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January 2

Same Path for the Small Intestines in (most) Humans?

Other than cases related to Situs inversus does the small intestines in people follow the same pathway? (i.e. something like from the Duodenum, travels right to the edge of the intestines, then toward the back, then down, etc, etc)Naraht (talk) 13:57, 2 January 2015 (UTC)

The articles anthropomancy and haruspex imply that there's enough variation to be noticeable, although those "arts" also looked at the color and other characteristics besides just the shape and alignment. Animals with abnormal innards were also forbidden as sacrifices, including at the temple in Jerusalem. In humans, many abnormalities are simply not discovered unless they have some effect. My sister-in-law did not know she only had one kidney until they did an ultrasound during her pregnancy. A search at google gives these results for "configuration of the small intestine". μηδείς (talk) 18:09, 2 January 2015 (UTC)

Thank you.Naraht (talk) 15:42, 6 January 2015 (UTC)

Indonesia AirAsia Flight 8501: passengers found strapped in

Re: Indonesia AirAsia Flight 8501. I read in the news today that "most of the passengers were found strapped into their seats". What is the significance of this fact? What would it lead investigators to conclude? My initial reaction (which may be incorrect) was: "well, of course, they would be strapped into their seats!" No? How is this significant exactly? I assume it must be important on some investigatory level. Thanks. Joseph A. Spadaro (talk) 17:06, 2 January 2015 (UTC)

Not sure that they have found any in seats but if the aircraft was flying through bad weather and turbulence then it would not be unusual for them to be strapped in. MilborneOne (talk) 17:12, 2 January 2015 (UTC)

If they weren't strapped in, that could mean several things:

1) There was a sudden incident, giving them no time to strap in, such as an explosion or collision.

2) They survived the crash and were evacuating the plane when they died.

3) They were forced out of their seats, as by hijackers. StuRat (talk) 17:21, 2 January 2015 (UTC)

Reason 1 is out of date for airlines in the parts of the world I've been in (which, however, do not include any part of Asia). Airlines now always ask passengers to keep their seat belts fastened when seated, in case of unexpected turbulence. --65.94.50.4 (talk) 19:56, 2 January 2015 (UTC)

My (limited) experience with a few airlines, all in the Asia region albeit not including Air Asia, is the same. I believe compliance was fairly high, although some may loosen the seatbelt. Nil Einne (talk) 08:00, 3 January 2015 (UTC)

High speed with high incident angle to the sea and the seat belt can tear the body in half. TWA flight 800 recovered many bodies as upper and lower torso. If they survived impact, I suspect most would unbuckle themselves unless they were unconscious. Those not buckled or braced properly may submarine under the seatbelt possibly leaving limbs or clothing behind. --DHeyward (talk) 19:47, 2 January 2015 (UTC)

Thanks, all. Joseph A. Spadaro (talk) 17:21, 4 January 2015 (UTC)

Do we have an article on medical cross-sections ?

Meaning a cross-section of a tissue sample, which is then examined on a slide. StuRat (talk) 17:19, 2 January 2015 (UTC)

Maybe histology is what you are looking for. If not, that article has links to some other related things. Looie496 (talk) 17:37, 2 January 2015 (UTC)

Tomography, in medicine, nowadays tends to refer to radiological methods; but the word "tomography" refers to studying images of slices. See also, microtome (the machine used to slice samples for clinical histology or research purposes). Nimur (talk) 18:58, 2 January 2015 (UTC)

Hmmm, generally speaking you tend to run into microtome sections of paraffin embedded tissue samples, cryotome sections of OCT embedded samples, and electron microscopy of sections embedded in an epoxy resin using a diamond knife or freshly broken glass knife (ultramicrotome). This need not be an exclusive list but I can't readily think of anything else smaller than a steak knife. Wnt (talk) 03:24, 3 January 2015 (UTC)

There is also the Visible Human Project which has to be the ultimate in cutting tissue cross-sections, although you would need humongous slides to mount them. Richerman (talk) 11:21, 3 January 2015 (UTC)

That's a good point, though it is a very different process - apparently gelatin and water were used and the sample was ground down, destructively, to the surfaces photographed, leaving no slides behind. So I guess technically it fails the OP's criteria... still, wish I'd thought of it. :) Wnt (talk) 23:47, 3 January 2015 (UTC)

Theroritically can EDTA administrated into the body?

or it's only for tubes? 194.114.146.227 (talk) 19:54, 2 January 2015 (UTC)

PLease see Ethylenediaminetetraacetic_acid#Medicine. --Dr Dima (talk) 20:49, 2 January 2015 (UTC)

Note that chelation therapy is real; however, it is also a quack magnet, and for every mention of sound medical practice by a skilled practitioner there are a hundred lunatics pushing for people to treat their bodies like test tubes. Whenever someone cites nothing but theory to support a treatment, some apparently logical deduction based on chemistry, skepticism is appropriate - because biology doesn't know theory. Until someone actually tries the treatment on a test population and comes back with statistically significant results, you know nothing - and neither do they. Wnt (talk) 03:19, 3 January 2015 (UTC)

January 3

Any one here proficient about Histamine & Appetite regulation?

Please see Talk:Histamine; The article could grow better if an expert in the field would add some data on this subject. Ben-Natan (talk) 06:39, 3 January 2015 (UTC)

why does listerine packaging say not to rinse mouth straight from bottle?

is it a weird cross contamination issue or what? 212.96.61.236 (talk) — Preceding undated comment added 11:37, 3 January 2015 (UTC)

Probably as a legalistic thing, i.e. to discourage you from absent-mindedly drinking it. Like other seemingly idiot-proofing warnings, like on those little moisture absorbing packets that say "Do not eat". ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:00, 3 January 2015 (UTC)

This, from Google Images, is a ca.2011 warning label. I don't see anything that says not to take it straight from the bottle, only a warning "do not swallow". Or is your label more recent? ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:09, 3 January 2015 (UTC)

Our bottle from yesterday says "Do not dilute, swallow, or swig from the bottle". From various talk pages; While the product will kill any germs in the "backwash" from the mouth to the bottle, it will eventually discolour and taste bad (worse). Fiddlersmouth (talk) 13:56, 3 January 2015 (UTC)

Also, a swig from a large bottle may tend to splash in your eyes, burning quite badly, I imagine. StuRat (talk) 00:11, 4 January 2015 (UTC)

There might be a clue in their use of that term "swig", which means a big gulp.[1] ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:20, 4 January 2015 (UTC)

A swig is between a sip and a mouthful (an unswallowed gulp), where I'm from. A reasonable amount for rinsing. It seems to me they just don't want your lip microbes screwing up their concoction. Might never happen, but there are a lot of filthy lips out there, and germs evolve every day. If something gets terribly funky (or just less effective) and a lawyer pursues it, they can tell him they warned you and hang up.

As for "don't dilute", they just want you to replace it sooner. Nothing wrong with water and mouthwash. Watery milk's no fun, though. InedibleHulk (talk) 23:46, January 4, 2015 (UTC)

Does it really say "swig"? I can't wait till I next have a reason to go buy store-brand Listerine and look at the overpriced brand-named product's label. μηδείς (talk) 03:09, 7 January 2015 (UTC)

Couldn't you just hit up a nearby DR and look at a label for free? I think another idea is that they want to discourage you from attempting to get wasted off of it. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 16 Tevet 5775 18:42, 7 January 2015 (UTC)

Here's a label: [2]. It says to use a cup, but doesn't use the word "swig". I also found other Listerine labels that don't specify to use a cup. StuRat (talk) 20:27, 7 January 2015 (UTC)

What is the way that EDTA prevents the clotting in the blood samples?

I read in the article here (EDTA) the next sentence but it dosn't explane the way: "EDTA is used extensively in the analysis of blood. It is an anticoagulant for blood samples for CBC/FBEs." 194.114.146.227 (talk) 15:15, 3 January 2015 (UTC)

It binds (aka sequesters aka chelates) calcium ions disolved in the plasma so that they are no longer available for the clotting cascade, in which calcium ions play a key role. No free calcium ions, no clotting. Dominus Vobisdu (talk) 15:19, 3 January 2015 (UTC)

science(cooking,heating)

Can a heating source (ie electrical hotplate) mantain the heat of an extremely hot pot with food in it forever, however it would not be able to bring something that was cold to that heat? — Preceding unsigned comment added by Neil rybak (talk • contribs) 16:55, 3 January 2015 (UTC)

I suppose so, in a theoretical sense. There is a certain equilibrium temperature which will be reached when the heat source and cooling are equivalent. However, the cooling rate depends on the temperature difference between the food and the environment. Combine these together and the temperature will asymptotically approach the equilibrium temperature. Depending on if the heated object starts above or below that equilibrium object, it will theoretically take forever to get to it, meaning that those two objects will never be the same temperature. However, the reality is that, after some period of time, the temps would be so close they could no longer be distinguished by any instruments we have. (Note that I ignored other factors such as all the water boiling off the food, which then changes the equilibrium temperature.)

