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June 22

Sound of Sound Waves Based off Certain Characterisitcs

Promise this is the last question I'll ask for a while. Given two curves f and g so f(t) >= g(t) for all t; a "template wave piece" w(t) with t ranging 0 to 1, w(0) = w(1) = 0, and there being 0 < a < b < c < 1 so w(a) > 0 is maximal, w(c) < 0 minimal, and w(b) = 0; and an increasing sequence of points t(0) = 0,...t(N) = k. Make a wave W by taking rescaled versions of w and placing them so that W on [t(3m), t(3m + 2] will have t(3m), t(3m+1), t(3m+2) correspond to 0, b, 1 on w (,but be mapped to the midpoints of f(3m+s) and g(3m+s) ) and the points x, y corresponding to a, c will have W(x) on f, W(y) on g. Essentially, f and g are upper and lower envelopes, w defines the "shape" of one full cycle of the wave, and t(i) determines a frequency. My questions are: what effects do these three components (w; f and g; t(i)) have on the sound of W? In other words, what characteristics of sound are controlled by the various components, even if only approximately? And, how do various transformations affect sounds: for example, doubling the distance between t(i)'s; or stretching out f and g, but adding points to t(i) to keep it relatively the same spacing; etc.? I apologize for any poverty in my description, thank you for any help:-) [also, is there a family of w's so that any wave W can be "closely approximated", in the sense of sound perception, by using it in this fashion with the same f, g, and t as in the original?]Phoenixia1177 (talk) 04:40, 22 June 2013 (UTC)

Or, if it's simpler, if someone could point me towards some free/opensource tools I could use to implement my own version of the above and just test it out. I'm fairly confident I could code something from scratch, but I think it would end up very inelegant and unuseful for analysis, so if there are any libraries that could help with that, I'm willing to try that and look into it myself.Phoenixia1177 (talk) 04:44, 22 June 2013 (UTC)

Since my description above isn't the best; what if, this is essentially the same, we took a periodic wave with max = 1, min = 0, and rescaled it so the maxs lay on f, mins on g, and where it crossed the midpoint between f and g was at points t(i)?Phoenixia1177 (talk) 06:18, 22 June 2013 (UTC)

I think you are describing a form of amplitude modulation, but I can't help with the rest of your questions. Gandalf61 (talk) 13:07, 22 June 2013 (UTC)

If you don't have MATLAB and you want to mathematically manipulate raw waveforms, you can use the free software Python Multimedia library. It can import and export PCM and WAV files, allowing you write simple software to directly edit the samples. You will probably also find Audacity helpful for visualizing the waveform, and for performing higher-level audio processing operations. Nimur (talk) 16:19, 22 June 2013 (UTC)

Octave_(programming_language) is essentially a free MATLAB clone, which would also work. SemanticMantis (talk) 18:10, 22 June 2013 (UTC)

Thank you for all of the answers, Octave looks very useful ( :-) ); far more useful than my DIY approach. It seems very difficult to track down any books/papers that deal with how the various aspects of sound waves link to actual types of sounds (hence my questions), I've found a lot of material that talks about how sound waves work, which is useful, but little of it makes clear how that impacts what you will end up hearing (perceptually, not physically). Maybe it's just something you have to experiment with.Phoenixia1177 (talk) 06:45, 23 June 2013 (UTC)

The same book I always recommend - which is available for free online: Physical Audio Signal Processing - starts off in the very first chapter: how does it sound? The book is a must-read for anyone who wants to work on home-brew waveform synthesis. Nimur (talk) 19:22, 24 June 2013 (UTC)

Why humans have more distinctive physical features than most other species?

Aside from sexual dimorphism, it's often hard to tell the difference between the representatives of one species (like between two mosquitos, two rats, two zebras, two chimps etc.) whereas humans feature various eye color, hair color, skin shade and so on. Even when considering a species that, like humans, lives almost everywhere (like mice), that species exhibits less physical features than humans. Is it because humans are a sort of evolution's apex or some other reason?--93.174.25.12 (talk) 08:51, 22 June 2013 (UTC)

First, who says your premise is true? Second, maybe you've heard western stereotyped comments such as "all Japanese look alike" (which they clearly don't, but that's the ironic point). Familiarity figures into it. Folks who study chimps or gorillas, for example, are easily able to tell one from another, as they spend so much more time with them than the average person does. Then again, maybe all penguins look alike to us. But maybe not to each other. To do this right, though, you would need to study the DNA variations in some particular species that you think "all look alike" and learn how genetic variations subtly affect appearance. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:30, 22 June 2013 (UTC)

If you make measurements, human faces are remarkably alike, which is one of the reasons automated facial recognition is so difficult. We have a phenomenally good ability to analyze human faces, to the point of pareidolia, where we see human faces where there are none, but as Baseball Bugs says, it's very common for people of all ethnic groups to have difficulty distinguishing the faces of people from unfamiliar ethnic groups, even though they have no difficulty distiguishing themselves from one another, and may well have the same problem in the reverse direction. I think this phenomenon may well be related to our hyper-acuity in seeing faces: the viewer is so busy processing the unfamiliar difference in the person's face to be able to distinguish finer differences. This is rapidly fixed by becoming familiar with many members of the unfamiliar ethic group -- which can be done quite easily by living in one of the world's more cosmopolitan cities -- at which point, you stop seeing the macro difference in overall features, and start seeing the micro differences that make each person individual. There's a whole world of academic research to be done about this, and its relationship to both racism, and the experience of self and other: I wonder how much has been done? -- The Anome (talk) 14:34, 22 June 2013 (UTC)

As ever, Wikipedia (via Google and TV Tropes) has the answer to my question: it's called the cross-race effect, and lots of research exists. And it looks like research has been done that directly addresses your question, albeit just across human and non-human primates: Pascalis, O.; Bachevalier, J. (1998). "Face recognition in primates: A cross-species study". Behavioural Processes. 43: 87. doi:10.1016/S0376-6357(97)00090-9. -- The Anome (talk) 14:42, 22 June 2013 (UTC)

And also this, which also directly addresses the issue you've raised: Heron-Delaney, M.; Wirth, S.; Pascalis, O. (2011). "Infants' knowledge of their own species". Philosophical Transactions of the Royal Society B: Biological Sciences. 366 (1571): 1753. doi:10.1098/rstb.2010.0371. -- The Anome (talk) 14:46, 22 June 2013 (UTC)

(ECx2) I think the premise is true. Looking at eye color, skin color, hair color, hair texture, height, and weight, humans do seem to have more variation in those characteristics than many other species. We could throw in things like the chin dimples and oriental/occidental eye skin fold differences to complete the picture. (Of course, people also sometimes choose to alter their appearance further, with differences in facial hair, tattoos, etc., but this isn't relevant to this discussion.) Those species which do show as much variety in appearance as humans are often those bred by humans, like dogs, cats, and livestock.

Now, why would this be ? Humans have had a relatively large population, with many isolated populations, in different geographic regions, for thousands of years. This is enough time to allow genetic drift to occur sufficient to change the appearance of a species, but not enough for the populations to diverge into separate species. In some cases, like skin color, there are actual genetic pressures based on geographic areas (equatorial populations needed darker skin to protect from skin damage from UV light, while polar populations needed light skin to allow enough UV through to produce vitamin D).

Another factor might be that people are social animals which use visual means of identification, so it's helpful if each individual has a unique physical appearance. In animals which primarily use smell for identification, they might look identical but have widely varying odors. And non-social animals just don't need the range of appearances as social animals, since they don't need to keep so many individuals straight.

Then some species have actual genetically identical offspring, like the armadillo with identical quadruplets. This virtually guarantees that they will look similar. Identical twins, triplets, etc., in humans are relatively rare. StuRat (talk) 14:47, 22 June 2013 (UTC)

I'd agree that the premise is probably wrong. I recall reading about a study that confirmed human babies' ability to tell the difference between faces of different monkeys. Adult humans see no difference, however. Unfortunately, all I could find is this BBC article, but the proper scientific article is out there somewhere. This suggests that although we, adult humans, cannot spot the difference, others can and it certainly exists. Surtsicna (talk) 14:54, 22 June 2013 (UTC)

Try this: Haan, M. D.; Pascalis, O.; Johnson, M. H. (2002). "Specialization of Neural Mechanisms Underlying Face Recognition in Human Infants". Journal of Cognitive Neuroscience. 14 (2): 199–209. doi:10.1162/089892902317236849. PMID 11970786., http://www.cbcd.bbk.ac.uk/people/scientificstaff/mark/PDFs/Specialization -- The Anome (talk) 15:01, 22 June 2013 (UTC)

The only way really to find out if there are really differences in the amount of difference would be to take photographs of many individuals of each species (perhaps about 1000 might suffice?), identify corresponding points (corners of eyes, nose or beak, ears, etc.) and measure, and then perform a statistical analysis of inter-individual variations within each species. -- The Anome (talk) 14:54, 22 June 2013 (UTC)

You might also consider that some other animals identify each other in non-visual ways. Extremely well. A mother bat can find her baby (even an adopted baby) in a screaming mass of thousands of other seemingly (to us) identical babies, in the dark. I couldn't do that with my own newborn in a well-lit room of only twenty other white babies.

Animals who differentiate with another sense (or eyes that can see beyond our colour spectrum and in ultra-high resolution), don't need to look different (or different in our eyes), for the same reason we don't need to smell, sound or feel different (though we do, to an extent). It'd be rather pointless.

And yeah, what they said. InedibleHulk (talk) 15:09, 22 June 2013 (UTC)

It's an interesting question: is increased variation in facial appearance something that is selected for, perhaps for improved ability to be the recipient of favourable social behavior from others, or merely a consequence of other factors like genetic drift, that happens to be latched onto by other mechanisms for those purposes? -- The Anome (talk) 15:14, 22 June 2013 (UTC)

Dogs (for example) exhibit hugely wider differences in size, shape and coloration than humans. It's true that the species has been selectively bred for these differences, but I think it throws your initial assumption into question. --ColinFine (talk) 15:41, 22 June 2013 (UTC)

Also, we have specialized brain parts devoted to recognize human faces. You can have a set of pictures of human faces that look totally different, rotate them 180 degrees and then they all look almost identical. Count Iblis (talk) 15:42, 22 June 2013 (UTC)

Number 3 on this list touches on that. It's also a great picture of Obama. (That first illusion is trippy as hell, too.) Our vision definitely isn't foolproof, but great with human faces. InedibleHulk (talk) 16:19, 22 June 2013 (UTC)

Related: sheep are very good at recognizing sheep faces [1], and it is hypothesized that better abilities to recognize individuals are tied to more social species. The idea is that better ability to recognize individuals is more beneficial in social animals than in non-social animals (e.g. humans and dogs, as compared to mice or rabbits). This allows for a synergistic selective pressure between social behavior and recognition. This sort of thing is very hard to demonstrate conclusively, but it is an explanation that fits most of our theories of behavior and genetics. For example, all the social insects are rather good at kin recognition.

