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November 25

Odd hummingbird aggression

Recently I saw an Allen's Hummingbird in my backyard, chasing a Lesser Goldfinch. It was clearly deliberate, since the finch would flutter from tree to tree, and the hummingbird would follow it and hover around until it left, several times until they both left the yard. The hummingbird in question is an adult male and appears to have declared my yard his territory (there's also a female of the same species in the front yard). I have never seen a hummingbird attack a goldfinch; in my experience they mostly show aggression toward other hummies, and occasionally squirrels. What could account for this unusual aggressive behavior? 75.4.21.125 (talk) 01:06, 25 November 2014 (UTC)

I'm not a hummingbird expert, but I was once a member of a bird forum where hummingbirds were a common topic of discussion. I seem to recall people saying that hummers could be quite scrappy little things, when the urge arose - even though they don't look like much. --Kurt Shaped Box (talk) 01:31, 25 November 2014 (UTC)

They sure are fierce! What seemed odd to me is that this one was attacking a creature that was neither a competitor (goldfinches, as far as I know, don't drink nectar or eat insects) nor a potential threat. And it only went after one goldfinch, ignoring all the others and the house finches, doves, jays, etc that were around75.4.21.125 (talk) 03:56, 25 November 2014 (UTC)

Birds as a clade are just territorial creatures in general and there are all manner of complex relationships between species that can lead to behaviours that at first seem counter-intuitive (and in some cases in fact are). But if you're capable of differentiating and sexing these species, you probably already know that. In this case, it's worth noting that when smaller birds, hummingbirds included, harass larger birds it often has more to do with protecting a nest or territory associated with a potential mate than general aggression prompted over feeding territory and other resources, and that seems to fit the bill (hah!) with the situation you describe, except this isn't really the season where aggression associated with mating is strongest, unless you are in a particularly warm latitude. Hummingbirds are also intensely curious creatures and have been known to follow other birds, creatures and objects around for a time, especially if they exhibit strong colors. Was the hummingbird making a racket or taking dives at the finch? Both are common when they are significantly agitated. Snow talk 05:04, 25 November 2014 (UTC)

I'm in Southern California and apparently some hummingbirds build nests in winter (I saw an Anna's Hummingbird doing so last January). And the hummingbird didn't dive (as Allen's often do when aggressive), but it did hover near the finch and seemed to have its feathers fluffed. 75.4.21.125 (talk) 14:40, 25 November 2014 (UTC)

Yes, hummingbirds whose territories extend into the tropics or otherwise warm habitats are known to mate year round, but even tropical and subtropical climates, October and November are the least likely months for nesting. On the whole, I'm inclined to assume this was just a mild territorial tiff on the part of the hummingbird. Though as to whether it has anything to do with the neighboring female, I wouldn't venture to guess in this case. My previous caveat that aggression towards larger species usually has something to do with nesting or mating not withstanding, hummingbirds are known to sometimes zealously guard a feeder, sometimes wasting a hours or even days chasing away all comers that it can get away with harassing even if it only has need to feed a handful of times itself. Conventional wisdom has it that they do with when preparing for migration, and though at first I assumed your little scraper wouldn't have much need to move much farther south (and would already be down there if he did), our article on the species says that it winters on the central coast of Mexico, so it's quite possible he's stockpiling nutrients from some source in your yard and was not going to risk any of it going to no damn finch, not when everyone knows those guys are yellow-bellied. Bwahaha! Snow talk 03:25, 26 November 2014 (UTC)

I'd agree with general territorial defensive behavior. A few other things: goldfinches don't sip much nectar but they will eat buds. So technically there could be some competition in the sense that a bud eaten by a finch will not be able to later produce nectar for the hummingbird. I'm not familiar with Allen's but the common ruby-throated is very curious, and will check out many brightly colored things. So it may have just been interested and not really attacking/defending. SemanticMantis (talk) 15:40, 25 November 2014 (UTC)

• As I have long warned, if hummingbirds had mouths like great whites', rather than beaks designed for stabbing they'd rule the world. μηδείς (talk) 17:41, 25 November 2014 (UTC)

Tip-of-the-pen phenomenon?

I know that there is this phenomenon called tip-of-the-pen, which is very similar to tip-of-the-tongue, but it occurs in cultures where the writing is not phonetic and more logogrammatic. A person knows the word and can say it, but just forgets how many brushstrokes there are in the single logogram/character and how to put it together meaningfully. I think "tip of the pen" is the official name for it, because I do remember a brief mention about it in a textbook. The brief mention was that the relatively new phenomenon is not well studied, but that may mean there are some insights into it, right? How many studies have been done on tip-of-the-pen up to this date, and are there any in English? 71.79.234.132 (talk) 02:14, 25 November 2014 (UTC)

It's unlikely to be a phenomenon in English because you can always rite yor wurds fonetikly. People make spelling mistakes in the process - I find that I sometimes get stuck on the correct spelling of a word - but never that same complete inability to write the word at all.

Another interesting (and perhaps related) phenomenon in English is almost the opposite. My wife will ask me to spell a word that she doesn't know - and the only way I can spell it for her is to first write it down and then read back what I wrote.

SteveBaker (talk) 03:12, 25 November 2014 (UTC)

Ack, I meant RESEARCH PAPERS in English. 71.79.234.132 (talk) 05:13, 25 November 2014 (UTC)

As Steve notes, it is highly unlikely for the phenomena to manifest in English as produced by a developmentally mature and fully literate person, owing to the fact that the entire writing system is comprised of a 26-character alphabet and couple dozen forms of punctuation. The tip-of-the-tongue phenomena is in large part owed to the vast (and increasingly large with each successive modern generation) stock of words a person learns over the course of their life, many of which may not be used regularly, leading to that typically rare, but vexing phenomena where you've half formed the linguistic representation of a concept and know basically the meaning of the word you are trying to conjure (note that we all almost always respond to this frustrating event with vague invocations of the definition: "It's almost synonymous with term X, but you only use it context Y and it's less absolute-sounding than word Z!") but are stuck as the language centers of your brain try to apply fuzzy logic to all the various phonetic, syntactic and semantic associations that might lead you to the proper form. The small sample of letters are used routinely and besides which are largely processed by different regions of the language centers of your brain. Tip-of-the-pen is similar in that there are large number of similar phenomena (logograms or pictograms) which may need to be recalled, though they too use still different, if somewhat overlapping, brain regions from those employed with an alphabet or syllabary.

That being said, there are extreme cases where English speakers and other practitioners of written languages that employ phonetic (rather than logographic) characters may have difficulty recalling or producing the appropriate characters, such as with the conditions agraphia, alexia, apraxia, and, depending on your definition, some forms of aphasia. These sometimes debilitating conditions usually occur as the result of stroke, head trauma or other neurological damage and, combined with modern imaging have actually been immensely helpful in helping to chart which parts of the language centers of the brain regulate which parts of language perception, conceptualization, and production, so in that sense there are actually is a significant body of work which treats the phenomena of the inability to produce usually easily recalled and produced characters in English (and a significant number of other languages). If you have access to JSTOR or another major academic database, I recommend plugging the above terms into it. Failing that, Google scholar will probably give you no shortage of hits, some of them open-content. If neither points you towards the information you need, however, or if you are having difficulty parsing what will largely be highly technical linguistic and neurological terminology, post a follow up comment and I'll see if I can't isolate some more germane and readily-accessible works. Snow talk 04:37, 25 November 2014 (UTC)

I think there is a complete misunderstanding of my request. When I said "English", I was referring to research papers written in English about the tip-of-the-pen phenomenon. But now that two people have misunderstood it, I think my original statement was written in a non-intentionally misleading way. 71.79.234.132 (talk) 05:18, 25 November 2014 (UTC)

I also have a neuroscience background (BS) in RL, so I at least have college-level knowledge of terms and anatomy. So, the real barrier is language. I can only read articles in English. 71.79.234.132 (talk) 05:20, 25 November 2014 (UTC)

Ah, ok, I see. Well, unfortunately I have less guidance to give in finding articles about the phenomena in neurologically healthy individuals speaking languages that employ a logographic writing system. :( A Google scholar search turns up these abstracts: 1, 2, 3, none of which I have access to just at the moment, but which all contain reference to "tip-of-the-pen" or "tip-of-the-brush", but which might be using them in a more literal sense than the figurative use you are seeking. In any event they seem more concerned with second-language acquisition than language cognition. This paper does treat the exact phenomena you are looking into, but not in significant detail. Unfortunately, I think you're going to find that this particular subject will not have much treatment in English, as it is a foreign concept to most English speakers. Sorry I couldn't be of more help with regard to the exact concept. If however you are looking at the phenomena under the lens of cognitive-/neuro-science, I still think looking at the above-mentioned conditions will give you a great deal of insight in the way the brain processes symbolism associated with linguistic processes. Best of luck! My formal background is also largely in cognitive science, and my first degree was in linguistics and thus the intersection of the two is always of fascination to me, so if this line of inquiry leads to other questions, don't hesitate to return here or contact me on my talk page. :) Snow talk 06:17, 25 November 2014 (UTC)

FWIW, this was recently (within the last month) discussed at the Language Log blog in the context of Chinese, where it was referred to as "character amnesia". {The poster formerly known as 87.81.230.195} 212.95.237.92 (talk) 13:49, 25 November 2014 (UTC)

In logographic writing systems, it's completely normal to know exactly how to pronounce a character and what it means, but have no idea how to write it. There's nothing surprising or psychologically interesting about that--if words in English consisted of random letters arranged in a random order, with no relation whatsoever to their pronunciation, you'd often forget how to spell a word. --Bowlhover (talk) 17:02, 25 November 2014 (UTC)

Ehh, no real need to talk down to the OP or dismiss his interest in this subject. Everyone who's participated in this thread thus far seems perfectly aware of the nature of the phenomena and is unsurprised that it occurs. Tip-of-the-tongue is a perfectly familiar and not altogether surprising phenomena as well and yet has been found to be immensely "psychologically interesting" to academics in neuro- and psycholinguistics who feel it provides a lot of insight into how the brain organizes conceptual phenomena, matches them to representative morphemes and handles associations between related semantic and phonemic classes, to just begin to list its implication. Suffice to say, whatever the nature of the interest, the OP is intrigued by this similar phenomenon and is looking for research upon it and our job here is to detail such resources, or at least point him towards them -- not condescendingly tell him what he clearly already knows and imply that there is no intellectual merit to his interest beyond that simple overview. Especially when there is in fact immense merit; there's no surprise as to why children make syntactic and morphological errors when learning language either, but studying the nature of those errors and the particulars of how they occur led to arguably the single greatest development in the history of linguistics with massive implications that reshaped the cognitive sciences and our understanding of how the human mind operates and generates some of the qualities that are most unique to our species. Snow talk 20:57, 25 November 2014 (UTC)

I wasn't trying to be condescending at all. I'm sorry if I appeared that way. I just thought that the OP might not know how normal it is to forget a character in logographic systems. It's more similar to forgetting a phone number than tip-of-the-tongue, because the characters often have no relation to how they're pronounced or what they mean.