To illustrate, here's a chart of how temps might change on 3 objects starting below, at, or above the equilibrium temperature:

Obj1  Obj2  Obj3
====  ====  ==== 
100   200   300
150   200   250
175   200   225
188   200   212
194   200   206
197   200   203
198   200   202
199   200   201
199.5 200   200.5
199.7 200   200.3
199.8 200   200.2
199.9 200   200.1

So now for some practical cooking advice. It can take very long to get food to the desired temperature using something with a low heat output like a hotplate. That means it will be warm, but not hot, for a long time, and bacteria can grow during that period. Thus, it's safer to initially heat the food elsewhere, like in a microwave oven, to quickly get it past that dangerous temperature and into the safe range, then move it to the hot plate to keep it in the safe range. StuRat (talk) 17:28, 3 January 2015 (UTC)

Pretty much in a practical sense, too. A good example is the hotplates that keep coffeepots warm under electric coffee makers. They have enough power to maintain temperature, but generally not enough to bring cold water up to the serving temperature for coffee (at least in a reasonable timeframe), nor enough to bring the coffee to a full boil. The power is carefully selected to balance cooling and heating. Dominus Vobisdu (talk) 18:04, 3 January 2015 (UTC)

Yes, they won't reach the same temp in a practical amount of time, and theoretically, they will never reach the same temp. StuRat (talk) 18:46, 3 January 2015 (UTC)

That's true for a low output hotplate, but an 1100 watt radiant cooker ring - also known as a hotplate - can get very hot and can boil a pan of water from cold fairly quickly. Richerman (talk) 21:21, 3 January 2015 (UTC)

From a physics point of view, the answer is "no". If the hot plate can maintain something at a particular temperature, it can eventually heat that thing to that temperature. As StuRat notes, the approach is slow and asymptotic. How long it takes to reach the target temperature depends on how closely you define the target's tolerances. Arguing that the food never reaches the equilibrium temperature is sensible mathematically, but physically is nonsense. Every measurement has some uncertainty, and most physical properties have fundamental uncertainties too. Even if you start with the food hot, you can never exactly maintain it at one particular temperature, to infinite precision. See also Zeno's paradox#Dichotomy paradox.--Srleffler (talk) 02:51, 5 January 2015 (UTC)

January 4

Llamas or alpacas?

Some months ago I uploaded this photograph at Commons and named it "Llamas at Shiprods", but since then I've been looking at photographs of both llamas and alpacas and now I'm not so sure. Is there a South American or a zoologist who can give me an authoritative answer? --Antiquary (talk) 18:40, 4 January 2015 (UTC)

The basic difference is size - llamas are much larger than alpacas, which are roughly sheep-sized whereas llamas are as tall as adult humans. Unfortunately there is nothing in the photo to indicate scale. It could be useful if you have any other information that can help deduce the size of these animals. Roger (Dodger67) (talk) 19:09, 4 January 2015 (UTC)

Nor is there anything to indicate scale in the other two photos I have of them, and my memory's a little vague too. But since they live half an hour away I'll go and check on their size tomorrow. Thanks for that. --Antiquary (talk) 19:59, 4 January 2015 (UTC)

• We used to feed the llama they kept at the local farmer's market about 15 times a summer for years until it died, and these look too small for adult llamas. It would be odd to have such a large group of juvenile llamas of the same size. But I think your best bet is to contact "shiprods" (we don't have an article on that) and ask them. I am sure they will know, given these are obviously not a flock that just wandered onto the property. Or maybe someone will know a determinative diagnostic test. In any case, I'd get in contact with the proprietor.

There is, of course, this very famous two-minute Llama documentary, but it is probably not a reliable source.

μηδείς (talk) 20:56, 4 January 2015 (UTC)

I'm not an expert on South American species, but the ears look more like alpaca ears. Llamas' ears look like bananas! Also, the area is well-known for its alpacas, see here. Dbfirs 21:06, 4 January 2015 (UTC)

I agree, they are alpacas. Their coats are typically more curly like that. Llamas have straighter coats, usually. But there are all kinds of breeds so don't quote me. 68.14.230.243 (talk) 23:31, 4 January 2015 (UTC)

The proprietors of that farm aren't on good terms with those of mine so the personal approach could be a bit tricky (Sussex is like that – see Cold Comfort Farm). Having taken another look at the beasties I find that even the largest is only the size of a large sheep as far as the body goes. That long neck does bring some of them up to close to my height (I'm 5' 8"), but even so I think we can all agree they're alpacas, so I'll have the file at Commons renamed. Thanks to all. --Antiquary (talk) 11:51, 5 January 2015 (UTC)

Thanks! Looks like a great story, I have ordered the movie of Cold Comfort Farm for my mother. μηδείς (talk) 19:00, 6 January 2015 (UTC)

Wikiquote will give you an idea of the style, though they leave out the famous darkly repeated line, "There's something nasty in the woodshed". --Antiquary (talk) 19:51, 6 January 2015 (UTC)

Alpaca. Polypipe Wrangler (talk) 04:00, 8 January 2015 (UTC)

If I claim something has a 90% chance of happening the next day

Can I be proven wrong? If it doesn't happen, that just means that we are within the 10% of it not happening.--Noopolo (talk) 19:39, 4 January 2015 (UTC)

But if you start making such claims everyday and the your predictions prove to be wrong in say 90% of cases, nobody will take you seriously after that. Ruslik_Zero 19:47, 4 January 2015 (UTC)

If you are talking about weather forecasting, I once heard it explained that when they say there is a 60% chance of rain tomorrow in a local postal code they mean that looking at the historical weather records that most matched the prevailing patterns right before the predicted day, on 60/100 of those following days it did rain. Now we also have all sorts of things like weather modelling for hurricane tracks, and predictions based on a consensus of models.

Your question as stated however, just seems like an invitation for debate which we have no grounds to answer with a reliable source. You seem to want to know if you can deceive people, and I suspect you know how good you are at that. If you don't, you'll need to take a survey not only of those people who talk to you, but also of those who have ceased to talk to you, and ask their opinion. μηδείς (talk) 21:06, 4 January 2015 (UTC)

If you claim there will be a 90% chance some particular extraordinary thing will happen, and it doesn't, then, since extraordinary claims require extraordinary evidence, I would challenge you to show how you calculated that 90% chance, and I could then disprove your method. StuRat (talk) 22:05, 4 January 2015 (UTC)

Note that the original question doesn't say anything about the claim being "extraordinary". RomanSpa (talk) 08:54, 6 January 2015 (UTC)

This is basically a math question. Looking at it simply, the number of correct predictions should follow a Poisson distribution. At some point though, a person has to evaluate the relative probabilities of a null hypothesis that you are lying vs. the odds that you were simply unlucky, which I think involves some degree of a priori assumption of your honesty. Normally in science we don't get a specific frequency with which a drug cures a disease or the like, and so we simply look for "statistical significance", but this isn't quite the same situation as that. In any case, a single lone prediction that is never repeated is, by its nature, outside the realm of scientific evaluation, and in the end a humanistic judgment will tend to vary by the author and his belief in whatever means you say inspired your prediction. Wnt (talk) 22:09, 4 January 2015 (UTC)

(ec) The technical term in forecasting for what you are asking about is the "calibration" -- as in: whether or not your probability assessments are well-calibrated. Typically, for something like weather forecasting, you can look back over all of the forecasts made e.g. for a whole year, which are likely to include a number of things predicted with 90% probability. Depending on what fraction of those forecasts turned out to be correct, you can then estimate the probability (or a confidence, if you're a frequentist) as to whether you may be systematically over-estimating or under-estimating the robustness of your forecast, if you're assessing probabilities of 90%. You may even be able to identify particular types of conditions under which the probability estimates appear to be systematically off -- though beware that such retrospective in-sample pattern spotting, once the data are in, can be notoriously deceptive. Jheald (talk) 22:33, 4 January 2015 (UTC)

Even with a single data-point I can still sometimes use some of the machinery of probabilistic inference -- particularly if I have two distinct hypotheses to compare -- for example, suppose my alternative to your model was simply a 50/50 chance of the thing happening or not happening. Then the fact of it not happening one time out of one would represent a Bayes factor of (0.5 / 0.1) = 5.0 against your model -- a Bayes factor on the borderline between "barely worth mentioning" and "substantial", according to Harold Jeffreys. The Bayes factor means that if beforehand I was predisposed to give odds of 5-1 on in favour of your model, eg because of my initial regard for your capability and previous good work, I should revise those odds to evens following the prediction failure.