Thus, I think it is fair to say that humans are rather good at recognizing and displaying individual identity. But, we are not alone in that aspect, and we are certainly no "evolution's apex"! (Actually, we are evolution's apex, in a sense, but then so is every other species alive today-- But that's a discussion for another day :) SemanticMantis (talk) 18:05, 22 June 2013 (UTC)

• The showiness of human faces, eye, eye color, breasts and buttocks, the fact that we have the largest penises among the apes is a result of sexual selection. We are like birds with showy feathers trying to gain mates. Were we not such a food-chain dominant animal we might visually plain as most rodents. μηδείς (talk) 18:49, 22 June 2013 (UTC)
  • And as furry. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:03, 23 June 2013 (UTC)

Headphone frequency range

Do all headphones have weaknesses somewhere in the frequency range? Is there such thing as a headphone which is strong and consistent throughout the frequency range? Why/why not? — Preceding unsigned comment added by Clover345 (talk • contribs) 09:34, 22 June 2013 (UTC)

Our article Electrical characteristics of dynamic loudspeakers is applicable also to headphones.--Aspro (talk) 13:40, 22 June 2013 (UTC)

Traditionally, deep base frequencies were difficult to achieve with tiny speakers. There are new technologies which do a better job there. I believe Bose Corporation is able to get deep base out of small speakers, for example, using the Bose Wave System, although I haven't heard of them mating this to headphones yet (it might still be a little too big for that). Bone conducting audio is another way to get bass you can feel "in your bones". Another concern is that bass takes more energy to produce, so will drain batteries more quickly. StuRat (talk) 14:25, 22 June 2013 (UTC)

Yes, the bass range is where headphones generally suffer. Part of that is because we pick up deep bass frequencies largely with our bodies rather than our ears, but part is also because it is hard to produce low frequencies with small vibrators. Looie496 (talk) 15:19, 22 June 2013 (UTC)

Just make enormous headphones. Problem solved.--Jerk of Thrones (talk) 06:12, 23 June 2013 (UTC)

is that why many people judge the quality of headphones on the bass? Clover345 (talk) 09:04, 23 June 2013 (UTC)

Might be worth checking out Stax earspeakers. I'm not too sure how flat the response is, but were certainly usable for 30 Hz signals such as idle booms in cars. I used to use them with a HEAD Acoustics binaural recording and analysing system. Cost about 100000 bucks all up. Greglocock (talk) 00:33, 24 June 2013 (UTC)

Here ya go, flat down to 20 hz, usual fun and games above 1 kHz (the interaction between the spekaer and the ear is complex at high frequency). http://wiki.faust3d.com/wiki/images/f/fd/StaxLa-p4_detail_sm.jpg. As somebody else pointed out, at low frequency a flat response for a headphone sounds as if there isn't enough bass, for example pipe organ music sounds good, but doesn't sound like you are standing in the cathedral. Greglocock (talk) 00:49, 24 June 2013 (UTC)

Yep - the problem with bass is that we don't hear it with our ears so much as feel it on our skin and in our gut. It doesn't matter whether your headphones can feed those very low frequencies into your ears - because that's not where you're sensing the experience. There doesn't seem to be any way to achieve that effect without literally bombarding the body with sound waves at the same frequency and amplitude as the live event. Since some of the things we like to listen to (like rock concerts and pipe organs) are pretty loud, the only way to get a truly realistic feel is to play the music (or at least the lower frequencies) incredibly loud - which tends to defeat the object of headphones! You could possibly imagine a skin-tight suit - (or maybe just a waist-band!) that would vibrate at the right frequencies to produce the feel - but that kind of vibration would likely leak bass sound into the air at the same kind of volume that the original live event would have done. So you're essentially doomed. There isn't a solution - even with hypothetically perfect headphones. SteveBaker (talk) 01:47, 24 June 2013 (UTC)

Eigengrau for the ears?

The article Eigengrau gives a name to the universal experience of greyness that we see when there's no light to see: is there a corresponding article, or indeed a name, for the hiss that we hear when there's nothing but silence to hear? Do deaf people hear this hiss? -- The Anome (talk) 14:22, 22 June 2013 (UTC)

The word I know of is tinnitus, although that's usually used to describe cases where the background sound perception becomes so loud as to be obnoxious. People with certain forms of acquired deafness can experience it, although it's most common with partial hearing loss. Looie496 (talk) 15:41, 22 June 2013 (UTC)

And by the way, the material in that Eigengrau article should be taken with a grain of salt. The sources are antiquated -- one is from the 1890s! Looie496 (talk) 16:37, 22 June 2013 (UTC)

On further investigation, the term "Eigengrau" has basically fallen out of use -- the last scientific papers to use it were published in 2000. Nowadays, I believe, this effect is generally thought of as a type of hallucination, but its mechanism is poorly understood. Looie496 (talk) 16:56, 22 June 2013 (UTC)

From the same source as phosphenes, perhaps? I get a lot of both. -- The Anome (talk) 19:28, 22 June 2013 (UTC)

As a sidenote, it is useful to realize that what we see when there's no light to see are truly random, thermodynamic noise driven, processes (mostly the spontaneous isomerization events of the opsin molecules AFAIK). By contrast, what we hear when there's no external sound is not only the random events in the auditory hair cells and ribbon synapses, but also all the audible-range vibrations generated by our body: blood circulation, heartbeat, breathing, oculomotor activity, peristalsis, salivation, and so on. Furthermore, our outer auditory hair cells are capable of generating active motion in response to the stimulus (although I do not know whether they exhibit any spontaneous active motion or not). --Dr Dima (talk) 20:44, 22 June 2013 (UTC)

Supersonic/Hypersonic Movement at Low Altitude

How fast could a vehicle/anything else move at low altitude (below 300 meters) without being destroyed or destroying the terrain? Is very low altitude hypersonic/supersonic flight conceivable (not counting fuel efficiency, of course!)? Longraptor (talk) 18:38, 22 June 2013 (UTC)

Are you asking for the speed at which terrain avoidance becomes the limiting factor in low-altitude supersonic flight? Or are you asking what other physical effect is the current limiting factor that caps the maximum airspeed in low-altitude flight?

The answers to either of these questions will be difficult to find, because state-of-the-art aeronautical capabilities tend to be unavailable in published resources. But you can take a look at terrain following RADAR to get a ballpark idea of current capabilities. And you can look at the specifications for modern air superiority aircraft to get an idea of the speeds of which they are (reputedly) capable. Most modern aircraft are designed for highest speed at high altitude, because that is the mission they are engineered for. Nimur (talk) 19:20, 22 June 2013 (UTC)

I think he means the speed at which terrain avoidance becomes the limiting factor. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 22:58, 22 June 2013 (UTC)

Our F-111 could fly at about Mach 1.2 (900 KEAS) at treetop height, the limiting factor being aeroelastic stress from dense, turbulent air at low altitude; our B-1 bomber is only slightly slower at low altitude. 24.23.196.85 (talk) 19:37, 22 June 2013 (UTC)

The 1999 7ECA Citabria that I fly starts losing engine power at "high altitude,", which is my speed-limiting factor above 5000 feet no matter how I lean the mixture; by my measurement calculated with my thin and light aviation-grade aluminum flight computer, I make Mach 0.16 at sea level and made just about Mach 0.145 at 5500 feet over California's central valley on a hot day. It may be about time to rate on a more complex aircraft. On the other hand, because I fly a taildragger, I am always "in a landing configuration" which means that I may legally fly at treetop altitude, per 14 CFR 91.119 - unlike our supersonic counterparts! Nimur (talk) 19:41, 22 June 2013 (UTC)

The US did some testing in 1968 on Sonic Booms Resulting from Extremely Low-Altitude Supersonic Flight: Measurements and Observations on Houses, Livestock and People with the McDonnell Douglas F-4 Phantom II. The test range was 5,000 to 8,000 ft (1,500 to 2,400 m) ASL, however the test flights were done at 85–125 ft (26–38 m) AGL and at speeds between Mach 1.1 (1,350 km/h; 837 mph) and Mach 3 (3,700 km/h; 2,300 mph) Mach 1.3 (1,590 km/h; 990 mph). CambridgeBayWeather (talk) 01:27, 23 June 2013 (UTC)

What are you talking about? The Phantom is not even capable of Mach 3 -- its limiting Mach number is "only" 2.4! 24.23.196.85 (talk) 00:31, 24 June 2013 (UTC)

Typo. It was supposed to be 1.3. I've corrected it. CambridgeBayWeather (talk) 00:58, 24 June 2013 (UTC)

This comes out to about 829 to 874 KEAS, which is pretty impressive! The Phantom must have been one tough bird in the structural sense! 24.23.196.85 (talk) 01:32, 24 June 2013 (UTC)

Sorry if I wasn't clear; I wasn't talking about terrain avoidance but factors such as atmospheric drag, air compression and so on. For instance, could you fly a fighter at treetop height at supersonic speeds without the airplane destroying the ground below or the air compression/friction tearing the jet apart. And what happens when you fly a fighter at maximum speed at low altitude? What are the air compression and friction forces involved? Longraptor (talk) 07:58, 27 June 2013 (UTC)

Chance of pregnancy per year vs age of parous and nulliparous premenopausal women

Where can I find a table giving the chance of pregnancy per year vs. age for parous and nulliparous, sexually active, premenopausal women? The tables at Contraception#Methods and Comparison of birth control methods#Comparison table give an 85% "failure rate" for the "No birth control" method, which I assume is an average across all women of child bearing age. I would like to be able to look up the comparable value for, for example, 50 year old, premenopausal, nulliparous, sexually active women. -- 179.202.36.245 (talk) 21:19, 22 June 2013 (UTC)

perhaps a graph like this would be helpful: http://www.babycenter.com/0_chart-the-effect-of-age-on-fertility_6155.bc --Digrpat (talk) 22:03, 22 June 2013 (UTC)

Thanks. I'd like to see how the right side of the graph would change if restricted to premenopausal women. (Separating parous & nulliparous would also be interesting, but not as important.) Your example gives me some better terms to search on, and I'll add a note if I find anything better. -- 179.202.51.55 (talk) 23:02, 22 June 2013 (UTC)

... and all I seem to find is that chart or something similar in a lot of places. It is attributed to "Management of the Infertile Woman by Helen A. Carcio and The Fertility Sourcebook by M. Sara Rosenthal" and the two data points on the right of the graph give a 5% likelihood of pregnancy over the course of one year for 45-49 year olds and 0% (presumably +/ 0.5%) for 50+. It would be interesting to learn the number of older participants in the study. -- 179.202.253.161 (talk) 20:54, 24 June 2013 (UTC)

June 23

Are there any human societies that...

Do we know of any human society with a significant number of people (> 100) that:

1. cannot control fire?
2. does not have a language that can express a nearly-infinite number of ideas?
3. cannot make stone or metal tools?
4. doesn't understand that sex causes impregnation?
5. does not have a religion or know about other religions (so atheists in a modern state don't count)?