Also, I'm a native Chinese speaker, so I have no idea how much a typical English speakers knows about logographic writing systems. I wasn't assuming the OP is stupid, since I don't think everyone should be expected to know about all the different types of languages in the world. --Bowlhover (talk) 21:31, 25 November 2014 (UTC)

Fair enough! It just seemed a little pointy, is all, and suggestive that the inquiry was about a superficial and uninteresting topic. But certainly I take you at your word that it was not nearly your intent; hopefully you'll take me at mine when I say my own response was meant only to defend against a perceived judgement of the value of the topic and the OP's interest and that the kindly tone you used to clarify the matter is well appreciated. :) Snow talk 22:21, 25 November 2014 (UTC)

Some native Chinese speakers grow up in China and are given a formal education in the Chinese language. Some Chinese speakers grow up overseas, usually in places where Mandarin is not the dominant language. The latter may be able to speak Chinese, but may not be able to read/write it unless given a formal education in Chinese writing. I am part of the latter population. I was raised mostly in the United States, and there was one year in my childhood where I got the opportunity to take a Chinese class and a piano class before I moved to a different state where the Chinese population seemed even smaller. Suffice it to say, I usually use Yabla Chinese and my knowledge of pinyin to decode my parents' speech and use of idioms. It's not a perfect method, because my parents speak Mandarin with a regional accent, but my pinyin approximations usually get me the right Chinese word most of the time. I can't speak for the normalcy of not being able to read/write Chinese characters. TBH, my dad uses a program to input pinyin and output the correct character, while my mom does not use pinyin at all. (They never learned pinyin in their childhood.) Luckily for her, there is a search engine that allows her to scribble brushstrokes onto the computer screen and find the right Chinese logogram. The time when they actually ask each other for help on a specific character is extremely rare. 71.79.234.132 (talk) 02:37, 26 November 2014 (UTC)

Interesting - so, is your interest on the phenomena of tip-of-the-pen purely a matter of curiosity about the occurrence itself or are you looking for learning/work around strategies for more practical purposes? Because I actually came across a number of sources on the latter topic when first responding, which I dismissed at the time as not germane to what you were looking for. Snow talk 03:02, 26 November 2014 (UTC)

Out of curiosity about the occurrence. As previously stated, I am just curious, because it's briefly mentioned in a now-sold textbook. The brief mention was really a caption to a picture on the side of the main text, and it basically said that the tip-of-the-pen phenomenon is one that is not well studied. But its nature is very similar to tip-of-the-tongue. So, what are the sources you found? 71.79.234.132 (talk) 05:34, 26 November 2014 (UTC)

Inserts in injection molding process

When Injection molding products made of liquid silicone rubber is it possible to have a set of inserts prepositioned inside the mold so that once silicone is injected they would be secured in it? Its just that I cant see any other way to secure metal parts within silicone body due to the inertness of silicone rubber. If it is possible, is it a common practise for the industrial scale production? Also how would you position such an insert in a way that is entirely covered with rubber from all the sides? Because in this case the insert can not have any connection points with the mould for it's prepositioning.195.94.247.199 (talk) 11:17, 25 November 2014 (UTC)

The easy way to do this is to create the moulding in two halves (or more layers), with the inserts placed at the edge of the first moulding, then sealed by the second moulding. The trick of using fine rigid wires is probably too fiddly for mass-production. Both methods leave a trace. Dbfirs 21:14, 25 November 2014 (UTC)

You can always fabricate difficult products in one step if if you allow a high percentage of waste/failed results but reliable results are usually only achived by splitting up the process into multiple steps. --Kharon (talk) 02:23, 26 November 2014 (UTC)

I suppose the positioning wires could be made out of something that will slowly dissolve, perhaps using a bit of solvent mixed in with the silicone. StuRat (talk) 15:58, 26 November 2014 (UTC)

Dry juice

Is it possible to dry juice or other drink in a powder ??

Why not? Ruslik_Zero

Yes, for various methods please see Drying (food).--Shantavira| 13:05, 25 November 2014 (UTC)

Milk and eggs are available dried. For fruit juice, it is normally concentrated, and then the water is re-added either by the consumer, or the packager. The latter is normally done for juices that are transported large distances by sea. CS Miller (talk) 13:23, 25 November 2014 (UTC)

I dunno, but I suspect that fruit juices contain live plant cells and drying them would kill the calls, at which point rehydration would produce something, but probably not what you would call juice. Which is why juices are typically concentrated, not dried. 50.126.104.156 (talk) 15:41, 25 November 2014 (UTC)

I have seen dried orange and lemon juices before, if that helps. --Kurt Shaped Box (talk) 18:26, 25 November 2014 (UTC)

See Drink mix for our (fairly limited) article on the subject, although I'm not sure something made from powder could be legally described as "juice" (rather than "fruit flavoured juice drink" or similar). Powdered fruit juice is a common component of field rations, and was part of the Apollo astronauts' daily diet. Tevildo (talk) 19:13, 25 November 2014 (UTC)

For example, if you tried to dry grape juice and reconstitute it, I suspect you'd get something raisin juice, instead. StuRat (talk) 16:01, 26 November 2014 (UTC)

Climate Change Explanation

I've been hearing about Climate Change for years, but I've never come across a good, solid explanation of the phenomena. I just saw a story in IEEE Spectrum that "Climate scientists have definitively shown that the buildup of carbon dioxide in the atmosphere poses a looming danger.", but when I follow the link I only find more of the same kind of stuff I have been seeing.

What I would like to see would include, at the minimum,

- an explanation of how much radiation is reflected/absorbed depending on the level of CO2 in the atmosphere,

- a historical record of global temperatures going back 100,000 years along with an estimate of how accurate those temperatures are, and

- a summary of CO2 sources and sinks and their relative size.

Oh, and without all the political claptrap that seems to the largest part of any story about climate change. Is that too much to ask? 50.126.104.156 (talk) 15:37, 25 November 2014 (UTC)

No, it's too little. The politics is crucial, since that determines whether we are going to see major cities worldwide abandoned to flooding in our own lifetimes, and mass migration due to crop failure. AlexTiefling (talk) 17:04, 25 November 2014 (UTC)

One problem is that everything you are asking for involves multiple layers of assumptions, models, indirect measurements, proxies, extrapolation and averaging. Even the historical temperature record is derived from indirect measurements once you go back beyond human record keeping. And, inevitably, the selection of relevant data, analysis methods and models involves a degree of subjectivity. Gandalf61 (talk) 17:32, 25 November 2014 (UTC)

The points above are apt, but to actually provide a good data source -- The place to go is the IPCC - they are an international body of scientists who have been examining the causes and impacts of climate change for quite a while now. Here is their front page . They issue lots of separate reports, on things like impacts on water or forest systems. Here is their synthesis report, which ties together all of the reports made for the 5th assesment report (AR5) It has all kinds of data, including a nice summary graphic on p.37 that goes back to 1850. There are many other IPCC documents that will go into more detail on the reconstructions we have for climate ~10k years ago, and others that will go into sources and sinks. There are still other sections/reports covering models and assumptions, as well as analysis of political actions and mitigation. But I think the synthesis summary is a good place to start for scientific consensus and apolitical reporting.

In my experience, anyone who claims the IPCC is politically biased or unreliable can be safely disregarded as a crackpot. They are the preeminent world body of experts and they will provide you with exactly what you ask for, if you are willing to look around a bit and read long documents. SemanticMantis (talk)

I think it is disingenuous to put forth the IPCC as the metaphorical spokesman for scientific consensus. The IPCC is one organization, and it happens to be a highly politicized organization; and while they do try to provide a survey of the state of knowledge, they are not the official headquarters-division to whom all of climate-scientists report!

I have read several of IPCC's reports in entirety; and I have read several more in brief. I recommend that anybody who wants to inform their opinion also read the IPCC reports. You can find them online at no cost.

You can read about the different types of report produced by the IPCC. I have found the Assessment Reports to be rather unpleasant; they are not laid out as well as a good textbook, but they are not as brief or to the point as a journal publication. When summarized into a sound-bite for the popular press, the important details (like which parts of a report are novel, and which parts are uncertain) are glossed over. However, that's not really so much the fault of the IPCC as it is the fault of an incompetent journalist!

I much prefer to read factual scientific information in peer-reviewed scientific journals. For example: Journal of Geophysical Research and Geophysical Research Letters are two excellent sources of information on geophysics, including planetary-scale climate. For summary reports, Eos is an excellent magazine-format that is very accessible to less-technical readers. You might also enjoy the oft-feisty "AGU Blogosphere" blog.