(If, on the other hand, if your prediction had succeeded, that would have given a Bayes factor of (0.9 / 0.5) = 1.8 in favour of your model -- a small positive confirmation, so I should have revised my initial odds of 5-1 in favour up to 9-1 in favour.) Jheald (talk) 23:03, 4 January 2015 (UTC)

The traditional method of scoring probability forecasts is the Brier score. The Brier score can be decomposed to give more detailed information on the probability distribution of the forecasts relative to the observations, especially the reliability and resolution. (Historical note, not in any RS that I'm aware of: Brier was a modest guy, and insisted on calling this the "P-score" rather than the "Brier score." One day he was talking to someone and realized they were confusing P-score with Peace Corps. So he finally relented and accepted the name Brier score.) Short Brigade Harvester Boris (talk) 23:00, 4 January 2015 (UTC)

You might be interested in our article on Probability interpretations or the Stanford Encyclopedia entry, Interpretations of Probability. The short answer to your question is no, you cannot be proven wrong simply according to whether the prediction happens or not. Your claim about 90% could be proven wrong on other grounds, however, depending on the exact topic. IBE (talk) 06:26, 5 January 2015 (UTC)

What if someone conjectures that there is a 90% chance of something happening, but that is a physical impossibility. As soon as he realizes this his confidence drops to 0%, but he does not reveal his realization. The next day, as he already knew, it did not actually occur (easy enough since it is a physical impossibility). Was his first proclamation wrong then? Or was it correct, because it reflected his 90% confidence at the time?

Note that I can actually think of an easy way to make this scenario quite realistic. A mathematician learns that his friends are about to announce a big proof of an open conjecture. He knows they've probably proven it's true, and given that they're respected mathematicians, and the paper was circulated in a small audience, he thinks that when they announce the next day, there will be an 80% chance that no major flaws are found and in fact it is a proper proof of the conjecture. So, he tells his other friend that there is an 80% chance that the proof that would be announced the next day is valid. Meanwhile, that night our hero receives an email from a distributed networking application he was working on. He was just messing about, but set it to try to find a counterexampple. He was shocked to find that it did, in fact, offer a counterexample. The conjecture was therefore wrong. His confidence drops to 0% - or whatever his confidence is in his calculations - since with the existence of a counterexample, whatever proof the mathematicians thought they had discovered for the conjecture is meaningless. As he checks the counterexample more and more carefully, or with collaborators, he will be more and more sure that there is a 0% chance of a correct proof of the conjecture being published the next day; since it is, in fact, false. 212.96.61.236 (talk) 07:17, 5 January 2015 (UTC)

Again, just check the Stanford article I linked above. Your best bet would be to read the stuff on subjective probability. Your argument sounds perfectly fine; it just depends on your interpretation of probability. It sounds to me like you are using a subjective account, in which case the original 80% was not wrong, just based on less information. Probability always depends on a lack of information, since that is exactly the information we gain when we discover the outcome. IBE (talk) 07:49, 5 January 2015 (UTC)

• There is a basic "sanity test" for predictions of this kind. If, for example, you examine all the cases in which some event was given a probability of 60%, then the predicted events ought to occur on approximately 60% of those occasions (plus or minus the statistical error range). If the predictions fail this test, they are miscalibrated. (I believe that many weather prediction systems fail this test badly.) Looie496 (talk) 14:55, 5 January 2015 (UTC)

Looie that is interesting, but can you give a reference? For example, in the interpretation where it is a confidence in belief, it doesn't really matter if it fails every time? For example, suppose mathematicians throughout history were asked what the probability is that (whatever) is true. In fact once the truth is known - e.g. look at some of these - http://divisbyzero.com/2010/08/18/mathematical-surprises/ then 100% of the predictions were false that claimed otherwise. So, it's like, are you saying if for 300 years people predict 80% that something will turn out to be a certain way, then if it isn't, all those must be wrong? So, it's not so simple I think! it's an interesting sanity test but a reference would be nice :) 212.96.61.236 (talk) 16:44, 5 January 2015 (UTC)

The thing is, a mathematical claim is either true or false, probability has nothing to do with it*, the truth is only in terms of entailment from the axioms of a formal system. There is a difference between an event_(probability theory) and the truth of a formal claim. So a statement about "X theorem is 90% likely to be true" is a very different statement from "There is a 50% chance this coin toss will be heads." Probability theory is an axiomatic branch of formal math, but we use words like luck and chance and odds in other ways in natural language. So you won't find any formal mathematical treatment of probabilities of mathematical statements being true, but you will find formal treatments of things that are well modeled (or at least intuitively described) by random variables. If you want a formal treatment of belief statements, then you may want to look into modal logic, specifically alethic modality and epistemic modality - Epistemic probability is just a redirect to our Bayesian page, but this highlights the crux of the matter, see frequentist for the complementary interpretation, as well as the links from IBE above.

*Of course this depends a bit on the interpretation and the epistemology that we're working in. The point remains, however, that there is not any one treatment of probability (either formally, or in terms of interpretation) that can include all the subtle differences in meaning that occur in phrases from natural language. (P.S. a ref for Looie's description is law of large numbers. The key thing to note is that Looie's description and the LLN apply only to events and experiments (with their formal definitions from probability theory), and does not apply to statements like "The continuum hypothesis is 90% likely to be true.") SemanticMantis (talk) 18:21, 5 January 2015 (UTC)

SemanticMantis, OBVIOUSLY I meant a proof within a given axiomatic system. E.g. under ZFC+ what are the chances that P=NP? Mathematicians can give a probability, given their confidence. Another example would be, before the 4-color theorem was proved, what were the chances that it was true (under the standard axiomatic systems etc). It was already very high (99%+) and a counterexample (where 5 colors were required) would have been absolutely shocking. That turned from 99%+ to 100.000% when the proof was verified. (and now should be 100.00000%, as it's well-verified.)

I also gave a very vivid account of a specific way to interpret a math probability: what are the chances that a proof published tomorrow will be accepted by the math community as valid, given that you know and respect the authors and the paper was circulated in private? (but you have not seen it). Again, you can give a probability! 212.96.61.236 (talk) 22:58, 5 January 2015 (UTC)

Remember we don't know what you do and don't know :) My main point was that the truth value of a mathematical claim is not an "event" in the sense of classical probability theory. As such, my belief is that the example statements are more the domain of modal logic than mathematical probability theory. SemanticMantis (talk) 15:06, 6 January 2015 (UTC)

January 6

Why no primates native to the US ?

Other than humans, that is. There are New World monkeys in South America and Central America, so why didn't any migrate north ? Just too cold for them in winter ? (I wouldn't think being unable to cross the desert would be a reason, since they could follow the coasts north.) StuRat (talk) 15:31, 6 January 2015 (UTC)

The article doesn't say. However, most New World monkeys are adapted to rain forest. There isn't tropical rain forest in Mexico, let alone in the United States. The time of the arrival of the New World monkeys in Central America was the beginning of a period of rapidly changing climate, since the closing of the Panama Strait is thought to have been one of the causes of Pleistocene global cooling and glaciation. There may have never been an environment to which they were adapted north of Guatemala. They haven't had nearly as long to expand into harsher environments as Old World monkeys - one or two million years as opposed to tens of millions of years for Asian temperate-climate monkeys. Robert McClenon (talk) 15:42, 6 January 2015 (UTC)

This pop-sci article addresses that exact question [3]. It confirms Robert's good points about the effects of global cooling and climate change in many areas. A few things to point out: Humans are not native to NA in the ecological sense of the word. We've just been introduced for a long time ;) Also, the article points out that there are primate fossils found in TX that date to ~43 mya, so there were at some point primates in what we now call NA (though I'm not quite sure where TX was 43 mya). SemanticMantis (talk) 15:58, 6 January 2015 (UTC)

There are actually monkeys in south-eastern Mexico, and primates have in the past entered North America via Siberia, such as Notharctus and Teilhardina_magnoliana, though these have since gone extinct. - Lindert (talk) 16:02, 6 January 2015 (UTC)