I suspect the answer to all of these is "no", but I'd be very interested in reading about any counterexamples. --50.125.29.131 (talk) 02:35, 23 June 2013 (UTC)

Define religion? As for your other questions, there is evidence from Lake Mungo that Australian Aboriginals, the people separated from the rest of the human race for longest, used fire and stone tools when they arrived in Australia at least 40,000 years ago. Given that the rest of the human race interacted with each other after that, there's not much doubt that everyone else had those skills. (That excludes many modern western humans who wouldn't know how to manage a fire or make a decent stone axe even if their life depended on it.) As for language and sex, I'll leave that to others. HiLo48 (talk) 02:54, 23 June 2013 (UTC)

To borrow the basic premise of James Burke's Connections series', the average human as recently as a couple of centuries ago knew everything they needed to know in order to survive. Everyone was a generalist. Thanks to the industrial age and the technology explosion, now everyone's a specialist, some to the point that they couldn't pour water out of a boot even with the instructions written on the heel. But as you suggest, all 5 of the OP's questions were addressed many thousands of years ago. ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:02, 23 June 2013 (UTC)

Language and sex are instincts, things written into our genetic code. I'm not so much speaking about specific languages and sex acts (say, "English" or "69"ing which are cultural and must be learned/taught). But this is birds and bees stuff. Birds always speak bird language to each other, and animals naturally know how and why to mate. It's part of being an animal.

On a somewhat related topic, I did read a book that said there are some societies that haven't figured out that a child has only one biological father. They believe that if a female's womb is fertilized by a number of men, the child will take on the characteristics of all the "fathers". For this reason, they believe it is advantageous for a woman to mate with a number of desirable men, so that the child will inherit all their best qualities. It also helps strengthen the group's social bonds because all the "fathers" feel a responsibility to protect the child and assist in its upbringing.--Jerk of Thrones (talk) 05:04, 23 June 2013 (UTC)

Cats (and apparently a small number of humans) sort of work that way. "Triplets" can have three fathers, but each kitten, of course, only one. InedibleHulk (talk) 13:30, 23 June 2013 (UTC)

The exact mechanism of human reproduction, as with other technological discoveries, is only fairly recently known, and more primitive peoples may not have heard about it. But the association between sex and reproduction has been known for countless thousands of years. The mechanism was thought to be the man planting a seed in the woman, like in a flowerpot, hence the terms "sperm" and "semen", both of which mean "seed". ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:09, 23 June 2013 (UTC)

Most societies have a hard time controlling fire, even if they know how to use it to their advantage. See List of California wildfires or, more generally, List of fires. InedibleHulk (talk) 13:22, 23 June 2013 (UTC)

Our article states that there is no evidence that the Sentinelese use fire. However, most details about these people are pretty uncertain. 129.234.53.163 (talk) 19:43, 23 June 2013 (UTC)

Currently, I don't know, but I vaguely remember that isolated pockets of aborigines in Tasmania had lost the ability to /make/ fire and didn't use fish traps when first contacted and then wiped out by the enlightened Europeans. Things haven't much progressed over there. Greglocock (talk) 00:38, 24 June 2013 (UTC)

With the exception of groups of deaf people who were not exposed to sign language until late in life, every human society has language. It would seem that all humans have ancestors who made fire, though I suppose there may be a few small "uncontacted tribes" who have lost the art. There are, or were until recently, societies without stone or metal tools (nothing more complex than a broken rock for temporary use like a chimp might use; in Hadza country there is no archeological evidence that there ever was a stone-tool technology), but AFAIK they've all had wood or bone tools that served the same function, so that's more a detail of material than of tool technology. There are traditional societies that essentially don't know or care much about religion, and many have no belief in an afterlife or maybe even in gods, but all seem to have some belief in unseen (supernatural) forces, so that's a question of how you define "religion". (An anthropologist would define religion as belief in the supernatural rather than specifically in God.) I don't know about sex. I've certainly read claims that some peoples did not (and maybe still do not?) understand the link between sex and procreation, but as with any claim for a negative, that would be difficult to demonstrate. I'd be interested in anyone who can elaborate on that. The results might not be what we'd expect: Medieval Europeans didn't understand how malaria was transmitted, for example (thus mal aria "bad air"), while some stone-age societies understand it to the point that they use the same word for malaria and mosquito. — kwami (talk) 01:20, 24 June 2013 (UTC)

• cannot control fire?

No, although this was alleged of the Tierra del Fuegans.

• does not have a language that can express a nearly-infinite number of ideas?

Unequivocally, no.

• cannot make stone or metal tools?

Unequivocally no, for stone; many for casting metal before Columbus or other modern contact. (Seee chalcolithic and iron age.

• doesn't understand that sex causes impregnation?

doubtful, but the question is too complex to address in less than a book.

One interesting fact is that the bow and arrow are known indigenously on every continent and subcontinent, including New Guinea, but excepting Australia, where the boomerang, unknown elsewhere, was used.

μηδείς (talk) 02:40, 24 June 2013 (UTC)

Not every society had shaped stone tools like fluted arrowheads that would be visible in the archeological record, though everyone in history has probably banged something with a rock. I'm not sure that's what anon. meant by stone tools, however. — kwami (talk) 06:03, 24 June 2013 (UTC)

Yes, but there is a huge conceptual difference between using a tool and making a tool. For example, there are species of birds that will drop a rock or use one as a hammer against a snail in order to break the shell. Those birds are using a tool - but they aren't making one. Chimpanzees have been observed stripping leaves from twigs in order to use them to poke into termite mounds...that is making a tool (albeit a very simple one). Even more, I doubt that a significant proportion of the members of our modern society have ever made a stone or metal tool. But even that isn't the question - the issue is whether they could do so if they needed to - not whether they actually do that. Technically, these people don't even have to know how to do it - within the scope of the question, it's enough to ask whether they could hypothetically figure it out. It's plausible to imagine a small village in the USA of 100 perfectly knowledgeable, well-educated people, none of whom has ever made a stone or metal tool in their entire lives. However, if they had to make a simple stone or metal tool - I'm pretty sure they could figure it out. It's really hard to imagine a society that couldn't do it if it had to. So I'd give this one a definitive "No!". SteveBaker (talk) 18:40, 24 June 2013 (UTC)

Boomerangs unknown outside Australia, Medeis? Not according to boomerang: places like Egypt, California, Arizona, India and Poland are mentioned. -- Jack of Oz ^[Talk] 06:19, 24 June 2013 (UTC)

Didn't suspect that. μηδείς (talk) 16:55, 24 June 2013 (UTC)

Regarding question #4 - The general conceit that a society doesn't "understand" the role of sex leading to babies is one with a long history in anthropology. For example, Bronisław Malinowski claimed in The Sexual Life of Savages in North-Western Melanesia that the people of the Trobriands did not believe or understand that babies were the result of sex. The problem is, outsiders often run into a problem of misunderstanding the difference between what is known and what the official story is; a bit like claiming Catholics truly think they drink blood and eat human flesh at church. That's... kind of the story, but only in a facile sense. Later researchers did not come to the same conclusion as Malinowski; they knew very well where babies came from, but the official story was that they were created by spirits of some kind (I'm a little rusty here). Anthropology is or was rife with something called bongo-bongo-ism, which was a belief that the people a researcher was studying were always "the most isolated" or "the most primitive" and thus had the weirdest or most exotic ideas and lack of knowledge of procreation was a gem. So, it's also possible that Malinowski was on some level aware that what he was writing was wrong, but kept it in anyway because it was a juicy bit. It did not, of course, hurt that he was writing about "dark-skinned savages" who of course might believe anything. On such clear consciences was the foundation of anthropology built. :) Matt Deres (talk) 01:17, 25 June 2013 (UTC)

When small children have not had "The Facts of Life" talk (even in my generation where there was no sex on TV or in movies that kids might see) - they often make guesses about this. They can tell, just from observing the world around them - that most children have (or had) both a mommy and a daddy. So while they can't know about the details of the sex act - they tend to guess that "getting married" or "lots of hugging and kissing" or "living in the same house" or "falling in love" is what spurs women to get pregnant. This is certainly an inaccurate view of things - but it's not SO inaccurate that it doesn't have some predictive value.

Even in spectacularly primitive societies, you'd expect adults to be able to deduce this fact at least as well as small children do in our society. That's especially true in societies with formulaic rules about when intercourse is allowed. Let's face it, some societies rigidly disallow sex before marriage and insist that a marriage is consummated before it becomes legal and final...in those societies, it would be almost impossible to distinguish whether getting married or having intercourse is the cause of pregnancy.

But pretty soon, people would start to notice things like if the man becomes impotent then no babies appear after that. It's really hard to imagine a society in which the true cause of pregnancy isn't obvious after just a couple of generations of observation and shared knowledge.

SteveBaker (talk) 16:39, 25 June 2013 (UTC)

But aren't you assuming that every society has such a thing as a "father" and "mother", who live together with their children in a segregated house? If everyone is having sex all the time (as implied by Sex at Dawn), with no concept of marriage, how will anyone associate sex with children? Not every society is monogamous. In fact, I think most are not. --50.47.81.232 (talk) 05:47, 26 June 2013 (UTC)

I think that in those kinds of more open society, it would be even easier to deduce that no girls ever get pregnant until they first have sex. When everyone knows who does what and to whom - this kind of thing would be even clearer. SteveBaker (talk) 19:31, 26 June 2013 (UTC)

Well, I don't think it's necessarily an obvious thing. For example, absent repression from adults, pre-adolescents engage in various forms of sex and sex play without conceiving a child. Married couples may have sex dozens of times without conceiving (or alternately have sex once and conceive triplets), and of course some people simply cannot conceive at all. This is all complicated by humans' concealed ovulation. The thing is, sex is not the kind of thing a society can possibly do without, unlike wheels, paper, plows, etc that might also seem equally obvious. Eventually, the penny will drop. Matt Deres (talk) 02:16, 27 June 2013 (UTC)

There's a bit of an overview here. Based on my readings and understanding, humans are generally monogamous in principle. Places where you find polygamy or polyamory are nearly always under special circumstances due to environmental or financial pressure, or involve only a select few members of the population (cv. the imperial incest of Ptolemaic Egypt. Here again, anthropology sometimes provides a skewed view; if 99.9% of a population makes do with a normal old spousal arrangement and a select few engage in sibling incest or brotherly co-husbands or some other juicy topic, do you think the 99.9% will be the part that gets written about? Not a bit of it! It's like studying pair bonding by reading Hollywood tabloids; the neat stuff gets publicized and the boring stuff is relegated to an appendix somewhere. Matt Deres (talk) 02:34, 27 June 2013 (UTC)

Why can we only eat living things (or things that use to be alive)?

How come the only edible things are plants and animals? I mean to a certain extent you can eat minerals like salt, but only in tiny amounts. Like I could eat a pound of steak or a pound of bananas but not a pound of salt. Plus I don't think salt has any calories.