But, the IPCC is widely-cited, and is, at its core, a literature review of other peer-reviewed research. So, to directly address the original questions: Grab the 2007 IPCC Assessment Report (2007 is the most current complete report, though a new report Climate Change AR5 will be forthcoming in the next few weeks). Among many thousands of pages of background material, it contains, in direct answer to the OP's specific asks:

• "a historical record of global temperatures going back 100,000 years along with an estimate of how accurate those temperatures are":
  • Chapter 05: Information from Paleoclimate Archives
  • Figure 5.3, Orbital parameters and proxy records over the past 800 kyr (including a sea surface temperature model)
• "an explanation of how much radiation is reflected/absorbed depending on the level of CO2 in the atmosphere":
  • Box 1, Figure 5.1, schematic illustration of multiple interactions between ice sheets, solid earth and the climate system which can drive internal variability and affect the coupled ice sheet–climate response to external forcings on time scales of months to millions of years
  • Chapter 07: Clouds and Aerosols.
  • Chapter 08: Anthropogenic and Natural Radiative Forcing.
  • Figure 8.1, Calculation Methodology cartoon; and in fact, this entire chapter.
• "a summary of CO2 sources and sinks and their relative size.":
  • Chapter 8.2.1, "Introduction" to atmospheric chemistry. Anthropogenic and natural inputs are considered.

Do we want to nitpick at any of these findings? Of course. Some of us are formally-trained geophysicists! But before we can nitpick, we have to first educate and inform ourselves.

I am inclined to believe that the role of atmospheric carbon dioxide - specifically, anthropogenic carbon dioxide - is greatly overstated by the popular press. But, that's not really the fault of the IPCC, or any of the other hard-working scientists who are seeking to elevate the discussion about climate-policy using factual evidence. Heck, the IPCC publishes a thousand-page scientific textbook that pretty much explains everything that we know - except that it's written at a level that is accessible only to physicists and chemists and climate scientists! Most people aren't quite autistic enough to spend a few days reading about the real science; for most people, it's much more fun to brand ones-self an "activist" and form an angry protest mob, because physics and chemistry are difficult!

If you're really new to the field of climate and meteorology, and you are looking for a very introductory textbook to meteorology, I can think of no better book than Aviation Weather. This entire textbook is available at no cost online as FAA Advisory Circular 00-6A. It has an excellent introduction to the Earth's atmosphere, its structure, and its dynamic processes, and it's written at the level of a very introductory university course.

Nimur (talk) 19:59, 25 November 2014 (UTC)

You say the IPCC reports are too long and hard for most people to read, but then you say you prefer primary literature? Certainly most non-scientists/can't won't read the primary literature, and I think the executive summaries from the IPCC are fairly accessible to an educated lay person. You can't really have it both ways- primary literature is too technical and popular press is low on content and high on politics. IPCC is certainly closer to the former than the latter, but it depends on the document in question. As for being a metaphorical spokesperson - there really isn't one as you know, but I was absolutely no being disingenuous -- the IPCC's broad conclusions are largely the scientific consensus. Virtually all the top names for each subfield are tapped to review and criticize IPCC reports. Each chapter had dozens of named reviewers, who had hundreds of helpers, and there was also an open comment period. There is no general finding reported by the IPCC that does not report the consensus of most of the top experts in each subfield. Of course experts will debate smaller details (model assumptions, exact year of a bad benchmark being hit, etc.), but IPCC is the closest thing we have to an official consensus on causes and effects of climate change. (Disclosure: I helped review a chapter of AR5). Surely it is better to offer the publications of a consortium of international experts than to tell the average joe to go read the primary literature. SemanticMantis (talk) 20:50, 25 November 2014 (UTC)

1) Carbon dioxide (CO2) enhances the greenhouse effect, causing more radiative energy to be trapped near the surface of the earth. Ultimately, nearly all energy in the atmosphere derives from the sun, and the sun's input isn't changing significantly, but the CO2 holds that energy closer to the surface. The analogy that is often used is something like putting on a winter coat. The coat itself doesn't generate any heat, but it holds in the heat allowing the person inside to stay warmer. For convenience, scientists often use a simplified description of CO2 impacts on radiation, wherein they equate the radiative impact of CO2 changes with an equivalent amount of excess sunlight at the top of the atmosphere. That is to say, if the sun increased by X then that's about the same as CO2 increasing by Y. This is an over simplification for a number of reasons, but it is a convenient framework for thinking about the problem of greenhouse gases, so it is widely used. For CO2, the equivalent top of atmosphere radiative forcing is

${\displaystyle \Delta F\approx 5.35\times \ln {C \over C_{0}}~\mathrm {W} ~\mathrm {m} ^{-2}\,}$

where C is the current CO2 concentration and C₀ is the preindustrial concentration (280 ppm). The logarithm comes about because the wings of the CO2 absorption band are approximately exponential. So, to give some concrete numbers. Today's CO2 level is about 400 ppm. So that is roughly the same as ${\displaystyle \Delta F\approx 5.35\times \ln {400 \over 280}=1.9~\mathrm {W} ~\mathrm {m} ^{-2}\,}$. Averaged over the whole Earth, the sunlight at the top of the atmosphere is about 340 W/m, so the impact of CO2 thus far is equivalent to about a 0.55% increase in sunlight. Now, 0.55% doesn't sound like a lot, but the average temperature of the Earth is presently about 288 Kelvin (15 Celsius / 60 Fahrenheit), and without the sun we'd be near 0 Kelvin (-273 C / -460 F). 0.55% of 288 K is still about 1.5 degrees C (2.7 degrees F) of warming. That's a very oversimplified way of looking at it, but still gets about the right magnitude of effect. A more sophisticated way is to introduce the notion of a climate sensitivity, which is just a fancy way of saying how much will the temperature change for a given amount of radiative forcing. Unfortunately, the climate sensitivity still has large uncertainties, but recent estimates suggest the equilibrium climate sensitivity is roughly 2 to 4.5 degrees C per doubled CO2 (= 0.5 to 1.2 degrees C per W/m radiative forcing equivalent). Using the present 400 ppm of CO2, that would lead to an estimate of 1.0 to 2.3 degrees C (1.7 to 4.1 degrees F) at equilibrium, i.e. allowing that CO2 levels stayed approximately constant for long enough for the oceans to reach a steady temperature. Observed warming since 1850 is about 1.0 C (1.8 F), at the low end of the predicted range, but the oceans are still absorbing heat and even if CO2 levels stopped increasing we would have a long time to go before temperatures stabilized. Dragons flight (talk) 20:12, 25 November 2014 (UTC)

For clarity: the IPCC uses and endorses the concepts of radiative forcing and climate sensitivity that User:Dragons flight described. These equations are essentially linearized models of perturbations to the thermodynamic balance. If one is so inclined, one can find more complicated models of planetary energy balance; but it's almost tautological that if we use a more complex model, that lends itself to more complex predictions that are subsequently more difficult to validate with observational evidence. After all, the modern theory of complex systems evolved out of a famous scientist's computational climate model! Nimur (talk) 20:25, 25 November 2014 (UTC)

And if you're not willing to read long documents (I'll be honest--I'm not), here are a few links to get the OP started.

Carbon cycle has a good chart showing the major carbon sinks/sources, along with how much they release/absorb per year. It doesn't have percentages, but you can compute them yourself.

Temperature of the Earth, with multiple sources for the past 100,000 years: --Bowlhover (talk) 21:21, 25 November 2014 (UTC)

3) Carbon in the Earth system can roughly be divided into four groups: atmosphere, biosphere on land (including both living and recently deceased plants/animals), oceans, and near-surface geosphere (carbon bound in rocks). Each of these pools include very large quantities of carbon and except for the geosphere fluxes between pools are also large. Environmental carbon is usually expressed as gigatons of carbon (GtC) equal to 10 kg of carbon, and only the carbon content is counted regardless of if it is bound to oxygen (as CO2) or some more complex organic form. Using the numbers in carbon cycle, the four pools of carbon contain roughly the following at present: atmosphere 720 GtC, biosphere on land 2,000 GtC, oceans 38,400 GtC, geosphere 75,000,000 GtC. As one can see the atmospheric piece is actually the smallest, while the geosphere pool is huge. A small fraction of the geosphere pool consists of exploitable fossil fuels, about 4000 to 6000 GtC. The fluxes between the pools are also large, except for those involving the geosphere. In addition, most of the exchanges are roughly symmetrical. For example, nearly the same amount of carbon moves from ocean to air as from air to ocean each year, about 90 GtC/yr, with an estimated net flux of only about 2 GtC/yr from atmosphere to ocean. Similarly from atmosphere to biosphere and from biosphere to atmosphere, the flux each way is about 120 GtC/yr, with a net flux towards the biosphere estimated at about 3 GtC/yr. With exchanges this large (e.g. 120 GtC/yr), the atmosphere and biosphere take only about 15 years to equilibrate, so for long-term purposes they can be imagined as a single pool. The ocean carbon pool is much larger, so it can take hundreds of years to equilibrate. The natural flux from the geosphere to the atmosphere and ocean is small, ~0.5 GtC/yr, and mostly due to a combination of weathering of rocks and volcanic activity. The net flux into the geosphere is even smaller at present, ~0.1 GtC/yr. By contrast, the carbon we are adding to the atmosphere by intentionally extracting and burning fossil fuels is about 8 GtC/yr. As we add this carbon to the atmosphere, it shifts into the biosphere and ocean. This redistribution is important to us as it presently offsets about half of what we emit. If we could magically stop burning fossil fuels tomorrow, then the atmospheric levels would decline for a long time as carbon dioxide continued to move out of the atmosphere and into the ocean and land. However, because the flux into the geosphere is so low, it will take many thousands of years, to move carbon out of the land/air/ocean system and return it to the ground.