As far as there not being appropriate habitats for primates in the US, I should think the Everglades would do nicely, if they could get there. Of course, there are pythons, alligators and other predators that would snack on them, but they are able to survive in other land environments filled with predators, unlike, say, penguins. The Hawaiian Islands would be an even better environment for them, if they could make it there. Louisiana bayous might be another possible habitat. StuRat (talk) 16:11, 6 January 2015 (UTC)

• The Isthmus of Panama closed only 3 million years ago. Since then consider that the opossum and the armadillo are the only major mammals to have made inroads as far north as US territory from South America. And those two animals have not yet extended their presence to their full potential range. Also, much of that period was colder than now, further restricting animals adapted to rainforests from moving north as Robert pointed out. The presence of any monkeys at all in South America is also a mystery, since it was separated from Africa by the Atlantic, long before monkeys showed up in the SA fossil record. This indicates a very rare colonization by rafting from Africa. As a side note, see also rewilding, although it wouldn't exactly apply to monkeys. Baboons in California would be a dreadful pest. μηδείς (talk) 18:43, 6 January 2015 (UTC)

What animals would be pushed out by Baboons in California (other than Humans, Baboons are obnoxious). Also, for California Baboons, I think the Chacma Baboon (South Africa and neighboring countries) would be the one that would fit in the best. Drop a Troop or two (say 200 animals) into the California Central Valley and they could survive indefinitely. Not as much fun as the Burmese Python in Florida, but close. (The main difference is that in Florida, the environmentalists want the Python gone and don't particularly care how its done (Shotgun, .45, Scud, etc)) — Preceding unsigned comment added by Naraht (talk • contribs)

I used the term pest as I had humans in mind. (Pythons are human-introduced, armadillos and east-coast opossums aren't.) Look also at the problem with langur monkey attacks on people in india. μηδείς (talk) 20:13, 6 January 2015 (UTC)

Popular Science: Why Are There No Native Monkeys in North America? -- ToE 23:44, 6 January 2015 (UTC)

Thanks, good info there, although the title is misleading as there are primates in North America (Mexico, and Central America, too, if you count that as part of NA). StuRat (talk) 03:01, 7 January 2015 (UTC)

Not to mention humans and the Sasquatch. μηδείς (talk) 03:06, 7 January 2015 (UTC)

That article is interesting, but the Anaptomorphinae are primitive Tarsiiformes, not even as derived as the South American Monkeys, let alone Eurasian moneys and apes. μηδείς (talk) 03:02, 7 January 2015 (UTC)

Note: Already linked by SemanticMantis above. Nil Einne (talk) 11:48, 7 January 2015 (UTC)

Oops, missed that! -- ToE 13:18, 7 January 2015 (UTC)

Ha! I guess I should work on my clarity and link style ;) SemanticMantis (talk) 16:06, 7 January 2015 (UTC)

Habitability of Alpha Centauri Bb

If it exists, Alpha Centauri Bb is not really a good candidate for life by the numbers - after all, it is at 0.04 AU from its star with a predicted surface temperature over 1100 K. However.... it is that close to its star, which means that it is tidally locked. Which means that the planet should have a dark side that (like Mercury's) is extremely cold. Unless... it has an atmosphere that spreads the heat to the dark side. That is, unless the hotside atmosphere has condensed on the dark side, either quantitatively removing all of it, or building up some kind of dike of frozen material that confines the superheated material to the near side.

Of course, the planet might have a moon, and even a tiny moon would bring bright warm day to the far side. Conceivably even the heat coming through the planet could warm the far side, though I assume by analogy with Mercury it basically doesn't; yet if the far side had deep crevices containing some atmosphere of gas that has escaped from the near side, it might build up more than on Mercury. Or a minor remnant of gas might warm it by any degree. It seems to me it should not be impossible for this planet to have Earthlike temperatures on its far side, and conceivably even places where there is a potentially Earthlike atmosphere.

Anyway, I'm wondering whether there is any real sourced discussion of the potential fates of darksides of tidally locked hot planets in general, or of the most "optimistic" scenarios for this planet in particular. Wnt (talk) 00:45, 7 January 2015 (UTC)

We have Hypothetical types of biochemistry and the categories to which it belongs, and there is the tidally-locked (albeit colder) 'Aurelia' from Aurelia and Blue Moon which gives a tidally locked scenario that works with some tweaking. The huge unknown is what sort of metabolisms in cells with heavier cell membranes and some solvent other than water might support. I suspect any body with a permanent and impure ocean of some sort will originate life as specualted in Origins of Order. μηδείς (talk) 01:23, 7 January 2015 (UTC)

Note in passing that Mercury has no permanent dark side; its rotation is tide-locked, but because of orbital eccentricity it's not 1:1. The sun appears to stand nearly still at perihelion, when the tide is strongest. —Tamfang (talk) 10:48, 7 January 2015 (UTC)

Clarification: For now I was looking to focus on habitability by Earth life or at least human colonists, i.e. supposing a scenario such as: the darkside is cold and therefore the light side has little atmosphere, but deep pools of atmosphere exist somewhere on the dark side, and some energy source exists such as a satellite to provide some 'sunlight' (apparently the Roche sphere should be 1/25 of Earth's, but 1.5 million km / 25 is still 60,000 km, allowing orbits up to "geostationary" (for Earth, not Bb) and slower, so the satellite could sort of mimic an Earthly day and night cycle, I think) Wnt (talk) 02:34, 7 January 2015 (UTC)

One worry would be things like stellar flares and coronal mass ejections. At that range they might wipe out any life on the planet, even the dark side. StuRat (talk) 02:40, 7 January 2015 (UTC)

In light of Wnt's clarification, I'd ask Wikipedia:WikiProject Astronomical objects what the temperature given in the template actually means. If the dark side (assuming tidal locking) is frozen and digging under the surface is an option, stellar falres shouldn't matter. It seems the mass implies sheltered human habitations should be possible if there are areas with temperatures closer to the frozen/liquid water interface at STP. The given temperature in the template may be a high or an average based on the brightest spectrum, and really doesn't say anything about the dark side. μηδείς (talk) 02:49, 7 January 2015 (UTC)

I'm thinking of the stellar flares that don't quite escape the star's gravity, and drop back down, potentially hitting the far side of the planet as they do so. StuRat (talk) 03:14, 7 January 2015 (UTC)

I'm not sure if Wnt wants his colonists to be able to walk freely in the atmosphere, in which case that would obviously be a huge issue, or whetehr they can just live underground, which should be possible with high technology and a suitable way to vent heat. μηδείς (talk) 18:20, 7 January 2015 (UTC)

I don't think having them locked underground in a refrigerator counts. But I'm skeptical that solar flares actually heat the dark side of a planet this way. I would blindly guess that radiation has a fair chance of being corralled by some magnetic field, or at least, not descending vertically to the bottom of deep canyons on the dark side, but I don't really know. Wnt (talk) 21:42, 7 January 2015 (UTC)

If you are assuming they live on the surface, but our article says the surface temperature averages 1100K, there's a contradiction somewhere. Regardless of irradiation, which I do think would be an insuperable problem on the dark-side surface, there would still have to be some way of keeping the heat down. Given the boiling point of water is 373K, even Venus should be more hospitable. μηδείς (talk) 21:37, 8 January 2015 (UTC)

Well, the nighttime surface of Mercury is one of the coldest places in the Solar System, so it seems like there should be some room to work in there. As for the radiation, I don't really pretend to understand [4] well, but my take is that a really strong solar wind sort of "pushes in" the magnetosphere of Mercury to the interior of the planet. This sounds like a bad thing, but what it means is that there are no Van Allen belts, no fancy loops of particles floating around; so far as I get it, the charged particles that would generate radiation pound the front side of the planet and ought to leave the rear side alone because there's nothing strong enough to loop it around to hit there. Wnt (talk) 23:02, 8 January 2015 (UTC)

January 7

What happens when the helium balloon enters the atmosphere ?

I have many thoughts about this question when I usually buy this balloon and left on. This will float in air after I don't know what happens to it. So I asked this question. Arvind asia (talk) 01:50, 7 January 2015 (UTC)

It may rise till it pops, or else the helium slowly leaks out and the balloon comes down somewhere. Releasing balloons is a form of littering. Graeme Bartlett (talk) 01:55, 7 January 2015 (UTC)

The balloon is already in the atmosphere when you are holding it; we all are, but here is scientist's answer: http://www.thenakedscientists.com/HTML/questions/question/2030/ Mingmingla (talk) 02:14, 7 January 2015 (UTC)

Helium balloons sold as novelties leak, shrink, and sink. Even metallically coated ones don't tend to stay afloat more than a week. Keep in mind also that buoyancy decreases as altitude increases. So the easy answer is no for the standard party balloon. μηδείς (talk) 02:56, 7 January 2015 (UTC)

‘no’ what? —Tamfang (talk) 10:43, 7 January 2015 (UTC)

No, it won't just (indefinitely) float in the air. μηδείς (talk) 18:17, 7 January 2015 (UTC)

Further to Graeme Bartlett's comment above, released balloons can cause suffering or death to wildlife and even to farm animals. See here for a "BirdGuides" opinion. Dbfirs 08:26, 7 January 2015 (UTC)

Can I flatten a thick magnetic stripe card with a microwave?

