, 28 July 2010 (UTC)

Wow — I don't really understand it either. It's either a restating of rather basic GR principles in a very stilted, technical style, or it is trying to be a very technical digression/exposition. In either case, it is not written clearly, or encyclopedically, at all, and it assumes far too high level of an audience understanding of the concepts to be very useful to most readers. It should be rewritten, at the very least. Other sections are much more clear, even when discussing complicated or technical aspects of the theory. --Mr.98 (talk) 19:01, 28 July 2010 (UTC)

I agree, it's too complicated for someone that hasn't studied at least some maths at university to understand. I haven't read through it fully, so I'm not sure how much of it ought to be included in the article. Some aspects of GR can't really be explained to the layman (not without simplifying it to the point of it being wrong), but those parts are probably not appropriate for an encyclopaedia. At the very least, it should be split out into a separate article. --Tango (talk) 19:39, 28 July 2010 (UTC)

Right, that's more what I was trying to convey. It's not that Wikipedia can't contain technical information only understandable to experts, but these should be "drilled down" a bit, not part of a general overview. Some of the concepts it appears to explain can certainly be done in more straightforward, non-technical language, like the equivalence principle, or the fact that GR is SR+gravity, or that light cones are important, etc. --Mr.98 (talk) 20:49, 28 July 2010 (UTC)

I've put a "confusing" tag on the section, for what it's worth. I invite everyone to comment on the talk page. Comet Tuttle (talk) 06:37, 29 July 2010 (UTC)

The article is giving a description of what is the meaning of the equivalence principle using a language that can only be understood by readers that have some experience with riemannian geometry. Dauto (talk) 18:31, 29 July 2010 (UTC)

Try Introduction to general relativity, a featured article. ~AH1^(TCU) 01:14, 2 August 2010 (UTC)

30% hydrogen peroxide...usually by weight or volume?

Sorry for this question -- it's kind of urgent-- googling doesn't help me. The particular catalog number I'm looking at is H325-500 (Fisher Scientific). Do people usually sell these things by weight or volume? I have to make a 200 micromolar solution of H2O2 in liquid HeLa cell culture media. I've calculated I need about 0.00465 microlitres of pure hydrogen peroxide per every mL of cell culture, but don't know how much 30% H2O2 to add. I figure I can ignore the 70% water in the Fisher stock solution, either way? John Riemann Soong (talk) 16:42, 28 July 2010 (UTC)

These guys say by weight. But it doesn't matter - it decays and won't stay at 30% once you get it, the decay rate depends on temperature, how often the bottle was opened, light, shaking, etc. I think you should be able to measure the percent content by measuring the density, since H2O2 is much more dense than water (1.44 g/cm^3). (It will decay while you are working with it, so work fast, avoid shaking it, and avoid catalysts.) Ariel. (talk) 17:00, 28 July 2010 (UTC)

My mass balance says 1.13 g/mL. (I truncated the extra digits since I probably got some latex dust on there.) Ummm, I'm really embarrassed to ask this, but how do I back calculate a weighted average? I knew how to do this! Once! John Riemann Soong (talk) 17:36, 28 July 2010 (UTC)

water = 1.00g/mL, H2O2 = 1.44g/mL, mixture = 1.13g/mL, x = percent H2O2

mixture = water * (1-x) + H2O2 * x

solve for x = (mixture-water)/(H2O2-water)

x = .295

(I should turn that into math markup.) Ariel. (talk) 19:33, 28 July 2010 (UTC)

Doh. I was trying to find a quick fix using google calculator and it wasn't coming to me. Google doesn't support algebraic notation, I guess. John Riemann Soong (talk) 20:09, 28 July 2010 (UTC)

Use http://www.wolframalpha.com/ next time. Ariel. (talk) 20:24, 28 July 2010 (UTC)

(Okay, it's close to 30% ...good enough for me! But I found that out by guess and check. Kinda unsatisfying.) John Riemann Soong (talk) 17:38, 28 July 2010 (UTC)