Related to this, the ability of the ocean to take up carbon is also rather complicated. Though it contains 38,000 GtC, only about 1% of that exists as CO2. Most of the remainder is either bicarbonate (HCO3) or carbonate ions (CO4). The balance between the ocean and the atmosphere happens when the partial pressure of dissolved CO2 in the surface water is equal to the partial pressure of CO2 in the overlying air, which sets the boundary condition; however, the transformation from CO2 to carbonate and bicarbonate is also influenced by the pH of the ocean and the abundance of cations (e.g. Ca). The influences of these factors are expressed through the Revelle factor, which expresses the change in total ocean carbon as a function of changing CO2 levels. In rough terms, a 100% increase in atmospheric CO2 equilibrates with about an 8% increase in ocean total carbon content. The consequence of this is that even though the ocean is a huge carbon pool, it can only capture about 50% of our fossil fuel emissions. The land captures another 35%, leaving ~15% of the emissions to linger in the atmosphere for thousands of years. Dragons flight (talk) 05:37, 27 November 2014 (UTC)

The fundamentals first. The laughable attempts to pass off CO2 sensitivity estimates based on the temperature record since 1850 should be regarded as stabs in the dark, as the error bounds associated with a temeperature reconstruction such as HADCRUT4 are large and ever increasing, once we go back beyond 30 odd years ago. Greglocock (talk) 21:44, 25 November 2014 (UTC)

Svante Arrhenius computed an approximate climate sensitivity from first principles around 1900. Since we are fairly far from climate equilibrium, it's indeed non-trivial to derive climate sensitivity directly from the recent temperature and CO₂ record. But then I don't think that is a major method used. --Stephan Schulz (talk) 16:16, 27 November 2014 (UTC)

it is a difficult subject. In absolute terms the changes are quite small, temperature is relative to absolute zero at -273°C so a change of 2°C is less than a single percent - and yet it means a huge change for us. It is difficult to get within a factor of 2 about the probable change, a lot of work has been done and the estimates and error bounds are the best that can be done at the moment. At the end of the day it comes down to whether you think all those scientists are actually doing their best to come up with a good estimate or whether you think they are practically all deluded or involved in a giant conspiracy. As to acting on what they say the question is rather like going to the doctor and being told you have cancer. Of course a lot of people will just deny anything is wrong with them, and sometimes nothing bad does happen as the outcome isn't definite, but is it a rational way of dealing with bad news? Dmcq (talk) 23:36, 25 November 2014 (UTC)

The effects of global warming on the human world is hard to predict, but the OP is asking for more definite information. The sizes of carbon sources/sinks and how much radiation CO2 absorbs are both measurable, the latter to a very high precision. --Bowlhover (talk) 00:24, 26 November 2014 (UTC)

I was explaining that what they were asking for was too much to ask for which is what they asked. Dmcq (talk) 08:44, 26 November 2014 (UTC)

• Read After the Ice Age by Canadian scientist E. C. Pielou who mentions the fact that the interglacial period we are enjoying (with its temperature maxima long over) has already begun it's next ice age cycle. μηδείς (talk) 03:53, 26 November 2014 (UTC)

• CO2 as a forcing is fairly easy to find in IPCC. I believe the total increase of CO2 from 1750 to present (50% increase) is equivalent to 1.5 W*m (the total from the sun is on average around 1500 W*m). Annual, seasonal, and daily fluctuations of CO2 are pretty large. Solar activity variation is on this order of magnitude. The larger concern isn't what's happened so far as it's not particularly significant (or even attributable to CO2), but the lifetime and accumulation of CO2 makes the 50 and 100 year projection significant. Also, it's not clear what happens to other GHG's such as water vapor so while the forcing of CO2 might be known, how it affects other forcings (i.e. how sensitive the climate is to CO2) is still being researched.
• There's nothing that will compare to the recent record. Even since 1850, natural variations have swamped the global warming signature. For example, glaciers that are in retreat since 1850 had periods of growth such as from 1950 to 1970. To see global wrming effects directly requires pulling a very small signal from data that naturally varies. It's also not understood why most of the surface warming is arctic with little tropical warming and antarctic cooling. It was only recently discovered that a lot of measured sea level rise in Greenland and even the landfall of Sandy was due to a teeter-totter effect of melting glaciers (land rises under the glacier, sinks in another place).
• Carbon cycle shows some of the numbers. Human contributions are mostly fossil fuel combustion and cement. It is a relatively small contribution and some of the sinks have actually adapted (i.e. oceans have absorbed about half of all human emissions which changes the pH of the oceans, also a warming ocean will start returning CO to the atmosphere). One of the difficulties in assessing the ultimate effect of global warming is that the contributions year over year are very small. Much smaller than natural variation which is why climate change must be studied over decades. It's also why weather variations cannot be attributed to climate change. --DHeyward (talk) 07:33, 26 November 2014 (UTC)

There is no "good, solid explanation" but we clearly see "good and solid" evidence that something is seriously going wrong(like rapidly melting glaciers). Additionally it is absurdly strange that every producer has to prove his products can cause no harm and that they are foolprove reliable but in the climatechange debate this seems turned around and made near impossible that way that even clear evidence is not enough to prove massive pollution is causing seriouse harm. --Kharon (talk) 16:04, 26 November 2014 (UTC)

Since we are coming out of an Ice Age wouldn't it be a bit odd if the glaciers weren't melting? Greglocock (talk) 19:39, 26 November 2014 (UTC)

The ice age cycle is approximately 100,000 years long. You would indeed not expect any noticeable changes after only 100 years, which is 0.1% of the cycle, but drastic changes have been observed in the past few decades. Look at the data and convince yourself that the ice age temperature changes are orders of magnitude too small to explain the recent warming. Also notice in that graph that we're already near the peak of the cycle, where natural warming rates are expected to slow down or reverse. --Bowlhover (talk) 20:17, 26 November 2014 (UTC)

You are assuming some sort of gradualism argument. Since the climate is chaotic there is no reason to assume that all changes should be slow. Greglocock (talk)

Here is a graph of temperature change over the last 450,000 years . This is part of a series of graphs of global temperature over different time scales. Each page links to the next longer and shorter time scales. The next shorter time scale is 12,000 years, which has estimates by several different methodologies plotted on the same graph, and can give you an idea of the inherent error in the estimations. Given that glaciation cycles last about 100,000 years, I find it useful to look at the 5 million year time frame (the next longer time scale). At some point continental drift comes into play, so time scales longer than a few million years are probably not useful in separating the anthropogenic component from the natural short-term baseline. It is still instructive to look at the 65 million year plot to see how much cooler it's gotten since the dinosaurs went extinct. Ice age gives a pretty good overview of natural temperature cycles, and includes the 450,000 and 5 million year plots I've mentioned (click on them to see the bigger version). I hope you're still reading in spite of the political diatribes.--Wikimedes (talk) 07:48, 27 November 2014 (UTC)

Image blurring

Is it possible to blur a printed image by layering something on it? Placing a mate film over it will not do as in this case blur effect comes at a price of desaturation? Can some kind of polarised film or flat lens do the trick?176.14.253.145 (talk) 21:03, 25 November 2014 (UTC)

Seeing imagery through slightly wavy but otherwise clear glass seems to do this. Also, seeing imagery through clear water but with a degree of disturbance at its surface seems to do this as well. Bus stop (talk) 01:35, 26 November 2014 (UTC)

They used to smear vaseline on the lenses of camera to make a soft focus effect. Not sure if it will work, but you could put glass over the image and see how it works on the glass. 217.158.236.14 (talk) 11:32, 26 November 2014 (UTC)

There exist soft focus lenses that use spherical aberration to create a soft focus effect. Diffusion filters can also be used for soft focus; thin nylon or silk fabric is sometimes tried, or one could buy a professional filter. Motion blur is a third way to blur an image. --Mark viking (talk) 11:56, 26 November 2014 (UTC)

November 26

Current in two circuits

Hello. I have a question from McMaster University's Physics Contest, which can be found here. For that last question, #10, I assumed that the current follows conventional current and that the "electrons" from the positive side of the left battery would flow in a counterclockwise direction through the bottom light bulb, up to the top light bulb, and to the negative side of the battery. Thus, the resistance in the first circuit would be greater than the second, and since the voltage is the same for both circuits, since V=IR, if resistance (two bulbs vs. one) increases, the current decreases, so I2 should be greater than I1. The answers, however, state that no current flows through the top light bulb at all! Can someone shed some light on this? Thanks! 74.15.5.210 (talk) 04:28, 26 November 2014 (UTC)

The classic way to solve these problems is to calculate the voltage at each junction, and the extrapolate current using Ohm's law. When a wire splits, voltage is identical. Let's say the batteries are at 5 V. If you look at that top bulb, that means the voltage on one side of that bulb = +5V, and the voltage on the other side of that bulb = +5V. If the voltage on one side = voltage on the other side, there is no potential difference, no EMF, so no current. Now, in BOTH circuits, the voltage at the top juncture = +5V, while the voltage at the bottom of each circuit is 0V. That's a voltage difference, so that means the bulb has a current. Since that voltage difference is the same in both pictures, the two currents have to be identical as long as they have identical bulbs. Don't try to figure out how electrons "move" or "flow". Just find voltage across every component and use ohm's law to find the current. --Jayron32 04:46, 26 November 2014 (UTC)

Assuming they are perfect batteries, the bottom picture is very straight forward and I₂ = V/R. Looking at the top picture, the same voltage is applied to the vertical light bulb by the perfect source on the right so I₁ = V/R. This means the currents are equal. When working through these types of problems, there are forced voltages with the battery. What's also identifiable is that the voltage across the second (horizontal) lightbulb in Figure 1 is 0 so this means the current through that bulb is 0. The difference is that in the bottom circuit, both batteries split the load while in the top circuit, only the right battery supplies current (assuming ideal sources). The answer is C). I1=I2≠0 --DHeyward (talk) 08:00, 26 November 2014 (UTC)

Confirm: C is correct. To understand it: If the left battery nears empty, the right will particially backup, but only up to a quarter of energy on each bulb. The lower bulb well emit less light by time, the upper bulb more until euqual. It is a quarter on energy on each bulb. The bulbs are in line. This halves the resistive load (doubles the ohms Ω walue) on the right battery causes half current. Half voltage and half current is a quarter of energy per bulb, see Ohm's law. --Hans Haase (talk) 10:42, 26 November 2014 (UTC)

Work hardening

I've read your article on work hardening and dislocations etc but how do you see this on a stress visualisation animation which changes as load is applied to a material over time. The visualisation is limited to a maximum of the materials yield stress. 194.66.246.125 (talk) 10:34, 26 November 2014 (UTC)

Diagramms are always limited and these are not much more that an example. Might even been put in there so the article isnt just text ;) Material science is a highly underestimaten and very complicate field. This starts with the fact that "stress" is not an uniform unit or measurement (shear-, bend-, swing-, notch impact-, torrision-, tension-, weight-"stress" etc..) and thus you would have to add a lot more diagramms. Additionally this all does change with each material, and even with each alloy. So what example would you like more? --Kharon (talk) 15:41, 26 November 2014 (UTC)

Rescue dog awareness of selection and rejection?