It was in a dryer. The Internet says use iron or hairdryer. I don't have one. (don't try without Googling it!) Maybe there's a microwave setting. Sagittarian Milky Way (talk) 03:32, 7 January 2015 (UTC)

I wouldn't count on it. Is there a T-shirt near you? They use a big square iron to press on letters and images and such. However, before doing that, I recommend you call the credit card company and see what advice they have, if any. If you're lucky, maybe they'll send you a replacement for free. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:36, 7 January 2015 (UTC)

Yea. A microwave oven is almost certain to ruin it. I take it it's warped ? Maybe you can force it through a card reader as is, until your replacement card arrives. StuRat (talk) 04:25, 7 January 2015 (UTC)

I assume you're trying to straighten a crooked magnetic stripe card. If an iron or a hairdryer is the right solution but you don't own one, can you borrow one? A "hack" that I read about on the Internet for ironing clothes without an iron is to use the bottom of a heated pan. I'm not recommending it, just mentioning it as an idea that I read about. Here's another idea for your consideration: bathe the card in hot water; if it softens, maybe you can bend it back into shape. (I've not tried it and can't vouch for its effectiveness or safety. If you decide to try it, you're doing it at your own risk.) I doubt the microwave would work. --98.114.98.174 (talk) 04:28, 7 January 2015 (UTC)

I say again that your best bet is to call the credit card company for advice. But one thing you could do, which seems like it would be potential less destructive than an iron or anything hot, is to place it on a table with the concave side down, and stack a bunch of heavy books on. Leave that for a few days and see if it makes any difference. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:37, 7 January 2015 (UTC)

Although it could well be the case, the OP didn't say it was a credit card. --98.114.98.174 (talk) 05:06, 7 January 2015 (UTC)

Whatever purpose the card serves the best thing to do would be to seek a replacement from the issuer. Why wouldn't you? Richard Avery (talk) 08:08, 7 January 2015 (UTC)

... however, having said that I've just tried a simple experiment with boiling water which works very well. After deforming the card I laid it on a flat chopping board, on the sink drainer, and gently poured boiling water over it. Perfectly flat. Leave it for a minute or so to cool and harden. I can't guarantee what happens with your card but it worked with a standard plastic credit card. Richard Avery (talk) 11:32, 7 January 2015 (UTC)

Does the magnetic stripe still work? ←Baseball Bugs ^{What's up, Doc?} carrots→ 13:11, 7 January 2015 (UTC)

Good question that I can't answer because the card is out of date so I can't check, but I doubt that 212°F is going to demagnetize it, but I'd be pleased to know. Richard Avery (talk) 16:25, 7 January 2015 (UTC)

So you're basically conducting an experiment? In any case, the next time you go to the store you could take the expired card, explain the situation, and ask them to run it through their scanner - just to see if it works. ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:47, 7 January 2015 (UTC)

Buy a gift card, warp it, fix it and then see. They will key it in by hand if it fails to read so no way to lose money or waste a real credit card. --DHeyward (talk) 10:48, 8 January 2015 (UTC)

Which they can likewise do with a regular credit card, assuming you have proper ID. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:13, 8 January 2015 (UTC)

What's an incident infection and what's a persistent infection>

What's an incident infection and what's a persistent infection?~~ — Preceding unsigned comment added by 199.119.235.169 (talk) 05:12, 7 January 2015 (UTC)

You might want to look at acute infection versus chronic infection. Accute infections are things like the cold virus, which infects the mid respiratory tact, and which the body normally eliminates quickly because the area is will infused with antibodies and blood vessels. Chronic infections like toe-nail fungus, tuberculosis, and leprosy tend to sequester themselves in areas away from blood flow. AIDS and retroviruses actually sequester themselves within nuclear DNA, where a normal antibody response won't eliminate them. μηδείς (talk) 18:12, 7 January 2015 (UTC)

If helium balloon goes on

When the balloon stops or pops ? If it goes on reaches the corona of sun or it will burst in atmosphere. Arvind asia (talk) 11:35, 7 January 2015 (UTC)

The balloon certainly won't reach the sun, and it will not leave the atmosphere of the earth. This is because the air gets less buoyant as it thins out with height, and the volume of the balloon cannot support the weight of the balloon envelope. If it pops it will be inside the atmosphere somewhere. The wind will blow it around though. Graeme Bartlett (talk) 11:47, 7 January 2015 (UTC)

A typical but often illegal application, due conflicts with and danger for air traffic was to use multiple baloons to lift equipment like radio transceivers or cameras into the air. One of the balloons was filled more than all others. When it bursts, the other balloons make the equipment falling down slower, but can not keep it in the air.[5] Do not try this! --Hans Haase (有问题吗) 13:40, 7 January 2015 (UTC)

I'm actually more disturbed by the atmosphere vs. corona of the sun as some sort of boundary. There is very basic knowledge that is missed by even posing the question. For what it's worth, helium is a very good heat conductor. It would interesting to see how expansion from the pressure difference compares to the temperature fall at altitude. --DHeyward (talk) 10:56, 8 January 2015 (UTC)

the balloon into Pacific Ocean

If the balloon with carbon dioxide gets to deepest part (mariana trench). It will be burst that's my guess or what happens to it. Arvind asia (talk) 11:44, 7 January 2015 (UTC) or if I filled with my mouth exertion this will also Sinks?

Balloons float on the surface if the sea, and would not sink. Graeme Bartlett (talk) 11:47, 7 January 2015 (UTC)

However if you did fill comesome container with carbon dioxide and then forced it down the carbon dioxide would turn into a liquid, as it would be colder than supercritical carbon dioxide. The container / balloon would be crushed or crumpled. This would happen at depths deeper than 720 meters. I believe that this liquid is denser than water and so would then sink. Some people think that unwanted carbon dioxide can be disposed of by pumping it deep in the ocean. However it would lead to ocean acidification. Graeme Bartlett (talk) 11:52, 7 January 2015 (UTC)

It might be time to change your "come container". StuRat (talk) 05:12, 8 January 2015 (UTC)

Probably before it liquified, the balloon displacement would be less than its own weight and would sink.. As a practical matter, this is done when snorkeling with weight belts (or scuba when holding breath during descent. The weight belt goal is that a few feet below the surface, the lungs compress enough to reduce volume and the diver changes from floating to sinking (when ascending, never hold breath with scuba). --DHeyward (talk) 11:19, 8 January 2015 (UTC)

balloon with exertion

Then the balloon is filled with mouth exertion taken into deep sea what will happen to it ? Arvind asia (talk) 13:01, 7 January 2015 (UTC)

The weight of the air inside the balloon will force the balloon to reach the sea surface. The skin of the balloon needs to resist this this force. As the pressure in the sea increases by depth, the air in the balloon will be compressed as well. The stretched skin of the balloon forces itself into its original condition. --Hans Haase (有问题吗) 13:18, 7 January 2015 (UTC)

The balloon, filled with air at the surface, will get smaller the deeper you take it. At 10 m depth it will be half the volume it was at the surface. This is shown in the second half of this video. -- ToE 13:13, 7 January 2015 (UTC)

If you can somehow get the balloon down to some small depth, then the pressure would indeed start to crush it - so it'll rapidly become a rather limp bag and then we can forget about it being a balloon and just consider how the contents fare. Consider the reverse experiment done with high altitude weather balloons. When they are launched, they are very limp bags that gradually swell to spherical shape at altitude...being at ground level is akin to your balloon being at the bottom of a swimming pool. It's less and less likely to burst as the skin gets less and less taut as it's pushed to the bottom.