I think CRC Handbook has a quick-lookup table (per "Viscosity and Density of Concentrated Hydroxide Solutions" new-feature listed in the ad for it in my recycling bin:). DMacks (talk) 17:45, 28 July 2010 (UTC)

OK thanks guys. I'm basically following a protocol outlined here, except using a549 cells and not astrocytes. H2O2 shouldn't oxidise the nutrients in cell culture media...right? Well I mean, it will probably do it to some extent, but when I make 200 micromolar H2O2 in cell culture media, most of it should remain unconsumed for 2 hours, right? John Riemann Soong (talk) 18:10, 28 July 2010 (UTC)

Well I'm going to take the plunge, but if I mix 1:1 solution of H2O2 and citric acid, should I observe a pH increase after a few hours? What about 1:1:1 H2O2, glucose and casein? John Riemann Soong (talk) 18:41, 28 July 2010 (UTC)

Smardale Gill viaduct - sandstone or limestone

Different sources describe this as being built from either "local pink sandstone" [1] or "local limestone" [2] [3]

I can't tell the difference from a photograph at 1km away.. Can anyone else? Also is it possible that it is made of both - in which case would either be more likely to be used as quoins/dressing. Also not to be confused with "Smardale viaduct" which is different. Thanks.87.102.76.166 (talk) 19:14, 28 July 2010 (UTC)

I would trust the nvt.org websites info over others, since this is their project. Also the stone doesn't look pink to me. Ariel. (talk) 19:28, 28 July 2010 (UTC)

It looks sort of pink here http://discoverbutterflies.com/how.html about half way down.. But mostly soot.87.102.76.166 (talk) 19:36, 28 July 2010 (UTC)

On the best picture of the viaduct I could find [4], it looks like limestone (from the grey colour). Mikenorton (talk) 23:50, 28 July 2010 (UTC)

do you have enough calories to get to the moon? (or: how fat do you have to be)

this is a purely armchair, arithmetic question: does a person have enough joules on their person to escape Earth's gravity and propel themselves to the moon. If not, how fat would a person have to be (at 3500 Calories per pound of fat) to have enough joules on their person for such a journey? This is just a classical physics armchair arithmetic problem, no need to include the usage of any equipment at all... —Preceding unsigned comment added by 92.229.14.166 (talk) 22:01, 28 July 2010 (UTC)

Earth's escape velocity is about 11.2 kilometers per second; you'll need just shy of that amount of kinetic energy to get over the slightly smaller barrier between the Earth and the Moon. In round figures, that's about 50 megajoules per kilogram. The energy content of fat is (as noted) about 3500 Calories per pound, which runs to (roughly) 40 kilojoules per kilogram. Back of the envelope says that if you were able to instantaneously convert all of the body's fat to kinetic energy and impart that to the non-fat body bits, you'd have to be a bit more than 99.9% fat. (Assuming I've not lost some orders of magnitude anywhere.) The problem gets even worse if you try to burn fat continuously on the way up, because then at least some of the energy goes into lifting fat that will later be burned. TenOfAllTrades(talk) 22:16, 28 July 2010 (UTC)

Oops. For some reason I was reading the energy content of fat as 37 joules per gram, rather than 37 kJ. Pay no attention to my numbers; they are wrong by three orders of magnitude.... TenOfAllTrades(talk) 22:43, 28 July 2010 (UTC)

Fat has an energy of 38 MJ/kg, the quoted Calories are kcal. That corresponds to lifting it 11,000 10,000 km.--Patrick (talk) 22:24, 28 July 2010 (UTC)

It doesn't work. Sorry. (Unless I did my math wrong.)

v = 25010 mph (escape velocity)

e = 1/2 mv^2 (energy)

e = m*38 MJ/kg (energy from fat)

m = x lb (x is the unknown amount of fat)

x lb*38 MJ/kg > 1/2 * x lb * (25010 mph)^2 (substitute variables, and note that it's an inequality)

solve for x. Result: x < 0. Meaning it doesn't work.