Are dogs in rescue centres likely to realise they're being selected and rejected? Are they trying to appeal to be chosen and disappointed when someone walks past or are they likely to have no idea at all what's going on? --78.148.108.62 (talk) 13:01, 26 November 2014 (UTC)

Im not an expert but dogs are mostly focused on their relation to the "leader of the pack". In the case of rescue duty the woman or man they always work with. From that point of view there is likely no difference between a "rescue team" and a "family". But to be certain we would have to ask the dogs. --Kharon (talk) 15:50, 26 November 2014 (UTC)

To clarify, you mean what our article describes as rescue dogs, not search and rescue dogs, right ?

I doubt that the dogs in a the pound know they are facing the gas if they don't get adopted. However, dogs have been bred for thousands of years to appeal to humans, so them acting friendly is the expected behavior, with exceptions for some that are in the pound because they are "defective" in that regard, or perhaps were abused to the point where they now fear all humans.

If the dog pound was full of wolves, instead, which are genetically almost identical to dogs, save the thousands of years of breeding for traits humans find desirable, then very few of them would act in a friendly manner (and those few would be the mutations). StuRat (talk) 16:07, 26 November 2014 (UTC)

Have you ever walked through a place where you can adopt a dog? I think Kharon's right that they will likely already be a bit focused on their caretakers, and Stu's right that they have no concept of death if they are not chosen soon enough. But-- they still are often bored and restless, as the caretakers don't have the manpower to give all the dogs all the time and care they need to have stimulating life. So, some dogs at shelters will indeed perk up and wag their tails, lick hands, or whine in pleasure as people come by. It's not so much that they have a concept of being chosen but I think many of them just want to make friends. If they are chosen and led out by new people, they look extremely happy. Seriously, go check out a dog adoption center. You aren't obligated to take any home, and you'll learn a lot about the variety of dog behavior in that context. SemanticMantis (talk) 18:22, 26 November 2014 (UTC)

I pet the cats at the local humane society whenever I've nothing better to do. (At first I went for at least a couple of hours every week; then I got more work and a pair of cats at home.) (Other volunteers take the dogs for daily exercise.) Most of the dogs seem more alarmed than pleased to see me; maybe they can tell I'm a vampire. —Tamfang (talk) 06:24, 27 November 2014 (UTC)

What are the differences between Thimmamma Marrimanu, Pando, Armillaria solidipes in Oregon, Posidonia oceanica in Mediterranean Sea?

I was reading about the largest organisms and I don't understand how the plants (like those 4 mentioned above) differ from each other. I would like an explanation for a layman as I'm not familiar with the subject.

For example, how is the way the banyan "spreads"/grows different from the aspen? They both seem about the same to me.

Are these plants only considered 1 single large plant because they are physically connected? Can 2 physically disconnected parts of the plant be reconnected again?

Thanks.

138.75.150.164 (talk) 15:29, 26 November 2014 (UTC)

An organism can be defined, very broadly, as a contiguous living system. Of course, in reality this definition is almost invariably restricted to only include contiguous living systems that possess the same or essentially the same genetic material throughout their extent, and/or to only include contiguous living systems where all parts are not just in contact with each-other but actively exchange some resources between them. That is, for example, a flock of sheep huddled together is not a single organism. A pine grove is not a single organism either, as the pines merely grow next to each-other. By contrast, an aspen grove (a clonal colony) constitutes a single organism when all individual trees are interconnected at the roots and can exchange water and chemicals with each other via the interconnected root system. Plants can form interconnected clonal colonies by various means. For example, some plants (like many grasses) send out roots or rhizomes that sprout new plants when they reach the surface. Some plants (like strawberry) send out runners that root at certain intervals. Some plants (like raspberry) produce roots when their branches touch the ground. Some plants (like banyan) send aerial roots down from its branches, and some of these roots with time become secondary trunks. Fungi ("mushrooms"), too, form interconnected clonal colonies by sending out their hyphae (mycelium) and producing new fruiting bodies from them; this often looks like a circle of mushrooms, and can be quite large. Does this answer your question? Please let us know. All the best, --Dr Dima (talk) 19:08, 26 November 2014 (UTC)

To your question on whether 2 physically disconnected parts of the plant be reconnected again, the answer is yes. You can do this experiment yourself, it is called grafting. --Dr Dima (talk) 19:13, 26 November 2014 (UTC)

I think you've explained it pretty well. OP and others may like to read up on ramets and genets, perhaps rhizomes and stolons. The general concept of plants spreading/growing through various non-sexual means is vegetative reproduction - some of those methods can leave the "parent" and "clonal offspring" connected as one organism, some end up separated. In the most confusing cases, whether the clone becomes a distinct organism is often a matter of chance, e.g. in the well-known spider plant. (I also took the liberty of linking the terms in the header for convenience.) SemanticMantis (talk) 20:17, 26 November 2014 (UTC)

Yes it answers my question. Thanks for the help! I have a few related questions: Is it theoretically possible for humans to cultivate/grow an artificial plant/fungi that is even larger than what nature has naturally made? (given sufficient land space) If it were discovered that there was a disconnect/break in the underground roots/mycelium/etc. of the organisms mentioned above (thereby reducing its total size), would grafting them back together make them one organism again? Thanks. — Preceding unsigned comment added by 138.75.128.131 (talk) 15:56, 27 November 2014 (UTC)

Von mises

Von Mises yield criterion (edit | talk | history | protect | delete | links | watch | logs | views)

Does von Mises yield criterion take into account material shape or does it only consider the fact that a particular material with a material shape has a yield stress which is a factor of sqrt3 more than that of the shape in pure shear? — Preceding unsigned comment added by 194.66.246.125 (talk • contribs) 16:05, 26 November 2014 (UTC)

In other words how do you mathematically predict the yield stress of a structure if you only know the material yield stress, Young's modulus and poissons ratio. Am I right in assuming this isn't enough information to predict this? What else do I need?

The von Mises criterion is useful when you have more than one stress acting on a point. For example, if you have tensile stresses acting along both the x and y axes, you might imagine that even with each stress being lower than the yield stress, the 2 acting in combination might be enough to cause yielding. The von Mises criterion gives an estimate of how big the 2 stresses can be before yielding occurs. Before applying the von Mises criterion, you need to find out what stresses are acting on the point in question, and this will require knowledge of the loading and geometry (unless, for example, the stresses are given to you in a class problem).

If you want to find the magnitude of a pure shear stress that will cause yielding, you set sigmav = yield stress (sigmay) and plug the shear stress (e.g. sigma12) into the von Mises criterion (the last equation in the mathematical formulation section of the von Mises article). This gives sigmay = sqrt(3)*sigma12. So the factor of sqrt(3) relating shear stress to the yield stress (tensile) is one case of the von Mises criterion.--Wikimedes (talk) 06:49, 27 November 2014 (UTC)

I'm actually trying to find a way to validate a finite element model of the von mises stresses on a structure with a uniform load applied. I'm trying to do this with theoretical values but I don't know how to produce theoretical values using what I have. 194.66.246.26 (talk) 17:55, 27 November 2014 (UTC)

100 billion coincidence

There are 100-140 billion stars in the Milky Way, probably more than 170 galaxies in the Universe, and about 100 billion neurons in the human body. The similarity of these numbers astonished me. What a coincidence that each of the stars in the galaxy corresponds to a galaxy. It also led me to think about the Anthropic_principle, where the constants of nature are so finely tuned that (apparently) to shift even one would make human life impossible. The fact that there are 100 billion neurons in the human body doesn’t fit into that equation, though, since the number of nerve cells is not a prerequisite to life but rather a part of life. Still, this is a very interesting coincidence. Not a question, I just couldn’t resist putting such an interesting factoid before you to see what you think. --Halcatalyst (talk) 20:12, 26 November 2014 (UTC)

As factoids go, I'd have difficulty accepting that it was 'interesting'. There are many (approximate) numbers one can find in relation to the human body, from the number of heads (one) to the number of electrons (which I will leave someone else to figure out... 2.3*10 ). That one of these numbers is somewhere near the number of stars in the Milky Way is accordingly entirely unsurprising. AndyTheGrump (talk) 20:20, 26 November 2014 (UTC)

Once again, the user per his user contribution s is basically a single purpose account; the purpose being to pose ref desk questions. So long as the OP is suggesting there might be as many as 17o galaxies in the universe, I think a private chuckle is perhaps the best response. μηδείς (talk) 20:23, 26 November 2014 (UTC)

What is with this weird criticism that pops up again and again? There's nothing wrong with using an account to mostly post questions here. To insinuate that that makes someone unwelcome is doing a disservice to the ref desks. I'd rather answer "asking-questions-only" than IPs, if only so I can more easily keep track of who I'm talking to. SemanticMantis (talk) 20:27, 26 November 2014 (UTC)

That there are roughly as many galaxies as stars in the milky way is at least an easily remembered heuristic. It's unclear on whether these "mean" anything, but you may wish to read up on pareidolia. Our pattern recognition skills were (and are) crucial to our survival, so it's not too surprising to see that ability produce many false positives. SemanticMantis (talk) 20:27, 26 November 2014 (UTC)

Don't you think it's interesting that the scale is from human to (what could be called) the basic unit of the Universe to the Universe itself? Another interesting factoid is that, starting from one meter (human size), there are about the same number of powers of ten going up to the size of the Universe and down to the size of a neutron. --Halcatalyst (talk) 20:37, 26 November 2014 (UTC)

That could help explain how the Greeks were able to invent the atom. On the other hand, how the article Anthropic principle's size is related to that of Sapience remains undetermined. --Askedonty (talk) 20:49, 26 November 2014 (UTC)

The OP may find the Dirac large numbers hypothesis interesting. Tevildo (talk) 20:52, 26 November 2014 (UTC)

+++ I have never posed a question to the reference desk (though I'm aware the practice stands somewhere between discouraged and forbidden, depending on your taste.). Visitors might appreciate a little courtesy from the reference librarians.