The problem is with how you get it down to that kind of depth. Just below the surface, the upward force on the balloon is rather high - it could easily displace a couple of liters of water - so the upward force would be a couple of kilograms at one g. So pushing it down to a sufficient depth to relieve the pressure on the skin is going to be hard. If you try to push a fully inflated balloon underwater with your hands, it invariably bursts before you get it even completely submerged because the forces involved aren't evenly distributed over the surface - and that causes it to tear. Tying a string around the knot at the bottom of the balloon and pulling it under that way causes other strains on it. The problem is that until the balloon is at a depth that significantly larger than it's own diameter, you're getting this differential pressure that's going to push it past breaking point before the air inside is compressed enough to relieve the tension on the skin. If you could take the balloon down to a depth of a few feet in a water-tight pressure vessel, then slowly and uniformly increase the pressure inside until it equalled the pressure outside - then released the balloon, I'm pretty sure it would survive. It would of course continue to try to rise to the surface until you lowered it to a depth where most of the the air would liquify...and (depending on the original size and weight of the balloon itself) might even start to sink. But I don't think it would burst. Of course there are other issues here. The temperature of the water might drop sufficiently to embrittle the rubber...or extreme pressure might promote ordinarily slow chemical reactions to happen more rapidly and thereby degrade the balloon...but those things are harder to describe without knowing lots more about the overall situation and the chemistry of the rubber. SteveBaker (talk) 14:48, 7 January 2015 (UTC)

If "mouth exertion" means air that you exhale, note that it's nothing like pure CO2. Normal air is roundly 78% nitrogen, 21% oxygen, and 1% argon, usually with some water vapor mixed into that. When you breathe, some of the oxygen gets replaced with CO2 and there may be some water vapor added, but the nitrogen is still 78% (before accounting for water vapor); and there still is more oxygen than CO2, which is why mouth-to-mouth resuscitation works. --65.94.50.4 (talk) 04:58, 8 January 2015 (UTC)

Design code factor of safety in prestressed concrete design

If a design code specifies that 0.9 should be used as a factor of safety for prestressed concrete design, I'm aware that this should be used when calculating the prestressed strain. However, should it also be used when calculating the tensile force in the process of calculating the ultimate moment of a prestressed concrete beam? I.e. Should the equation be 0.9*(prestress/1.15)* area? 94.3.137.225 (talk) 21:15, 7 January 2015 (UTC)

A US-centric answer, based on ACI 318:

Some pedantry, first. I think you're talking about a "strength reduction factor" of 0.9, not a "factor of safety". A factor of safety would normally (a) be larger than one, and (b) would compare the capacity to the expected demand. You multiple the "nominal strength" by the "strength reduction factor" to get the "design strength". You then compare this to the "required strength" due to the applied loads multiplied by "load factors".

A strength reduction factor is applied to the overall strength of the member, not to the prestress strain used to evaluate internal strains and forces. The adjustment to prestress strain you would make would be a reduction for prestress loss, but not a factor of safety or a strength reduction factor. Indeed, somewhat counter-intuitively, the prestress strain (that is, the strain induced in the prestressing steel due to the prestressing force, prior to loading the beam) has no effect on the ultimate strength of the beam. So I can think of no time when you would multiply the strain or tensile force by a strength reduction factor.

If you're asking about a non-US code, I can't help you. If you make a note of that here, maybe someone else can help. --Floquenbeam (talk) 21:41, 7 January 2015 (UTC)

January 8

Negative coefficient of friction

I was reading the article on friction in the section about negative coefficients of friction, where it discussed the force of friction decreasing with an increase in the normal force. However, shouldn't these mean that the force of friction is inversely porptional to the normal force? A negative coefficient of friction would mean the force of friction would be negative (which in terms of vectors would mean working in the same direction as the applied force), but it would still increase with an increase in the normal force. Am I wrong here? Thanks, --T H F S W (T · C · E) 04:34, 8 January 2015 (UTC)

I agree with your interpretation. However, as far as I know, that doesn't exist in the real world, while what they described does. One example that comes to mind is ice skating, where the friction is reduced once the pressure builds in the area under the blade and melts the ice, so the skater is then gliding on water on ice. I'd call that a "negative change in the coefficient of friction". Of course, that's more of step function than a continuous case. StuRat (talk) 04:58, 8 January 2015 (UTC)

It is true that there is high pressure under a skate blade, which lowers the freezing/melting point, but it's a myth that this results in melting that makes skating possible. Artificial ice rinks are normally maintained at temperatures below the lowered freezing point. The truth is more complicated and involves other factors. --65.94.50.4 (talk) 05:09, 8 January 2015 (UTC)

Great link. I love it when myths are busted. 196.213.35.146 (talk) 10:08, 8 January 2015 (UTC)

Well, if it was due to friction that the ice melts, then you'd expect it to be very hard to get started moving on skates, since there's no frictional heating until after movement begins. Note that the pressure lowers the melting point, but the increase in pressure also heats the ice. As to the argument that water takes up less volume and therefore the pressure would decrease when it melts, this ignores the fact that the skater will simply sink down by a microscopic amount into the ice, to restore the pressure. StuRat (talk) 19:02, 8 January 2015 (UTC)

I agree that it's a misleading heading. I've put "negative" in quotes until someone comes up with a better way to express the concept. Dbfirs 09:45, 8 January 2015 (UTC)

It may be misleading, but for better or worse a lot of scientific terminology is misleading to the uninitiated, no? That doesn't mean we get to change it on WP, we should be consistent with the literature. The authors of the cited paper say in the abstract "This leads to the emergence of an effectively negative coefficient of friction in the low-load regime." - I don't think it's our place to change the terminology that has been accepted in a Nature publication. It is unclear to me whether your solution of scare quotes is better than calling the section "effectively negative coefficient of friction" - any thoughts from the group? SemanticMantis (talk) 16:20, 8 January 2015 (UTC)

If we quote something which is believed to be in error, we should put "(sic)" after it, to show this. StuRat (talk) 16:58, 8 January 2015 (UTC)

Sure, as a general practice, but I don't believe this specific case to be an error, and in general I would doubt our understanding before I would doubt the findings of Nature paper (sure, they occur, but much more rarely than errors in WP). SemanticMantis (talk) 20:09, 8 January 2015 (UTC)

Note that it is the coefficient of friction that is negative, not the force of friction. The coefficient relates the normal force to the frictional force, and is dimensionless. In this case, the coefficient is negative, because increasing normal force decreases friction (in at least one very special scenario) - read the abstract of the paper cited in our article here [6]. I actually think the article is fine how it was - it makes sense if you've read and understood everything up to that point. SemanticMantis (talk) 16:20, 8 January 2015 (UTC)

(ec) Note that a negative coefficient of friction invariable would lead to a negative frictional force:

Ff = μFn

-Ff = (-μ)Fn

StuRat (talk) 19:00, 8 January 2015 (UTC)

Yes, what SM said. It's not as counter-intuitive as you would first think, because there is adhesion involved; there is a resistance to sliding even under zero normal load. The slip resistance is a constant (adhesion) plus a coefficient of friction times the normal force, and in this case that coefficient would be negative. But this is just decreasing the adhesion under increased vertical load; no one is saying that this could overcome the cohesion and start "pushing" in the same direction as the applied load. --Floquenbeam (talk) 17:02, 8 January 2015 (UTC)

Floquenbeam's explanation makes sense. But, there still can't be a fixed negative coefficient of friction, as that would indeed eventually lead to a frictional force, at high normal force ranges, which surpasses the adhesion force. So, the coefficient of friction must be variable, and only negative at certain low ranges of normal forces. StuRat (talk) 17:05, 8 January 2015 (UTC)

Yes, as SM already stated above, it's an "effectively negative coefficient of friction in the low-load regime." It's variable, and no one is saying it continues this behavior at higher loads. --Floquenbeam (talk) 19:07, 8 January 2015 (UTC)

I've changed the wording to an exact quote of the source, but left the scare quotes in the heading. Will this suffice?
I've also moved the section to its proper place after the table of conventional positive values. Dbfirs 19:41, 8 January 2015 (UTC)

Thanks, that's better. I personally don't like the scare quotes, because it seems to me the coefficient is literally negative under the specific regime studied. But I don't feel strongly enough about it to argue or change it :) SemanticMantis (talk) 20:06, 8 January 2015 (UTC)

If I'm not mistaken, it still opposes the applied force. The proportion of opposition gets smaller as more force is applied. I think a hydrofoil can be modeled as a negative coefficient of friction. Motion lifts it, drag is reduced, efficiency increases. It can be modelled other ways with more conventional positive coefficients but it's not as cool. --DHeyward (talk) 02:49, 9 January 2015 (UTC)

Snow Extrusion

Though the illustration might not demonstrate it very well, I'm interested in the natural phenomena of when snow forms an extended extrusion-like structure growing from behind of objects like trees or fences. I assume it has something to do with wind, but how exactly does it work? 176.14.195.212 (talk) 12:36, 8 January 2015 (UTC)

This is a very interesting question, and it turns out to be very difficult to describe and understand all the things snow and wind can do! Here are some nice descriptions of how snow interacts with snow fences - [7] [8]. I don't know of a specific term for the influence of trees/fences on snow, but Penitentes is a word for spire-like snow formations - these form from wind but also due to interactions with temperature and dew point. The general concept that would apply to snow/fence interactions is Aeolian_processes (sometimes spelt 'Eolian'). These processes can also cause pattern formation and have can have some degree of self organization. Behavior of snow due to wind is an active area of research, and there is a lot we still don't understand. Here is an example of a recent empirical paper on snow/wind dynamics [9], and here is a nice overview from the USGS [10]. There are also lots of simulation models and theoretical mathematical treatments, but those can get pretty heavy and might not be that useful for a general audience. An unrelated but interesting water 'extrusion' is ice spike. Both this and the photo you show (and the formation of snow flakes themselves]] are examples of dendritic growth.