BIG NOTE: This is assuming you are lifting all the fat into orbit. Which you may or may not be doing depending on how you burn the fat. Ariel. (talk) 22:30, 28 July 2010 (UTC)

If we assume a person weighs m without any fat, and we need to get them to 11.2 km/s, that's about m*6.3 x10⁷ J/kg. That's about 1.5 x10⁴ kcal/kg, and fat stores about 9000 kcal/kg so that's about 1.6*m of fat. If you could burn it all instantly and convert 100% efficiently into kinetic energy then you could escape Earth. So if a person weighed 50kg without fat, they would need about 83kg of fat. Rckrone (talk) 22:37, 28 July 2010 (UTC)

As Rckrone mentioned, if you don't carry any the fat with you (i.e. you burn it all at once), then it's possible (but note a real rocket does not do that). For a 150lb person it's: 246.716lb of fat. Ariel. (talk) 22:41, 28 July 2010 (UTC)

If you climbed a really long ladder to space instead, would you consume more or less energy? John Riemann Soong (talk) 10:36, 29 July 2010 (UTC)

Climbing a ladder would mean that you are consuming fat via your cell processes, not actually releasing all of its energy in a theoretical situation. Since cell processes aren't 100% efficient, it may take more energy (please correct me if I'm wrong). --Chemicalinterest (talk) 11:03, 29 July 2010 (UTC)

Plus in the ladder climbing scenario, you would starve to death before reaching the moon since it would take years to climb that ladder, and you have baseline metabolism robbing you of energy. Googlemeister (talk) 12:46, 29 July 2010 (UTC)

Well let's say you have exceptional climbing ability. What I meant to ask is -- since you're relying on a normal force pushing you back, you don't need to reach escape velocity. Does that save energy, or no? John Riemann Soong (talk) 13:21, 29 July 2010 (UTC)

If the earth did not rotate then it doesn't help at all - you could climb to the top, but to actually reach the moon you need the same total energy as the escape velocity. And escape velocity takes into account the energy of climbing out of gravity. But the earth does rotate, so by climbing up a ladder you allow the earth to spin you, if the ladder is long enough to reach geosynchronous orbit then the earth provides most of the energy you need. You just need enough to climb up against gravity. Ariel. (talk) 16:31, 29 July 2010 (UTC)

In the ladder scenario, one you got to the height of the moon, it would at some point, crash into you at lethal velocity. Googlemeister (talk) 18:28, 29 July 2010 (UTC)

Looked at another way, how much matter, in the form of fat, if converted to energy, would be needed to propel a 100 kg person to the moon, if E = MC²? Edison (talk) 05:08, 30 July 2010 (UTC)

There is no practical way to get a hydrocarbon, let alone cellulite, to undergo the kind of nuclear reaction that would release even a small amount of energy in this way; and there definitely is no practical way to annihilate the entire fat molecule either to convert its entire mass to energy; so if this is strictly a gedanken-experiment, the fact that you are using "fat" as the mass to be converted to energy is irrelevant. Nimur (talk) 05:16, 30 July 2010 (UTC)

To accelerate 100kg to the escape velocity of the earth will require the energy in 69.54 micrograms (6.954x10^-5 g) of matter - any matter, not just fat. Ariel. (talk) 05:22, 30 July 2010 (UTC)

The potential energy increases from -63 MJ/kg at Earth to -4 MJ/kg at the Moon (-1 MJ/kg w.r.t. Earth, and -3 MJ/kg w.r.t. the Moon), so with constant mass it is an increase of 59 MJ/kg. If fat is burned instantly the amount needed is 59 / 38 = 1.55 times the mass of the payload, and to infinity 63 / 38 = 1.66 times the mass of the payload (the 1.6*m already mentioned above). Ignoring the rotation of Earth, for climbing the ladder with 100 % efficiency while burning fat it seems we have a mass reduction by a factor e for every increase of the potential field by 38 MJ/kg, so to infinity mass is reduced by a factor e ^ 1.66 = 5.3. For a ladder to the Moon we have to climb to the point where we start descending. From there we can recover energy with suitable equipment, but to convert that back to body fat requires some material to be found along the way.--Patrick (talk) 09:22, 30 July 2010 (UTC)