I was looking for intelligent answers, which I generally get to questions I put to Misplaced Pages. --Halcatalyst (talk) 20:59, 26 November 2014 (UTC)

If Dirac relates "ratios of size scales in the Universe to that of force scales," I guess I can do something of the sort too. BTW, I was just interested in thoughts, not looking for meaning. Thanks for those who have contributed thus far. --Halcatalyst (talk)

You said it yourself: it's a coincidence, nothing more or less. To read about crackpots who read too much meaning into coincidences, see numerology. --Bowlhover (talk) 02:05, 27 November 2014 (UTC)

You may want to check out Benford's law. The apparently disproportionate quantity of ones as the leading digit when measuring items is a much-studied phenomenon and not at all related to numerology or pseudoscience. Matt Deres (talk) 19:33, 27 November 2014 (UTC)

Well the OBVIOUS conclusion is that it's not a coincidence but the universe is in fact a giant brain!! And of course there's only one brain it could be: It's the brain of GOD! Of course I don't I don't believe any such thing, but just demonstrating how easy it is to dive down the rabbit hole. Vespine (talk) 03:50, 28 November 2014 (UTC)

so my fart could be God's brain fart?!66.87.116.95 (talk) 16:09, 28 November 2014 (UTC)

Physicist Richard Feynman has a great quote relevant to such coincidences: "...on the way to the lecture, and I came in through the parking lot. And you won't believe what happened. I saw a car with the license plate ARW 35W. Can you imagine? Of all the millions of license plates in the state, what was the chance that I would see that particular one tonight? Amazing!"

The joke, of course, is that the probability of this coincidence is in fact very low if it were predicted (pre-observation); but post-observation it ceases to be a probabilistic situation at all.

If the rough approximation of the order of magnitude of the count of stars did not match, would you have noticed or remarked on its likelihood at all? What about all the other irrelevant cases where some value is approximately equal to a few hundred billion, plus or minus a couple orders of magnitude? Are these coincidences as well? Can you meaningfully compute the probability of such coincidental observations? Nimur (talk) 19:25, 28 November 2014 (UTC)

Freezing temperature for water

When the temperature hits 32 degrees Fahrenheit (or lower), the liquid form of water turns to ice (i.e., it freezes). When I look at my "weather app" on my computer, it always says something like this (for example): "Today, the temperature is 53 degrees, but it feels like 43 degrees." And I believe it is the wind chill factor that makes the temperature "feel" colder than it actually is. So, let's say that on some given day, my weather app says: "Today, the temperature is 38 degrees, but it feels like 28 degrees." What happens to water in that case? Does it not freeze because the temperature is higher than 32 degrees? Or does it freeze because the temperature "feels" like it's less than 32 degrees? Thanks. Joseph A. Spadaro (talk) 23:06, 26 November 2014 (UTC)

Related question: Misplaced Pages has an article for boiling point, but not for freezing point? Joseph A. Spadaro (talk) 23:11, 26 November 2014 (UTC)

The water would still stay liquid. It feels like 43 degrees to you because you are hot and loose heat quickly when the wind is constantly moving cold air past you. Humans can't actually sense temperature; we sense how quickly heat is being transfered (which is why a block of metal feels colder than a book at the same temperature). To water near 38 degrees, the air isn't that much colder, so it looses heat much more slowly than you (although the wind still makes it cool faster). As for the second question, it's because melting point and freezing point are the same thing. I hope this helps! --T H F S W (T · C · E) 23:44, 26 November 2014 (UTC)

No offense, but your answer actually confused me even more. Joseph A. Spadaro (talk) 00:58, 27 November 2014 (UTC)

Let me try to unconfuse you: 1) Wind chill factor has to do with how quickly heat transfer happens from your skin to the air. The reason why you feel colder when the air is moving is that the moving air carries heat away from your body faster than still air would. Thus, if the weather says "38 degrees F, with a wind chill factor of 28 degrees F", what that means is that your body will lose heat as though it were a windless day at 28 F, though the actual air temperature is 38. The difference is not in actual temperature, the difference is in how fast two bodies of different temperatures equilibrate. When the air moves over the warmer body, it will cool off faster. But it can never cool off to a temperature lower than the ambient temperature. Thus, if the air is at 38 F, the water will never freeze. If the water is at, say, 50 F, it will get down to 38 faster if there is wind than if the air is still, but it can never drop to below the ambient temperature, which is why it will never freeze, no matter WHAT the wind chill factor is. 2) Freezing point and melting point is the exact same thing: the only difference is the direction the temperature is moving. If the temperature is going up, we call the temperature the "melting point". If the temperature is going down, we call it the "freezing point". But the two are identical. --Jayron32 02:17, 27 November 2014 (UTC)

Water can indeed become colder than the ambient temperature, because it loses heat through the latent heat of evaporation and not just by sensible heat. This can be enough to cause the water to freeze when ambient air temperature is above freezing. Peggy LeMone has a nice little article here. Short Brigade Harvester Boris (talk) 03:22, 27 November 2014 (UTC)

Yes, Jayron's usually excellent answers have a glitch here because a wet cloth, or a windscreen, can freeze in a cool breeze that is above 32 F. See Wet-bulb temperature for the technicalities. Dbfirs 13:24, 27 November 2014 (UTC)

• There's no freezing "point" of water unless one looks only at temperature, without regard to the energy of the system. Water at 32F can be liquid, solid or slush. Water requires more energy to be removed from the system to go from liquid at 32F to solid at 32F than it does to drop a degree from 33F to 32F liquid or from 32F solid to 31F. See water and enthalpy of fusion. μηδείς (talk) 22:56, 27 November 2014 (UTC)

Thanks. All the answers were very helpful. Thank you. Joseph A. Spadaro (talk) 16:54, 28 November 2014 (UTC)

November 27

Availability of phase change material fabrics

Are their phase change material fabrics available to the public (in the UK) for use in domestic sewing projects? --78.148.108.62 (talk) 05:55, 27 November 2014 (UTC)

Ebay sells everything. £15 per yard. Plus a ridiculous amount for postage etc.--Aspro (talk) 18:33, 27 November 2014 (UTC)

Von mises

The article on Von Mises is very confusing. Can someone explain simply how you can use it to explain where and when yielding occurs on a material? If for example, I know the pressure on the material, and the material properties, how do I use those values to calculate when and where yielding occurs? — Preceding unsigned comment added by 194.66.246.71 (talk) 19:43, 27 November 2014 (UTC)

That's first year stuff in an engineering degree course, and I must admit it took me two goes to undertsand von mises, and I've now forgotten it again. As such, a post on a forum like this isn't really adequate. Can I recommend that you read JE Gordon's Structures, or things don't fall down? http://www.amazon.com/Structures-Things-Dont-Fall-Down/dp/0306812835 It should be compulsory reading for anyone who is interested in stress analysis. Greglocock (talk) 21:51, 27 November 2014 (UTC)

Amylase Inhibitors

How does do he take the pure oxygen in the glass in his hands?

I saw in this page a picture of a guy who takes a glass that inside there's oxygen . According to what I know about the oxygen, the oxygen can not be in the state of matter of liquid when it's up to -183. So I believe in this place it's not -180 degrees (you can understand it according to the wearing of this man). I think it should be broken by the higher level pressure that should created when this oxygen appears such as this temperature (unless the oxygen in a appropriate strong cylinder)5.28.173.111 (talk) 23:22, 27 November 2014 (UTC)

The oxygen is cold so it is liquid. It's warm outside so the liquid is boiling and evaporating, but it takes time to evaporate, so the man has time to check the liquid oxygen. Ariel. (talk) 23:26, 27 November 2014 (UTC)

Sorry to piggyback a question onto this, but this actually made me wonder. I understand the above, but I kind of get where the OP is coming from too. For example, the liquid inside a butane lighter immediately and violently evaporates if exposed to regular pressure, like if the lighter casing is broken, I have witnessed this first hand on several occasions. The boiling point of butane is only -1 °C, the boiling point of oxygen is -183 °C. Why doesn't the butane "boil" away slowly like the oxygen? If you cooled down a lighter below -1 °C, like in a freezer, and THEN broke the lighter would it also boil away slowly like the oxygen? Vespine (talk) 03:38, 28 November 2014 (UTC)

It's the mass-volume, temperature and pressure. Normally, we usually think of the liquid as being room temperature and coming to an equilibrium pressure (like LP gas). Liquid oxygen is not that case, though. It can be chilled while near atmospheric pressure to a liquid. The dewar flask keeps it from absorbing heat and limits the external heat needed to boil it away. The rate at which heat can be exchanged regulates the boil (and pressure). If it's not in a temperature insulated tank, it will be a gas at very high pressure. You can feel the heat exchange process by filling and releasing a compressed gas (expansion feels cold, compression gets hot). --DHeyward (talk) 04:02, 28 November 2014 (UTC)

If you break a container that starts under pressure, the liquid is already well above its boiling point to begin with, and reaching an equilibrium based on pressure tends to be fast and forceful. Cooling the butane lighter should help. However - I would have to look up to know for sure - I am suspicious that butane might have a lower heat capacity in liquid form than oxygen, which would make it evaporate faster (the lower the heat capacity, the more has to evaporate to compensate for the same leakage of heat through the insulation). Still, the rate of heat leakage in a container will be proportional to the temperature difference, so it should still be much slower to boil than oxygen in the same container when they both start off at boiling point and atmospheric pressure. Wnt (talk) 05:37, 28 November 2014 (UTC)