If you have any more specific questions I might be able to find more suitable references. In the meantime, let's all enjoy these beautiful photos that we get searching /eolian snow pattern/: [11] or simpley /penitentes/ [12] :) SemanticMantis (talk) 16:06, 8 January 2015 (UTC)

Winter mountaineers in UK call this "rime ice" but we have an article on the same subject called Hard rime. On the hills, you can determine the prevailing wind direction (useful for avalanche prediction) because the ice grows into the wind. See Avalanche, the Basics - Part 2: Staying Safe; "Rime Ice is caused when super-cooled water vapour hits a freezing object (rocks, fence posts etc). Counter-intuitively, rime grows into the wind rather than away from it, so the direction it points is another handy indicator of recent wind direction" (just over halfway down the page). I rather like this picture. Alansplodge (talk) 16:32, 8 January 2015 (UTC)

Just what kind of person would be so easily impressed as to take such an interest in structures that arise out of snow anyway... Snow talk 11:22, 9 January 2015 (UTC)

The kind of people that try to avoid having your electricity supply or mobile phone cut off in Winter, or ensure cars going across bridges don't get impaled by falling icicles. Or any people who are generally interested in strange phenomena. Dmcq (talk) 12:00, 9 January 2015 (UTC)

@Dmcq: Just so you don't walk away with the wrong impression of me, can I trouble you to take a look at my full user name? Snow talk 16:28, 9 January 2015 (UTC)

Ha, until any sarcasm punctuation becomes commonly available, this is a situation where a sarcasm tag might have helped (e.g. '/s', '</s>', '/sarcasm', etc. :) SemanticMantis (talk) 16:45, 9 January 2015 (UTC)

I had considered that, but the problem is that it wouldn't necessarily have delineated that the sarcasm was self-effacing and I hoped that keeping my name at full scale would make that point more clearly. Oh well, just a reminder as to one of numerous reasons I don't attempt humour here as a general rule. :) Snow talk 02:47, 10 January 2015 (UTC)

Human only (or close) diseases.

According to their articles, both Smallpox (Variola Major) and Polio are found in nature only in Humans. (It apparently is possible to give smallpox to a primates, but no cases have been observed in the wild). Any idea where I could find a list of diseases that (like these) are more or less restricted to humans?Naraht (talk) 15:54, 8 January 2015 (UTC)

Would you include mental diseases ? I imagine many of those are human-only, as more complex brains are prone to more complex disorders. StuRat (talk) 16:55, 8 January 2015 (UTC)

Lots of zoo animals develop mental disorders, Stereotypy_(non-human) covers one common symptom. Even stuff like schizophrenia, which seems very human-centric by definition, is studied by Animal_models_of_schizophrenia. It's not clear to me if it's fair to say these rodents and primates "have schizophrenia". SemanticMantis (talk) 20:03, 8 January 2015 (UTC)

Unfortunately, Wikipedia seems to be a little deficient here - there are 219 entries in Category:Zoonoses, but only 216 entries on List of infectious diseases. Ideally, the diseases the OP is looking for would be those which are on the second list but not the first. Tevildo (talk) 19:57, 8 January 2015 (UTC)

If you're willing to include parasites, then several of these are human-specific, e.g. Louse#Lice_in_humans. SemanticMantis (talk) 20:03, 8 January 2015 (UTC)

You can look at Eradication of infectious diseases as a human infectious disease can only eradicated if it is human specific. Ruslik_Zero 20:21, 8 January 2015 (UTC)

That's a very good point, thanks! However, Malaria is on that list, and it definitely lives in mosquitoes as well as humans, though it doesn't give them the same symptoms. SemanticMantis (talk) 20:36, 8 January 2015 (UTC)

Plasmodium can not reproduce in mosquitos and humans are the only secondary hosts. Ruslik_Zero 20:54, 8 January 2015 (UTC)

That's not necessarily true; you could eradicate it both in the human population and any other carrier populations (though unfortunately for members of that other species, the likely approach would be (and has at times historically been) to eradicate the carrier population itself. In any event, it's quite likely there's never truly been a human-specific pathogen; all infections to which humanity has been subject have arrived in the human population through zoonoses at some point or another, and there's no way of knowing with any degree of certainty that there's even so much as a single pathogen which entered the human ecological niche and then mutated into a form that has never since infected another member of any other species. Certainly there might have been cases where the only per-existant animal vector(s) disappeared to extinction, but these are surely a great rarity as well. Non-communicable diseases are of course another matter entirely, but I rather suspect Naraht was excluding them by principle. Snow talk 11:18, 9 January 2015 (UTC)

Beaver poo

Mice don't "hold it in" but rather urinate and defecate more or less constantly. Is this also true of larger rodents, such as beavers ? StuRat (talk) 17:25, 8 January 2015 (UTC)

According to [13], beaver droppings are found in the early morning at the water's edge. I don't know if that means they do it overnight and it's only found when the sun rises, or if they do the business at first light, but it implies they hold it in through daylight hours. Mogism (talk) 17:31, 8 January 2015 (UTC)

Are siblings the most genetically similar people to a person?

And if so... if one sibling is smart, and their sibling(s) is/are dumb, does that not demonstrate that the factors that determine smartness and dumbness are predominantly environmental and not genetic? 69.121.131.137 (talk) 22:32, 8 January 2015 (UTC)

As for the first question, apart from identical twins, the closest genetic relationship is that between two siblings or that between a parent and his/her child. A child has inherited 50% of its genome from each of its parents, so is 50% identical in its genome to either parent. Likewise you can calculate that two full siblings share on average 50% of their genome.

As for the second question, no, that does not logically follow, at least not from just a few cases. Children can inherit different genetic material from their parents, and so they need not share between them any of the genes which influence intelligence. In fact theoretically they need not share any genes. On average, they share 50% of their genes, but in individual cases it may be 60% or 45% or even 0% (though this would be exceedingly unlikely). - Lindert (talk) 22:45, 8 January 2015 (UTC)

(ec) Usually this is addressed with a twin study. Twins who are genetically identical are compared to those who share 50% of their genes, and the difference is considered. Of course, it might not be foolproof (what if the smart twin was sneaking in and takes tests for the dumb one, affecting how they are later treated, or if the teachers have a visually driven bias) but it's a pretty good way to look at it. Wnt (talk) 22:49, 8 January 2015 (UTC)

(ec) Siblings have 50% genetic overlap, the same as the overlap between a parent and child. That isn't enough to determine whether differences are due to environment or genes. However, identical twins have 100% genetic overlap, so the differences between them are much easier to interpret. The most powerful test of environment-versus-genes is to compare identical twins reared apart with identical twins reared together. It's hard to find good data, because the number of identical twins reared apart is quite small, but the data that exists is extremely useful. Looie496 (talk) 22:51, 8 January 2015 (UTC)

Because the exact proportion of "shared" genes in siblings can theoretically vary between 0% and 100% (though with an average of 50%) it is possible to have more "shared" genes with other people than with your sibling. (Note that these percentages refer to the genes that can vary between two people (i.e. your parents), and not to genes that you "must" have in order to be human rather than some other species). Your question about the factors determining intelligence is not yet resolved, though scientists are hard at work on it. Geneticists talk of the heritability of different traits. As you will see from our article on the heritability of IQ the best estimate of the heritability of intelligence seems to be about 50%. That is, about half of the variability of intelligence among the human population at large can be explained in terms of a genetic component. However, this figure refers to the population as a whole, and, because we don't know the proportion of genes you share with your sibling, we can't reach any conclusions about the relative impacts of nature and nurture in your particular case. RomanSpa (talk) 00:41, 9 January 2015 (UTC)