Direction of current

http://www.tqa.tas.gov.au/4DCGI/_WWW_doc/009120/RND01/PHY5C_Paper.pdf
Question 9 (a) (ii)
How do you do it? 115.178.29.142 (talk) 22:21, 28 July 2010 (UTC)

Well, how far have you gotten, and what has you stuck? TenOfAllTrades(talk) 22:24, 28 July 2010 (UTC)

Check you understand or already know Fleming's left hand rule for motors and Fleming's right hand rule. Because the ions are moving that's like an electric current - big clue - the positive and negative ions moving in the same direction are like currents in opposite directions. I'll give more info. if you are still stuck. (also remember that the direction of the electric current is from positive part to negative part) Sf5xeplus (talk) 23:23, 28 July 2010 (UTC)

It's the second part of the question that I can't do (part (ii) i.e. the direction of the current through the voltmeter), not the first part (part (i)).115.178.29.142 (talk) 00:11, 29 July 2010 (UTC)

Huh? The second part is the simple bit, if you can do the first part! Maybe if you read our small section on conventional current, you will see the answer (the question is asking if you know what conventional current is). Physchim62 (talk) 04:05, 29 July 2010 (UTC)

can you tell just by the honk whether a man or woman is blowing their nose?

can you tell just by the honk whether a man or woman is blowing their nose, a child or adult, etc.? —Preceding unsigned comment added by 92.229.14.166 (talk) 22:31, 28 July 2010 (UTC)

How about you, can you do it? Is this a poll? Some people are presumably better than others at this sort of thing. I probably could tell a child, but not the difference between a man and a woman. Is this really a serious question? Ariel. (talk) 22:48, 28 July 2010 (UTC)

obviously by "can you" I mean "can one". I was thinking by analogy with voice (clearly different for males and females, very few voices are hard to tell which), due to anatomical differnces. In some ways there is anatomical similarity with honk production, namely lungs are also involved. where is honk produced? in the nose, presumably. so, again, would men have larger or more cavernous noses on average? Anyway these are just possibilities, the answer could be "unlike voice, there is no discernible difference between male and female honk". But I would like to know your reasoning if that is your answer. 92.229.14.166 (talk) 23:20, 28 July 2010 (UTC)

It's really hard to believe that anyone would study such a strange matter - so it's unlikely that we'll find a good answer for you. SteveBaker (talk) 02:18, 29 July 2010 (UTC)

I agree that it is most unlikely that any definitive answer is available, but I would put my money on the answer being "no" (discounting the fact that, in many cultures, women find it less acceptable to blow their noses loudly). Perhaps an ENT specialist would know about anatomical differences (if any) between genders, but I suspect that variability within each gender completely swamps any slight gender difference. Is there a significant difference in head size between genders? Dbfirs 07:03, 29 July 2010 (UTC)

I smell an Ignoble prize. Googlemeister (talk) 12:46, 29 July 2010 (UTC)

Absolutely not. I know a woman whose nose honk is quite loud and impressive, such that one would have thought it came from Paul Bunyan or the Jolly Green Giant. Edison (talk) 05:01, 30 July 2010 (UTC)

Are we all epigeneticists?

From some book:

"one of the great controversies, that of preformation versus epigenesis and this was settled primarily by reference to chick development. The preformationists thought that the entire individual was present in miniature in the egg or, alternatively, within the sperm and that it simply grew until it hatched; there was thought to be no differentiation, merely growth. The epigeneticists considered that both growth and differentiation were involved and were necessary. Today, we are all epigeneticists."

Is this the correct use of the word epigeneticist? --92.25.227.155 (talk) 22:46, 28 July 2010 (UTC)

The roots epigenesis (biology) and epigenetics are clearly different in meaning; "epigenesis" applies to a theory of developmental embryology and "epigenetics" relates, in a very general sense, to structural changes that control the expression of genes (though interestingly quite important in regulating embryogenesis). I suppose one could call a scientist who studies epigenetics to be an epigeneticist, but I don't hear that term used very much. Given that preformation has been soundly debunked in favor of a complex developmental process resembling epigenesis, the author of your quote is presumably saying that there is no one left who still thinks preformation is a viable theory. Maybe he or she thought the term "epigeneticist" was just better than "epigenesisicist". --- Medical geneticist (talk) 23:32, 28 July 2010 (UTC)