But wouldn't something flammable like gasoline have calories? Yet I'm sure gasoline is poisonous and not very nutritious.

Please explain.--Jerk of Thrones (talk) 04:49, 23 June 2013 (UTC)

Oh, I guess gasoline is also made up of things that use to be alive. When I was in school, they told us oil was made out of dead dinosaurs. In fact, Sinclair_Oil_Corporation's logo is a dinosaur. So maybe that wasn't the best example of possible caloric foods that aren't made up of plants and animals. Still, I would like an answer to my question.--Jerk of Thrones (talk) 04:54, 23 June 2013 (UTC)

Petroleum could theoretically be dinosaurs, but more likely large animals like that were eaten or decomposed before they had a chance to be buried in sediment. Mainly made of the little corpses which floated to the sea floors unnoticed, like zooplankton, algae and tiny fish. I don't think there's any way to tell what a given sample is made of, though, this far along. InedibleHulk (talk) 13:03, 23 June 2013 (UTC)

The Nutrition article might be a good start. ←Baseball Bugs ^{What's up, Doc?} carrots→ 04:57, 23 June 2013 (UTC)

(edit conflict) Your body is not able to digest and extract energy and building materials out of anything. Inside your body are substances (mostly enzymes) and processes (things like the Kreb's cycle, which are carefully tailored towards utilizing certain substances, either for their ability to provide energy, or for their ability to provide material your body can use to build itself up. Macronutrients is the term for these substances, which make up the bulk of what you eat (micronutrients include things you need, but only in trace amounts; basically vitamins and minerals). There really are only three classes of macronutrients: carbohydrates, which are your primary dietary source of energy, though your body gets energy from other macronutrients, what it doesn't get from carbohydrates is anything except energy. There are lipids, which also provide energy (at a much higher energy density, but lower absorbtion rate, that carbohydrates), though many lipids also provide building blocks (cholesterol, for example, is present in cell walls and is used by the body as a source of the basic steroid structure vital to many hormones and other compounds in your body). Proteins also provide energy, at roughly the same density as carbohydrates, but proteins are also very important as a source of amino acids which your body uses to build other proteins, which are much of the primary structural and functional components in your body. While you can make some amino acids from scratch, there's a bunch of essential amino acids you must consume, since your body cannot make them. The thing is, this is essentially all your body can metabolize for energy and building material. You can't just eat any substance that burns, your body has no way of dealing with it, because you lack the compounds and processes to effectively use it. You've got those three, and that's about it. And those things are only made by other living things (technically, any of them can be created in a "man-made" way from first principles without starting with living material, but the process is so inefficient and expensive, there's really no point). You can't get protein from a rock. --Jayron32 05:02, 23 June 2013 (UTC)

Well, you're made up of carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus. You drink water freely, you breathe oxygen, and N, S, P are normally thought of as mineral supplements more than food. That leaves carbon. There is a close relationship between organic compounds as carbon-containing and life-derived, because by and large living things get their paws on every bit of carbon in the cycle, so there's nowhere much else to take it from. Even the CO2 in the air comes from formerly organic sources, and you'd have to be photosynthetic to 'eat' it. Wnt (talk) 06:25, 23 June 2013 (UTC)

Just a point of order: You get sulfur, nitrogen, and phosphorus from living sources: sulfur and nitrogen you get from proteins; I'm pretty sure you get all of the nitrogen you need from proteins, and probably also sulfur. You get phosphorus from stuff like nucleic acids. Most dietary minerals can be gotten from living sources as well (iron is plentiful in food with blood, like black sausage, as well as many vegetables like broccoli, iodine from seafood, etc. The only stuff you need to get from outside of your food (that is, consuming the bits of other recently living beings) is oxygen. --Jayron32 12:44, 23 June 2013 (UTC)

Oh, certainly; I didn't mean to suggest that you couldn't or didn't get them from living sources, only that with some gaming of the rules I could probably think of some contrived artificial diet which provides them separately in a form that can be incorporated (though due to essential amino acids not all of them). For phosphorus and sulfate that is easy - for nitrogen (other than nitrate), much more tricky - maybe you could connive to reverse the glycine cleavage system? But in any case we think of nitrogen as a waste product from all the things people have to eat, rather than as a needed foodstuff in itself. Wnt (talk) 18:02, 23 June 2013 (UTC)

Also the fruits and vegetables themselves like the aforementioned bananas are not living organisms, so you eat non-living stuff as well. Brandmeister^talk 10:31, 23 June 2013 (UTC)

Well, it's part of a living organism. That you don't eat every organism whole doesn't seem to be the trouble the OP is having; he seems to be having trouble understanding why food has to come from other living organisms (including parts we slice off of them) as opposed to substances which are either non-living, or so far removed from living as to contain no recognizable nutrients, like petrochemicals. --Jayron32 12:33, 23 June 2013 (UTC)

The lack of digestibility of petroleum products and coal, like the indigestibility of cellulose, seems like an evolutionary metabolic accident with some degree of chemical basis - in the case of fossil fuels, it is just harder to work with carbon compounds before some oxygens or nitrogens are brought in to activate them. Wnt (talk) 12:51, 23 June 2013 (UTC)

It's because we're at the top of the Food chain. There are plenty of organisms (plants, some bacteria, etc) that only consume the raw materials: Oxygen and CO2 from the air, water, nitrogen compounds from the soil, etc. However, we've evolved to let those other living things do all the work of turning those very basic materials into things like sugars and proteins - so we don't have to. If you think about it - it's much more efficient for us to eat an apple than it is to get those same nutrients by making them from scratch like the apple tree had to. We don't need that vast area of chlorophyll-filled leaves to gather sunlight to make sugars from CO2 in the air and water in the soil. Instead, we let the tree do all of that work - and just steal it's offspring at the end. Since other living things need all the same chemicals that we do, taking the life of a predator (even if only predating on plants) means that we get pretty much everything we need to survive from the things we prey upon. SteveBaker (talk) 13:24, 23 June 2013 (UTC)

• It might be useful to mention alcohol here -- ethanol, specifically. We don't usually think of it as a food, but it's actually a very strong source of calories. (By weight, it's nearly as calorie-dense as fat.) The ethanol that we consume if a byproduct of life, but not really part of a living thing. Looie496 (talk) 20:19, 23 June 2013 (UTC)

This source may suggest that some microbes "eat" something similar to "rocket fuel". I also find something that may be similar at Microbial corrosion. Bus stop (talk) 18:34, 23 June 2013 (UTC)

Microbes eat lots of odd things. In contrast, humans cannot digest cellulose - nor, apparently, can termites; except they have microbes in their innards which do the job for them. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:03, 24 June 2013 (UTC)

Well, plants eat CO2 from the air, if we're going outside the animal kingdom. Looie496 (talk) 01:28, 24 June 2013 (UTC)

• This has been answered clearly above. Basic life depends on the utilization of carbon and nitro-carbon compounds. Humans are top-scale apex predators that get the sugars, proteins, and lipids they need from basically every lower rung on the food-chain. That is what intelligence is for, selecting and taking advantage of the richest food sources. If the OP is unclear he should ask more specific questions. μηδείς (talk) 02:32, 24 June 2013 (UTC)

Sex ratios

I have learned that beach nourishment can cause the temperature of the beach sand to change,distorting the sex ratio of sea turtle populations (e.g cooler sand causes more embryonic sea turtles to become male). If you have an unbalanced ratio of females to males, would this cause the population of sea turtles in an area to decline?99.146.124.35 (talk) 17:17, 24 June 2013 (UTC)

Temporarily, but the few turtles who can still have male offspring in hot sand will have more grand-children than those that can only have female offspring, and therefore, over several generations, the genes that allow "making male in hot beaches" will become more common and the population can re-stabilise. Of course if the temperature variation is so wide that it prevents all males to be born, and it lasts for a long time, then this can cause an extinction. --Lgriot (talk) 08:37, 25 June 2013 (UTC)

Doubtful, Lgriot. Temperature-dependent sex determination is evolutionarily robust - the temperature ranges within which different genders arise may shift, but the system itself will most likely remain. To the actual question, it's possible that the shifting ratio of genders is actually of benefit to the turtles, and cancels out some harm caused by the non-optimal temperature. You may wish to read the article I have linked to. The actual purpose of temperature-dependent sex determination is only poorly understood, but it seems to have withstood the test of time, so it is probably good for something. Someguy1221 (talk) 08:44, 25 June 2013 (UTC)

(This question has just been re-asked...below...) SteveBaker (talk) 16:26, 25 June 2013 (UTC)

I have not said that the system would NOT remain, what makes you think that, Someguy? I do think however that the temperature range that a species can handle could shit up or down, due to obvious selection pressures, if the temperature change remains for many generations. And what I said about axtinction is for very wide variations (somethign crazy, like 25 deg celcius), minor variations (5 degrees or less) could simply lead to an adaptation. --Lgriot (talk) 09:08, 26 June 2013 (UTC)

Trees in the Piazza della Scala

Trees in the Piazza.

What trees surround the statute in the Piazza della Scala in Milan? It looks like linden trees, but I'm curious as to which species. Gabbe (talk) 09:08, 23 June 2013 (UTC)

Hard to be sure from the photo, but they look like Tilia cordata to me. Deor (talk) 12:09, 23 June 2013 (UTC)

Agreed. Alansplodge (talk) 14:12, 23 June 2013 (UTC)

Yup, as far as I know, that bracht bract is a distinguishing characteristic, and is clearly visible in the photo. In the US, we call these trees "little leaf linden." SemanticMantis (talk) 19:32, 23 June 2013 (UTC)

Would that be bract? Richard Avery (talk) 07:14, 24 June 2013 (UTC)

Yes, "linden" is probably the more sensible name, but a bit too Germanic for us Britons. Apparently, "lime" comes from the Middle English "lynde" which is not too far away.[2] As a small child, I was always hoping to find a lime on a lime tree - one of life's little disappointments. Alansplodge (talk) 13:00, 24 June 2013 (UTC)

Seed preservation mechanism

What is the mechanism that keeps a seed 'alive' for many years before it germinates? Is there any cell activity during that time? Is there any 'life' in the seed? Gil_mo (talk) 12:15, 23 June 2013 (UTC)

Have you read our article "Seed dormancy"? It seems to cover this in great detail. Evidently there isn't a single answer because different seeds handle this differently.

As a general observation, we humans tend to greatly over-estimate the amount of resources that plants and animals require to survive. That's because we're warm-blooded and our bodies consume large amounts of energy even if we're doing absolutely nothing - our brains alone consume massive amounts of oxygen and nutrients even when we're asleep - in order to get oxygen to power those heat generators and that big brain, we have to actively breathe - so our chest muscles are working all the time providing air flow and the heart has to beat at a reasonable rate to keep the oxygen flowing to where it's needed. We simply can't just shut down and do nothing.