I saw my doppelganger at a train station a few years back. Looked nothing like my brother. Can't speak for the genes beneath the skin, but my resemblance was uncanny. InedibleHulk (talk) 00:48, January 9, 2015 (UTC)

• Looie's answer is the correct one in general, but both male and female children bear their mother's mitochondrial DNA, so are slightly closer to each other and their mother than their father in that respect. There's also the question of the Y chromosome. Since the Y carries fewer genes than the X, again, children are closer to their mother, but two brothers, each carrying the same Y, are thereby closer to each other and their father than to a sister not carrying the identical Y. Ex chromosomes cross over, so the exes inherited by sisters are not necessarily identical, while the wyes carried by brothers are.μηδείς (talk) 01:33, 9 January 2015 (UTC)

Sisters do have identical X-chromosomes, since their father only has X-chromosome. Both sisters necessarily inherit all of the genetic material in their father's single X-chromosome (unless some genes could cross over between the father's X and Y). Of course the X-chromosomes they inherit from their mother could be quite different, but in that respect they are no different from two brothers either. - Lindert (talk) 09:59, 9 January 2015 (UTC)

There actually is a portion of the Y chromosome, the pseudoautosomal region, that can recombine with the corresponding portion of the X chromosome. It only comes to about 5% of the Y chromosome, though. Looie496 (talk) 16:31, 9 January 2015 (UTC)

One thing to clarify: First, let's ignore things that can alter the 50% from each parent (the things Medeis mentions, but also genetic disorders like XXY or XYY, etc), and focus on the simplified 50/50 model of genetic inheritance from each parent for alleles in nuclear DNA. Now, a parent is guaranteed to share 50% of your alleles ( not genes, let's be precise here :), and cannot share any more or less unless you get into edge cases. We don't know exactly which alleles are shared, in part due to recombination. In contrast, a sibling shares 50% as an expected value. So the situation is this - if you want a "safe bet" for most shared alleles, pick a parent, you'll never be far off from 50%. If you want to potentially maximize the shared alleles, pick a sibling, who will share more than 50% of alleles roughly half the time. As Lindert points out above, a sibling has the potential to share much more than 50% with you, but can also be lower, and this makes for some interesting differences, depending on our motive for finding a highly similar person. SemanticMantis (talk) 16:41, 9 January 2015 (UTC)

January 9

Trustworthy sources of Windows builds of open source software?

Some of the open source software I use is hosted at Sourceforge. I've stopped downloading Windows installers from SF since reports came out in 2013 that installers hosted there were bundled with extra/unwanted software. Are there trustworthy alternative sites for Windows builds of open source software, ones that don't bundle extra stuff in the installers?

Are there ways to confirm that no unwanted extras are bundled with an installer? --134.242.92.2 (talk) 16:02, 9 January 2015 (UTC)

Are you talking about malware, or just spam-like junk? ←Baseball Bugs ^{What's up, Doc?} carrots→ 16:22, 9 January 2015 (UTC)

Not sure about what's bundled in the case of SF, but I do want to avoid both categories.

*** I inadvertently posted the question here instead of the Computing RD. I've moved the question there. Please post follow-up there. --134.242.92.2 (talk) 16:26, 9 January 2015 (UTC)

";" issue

Can some review this section please (https://en.wikipedia.org/wiki/Human_evolution#Divergence_of_the_human_clade_from_other_great_apes). Iss ";" in the end of the last word, an error? -- (Russell.mo (talk) 16:58, 9 January 2015 (UTC))

Yes, that was a typo, and I fixed it. I'm now a little confused by the styling of "Ardipithecus ramidus" as "Ar. ramidus" - normally we only use the first letter of a genus name when describing the species, and the article for A. ramidus just says "A. ramidus" as I would expect. Our style guide Wikipedia:Manual_of_Style#Scientific_names is silent on the issue. Before I change these to single letter abbreviations for genera does anyone want to defend the abbreviations as they are currently used in this section? I can see the desire to avoid confusion with e.g. Australopithecus, but the two-letter genera still looks wrong to me... SemanticMantis (talk) 17:12, 9 January 2015 (UTC)

Ok I've found this style advice that says the two letter abbreviations are to be avoided but are tolerable in some publications to avoid ambiguity: [14], citing "Butcher’s Copy-editing" as the style guide. SemanticMantis (talk) 17:17, 9 January 2015 (UTC)

Damages caused by too much starring at a screen (be it TV, computer or smartphone)

What could happen to my eyes, when we spend many hours starring at a screen? (I mean a modern TFT or LED backlight, not that old TVs.). Is this associated with any illnesses, poor vision or whatever? How can I know whether High-energy visible light is real or just a urban legend? How can I know if screens will cause another illness down the road? After all we didn't evolve starring at an illuminated screen. — Preceding unsigned comment added by Noopolo (talk • contribs) 18:25, 9 January 2015 (UTC)

At the very least, there's the problem of literally "staring" (not "starring") at a screen too much, be it TV or your computer screen, in that you might not blink enough, and your eyes might tend to get dry. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:20, 9 January 2015 (UTC)

See eye strain, computer vision syndrome, and this link from the Mayo clinic [15]. SemanticMantis (talk) 21:10, 9 January 2015 (UTC)

Oh and you can tell that high-energy visible light is not an urban legend because you can check the references at High-energy_visible_light#References - many of which are peer-reviewed scientific literature. You can also presumably see the color blue. SemanticMantis (talk) 21:12, 9 January 2015 (UTC)

One problem is always having the same focal distance to the screen, which means you don't exercise the focusing muscles in your eyes and they atrophy. StuRat (talk) 22:31, 9 January 2015 (UTC)

Source please? This is simply not how the physiology of this organ works. Snow talk 02:41, 10 January 2015 (UTC)

Apparently, Medieval teenagers were also the demographic to stare at illuminations all day until they grew too old and blind. But at least they were reading. InedibleHulk (talk) 02:53, January 10, 2015 (UTC)

What's the problem of putting metal objects into a microwave oven?

I get that a sharp object will release sparks, but what would happen if I put a metal bowl with a metal top and water inside into the microwave? Would it get hot and heat the water, while blocking the microwaves that won't heat the water directly?--Noopolo (talk) 19:49, 9 January 2015 (UTC)

Microwave oven explains the consequences of putting metal objects in the microwave. ←Baseball Bugs ^{What's up, Doc?} carrots→ 20:17, 9 January 2015 (UTC)

On rare occasions, you can also get the same arcing without metal. I managed to get it with a saltine with a jalapeno pepper and cheese on top. StuRat (talk) 22:27, 9 January 2015 (UTC)

Olives make cool sparks and jump around, if it's just them in there. InedibleHulk (talk) 03:02, January 10, 2015 (UTC)

January 10

Butterfly Flight

How does a butterfly flap its wings and change direction while in flight?--75.171.82.75 (talk) 01:11, 10 January 2015 (UTC)

They use muscles on their abdomen to flap the wings, and changing direction, I suppose, involves flapping one side harder than the other. Another possibility is wing warping. StuRat (talk) 01:21, 10 January 2015 (UTC)

The aerodynamics of butterfly flight has been the subject of multiple scientific studies - it is more complex than it might at first seem, and may involve different mechanisms for different phases of flight. This [16] Nature paper is unfortunately behind a paywall, but is well worth looking at if you can access it. AndyTheGrump (talk) 01:40, 10 January 2015 (UTC)

Welch's

The method of pasteurizing grape juice to halt the fermentation has been attributed to a British physician and dentist, Thomas Bramwell Welch (1825–1903) in 1869. I am not happy with the wording and lack of a source. Wasn't pasteurization known before? Are there any specifics to that method? Isn't "has been attributed to" classic weasel wording that should be avoided? --92.202.13.41 (talk) 03:16, 10 January 2015 (UTC)

That doesn't indicate that he invented it, only that he used it. According to Louisization Pasteurization, the process was invented in 1864, initially for milk of course. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:58, 10 January 2015 (UTC)

PG-1302-possibly a pair of black holes close to colliding

The news article I just read said these 2 black holes will probably collide in a million years. It also said the energy released at that time could be as much as 100 million supernovae, with spacetime warping effects. My questions are 1) Even allowing for the very great distance, billions of lightyears, could that released energy, a million years from now, still damage the life on Earth, assuming life on Earth then is similar to life on earth now? 2) Could the spacetime warping be large enough, even with the very great distance, so that in ordinary life,(not just when using sensitive scientific instruments) a human's senses could notice definite effects on spacetime, assuming humans exist then? thanks.2601:7:6580:5E3:9138:4390:6740:EBCC (talk) 03:41, 10 January 2015 (UTC)