The cryogenic dewar tanks are preferred for supplying heavy users because the tank doesn't have to be purged when it's refilled. Just the glass flask is a poor conductor so most of the heat to boil the oxygen is from air above and that can be controlled somewhat (note the duct tape). The cryogenic storage tank will usually have various ports for high pressure, low pressure and liquid. In a flask, the liquid appears to be boiling until it is gone. For oxygen, it will go from the liquid Dewar flask to an evacuated high-pressure tank. Contaminants and catalysts create hazards in the cylinders (i.e. sea water in emergency O2 scuba rescue dive tank that is filled with pure, high pressure O2 ->salt water reacts with the metal much quicker than atmosphere. Oil from a compressor/concentrator that accumulates in a gas cylinder can be a fire hazard - for those reason, Oxygen compressed air tanks are evacuated before being filled but the liquid storage tanks can be refilled continuously as needed). --DHeyward (talk) 03:48, 28 November 2014 (UTC)

An interesting question. It's worth pointing out this is a high-resolution image. So far as I can tell, the way the man's gloves look makes me think that they are actually above freezing, with just bits of frost from having reached into someplace colder. The oxygen in the container seems to be boiling, as I'd expect. But there isn't very much vapor going around, even though this sure doesn't look like a Dewar flask. So the nature of the material of the container is very much open to question; I have a hard time thinking it is a single layer of glass based on the apparent insulating quality; nor would that seem especially safe... but I don't think many types of plastic would be a good idea... I have a wild guess it might be made out of silicone but certainly am not in a position to know that. Anyway, the loose foil seal at top is a dead giveaway that this is not under pressure, so the rate of boiling of the oxygen directly reflects the insulating quality of the container. Wnt (talk) 05:28, 28 November 2014 (UTC)

It's not hard to fill a standard glass beaker a third or half full of liquid nitrogen and get an effect similar to what's seen here once the glass has cooled down. On initial filling, there is somewhat violent boiling at the liquid/glass interface, but then it settles to a gentle boiloff. Can't keep it for long-term storage, but even simple glass must have enough insulating ability (poor enough thermal transport properties or whatever technical parameter) even without film boiling. DMacks (talk) 06:10, 28 November 2014 (UTC)

If humidity is low, so not much water condenses and freezes on the glass, then it is possible to look like this. It is either glass or quartz glas, because polymer and liquid oxygen together is bad idea. It is not double walled, so it is probably regular beaker glas and after the initial cooling stage (violent boiling) the boiling would be slow and the ice crystals were probably wiped away before the picture was taken. More interesting are the liquid nitrogen YouTube clips of man pouring it to his bare hands. Gergo vassilev (talk) 16:00, 28 November 2014 (UTC)

Leidenfrost effect/film boiling insulates both ways:) LN2 onto your hand is no problem, especially if your hand is not cupped deeply. Dipping your hand into it is more interesting. Or an ALS LN2 Bucket Challenge. Dipping your hand into molten lead is even more-so. Lest you think I'm making all this up, those last two are cited in the article I linked. DMacks (talk) 18:47, 28 November 2014 (UTC)

Ooooh. I just realized that this photo was taken at Eielson Air Force Base in Alaska, where temperatures can drop to 50 below. Even if the room temperature is comfortable, the amount of humidity present might still be less than anything I am used to, so yes, there could be an unexpected lack of water vapor condensation! So yes, it might be plain glass after all... though I'd still think someone might worry about what might get wet with liquid oxygen and explode if it breaks. Wnt (talk) 19:05, 28 November 2014 (UTC)

November 28

Most viewed health topics on Misplaced Pages

I recently read in a news article that Misplaced Pages allows free access to its data on the most frequently searched topics. As I understand it, this information can also be broken down according to language (but not to geographical location).

If this is the case, I would like to know which health topics are most commonly viewed on Misplaced Pages in both English and Arabic. A list of up to about 2,000 topics in each language would be ideal, but otherwise I would settle for a shorter list!

Alternatively, if it’s not possible to stratify according to health topics specifically, I would also be interested in the same lists in a similar category (e.g. medicine, science, biology, etc). — Preceding unsigned comment added by 14.203.101.110 (talk) 00:39, 28 November 2014 (UTC)

The main portal for page stats is http://stats.grok.se/ Which will let you look up individual pages or download count files for all requests. There is a top list but it doesn't seem to have been updated in several months and shows some spurious requests (probably due to bots and other automated web processes). The most visited pages on a month to month basis are often typical issues that are being highlighted in the news (e.g. new movies, celebrities, wars, etc.) As far as medicine goes, I suspect that the Ebola related pages have rated very highly in recent months. As far as I know, there are no preexisting subcategorized lists of page views for medicine or any other topic. In principle one could be created though, either by hand, or by selecting a subset of pages that are already labeled with categories associated with medicine. That would presumably take someone with a bit of programming skill however. Dragons flight (talk) 01:24, 28 November 2014 (UTC)

See Category:Lists of popular pages by WikiProject.

—Wavelength (talk) 03:11, 28 November 2014 (UTC)

You may also want WP:5000; it only gives results per week, not long-term, but since most health topics generally don't get a ton of spikes from news coverage, you'll be able to make a decent guess on "most popular" by checking a few weeks' entries. If you have a bot or a way to scrape content, you can easily amalgamate statistics by months or years. Nyttend (talk) 03:58, 28 November 2014 (UTC)

Using Wavelength's link, you can see a list of the 1000 most popular WikiProject Medicine pages at Misplaced Pages:WikiProject Medicine/Popular pages. John M Baker (talk) 15:35, 28 November 2014 (UTC)

What's the thickness of a clothing to prevent mosquito bites?

I want to visit South America, and I want to protect myself from mosquito bites. How thick should a clothing be to prevent the piercing of a southern american mosquito? What is the minimum thickness? How deep can southern american mosquitoes pierce into the human skin? 173.33.183.141 (talk) 03:31, 28 November 2014 (UTC)

I don't think it's primarily a question of thickness, but more of the quality and density of the weave. I've never experienced mosquitos biting through a normal dress shirt, but I'd be less sure about a t-shirt, even if technically thicker. If you want to be sure, use something like DEET or Icaridin on the skin and Permethrin on clothing and mosquito nets. Famous brands here in Germany are NoBite and Autan, but international branding seems to vary a lot. --Stephan Schulz (talk) 03:48, 28 November 2014 (UTC)

Thanks. Do southern american mosquitos have longer piercing heads than the north american mosquitos? 173.33.183.141 (talk) 21:30, 29 November 2014 (UTC)

Sublimation and temperature change

Take a quantity of water and evaporate some of it, and the rest cools to an extent. Take a quantity of ice and sublimate some of it; will the rest become colder? Nyttend (talk) 19:25, 28 November 2014 (UTC)

Yes, the ice becomes colder. It is this same phenomena which is used to cool spacesuits. That is why NASA came to over-look the presence of water on the moon during the Apollo era. The H2O that the NASA scientists found in the moon samples, they concluded was just man-made contamination. However, the Soviets knew but the Americans never read their science papers.--Aspro (talk) 20:18, 28 November 2014 (UTC)

Function generator design

Function generators are usualy designed with the primary waveform generated being a triangle wave created by charging a capacitor with a constant current. At higher frequencies than about 3-5 MHz, however, the comparator used has to be very fast and the triangle wave distorted to operate the comparator as fast as possible. I was wondering if there were any function generator designs that used a square wave produced by a voltage controlled oscillator as the primary waveform. Triangles can then be produced by integrators and sine by shaping the triangle as usual. Are ther any problems with this approach and are there any manufacturers using this technique especially for fast (20MHz) generators?--86.157.138.192 (talk) 19:32, 28 November 2014 (UTC)

That might have been true 40 years ago, but any modern function generator will be purely digital, using a DAC to create the waveforms. Apart from the audiophile market (which is more art than engineering), there's very little analog equipment for use at low frequencies available these days. However, I'm sure it would be possible to design an analog function generator along those lines, it just wouldn't be a commercially viable proposition. Tevildo (talk) 21:13, 28 November 2014 (UTC)

20MHz triangle and sine from a DAC??--86.157.138.192 (talk) 21:22, 28 November 2014 (UTC)

120 MHz! It's amazing what they can do these days ("these days" starting in about 1995). Tevildo (talk) 21:42, 28 November 2014 (UTC)

Indeed! Our article is direct digital synthesis. And if you have unlimited budget, you can get direct digital synthesizers deep into microwave bands - arbitrary digital waveform synthesis at tens and hundreds of gigahertz! Such devices are used for satellite communication and microwave RADAR design and test.

But we don't even have to look into wacky aerospace and defense technologies to find such circuitry! Chances are high that you've got one of these K-band digital synthesizers - or one like it - built into your home computer!

Nimur (talk) 00:04, 29 November 2014 (UTC)

Universe - universe = 0?