This leads us to be amazed that cold-blooded animals, plants and many other living things can survive on incredibly small amounts of food and water because their bodies can more or less completely shut down. For example, a crocodile can live for an entire year without food...but we're in trouble after just a few days and probably dead within a month. Seeds are not doing any work - they aren't growing, moving, thinking, generating heat - nothing! So they use more or less zero energy and there are documented cases of seeds germinating after being stored in stone jars for 2000 years - using just the food and moisture stored inside the original seed when the parent plant dropped it.

SteveBaker (talk) 13:17, 23 June 2013 (UTC)

As David Attenborough once said (I think) "Ain't nature wonderful". Richard Avery (talk) 14:52, 23 June 2013 (UTC)

Thanks SteveBaker. Gil_mo (talk) 21:39, 23 June 2013 (UTC)

June 24

Africa, Australia, South America, versus Eurasia and North America

The continents of Africa, Australia, and South America are fairly convex in shape with little in the way of inland seas, peninsulas, and islands compared to North America and Eurasia (or Antarctica below the ice). Is there any geophysical causal explanation for this, or, at least, any geophysical terms for it outside of chance? Thanks. μηδείς (talk) 02:26, 24 June 2013 (UTC)

If you mean convex in the sense of polygon or a convex hull (or any of the related mathematical definitions of "convex"), then every continent is non-convex. For one counter-example, the whole of West Africa juts westward, forming the Gulf of Guinea; Africa is non-convex (a straight line - or a geodesic great circle path - from Accra to Luanda crosses water). There are thousands of other easy examples of the non-convexity of these continents. So, it seems you're using the phrase "convex" more loosely and subjectively, and therefore there probably isn't a geological reason why you perceive the shapes as you do. Some other factors contributing to your perception might include the map projections that heavily distort geographic scale. If you're interested in scale-length conundrums - in other words, how large or small a coastal feature needs to be before it is "negligible," you might read coastline paradox to see some approaches that geographers use to deal with the fractal-like nature of geographic shapes. Nimur (talk) 06:15, 24 June 2013 (UTC)

I strongly suspect that glacial activity is largely to blame for the intricate shape of the shorelines of Northern Eurasia, Nunavut, and Antarctica. --Dr Dima (talk) 06:33, 24 June 2013 (UTC)

We have a nice little animation showing how the continents have evolved since Pangea. The good fit between South America and Africa was part of the genesis of the Pangea theory. SemanticMantis (talk) 19:38, 24 June 2013 (UTC)

Non-convexity of Africa, due to Brazil

There is such a thing as convexity, and perhaps it can be measured [3] (though I didn't read that last source, and my prejudice is that moving-windows are indicative of a less than theoretical approach) Yet ... I would expect the net convexity of a continent to be, well, 360 degrees, no more, no less, right? (if that's how you even measure it) My feeling is there is a valid question here, if but we could grasp it. Wnt (talk) 21:59, 24 June 2013 (UTC)

Obviously I am using the term convexity relatively. (To point out that Africa has an armpit where Brazil used to be, and so is not a perfect circle, strikes me as laughably pedantic.) Australia, South America, and Africa are obviously not round, but they also obviously have coasts with a lower fractal dimension than do North America and Eurasia. Dr. Dima seems to be on to something with glaciation at least being relevant in the case of the Canadian north coast--although I don't understand the mechanism of those islands' creation. μηδείς (talk) 22:18, 24 June 2013 (UTC)

Wnt, convexity is a property of a set or a function; convexity is not a scalar quantity; convexity is not measured in degrees. One boundary-curve is not more or less convex than another. Evidently, the OP is attempting to describe some subjective or heuristic property of these shapes, but is not using the correct terminology.

For example, we could say that fjords have more structure than bights at short length-scale. This has nothing to do with whether either coastal feature is convex. I would also avoid guessing which coastline or continent obviously has lower fractal dimension, because that is not a parameter that is easy to estimate by visual inspection. Nimur (talk) 22:37, 24 June 2013 (UTC)

I'm sorry if my answer struck you as "laughably pedantic", but I have no way of knowing what you, or any other posters or readers, may know. You were indeed using "convex" in a way that is unfamiliar to me, and in contrast with the definitinos that I do know. I also agree with Nimur's objection above, there is nothing obvious about the claim that Africa's coastline has lower fractal dimension than NA. I also agree with Wnt that there might be an interesting question here, but it will be very challenging to specify exactly what geometric or topographic feature you want to get at. SemanticMantis (talk) 00:40, 25 June 2013 (UTC)

Probably there are as many answers to the question as there are ways that the features in question are formed. In terms of peninsulas, the Delmarva Peninsula was formed from deposits from the flooding of the Susquehanna River at the end of the last ice age (not likely to happen with the Congo River, but the Amazon?), Florida began as a piece of Africa that went with North America when the two continents separated (maybe just chance that a piece of NA didn't split off and go with Africa?), and Kamchatka appears to have been formed by volcanism. I believe the west coast and southern tip of South America have quite a few islands (and fjords), and glaciation works as an explanation there as well. Apparently there was an inland sea formed by the Amazon about 15 million years ago. I'm not sure of the exact definition of an inland sea, but Lake Makgadikgadi (now the Okavango basin) might count and I expect the Great Rift Valley will be one in the future.--Wikimedes (talk) 02:44, 25 June 2013 (UTC)

I am really interested in features at a larger scale than river deltas--but your points are take. μηδείς (talk) 03:25, 25 June 2013 (UTC)

Thinking about this a little further, it does seem relevant that Africa was at the center of Pangaea, and hence its relatively smooth coastlines were formed by rifting that proceeds along the relatively straight mid-ocean ridges, the same applying for the opposing coasts of the continents that moved away from Africa. The relatively smooth west coast of South America seems to be the converse, a long line of subduction in which any detail has basically disappeared under the Andes. And Australia is actually the exception that proves the rule, since New Guinea is actually integral to it, and the very complex geography to its north is due to mountain folding and volcanism, which doesn't currently exist on, say, the east coast of South America. Pangaea seems to be trhe relevant factor. μηδείς (talk) 03:26, 25 June 2013 (UTC)

Coast is indeed turning out to be an interesting article. μηδείς (talk) 04:33, 25 June 2013 (UTC)

This is an interesting question. For Africa I wonder if it is in part due to the continent being largely a plateau (or a series of plateaus) without a lot of low lying coastal plains. [4], Africa as a whole is a vast plateau of ancient rocks. Also our article Geography of Africa (I note the map shown under Geography of Africa#Plateau region is strange as it shows higher elevations as green and lower as brown—opposite from the way elevation maps are normally done). I also wonder how plate tectonics relates. Plate boundaries are involved with things like the Gulf of California, the Caribbean Sea, as well as a lot of the complexities along the eastern edge of Asia—and of course the Mediterranean Sea the Red Sea, both of which involve Africa. But I am just speculating. Pfly (talk) 07:09, 25 June 2013 (UTC)

(ec)Emergent coastlines tend to be smoother than submergent coastlines. On a submergent coastline hills and valleys formed above sea-level become drowned and thus the coastline becomes more convoluted. On an emergent coastline the beach used to be below seal-level where there is no riverine erosion to form complex hill and valley topography. Roger (Dodger67) (talk) 07:23, 25 June 2013 (UTC)

What is this

I took this on a trip a few days ago, and don't know what it's called. If anyone can identify it from the picture and rename the file, that would be great. →Σσς. (Sigma) 07:33, 24 June 2013 (UTC)

It's a male Widow Skimmer, Libellula luctuosa. A male dragonfly, not a male widow skimmer :) --Dr Dima (talk) 07:56, 24 June 2013 (UTC)

Tetracoordinate B³⁺

This book (while stating that B³⁺ isn't known) gives an estimated value for the ionic radius of the 4-coordinate B³⁺ ion. It gives a negative value(?!) What is that supposed to mean? Double sharp (talk) 13:22, 24 June 2013 (UTC)

There is no such thing as a generic tetracoordinate B³⁺. Not as in it hasn't been detected yet, but it doesn't make sense to refer to one. 'Tetracoordinate' means that three ligands are bonded to the boron centre, and changing the ligand will change the hypothetical radius of the ligated ion. Plasmic Physics (talk) 13:49, 24 June 2013 (UTC)

Lucky I didn't take and use their ionic radius info, then... Double sharp (talk) 14:33, 24 June 2013 (UTC)

Based on the pattern, maybe the negative-sign is a typo (should be 25 not –25)? But we can't speculate like that, especially since the value itself is said to be estimated without further reference. As Plasmic Physics notes, Ionic radius does vary a bit; but not that much...there is still a periodic trend and standardly used values. Our article even has two cited values for B³⁺, one of which is 27 (consistent with the "negative-sign is a typo" in the source that Double sharp is seeing). I don't have access to that full article though, so I can't tell the coordination or experimental basis for the values. Tetracoordinate would be four ligands not three. DMacks (talk) 16:55, 24 June 2013 (UTC)

Sorry about that, I crossed my thoughts. I meant four, not three. Plasmic Physics (talk) 23:32, 24 June 2013 (UTC)

(ec) I'm not sure why the website the OP references says the B³⁺ is unknown, as this is not the case. I expect that the negative sign somehow migrated from the row below, but however it got there, -25pm is a typo and not some new type of matter or a mathematical formalism carried too far. Inorganic Chemistry by Shriver an Atkins (p.25) gives 12pm (actually 0.12A) as the ionic radius for 4-coordinate B³⁺, citing Shannon, Acta Crystallogr. A32, 751 (1976). Advanced Inorganic Chemistry by Cotton and Wilkinson (p.45) gives 20pm as the radius estimated by both Goldschmidt and Pauling (no reference given), but this is for 6-coordinate B³⁺, which seems unrealistic (having said that, I'm sure someone will come up with an example of a 6-coordinate boron ion). 20pm is also given in the General Chemistry textbooks by Pauling (p.175, again mentioning the 6-coordinate rocksalt structure) and McQuarrie and Rock (p.253). I'm a solid state chemist by education, and would go with the Shannon radius unless I knew that the boron ion in question was a strange 6-coordinate species. Defending my choice on a Wikipedia article talk page against someone who supported 20pm with the other 3 sources might take some work however (including checking to make sure that 12pm wasn't a typo in Shriver-Atkins or the original Shannon paper).--Wikimedes (talk) 23:45, 24 June 2013 (UTC)

Echinocactus grusonii frost tolerance

Can Echinocactus grusonii survive winter outdoors in the Mediterranean climate? How well does it tolerate the combination of low temperature and possibly moist substrate? I've been Googling for days but for some reason I haven't been able to find the answer. Surtsicna (talk) 14:04, 24 June 2013 (UTC)

Well, our article says "excess water in cool conditions may lead to rot". The average minimum cold-season temperature requirement (12C according to our article) might also be a problem in some Mediterranean climate zones. Where are you exactly? Looie496 (talk) 15:14, 24 June 2013 (UTC)