We are all epigeneticists if you are using the terms of the 19th century embryological debates — we do believe that development is crucial, and even the most hard-line hereditarians do not believe in the preformation hypothesis in the terms it was believed in the 19th century. We are not all epigeneticists if you are using the term as it came into usage in the late 20th century as applied in the term "epigenetics". Personally I think it is a misleading phrase — a more accurate way to put it would be to say that we are no longer preformationists. (What we "are" here is more defined by the negative by the positive, because we don't really believe everything the 19th century "epigeneticists" believed, I am sure.) --Mr.98 (talk) 01:16, 29 July 2010 (UTC)

When everyone takes the same label - there is no need to use the label anymore because it loses all linguistic value. There used to be heliocentricists and geocentricists (those who believed the sun was at the center of the solar system and those who believed the earth was at the center) - but now that we are all heliocentricists, we don't need to use the word anymore. That doesn't make the use of the word incorrect - but rather just obsolete. SteveBaker (talk) 02:16, 29 July 2010 (UTC)

I don't think it's quite true that the word is obsolete if the position is debunked. We still want to be able to talk about the historical debate. Rckrone (talk) 05:27, 29 July 2010 (UTC)

True, but we also need to be careful about our use of terms: probably everyone on this page accepts that there are things called "atoms", but that doesn't make us "atomists" in the sense of Ancient Greek philosophy! Physchim62 (talk) 06:50, 29 July 2010 (UTC)

But we're not really heliocentrists — we don't believe the sun is at the center of the universe, which was what the original heliocentrists believed (see Heliocentrism). That's kind of my point — we actually don't subscribe to the beliefs of the "winning" group so much as we have repudiated the beliefs of the "losing" group. It's not that we all became heliocentrists, but rather that we are simply not geocentrists. The nature of this kind of scientific change (if one can generalize it) is not so much that we all switch to some winning view, but we go away from the losing view, and a whole new set up complicated views opens up. It is more accurate to just say that nobody (to a rough approximation) believes the old view anymore, rather than saying that everybody believes the new view (which is a vast oversimplification). --Mr.98 (talk) 13:36, 29 July 2010 (UTC)

Sun Exposure, Skin Cancer and Vitamin D

I read a New York Times article about how being outside, minimally clothed and unprotected by sunscreen, is an excellent way for one to acquire his healthy dose of Vitamin D. I have also been told for my entire life that doing these things will give me sunburns and horrible skin cancer. I would like to believe that the NYT version is true, because I wouldn't need to worry about sunscreen anymore. Is there a dermatologist in the house? Can anyone sort this out for me? Thanks. Postprehistoric (talk) 23:31, 28 July 2010 (UTC)

you could try Risks and benefits of sun exposure which quotes from a study "there is not enough information to determine a safe level of sun exposure at this time" ,, also "Despite the importance of the sun to vitamin D synthesis, it is prudent to limit exposure of skin to sunlight". You also still would want to avoid sunburn for all the reasons. 87.102.76.166 (talk) 23:52, 28 July 2010 (UTC)

My understanding is that vitamin D can prevent skin cancer, but it only takes 15-20 minutes to max out the vitamin D production, anything more than that is not necessary. See also Sunburn#Controversy over sunscreen and Sunscreen controversy. Sunscreen might not help at all. If you do use it I would pick one with titanium dioxide or zinc oxide, because they are considered far more effective at preventing real damage (as opposed to reddening, which all kinds prevent). This subject has massive debate going on right now, no one can give you a definitive answer. Some studies even show that using sunscreen actually increases the risk of melanoma. The only thing (I think) everyone agrees with is: Get less sun and take vitamin D supplements instead. (But simply less sun without vitamin D might be worse than more sun.) Ariel. (talk) 00:21, 29 July 2010 (UTC)