If our universe was created from nothing, and we dont seem to have found much antimatter so far, is it possible that an anti universe was created at the same time as the matter universe? --86.157.138.192 (talk) 21:35, 28 November 2014 (UTC)

But if there was nothing ("0") befor, what created or caused the universe? The theory of an antiuniverse is scientificly as bad (not proven) as the famouse Bigbang theory. Some astrophysists still belive in the theory that this universe has simply always been here. --Kharon (talk) 01:55, 29 November 2014 (UTC)

Mathematically, that notion doesn't work. ←Baseball Bugs carrots→ 03:03, 29 November 2014 (UTC)

In fact, the idea that the universe "has always been there", strikes me as the cosmic equivalent of the "Turtles all the way down" story. ←Baseball Bugs carrots→ 22:32, 29 November 2014 (UTC)

Well, as explained in the antimatter article, the idea is apparently not totally dead even that antimatter could exist in large amounts somewhere in our observable universe. It is also possible that the observable universe encompasses a large region that is entirely matter, but that there is a variation on a larger scale even than the entire universe we see, so that other regions may be mixed or entirely antimatter (which isn't far from the OP's suggestion really, except the two were once connected as a single region of space but now "you can't get there from here" due to cosmic inflation). But CP violation in baryogenesis is still the more likely looking answer, since there are observed deviations. Wnt (talk) 04:52, 29 November 2014 (UTC)

The concept of a zero-energy universe does not depend on equal amounts of matter and antimatter. -- ToE 16:51, 29 November 2014 (UTC)

Question About the Elimination of Energy

Since energy can be neither created nor destroyed therefore does Einstein’s energy equation equitable with any other forms of energy such as P.E, K.E, Work Done….....?162.157.249.151 (talk) 22:22, 28 November 2014 (UTC)eek

Yes. However, while Einestein's equation says that the total energy of a system remains constant, it does not say that it cannot be converted into other forms of energy. Potential energy is frequently converted into kinetic energy (dropping objects, burning fuel, electrical discharge, etc.) and vice versa. Is this what you are asking? --T H F S W (T · C · E) 23:27, 28 November 2014 (UTC)

NMR basic problem

I have a relatively basic NMR question, but I am having trouble figuring it out. The chemical formula is C5H10O. The chemical shifts are 1.3 (singlet, integration 2 cm), 1.9 (singlet, integration .3 cm), 5.0 (doublet, .2 cm), 5.2 (doublet, .2 cm), 6.0 (doublet of doublets, .2 cm). The problem also says the peak at 1.9 ppm is solvent and concentration dependent. Does this mean it is -OH? I know there is a C=O. The spin spin splitting is throwing me off. — Preceding unsigned comment added by Pinterc (talk • contribs) 22:34, 28 November 2014 (UTC)

Do you know if that's the molecular formula, or the empirical formula? That is, do you know if the molecular weight is ~86, or could the compound be something like C₁₀H₂₀O₂ or C₁₅H₃₀O₃? (Getting mass spectroscopy results greatly helps NMR determination.) You may want to also double-check your integrations. As written, they sum to 2.9, meaning that each proton should account for ~0.3 (assuming 10 protons) - which means you're getting something like a 6:1:1:1:1 ratio, and a fair amount of error on integration amounts. (Although if you're using an empirical formula, you might be running 30 protons, with possibly more like a 20:2:4:2:2 or 21:2:3:2:2 ratio.) But if the "2 cm" is a typo for "0.2 cm", then you're summing to 1.1, and getting more of a 2:2:2:2:2 ratio. All this, of course, is complicated by the solvent and concentration dependance of the 1.9ppm peak. You may want to figure out what about the peak is concentration/solvent dependent: is it just chemical shift, just integration, or both? You're pretty saturated, though, so that's going to limit you. Do work it out yourself, but I think the carbonyl requirement is going to take up your unsaturation allotment. The splitting pattern itself isn't too hard to accommodate. (You have to remember that if a proton is split, it's going to be splitting another proton in turn, so that constrains how the doublet of doublets and the two doublets are related to each other. Do you have the J values for the coupling constants? In this example it's probably going to be uninteresting, but matching the J values of the coupling constants can be used to figure out which proton is splitting which other proton.) The concern I might have about the split peaks is their shift - ca. 5 ppm and a general lack of unsaturation in the molecule implies some sort of relationship to the oxygen(s). You also have quite a small number of peaks in comparison to the number of protons (especially for larger multiples of an empirical formula) - that usually (but not always) implies a high degree of symmetry in your molecule. -- One suggestion I would make is to break the problem into parts: list a bunch of different molecular fragments which can account for different portions of the data at hand. Then see if you can come up with a way to merging those fragments together to account for all the data. -- 160.129.138.186 (talk) 00:03, 29 November 2014 (UTC)

There's already some confusing idea if C5H10O is the actual molecular formula: the proposed C=O is the oxygen atom, so there's no other oxygen left to be the OH oxygen. DMacks (talk) 05:10, 29 November 2014 (UTC)

Per NMR spectroscopy, "Coupling to additional spins will lead to further splittings of each component of the multiplet e.g. coupling to two different spin ½ nuclei with significantly different coupling constants will lead to a doublet of doublets." This alone implies a CH - CHR - CH structure. I don't see a good table at chemical shift; we should have something like . I fooled around with this for a bit and couldn't think of any ideas; is a useful link but I'm stumped. Someone ought to be able to recommend some searchable NMR database that might come through here. Wnt (talk) 01:47, 29 November 2014 (UTC)

Chemical shift is the general idea, not specifically 1H. For information specific to that, see Proton NMR. But the table there is confusing as hell...seems entirely focused on "what else is attached to the C with the H", making it hard to identify the aldehyde structure as such and except for that case omitting all other H that are not on sp C (no vinyl or aryl or OH or NH themselves, just the C_α to it). DMacks (talk) 05:18, 29 November 2014 (UTC)

• You've also got 5 peaks, which implies 5 unique carbons. What are the splitting constants? You can sometimes match neighboring bits by matching splitting constants... --Jayron32 13:32, 29 November 2014 (UTC)

November 29

What are the chances of getting hpv from oral sex?

What are the chances of getting hpv from oral sex, not the chances of oral cancer from hpv? I asked a similar question a few days agoWhereismylunch (talk) 04:28, 29 November 2014 (UTC) ″

Fairly sure the answer will depend on factors like whether any form of barrier protection was used, the sex of the recepient, and whether you're referring to the risk to the receiving or giving/performing partner. Also the presence or absence of open sores or wounds on the mouth of the performing partner, the number of times and whether the people involved have HPV or at high risk of it (e.g. sex workers). The difficulty of seperating these means some figures will be averages of them (for example, I don't think anyone is going to try to come up with a figures for a person who's received oral sex 1x, 2x, 3x, 4x.... during their lives), but I don't think anyone is going to come up with a random single figure for the risk of getting HPV from oral sex. Nil Einne (talk) 13:36, 29 November 2014 (UTC)

But on wikipedia they have a random single figure for aids from anal sex.Whereismylunch (talk) 18:11, 29 November 2014 (UTC)

Hydrogen roasting

Molybdenum and tungsten is produced by roasting the oxides under hydrogen gas. What makes the ore of one metal better qualified over the ore of another? Which ores were this technique first applied to, for the purpose of refining the metals? Plasmic Physics (talk) 09:13, 29 November 2014 (UTC)

Red Bull Stratos

The person might have been burned during re-entry. But he did not. But spacecrafts get fire during re-entry. Please explain why? --IEditEncyclopedia (talk) 10:39, 29 November 2014 (UTC)

See Aerodynamic heating. The guy probably got warm from the friction, but he wasn't going fast enough to cause combustion. The typical "shooting star" comes into the atmosphere at a very high speed and burns quickly. Speed seems to be the key issue. ←Baseball Bugs carrots→ 12:27, 29 November 2014 (UTC)

Also, try this: Rub your hands together very fast... Do they get warm? That's why things get hot on re-entry. Friction causes objects to heat up, the faster something is "rubbing" against something else, the more heat is generated. An object such as a meteor or a space craft is moving very fast indeed, and as such, generates a lot of friction with the air of the earth's atmosphere. --Jayron32 13:28, 29 November 2014 (UTC)

Friction is too much of an over simplification when it comes to de-orbiting craft and lumps of comic rock. At these velocities the air stops moving before it gets to the leading surface (called something like the stagnation point). So low flow, low friction! The bulk of the heating comes from compression in this case. The temperature of this air at this point (when it has been turned to plasma) is enough to vaporize all known materials. Fortunately it is not in direct contact with the heat shield (because there is no flow) and so most of the thermal energy radiates away. At lower speeds, the air conducts away much of the heat caused by friction alone, because it is in contact and thus convention is the main method of heat transport. --Aspro (talk) 14:53, 29 November 2014 (UTC)

An important point (not mentioned yet) is that the intrepid Mr Baumgartner only _fell_ to Earth, he was never in orbit. A spacecraft in orbit will be moving much more quickly on re-entry than one which has just been launched straight up, so there's much more energy to dissipate in atmospheric heating on reentry. Tevildo (talk) 15:17, 29 November 2014 (UTC)

Absolutely! That's the huge difference between the two examples. For skydiving from orbit (via an emergency, one man, inflatable reentry device), see MOOSE.-- ToE 16:46, 29 November 2014 (UTC)

I agree. The free fall from a high altitude balloon is much slower than typical orbital speeds. For a somewhat analogous situation see also space elevator. Mihaister (talk) 23:22, 29 November 2014 (UTC)

Snow-resistant buildings

How can buildings be constructed to be able to support four meters of snow without being damaged?

• New York's Cuomo warns snow-hit Buffalo of risk to roofs—Reuters (November 24, 2014)

—Wavelength (talk) 17:32, 29 November 2014 (UTC) and 19:10, 29 November 2014 (UTC)

Use a steeper roof pitch. Plasmic Physics (talk) 21:36, 29 November 2014 (UTC)

How steep would it have to be to avoid all snow accumulation ←Baseball Bugs carrots→ 22:30, 29 November 2014 (UTC)

Houses built in Northern latitudes typically have steep roofs for this exact purpose. This image is from the main article on roofs. Mihaister (talk) 23:30, 29 November 2014 (UTC)

Can you mix ants of the same species but of different ant colonies?

If you pick ants from one ant colony and place them in a totally distinct (but of the same species) ant colony, would they come well along? --Senteni (talk) 19:15, 29 November 2014 (UTC)

There has been considerable research on this topic. A Google Scholar search for 'ant colony recognition' will provide a starting point. Ants communicate via scent (notably pheromones), and it seems that each colony (or possibly supercolony ) has a distinct scent. AndyTheGrump (talk) 20:30, 29 November 2014 (UTC)

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