I am arguing over this with a friend who claims that the species can survive a winter in Dalmatia, Herzegovina and Montenegro, which I doubt. I too looked at our article first, but it's hardly helpful; there are very few cacti (and indeed very few plants in general) that would not have a rot problem due to "excess water in cool conditions". If the cactus cannot stand a temperature approaching 0 C (no matter how briefly), then it surely cannot survive in the said regions. Surtsicna (talk) 15:44, 24 June 2013 (UTC)

Having lived in Tucson, I can tell you that these cacti can definitely stand brief exposure to 0 C, or even significantly below that. There is no type of barrel cactus that can survive a long-lasting hard freeze, though. It seems very dubious that they could survive in the harsh mountainous conditions of the areas you mention. Looie496 (talk) 17:19, 24 June 2013 (UTC)

Those aren't entirely harsh mountainous areas. There's the Neretva valley, the seaside, and the urban areas in general. Frost is very rare there, but does happen sometimes. It even snows once in a few years. If the plant could survive brief frost combined with heavy rainfall or a few snowflakes (as opuntias and rebutias do), he might be right. Surtsicna (talk) 22:08, 24 June 2013 (UTC)

I am unfamiliar with Dalmatian and Montenegran geography and climate, however, I'm fairly confident that this cactus will grow in some places that have the mediterranean climate type. This page [5] says it is "hardy, to 10 F, at least." Also, usually managed gardens are a little warmer and more protected than the surrounding countryside (e.g. urban heat island, garden wall, etc). So often, plants can survive in gardens, even in locales where they might die in the wild. I've seen these growing all over California, including in the mediterranean zone. All the other sources I see indicate hardiness well below 0 C, and seem to agree that 10-20 F is fine [6], [7]. Also I believe larger, mature plants will be hardier. By the way, the key term that got me these results was "hardiness." SemanticMantis (talk) 16:21, 24 June 2013 (UTC)

Bear in mind that an "average minimum cold-season temperature" will refer to an average of both day and night temperatures over the season in question. Being mostly (here I generalise somewhat) "hot" desert plants, many (gen.) cacti can stand "brief" (i.e. night-time) temperatures of zero or below because many (gen.) "hot" deserts, being cloudless, sometimes-to-often experience such night-time temperatures. {The poster previously known as 87.81.230.195} 212.95.237.92 (talk) 17:08, 24 June 2013 (UTC)

Thanks! English is not my first language, so I found the term hardiness a bit misleading when I first encountered it. You both seem to agree with my friend, then? Surtsicna (talk) 22:21, 24 June 2013 (UTC)

Yes, I think your friend was right, that this plant could be kept in a garden in e.g. Dalmatia, and successfully overwinter. I don't think doing so would always' succeed though! I'd be much more confident at lower elevations, in a city, with a garden wall. Remember, microclimate can be very important in these cases. I must admit I have not personally grown that cactus in that climate, but thanks for the interesting question! SemanticMantis (talk) 00:07, 25 June 2013 (UTC)

eggs

I have learned that beach nourishment can cause the temperature of the beach sand to change,distorting the sex ratio of sea turtle populations (e.g cooler sand causes more embryonic sea turtles to become male). If you have an unbalanced ratio of females to males, would this cause the population of sea turtles in an area to decline?99.146.124.35 (talk) 17:17, 24 June 2013 (UTC) — Preceding unsigned comment added by 99.146.124.35 (talk)

Yes, and it is actually occurring now with other species as well. Plasmic Physics (talk) 23:29, 24 June 2013 (UTC)

You may be right about either claim, but SemanticMantis (talk) 00:24, 25 June 2013 (UTC)

Unclear. I don't have time to dig into the academic literature, but searching google scholar for /sex ratio sea turtle/ would be informative, especially with the Latin name. In general the sex ratio is broadly compatible with the selective pressures that a given species experiences. Turtles have evolved to reproduce viable populations, in conditions with variable temperatures. So in a sense, they are very used to shifting sex ratios. Actually, the temperature-dependence of sex gives them some ability to control sex ratio by behavior, and that could potentially help them adapt to changing conditions. Still, sea turtles are broadly in decline and endangered, and what you suggest may be a factor. For more interesting results, you could try to add /climate change risk/ to the previous search. SemanticMantis (talk) 00:24, 25 June 2013 (UTC)

PMID 21246989 provides some relevant information. It states:

• Egg temperature affects sex ratio for a variety of sea turtle species, citing Standora 1985
• Relocating nests results in temperature-related shifts in sex ratio, citing Spotila 1987
• Quote: A one-half degree deviation from a 29.5°C pivotal incubation temperature can change the sex ratios of leatherback hatchlings to nearly 100% female (warmer temps) or male (cooler temps) (Binckley et al. 1998). citing Binckley 1998

Sorry I have not answered the second part (and really the heart) of your question, i.e. the impact of skewed sex ratio on population size. That seems like a very complex issue. -- Scray (talk) 03:46, 25 June 2013 (UTC)

I see that this question is basically a duplicate of "Sex ratios" above, where the discussion reflects some of the complexities I was considering. -- Scray (talk) 11:27, 25 June 2013 (UTC)

Since sea turtles do not appear to be monogamous - one male turtle could impregnate large numbers of females. So providing the sex shift is in favor of females, and providing it's not so extreme as to impact genetic diversity, there might not be a huge problem. However, if the shift is in favor of more males, then the direct reduction in the number of eggs laid would have a huge impact on the population. Sea turtles rely on vast number of hatchlings appearing at more or less the same time in order to overwhelm the local predators - when the numbers decline only slightly, the resulting population crash can be spectacular. Fortunately, global climate change is warming the beaches, resulting in more females. But there is a limit to that. When there are vastly fewer males, reduced genetic diversity and the inability of females to find a male partner will be a serious matter. Another saving factor is that turtles are long lived. They have a reproductive span of 50 or more years. Since the temperature of the beaches will occasionally be lower just because of natural variations in the local weather, there should continue to be years when substantial numbers of males are still produced.

However, this is a complex matter - and any disturbance to the ecology is to be feared because the consequences are hard to forsee.

SteveBaker (talk) 16:17, 25 June 2013 (UTC)

June 25

Health benefit of anthocyanin in Montmorency cherries?

I purchased a bottle of concentrated Montmorency cherries juice, produced by www.countryspoon.com, it states that there are more anthocyanin in these cherries than black raspberries. When checking at your site it shows choke berries and black raspberries as the highest, but sour cherries weren't even listed. What would be the value of this concentrate, was it over looked in your research or is it an advertising hype? Thank you so much for your time in reviewing this question!

Crazycookin — Preceding unsigned comment added by 99.162.85.189 (talk) 15:45, 25 June 2013 (UTC)

See Anthocyanin#Potential_food_value. There is little evidence that consuming anthocyanins will have any significant benefit to health. AndyTheGrump (talk)

Indeed, the evidence is that these chemicals don't even make it past your digestive system. Eat the cherries (and raspberries and choke-berries) if you enjoy them - otherwise, it's BS. SteveBaker (talk) 16:08, 25 June 2013 (UTC)

Agree. Always assume that any marketing claims about health effects of food are total BS, and you'll rarely be wrong. Draw your information solely from qualified conventional medical sources, and even then, shy away from anything that is preliminary in nature, rather than established practice. The polular press does a lousy job of reporting medicine and science, as do pop-lit books such as self-help books. Be very wary of words like "breakthrough", "latest research", "discovery", and especially anything like "ancient Chinese secret". Those are marketing terms. Claims that seem extraordinary almost certainly are. Health care attracts quacks like a light attracts moths. Be skeptical and build up your critical thinking skills. Dominus Vobisdu (talk) 16:26, 25 June 2013 (UTC)

What they said. Eat a balanced diet with a wide variety of protein and vegetable foods, avoid processed foods and favor whole foods (i.e. eat the stuff that comes right off of the tree or is a recognizable part of of a critter, avoid stuff that's in boxes or frozen in shapes that resemble nothing from nature, or have ingredient lists longer than about 3 items). Don't overindulge. Exercise often. That's about all the advice that medical science can reliably give you on how to maximize your health via your diet. Any claims that a specific compound, chemical, vitamin, etc. is all you need or a miracle ingredient, or whatever, are usually very specious. Eat these foods if they taste good, as part of an otherwise balanced diet, but don't focus on odd micronutrients with extravagant health claims. --Jayron32 20:24, 25 June 2013 (UTC)

There is research in this area: Pharmacokinetic study of the absorption and metabolism of Montmorency tart cherry anthocyanins in human subjects says they found unmodified anthocyanins in plasma. This seems to have some data on the level in cherries but comparing the level in two kinds of fruits when drinking a concentrate seems irrelevant. 75.41.109.190 (talk) 15:13, 26 June 2013 (UTC)

(My Unsupported Opinion) There was a huge amount of attention paid to antioxidant activity in the 1990s, continuing I think to some degree to this day. It always was ridiculous, even from the beginning - humans aren't test tubes, and aging isn't a chemical reaction - but a lot of people got a lot of grant money out of it. Wnt (talk) 18:40, 26 June 2013 (UTC)

June 26

Homemade explosives, part 2

I've recently been re-reading the third part of The Gulag Archipelago, and it brought up a technical question: In the part describing the uprising at the Kengir (Dzhezkazgan) hard-labor camp, one of the defense measures taken by the zeki (inmates) was to make homemade bombs from sulfur and calcium carbide, with which they reportedly later knocked out one of the tanks sent in to suppress the uprising. My question is, can such a device really knock out any tank, or specifically a T-34? Or was that an erroneous report on Solzhenitsyn's part (or maybe even a misreading on my part)? (Note: by "knocked out", I don't mean a complete K-kill, but an F-kill or M-kill, which would still put the tank out of combat.) 24.23.196.85 (talk) 01:02, 26 June 2013 (UTC)

It's hard to tell without more information, but at least in concept it is possible: calcium carbide, acidified, with sulfuric acid or the like, produces acetylene, which can be burned with oxygen to make a cutting torch that could be used to slice apart the tracks on the tank and, eventually, even to open up the armor! :) An explosion of acetylene and air could also, in theory, launch the tank so far and fast up in the air that it would kill everything inside. See also [8] Sulfur itself apparently reacts violently with carbides [9]. There may be important aspects of the chemistry I'm missing here. My bet, however, is that they "knocked out" the tank by welding something together or melting it apart in a far more localized way than a true high explosive would do. Wnt (talk) 06:28, 26 June 2013 (UTC)

I'm not an explosive expert but I would bet you could make a pretty good explosive out of calcium carbide, capable of disabling a tank. It might take one or two more common ingredients other then sulfur, maybe like sodium peroxide, but perhaps the author is just being cautious and responsible by not providing a ready recipe for a home made bomb. If a grease covered sock with some tnt can do it ;) Vespine (talk) 06:44, 26 June 2013 (UTC)

Actually, the "just use some TNT" bit omits the detail of a blasting cap - I think that usually, the hobbyist/terrorist/freedom fighter finds that the most fearsome part, since a primary explosive is designed to go off with little provocation. Then again, TNT explosives predating IMX-101 and the like were subject to the possibility of going off by bullet or in a fire - I don't know how likely it was though. Wnt (talk) 18:38, 26 June 2013 (UTC)

Hit it in the right spot(s), and a tank can be surprisingly easy to 'take out' - more so if 'take out' refers to a mobility kill, firepower kill or mission kill as opposed to a catastrophic kill. You don't even need explosives to do it; during the Winter war the Finns took out Russian tanks with incendiary bottles, and during the Second Italo–Ethiopian War several Italian tracked vehicles were disabled by having their drive-trains jammed. WegianWarrior (talk) 06:54, 26 June 2013 (UTC)

My grandfather was in the Warsaw uprising, and frequently tells the story of the 14 year old kid who took out two tanks by getting close enough to put a petrol bomb in the right place and legging it (he looked young for his age, so the Germans didn't realise he was a combatant until too late). MChesterMC (talk) 08:31, 26 June 2013 (UTC)

What is the speed of sound in liquid diamond?