I don't have a reference to hand, but apparently you can get enough vitamin D by spending about 10 minutes outside on an overcast day with just your face and arms bare. In fact, you can get enough vitamin D just from eating a balanced diet without any sunlight. So, in short, don't worry about vitamin D. (This is all assuming you are reasonably fair skinned. If you black and live somewhere at reasonably high latitude, then vitamin D can be more of an issue.) --Tango (talk) 00:36, 29 July 2010 (UTC)

It isn't a question of getting enough vitamin D. Vitamin D is a powerful antioxidant, and there is reason to think that high levels of it may have a protective effect against cancer. But that's based on theory and isn't backed up by much actual evidence, one way or the other. Looie496 (talk) 00:41, 29 July 2010 (UTC)

Medical advice? Aaadddaaammm (talk) 07:26, 29 July 2010 (UTC)

The times given above (10 minutes sunlight on face and arms) so far as they may be useful are only applicable to white skinned individuals. Times are longer if you have a tan. Longer again if you have olive skin. The times may stretch to over an hour for some. --203.202.43.53 (talk) 03:27, 3 August 2010 (UTC)

About vitamin D, I think the evidence now strongly points in the direction to the recommended levels of intake being way too low, the optimal levels being so high that it even exceed the current official maximum safe dose. It takes time for the health officials to update the recommended dose, but as this article points out, the expert themselves are using vitamin D supplements themselves at levels they think are healthy which is of the order of 5,000 IU per day.

One has to note that a vitamin D dose of the order of 10,000 IU per day is entirely natural, it cannot be compared to e.g. taking a high vitamin C dose that you can only get that from supplements. E.g. bushmen in Africa don't wear much clothes and hunt for meat during the day for hours when the UV index can be as high as 12. They then get a dose of 10,000 to 20,000 IU of vitamin D and not much more than that, because of a dynamical equilibrium between vitamin D synthesis in the skin due to UV radiation and vitamin D being broken down by UV radiation. To get an overdose of vitamin D you need to take 100,000 IU every day for several weeks.

Since the 17th century more and more people have been living and working indoors causing extremely low vitamin D levels leading to problems with calcium absorpion from food. To prevent this, you only need to take very low doses of vitamin D, a few hundred IU per day is enough. This is what the current recommendation is based on. But new evidence suggests that this is low dose is similar to the miniscule dose of vitamin C you would need to take to prevent scurvy.

If we had all stopped eating fresh vegetables and fruits millennia ago and getting the minimum amount of vitamin C to prevent getting scurvy, we may well have set the recommended dose of vitamin C to be a lot less than found in a single apple and one apple would perhaps be the maximum safe dose as there would not have been the rigorous medical evidence that eating several pieces of fruit per day does not cause some unknown horrible illness many year later. This logic would set the officially recommended dose but, of course, the experts in the field would know that from a more reasonable point of view this is all nonsense and there would likely be evidence that a higher dose is actually beneficial. What you would see is that the experts themselves would not stick to the official guidelines, which is exactly what is happening in case of vitamin D.

References:

http://www.eurekalert.org/pub_releases/2010-07/tes-vdd072710.php

www.naturalnews.com/029312_immune_system_vitamin_D.html

http://www.webmd.com/parkinsons-disease/news/20100713/vitamin-d-may-lower-parkinsons-risk

http://www.aafp.org/online/en/home/publications/news/news-now/health-of-the-public/20100727vitamind-cognition.html

http://www.medscape.com/viewarticle/724646

http://news.xinhuanet.com/english2010/health/2010-07/03/c_13381512.htm

http://www.webmd.com/baby/news/20100504/high-doses-of-vitamin-d-may-cut-pregnancy-risk

http://www.reuters.com/article/idUSTRE62I3MK20100319

http://www.webmd.com/asthma/news/20100128/vitamin-d-may-ease-asthma

Count Iblis (talk) 18:40, 29 July 2010 (UTC)

A tan from sun exposure by itself can provide an SPF of 4. However, this wouldn't prevent harmful sunburns. Using sunlight to fill up on Vitamin D would have been viable in the past, but nowadays it's more difficult to do this safely due to the ozone hole, but instead of sunscreen you could use sunblock. ~AH1^(TCU) 01:04, 2 August 2010 (UTC)