- and what does the stuff look like? - I fluctuate between imagining something like graphite and something like, well, liquid diamond...

Thanks Adambrowne666 (talk) 10:14, 26 June 2013 (UTC)

A phase change doesn't preserve a network solid's characteristics. Meaning, that there is no such thing as liquid diamond. Molten diamond is just molten carbon. Plasmic Physics (talk) 11:07, 26 June 2013 (UTC)

yeah, i was expecting someone to say this - thanks for the reply - I don't quite understand it either, but check out the link, and the original paper linked in the article - it seems if carbon is under sufficiently high pressure and temperature, scientists are happy to call it liquid diamond. Adambrowne666 (talk) 11:11, 26 June 2013 (UTC)

Perhaps it is a metastable phase consisting of nanodiamond fragments, like unsaturated adamantane with dangling bonds? Plasmic Physics (talk) 11:21, 26 June 2013 (UTC)

(edit conflict) Here's a visualisation: a diamond is to carbon, as a windowpane is to glass. A molten windowpane is just molten glass. When you melt a windowpane, you compromise its shape, the completely liquid glass produced, does not contain bits of windowpane, nor does it consist of windowpane, though it originated as from a windowpane. Molten glass is the same, independent of the method used to prepare it, as long as the temperature, pressure, and recipe remains constant. So it is with molten carbon. Plasmic Physics (talk) 11:17, 26 June 2013 (UTC)

If the liquid is indeed a mixture of nanodiamond fragments, then perhaps carbon compares better to sulfur than to glass. Plasmic Physics (talk) 11:25, 26 June 2013 (UTC)

See diamondoid, to know what I'm talking about. Plasmic Physics (talk) 11:33, 26 June 2013 (UTC)

Is there no clue in the links provided? - I admit it's well beyond my understanding. Adambrowne666 (talk) 11:57, 26 June 2013 (UTC)

No, it seems like the journal article may have been misquoted. It seems like what they are talking about, is liquid carbon with diamondoids floating on top, not a single phase system with uniform properties. Just like an ice cube covered in dust. Plasmic Physics (talk) 12:12, 26 June 2013 (UTC)

Perhaps, this system reflects the freezing range that lies between the solidus and the liquidus. Probably, what is occurring, is that the freezing range expands with pressure, making the system less susceptible to pressure and temperature variations. As a result, it should be easier to maintain such a metastable state. Plasmic Physics (talk) 12:32, 26 June 2013 (UTC)

It follows that the study may assume that at a certain depth in those gas giants, a temperature and pressure exists that lie within the freezing range. Plasmic Physics (talk) 12:38, 26 June 2013 (UTC)

For the diamondoids to be differentiated from the liquid carbon, it is necessary for a freezing range temperature-pressure pair to coincide at the carbon-mantle interface. Plasmic Physics (talk) 12:43, 26 June 2013 (UTC)

The Nature paper linked from the phys.org article here talks about extending "the phase diagram of diamond", though I can only get the title and a small amount of the abstract. If someone with access could have a look, it would probably answer a lot of questions. It may be that the final state is liquid carbon, but the phase changes to get there are heavily dependent on which allotrope is considered. MChesterMC (talk) 15:00, 26 June 2013 (UTC)

• Here is a link to the abstract of the paper in question. It does not speak of "liquid diamond" -- it says that diamond melts at high pressure to a complex metallic fluid state. Looie496 (talk) 15:17, 26 June 2013 (UTC)

• Harrumph. Carbon has a liquid-liquid phase transition [10] The high pressure phase is largely sp3 bonded, i.e. liquid diamond. Wnt (talk) 18:25, 26 June 2013 (UTC)

Thank YOU, Wnt! Adambrowne666 (talk)

So then, my post at 11:21, 26 June 2013 (UTC) is correct, except for the 'metastable' part? Plasmic Physics (talk) 01:40, 27 June 2013 (UTC)

What makes the presence of sp3 bonding so uniquely diamondine? Doesn't Lonsdaleite also contain sp3 bonding? Plasmic Physics (talk) 01:45, 27 June 2013 (UTC)

Yeah, good on you, Plasmic - but in the meantime, can we answer the questions please? - what are the properties of this stuff, whatever we want to call it?Adambrowne666 (talk) 05:12, 27 June 2013 (UTC)

Diplazium esculentum

Does anyone know if this fern has nectaries? Aaadddaaammm (talk) 12:48, 26 June 2013 (UTC)

The nectaries article you linked cites a recent review which probably sheds some light on whether it is one of the species [11]. Unfortunately I can't access it right now either. You (or anyone here who wants to be nice!) could take a request to Wikipedia:WikiProject Resource Exchange or otherwise ILL it to get a copy. Another approach would be to e-mail the author and ask, or ask for an electronic copy etc.

If you do, it would be great if you could copy out the list of species known to have them to the article. They can't copyright a mere list of species believed to have this feature.

Last but not least... when dealing with a group where a feature is widely present, it is very possible you could take a sample yourself under a microscope and find them (or some vestige thereof) even if they are not already known to exist, and actually make a research discovery! :) Wnt (talk) 18:33, 26 June 2013 (UTC)

I have a pdf of the article, email me if you want a copy. I'll be skimming it, looking for any lists I can paste here, and/or this particular species. SemanticMantis (talk) 18:52, 26 June 2013 (UTC)

Extrafloral nectary on a fern, relatively rare.

Now, this is interesting. Our photo of a fern at Nectar#Extrafloral_nectaries (EFN) also appears in the Weber & Keeler article. Our photo is credited as "own work" from our own ref-desker user:Obsidian Soul (does linking like that give him a notification?). Perhaps s/he also contributed to that review article, or knows something of this matter? I hope at least that he can confirm he is the source of the photo.

Anyway, here's a list of clades/orders with known EFN (sorry for lack of formatting, it's a 4-col table)

The only fern clades mentioned in the article are Cyatheales and Polypodiales. Polypodiales does contain D. esculentem, via Athyriaceae, but neither genus nor family name occurs in the article. Fern EFN seem to be the exception, as 99.7% of known species are Angiosperms. Nevertheless, they were known to Darwin, and he seems to have been slightly wrong about them, see (Darwin F. 1877. On the nectar glands of the common brake fern. Journal of the Linnean Society of London (Botany) 15: 398–409.)

So, no conclusive answer from that article. The fern in question is in a fern order known to have EFN. I can't find any published source saying they do, but it's certainly possible. Best bet, as Wnt suggests, is to get a sample and a hand lens! SemanticMantis (talk) 20:06, 26 June 2013 (UTC)

Clades known to have EFN

{{Major clade(s)/order Early tracheophytes Ferns Cyatheales Polypodiales Gymnosperms Early angiosperms Magnoliids Monocotyledons Alismatales Asparagales Commelinales Dioscoreales Liliales Poales Zingiberales Early eudicots Proteales Ranunculales Rosid I: Fabidae Cucurbitales Fabales Fagales Malpighiales Oxalidales Rosales Rosid II: Malvidae Brassicales Crossosomatales Malvales Myrtales Picramniales Sapindales Other core eudicots Caryophyllales Ericales Santalales Saxifragales Vitales Asterid I: Solanidae Gentianales Lamiales Solanales Asterid II: Asteridae Aquifoliales Asterales Dipsacales Families with EFN/total families (%) 0 (0) 1/8 (12.5) 3/15 (20) 0/15 (0) 0/7 (0) 0/5 (0) 2/14 (14) 4/14 (28) 1/5 (20) 1/5 (20) 2/11 (18) 3/17 (18) 2/8 (25) 1/4 (25) 2/7 (29) 1/7 (14) 3/4 (75) 1/8 (12.5) 13/39 (33) 2/7 (29) 3/9 (33) 2/17 (12) 1/7 (14) 4/10 (40) 5/9 (56) 1/1 (100) 5/9 (56) 9/34 (26) 8/25 (32) 1/13 (7.7) 2/15 (13) 1/1 (100) 3/5 (60) 13/23 (52) 2/5 (40) 1/5 (20) 3/11 (27) 1/7 (14) Genera with EFN/total genera (%) 0 (0) 2/15 (13) 7/252 (2) 0/79 (0) 0/12 (0) 0/154 (0) 4/166 (2.4) 51/1122 (4.5) 1/68 (1.5) 2/21 (9.5) 3/67 (4.5) 11/997 (1.1) 10/92 (11) 6/85 (7.1) 3/199 (1.5) 23/129 (18) 113/754 (15) 1/33 (3.0) 136/716 (19) 2/60 (3.3) 18/261 (6.9) 3/398 (0.75) 1/12 (8.3) 59/338 (17) 18/380 (4.5) 1/2 (50) 32/471 (6.6) 32/811 (3.9) 22/346 (6.9) 1/151 (0.66) 2/112 (1.8) 3/14 (21) 37/1118 (3.3) 96/1059 (9.6) 19/165 (12) 1/21 (4.8) 22/1743 (1.5) 2/45 (4.4) Species with EFN/total species (%) 0 (0) 2/663 (0.3) 37/6962 (0.1) 0/850 (0) 0/175 (0) 0/2929 (0) 9/4560 (0.20) 106/26070 (0.40) 1/812 (0.12) 71/1037 (6.8) 7/1558 (0.45) 35/18325 (0.22) 31/2111 (1.5) 6/1710 (0.41) 4/4445 (0.09) 41/2295 (1.8) 1020/20055 (5.2) 2/1055 (0.19) 1028/15935 (6.5) 2/1815 (0.17) 249/7725 (3.2) 6/4765 (0.13) 1/66 (1.5) 305/6005 (5.3) 69/11027 (0.63) 1/46 (2.2) 57/6070 (0.92) 116/11510 (0.95) 170/11515 (1.5) 2/1992 (0.10) 4/2470 (0.16) 8/850 (0.94) 55/16637 (0.34) 292/23810 (1.2) 107/4080 (2.7) 1/536 (0.19) 46/26870 (0.19) 48/1090 (4.4)}}

How much should it cost to replace the propeller shaft in my 2001 BMW 740i?

I was quoted nearly 1800 including 1200 or so in parts and 420 in labor plus tax and disposal fees, is this fair? Also I already signed the estimate I think, if I find another mechanic, do I have a way out?108.212.70.237 (talk) 13:45, 26 June 2013 (UTC)

Where are you and what currency are you working in? Generally when people don't bother posting their location, it's the US. Is that the case here? Also, isn't this probably better at Misc? 131.251.133.26 (talk) 13:48, 26 June 2013 (UTC)

It says science and technology and I am in Oakland, California and working in US dollars obviously.108.212.70.237 (talk) 20:52, 26 June 2013 (UTC)

As to "do I have a way out", that would be legal advice, which we can't help you with. You would need to talk to a lawyer in your jurisdiction. Rojomoke (talk) 13:58, 26 June 2013 (UTC)

That's not what I said, I want to know which is information available about such matters which law or laws cover this theme are they federal financial laws or are they California state vehicle code laws? I am just asking for information not an answer.108.212.70.237 (talk) 20:54, 26 June 2013 (UTC)

The way to confirm an estimate is to find the part prices and the amount of labor involved. You can check online parts sites and call a BMW dealership for a part cost. The labor price sounds fair to me (in the US) - there is a decent amount of work involved, and they also rolled in disposal and taxes to that number. If you want to confirm it with a reference, estimator's guides are published that give labor time estimates - you could check with your local library to see if they have one available that covers your vehicle. $75/hr is a good low-end labor rate, so you multiply that by how many hours the guide suggests. 209.131.76.183 (talk) 16:08, 26 June 2013 (UTC)

re post aboove: Sounds like the OP went to a registered dealer who's charging him the book price. For a car that age he might be able to google local owners club that know of back-street auto-shops that are both reliable and can do the same thing cheaper. Insistently: A prop-shaft is a pretty easy thing to replace oneself. If you don't know how to take out the circlips with out circlip pliers then you might need to buy one of those but it really is a p-of-p. 420 in labour? If that's US dollars and not Honkong dollars or European Croners then I am in the wrong job – bring it over to me and I'll do it for you. Mind you a auto-shop has loads of overheads so it bound to cost more. Do you have a way out? Have you left the car with them and have they started work on it -if not then yes.--Aspro (talk) 16:24, 26 June 2013 (UTC)

Note that BMW's have a split prop shaft, with a carrier bearing between the two halves - like on trucks. There is not a single prop shaft as is typical with older US RWD cars. On the 740i the uv joints are not attached with circlips. BMW makes the whole thing, 2 prop shafts and uv joints as a single replaceable unit. Also note that the price quoted may include other items the mechanic found appropriate. This is the same OP that asked about vibration on mild acceleration a week ago, saying he had no cash. Therefore, as explained then, the car may be a cheapy that has not been properly serviced. Indeed prop shaft / uv joint failure will not happen if the car has been properly serviced since new. — Preceding unsigned comment added by 120.145.9.177 (talk) 00:56, 27 June 2013 (UTC)

If those are new, original, BMW parts - bought from a dealership who has to make a profit on them - then probably that's the right price. But with something like a prop shaft, and for a car that old, you'd probably be better off getting a used one from a junkyard or something: This guy will sell you one for $150. These guys have new ones for $630 and "remanufactured" ones for $450. Labor charges are quite variable. BMW dealerships charge around $600/hour here in Texas - I doubt you can change a prop shaft in much less time than that..."disposal fees" on a prop shaft shouldn't be significant. A non-BMW garage would likely have lower labor rates - but with mechanics who are less familiar/trained with that car, it might well take them longer to do the job. So I don't find the labor charge too unreasonable by US/Texas standards.

Good to hear that there are better part prices out there - I recommend that if the OP isn't comfortable doing the work himself, he should try calling around other local mechanics. Mention the part price online, and if the mechanic can't match it, see if they're willing to install it. Some mechanics require that they handle everything, and others allow you to bring your own parts. In my experience, $75/hr is a pretty common low-end rate, which makes the $420 be about 5 hours plus $50 for the taxes/fees mentioned. I don't know the details for doing the job on his car, but it doesn't seem unreasonable to me, especially for a non-BMW shop. 209.131.76.183 (talk) 17:24, 26 June 2013 (UTC)

As for whether you can get out of some agreement that you signed - that would be legal advice - and we're not allowed to give out legal advice here on Wikipedia. I bet if you asked them nicely to use a used or "remanufactured" prop shaft instead of a new one, they'd be OK with that. SteveBaker (talk) 16:28, 26 June 2013 (UTC)

Okay FindLaw seems to have this page FindLaw but perhaps there is a more comprehensive guide on auto repair laws which is what they seemed to be called, are there any mentions in consumer law? Also UDAP (Unfair and Deceptive Acts and Practices) Laws seem to have a lot to do with it possibly, but I still don't see which laws cover estimates or contracts for work. I wasn't given a copy, does that law take that into consideration? I haven't paid and said he wouldn't give me estimate until I did but I think this has more to do with estimate shopping, no?108.212.70.237 (talk) 21:20, 26 June 2013 (UTC)

As I explained earlier - we are absolutely not allowed to provide legal advice or to entertain discussion of your own findings. It is inappropriate for you to post such things here (even in response to your own question. Please read Wikipedia:Legal_disclaimer. SteveBaker (talk) 03:41, 27 June 2013 (UTC)

Frame shifting indel mutation confusion.

I've been reading this paper - http://genome.cshlp.org/content/23/5/749.full.pdf as an amateur but I'm confused by something.

It states on page 755:

"After accounting for these biases, we observed consistent depletion of indels across genic sequences relative to flanking intergenic regions, with coding sequence (CDS) displaying the strongest depletion of particularly frameshift indels (Fig. 3B). As a result, frame-preserving indels, and in particular indels of 3 bp in length, are the most abundant within CDS (Fig. 3C). Indel rates are also markedly reduced across a broad spectrum of functional noncoding sequences in the human genome (CNCs), and mild but significant reductions are seen in 59 UTRs and introns."

Which I take to mean that indels of length 3 are conserved while indels which cause a frame-shift are more subject to purifying selection within coding sequences (i.e. exons).

But on page 757 it states:

"As our set includes many indels within exons, we sought to examine their influence on gene expression and their relationship to complex trait associations. We first observed that frameshift-causing indels of lengths 1, 2, 4, and 5 were enriched with significant (FDR<0.5) exon-level gene expression associations compared to in-frame indels of length 3, a signal that itself is significant (Fisher’s exact test, P = 0.031) and is consistent with the action of nonsense-mediated decay (Fig. 4B). Further tests indicate that this signal is unlikely to be the product of length-driven differences in genotyping accuracy (see Methods)."

I'm not sure I understand what this means. Is it saying that genes with indels of length 3 are less expressed than genes with indels of lengths other than 3? Wouldn't nonsense-mediated decay act in the opposite direction, with frame-shifting indels casuing more premature stop codons? 87.194.131.188 (talk) 22:20, 26 June 2013 (UTC)

Lobotomy

What would the process of having a lobotomy (fully conscious, assuming an analgesic is given to relieve pain but leave other awareness unimpaired) feel like? I understand there are obviously no primary sources for this procedure so could a conjecture be made based on the parts of the brain that are affected?

Thanks.

24.92.79.193 (talk) 23:19, 26 June 2013 (UTC)

We don't do conjecture here. You're free to read Lobotomy and arrive at your own conjectures, but it would be quite inappropriate for anyone here to give their own opinions or conjectures. Of course, if reliable sources DO exist that answer your question, people should be free to link to those sources so you can read them. --Jayron32 23:53, 26 June 2013 (UTC)

Tsunami physics

The tsunami article alleges that a tsunami's wavelength is on the order of hundreds of kilometers long. But if a tsunami is caused by an earthquake, an event which lasts no more than a few minutes, then the tsunami's period cannot exceed a few minutes either. How then does a tsunami have such a long wavelength?

Also, I remember learning that a tsunami's long wavelength was somehow responsible for its large destructive powers. I don't remember why (something to do with energy), could someone help fill in the gap?

Finally, how does a tsunami not die out after travelling such large distances? 74.15.137.221 (talk) 01:56, 27 June 2013 (UTC)

My understanding is that a tsunami does not have a single wavelength, but rather a range of wavelengths, as it is originally produced by a disturbance that is rather localized in space and time. Because of the dispersion relation of the ocean waves, the waves of different wavelength have different velocity (that is, different phase velocity and different group velocity). As a result, the tsunami becomes progressively broader as it travels away from where the earthquake has happened. Also, if I remember correctly, deep-water waves of shorter wavelengths dissipate faster than the longer ones. --Dr Dima (talk) 02:43, 27 June 2013 (UTC)

Imagine that you whack a pendulum to make it start oscillating. The pendulum may have a period of several seconds, even though your hand was only in contact with the pendulum for a tiny fraction of a second. That's because the pendulum's period is determined by its physical characteristics--specifically its moment of inertia and center of mass--and not by your initial whack. Similarly, a tsunami's wavelength is determined by the physical characteristics of the ocean, not by the earthquake that caused it.

A tsunami's long wavelength means that when a leading trough first hits a shore, the shoreline recedes for a while before the peak hits (see Tsunami#Drawback). That doesn't make the tsunami more destructive, but it does mean that lots of people will be out collecting seashells in the newly exposed sand, unaware that they're about to drown. --50.125.28.190 (talk) 06:15, 27 June 2013 (UTC)

June 27

Plausibility of leaving message for police with bare finger?

In season 2 episode 4 "By the Book" of the crime procedural television series White Collar, a kidnapping victim, as she is being taken from her home, uses her bare finger (it is not dipped in ink or any other marking or sticky substance) to invisibly rub/spell out a word on the surface of her non-dusty (so she was not spelling out a message in dust) dresser without her kidnappers knowing. Later, when the FBI dust the crime scene for fingerprints, their dusting reveals the word she left, which the FBI uses as a vital clue that enables them to track down her kidnappers and her location and rescue her. Is this actually plausible, that the bare finger secretes enough liquids that, just by rubbing your bare finger on a surface, you can leave messages that the police will then be able to find? —SeekingAnswers (reply) 04:26, 27 June 2013 (UTC)

Remarkable claim about handaxes

I was doing research on the handaxe and found these remarkable claims from this page:

"Handaxes were known to the ancient Greeks, who believed them to be the thunderbolts thrown down by Zeus, the Tree-splitter. They were held to be sacred and were put on display in the temples, such as the Temple of Apollo at Delphi, which had two of them."

I'm highly skeptical because I haven't seen these claims in any other source. Can anyone substantiate or refute them? --50.125.28.190 (talk) 05:58, 27 June 2013 (UTC)

See Labrys. --Dr Dima (talk) 06:02, 27 June 2013 (UTC)

TREES & SOIL WATER

Which plant takes more water than all other plants? — Preceding unsigned comment added by 112.79.37.226 (talk) 06:13, 27 June 2013 (UTC)

SOIL WATER

Which plant takes less water than all other plants?