:Ideally, since when you view it at home, you "become" the audience, then they should have the left channel be audience left. That way, if an actor looked to the left (or on radio, said "Hey, you on the left in the funny hat...") and asked somebody on the left side of the audience a question, the answer would seem to come from the correct place. However, in shows where there's no interaction with the audience, it wouldn't much matter. [[User:StuRat|StuRat]] ([[User talk:StuRat|talk]]) 20:39, 18 July 2012 (UTC)
:Ideally, since when you view it at home, you "become" the audience, then they should have the left channel be audience left. That way, if an actor looked to the left (or on radio, said "Hey, you on the left in the funny hat...") and asked somebody on the left side of the audience a question, the answer would seem to come from the correct place. However, in shows where there's no interaction with the audience, it wouldn't much matter. [[User:StuRat|StuRat]] ([[User talk:StuRat|talk]]) 20:39, 18 July 2012 (UTC)
== Why biologist know so little mathematics? Why are they less refined that, say, physicist ==
Both fields can be equally demanding, but biologist seem to be less 'deep'. [[User:Medeis|μηδείς]] ([[User talk:Medeis|talk]]) 21:26, 18 July 2012 (UTC)
Revision as of 22:27, 18 July 2012
Welcome to the science section of the Wikipedia reference desk.
The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
Cognitive biases and predictions of the end of Moore's Law
Do any purely psychological explanations exist behind why the various forms and corrolaries of Moore's Law consistently continue for longer than experts predict, making it an exception to the usual optimistic bias of technology predictions? NeonMerlin 00:13, 14 July 2012 (UTC)[reply]
Are you asking why the experts are too pessimistic? Or are you asking whether Moore's Law is an illusion? I don't see how to make the question make sense if it doesn't mean one or the other. Looie496 (talk) 00:18, 14 July 2012 (UTC)[reply]
Judging by the word any I take it he means both. 203.27.72.5 (talk) 00:25, 14 July 2012 (UTC)[reply]
Because the serious limits don't start to become evident until 2016-2022? 71.212.249.178 (talk) 00:38, 14 July 2012 (UTC)[reply]
And the reason for that is intense competition pressure. To stay on top of the game, semiconductor companies continually make huge investment in research, so that each technical bottleneck is broken just in time to keep Moore's Law in place. The rate of Moore's Law is determined by the cost of research and time-to-market http://en.wikipedia.org/wiki/Time_to_market. Both are relatively constant, hence Moore's Law is fairly constant. The explanation is not psycological, its commercial. Ratbone124.182.22.24 (talk) 01:28, 14 July 2012 (UTC)[reply]
I think the point is that that's what they always say. The supposed end of Moore's law is always just around the corner when the "serious limits" start to kick in, yet in 50 odd years it's never actually happened. 203.27.72.5 (talk) 01:14, 14 July 2012 (UTC)[reply]
The optimistic bias in technological predictions is just a lack of imagination on our part. When asked to imagine what the world will look like in the future, we might say something like "cancer will no longer be a problem". If we're pressed as to how that will happen, it's usually the most obvious hyped up area of research today, like genetic thearpy or nano-robots or something like that. History has shown us that we will probably be blindsided by some unforseen breakthough and after that we'll think it was obvious and wonder why we didn't think of it sooner. We don't have the android technology seen in the 1979 film Alien, but in that film, the computers were all using a text based operating system and had tiny CRT monitors. It's easy to think of technology giving us stuff like interstellar travel and life-like robots, but thinking of the more subtle things that take incremental advances but improve our lives by so much requires more imagination than we have. The advances won't be the ones that we think they'll be, but they'll still be awesome, and that's reflected in genuine, objective measurements of technological advances, like with Moore's law. 203.27.72.5 (talk) 01:26, 14 July 2012 (UTC)[reply]
"in that film, the computers were all using a text based operating system and had tiny CRT monitors. " Not only that, but it made a sound each time a character appeared on the screen! And the speed was about 10-20 characters per second. Bubba73You talkin' to me? 03:30, 14 July 2012 (UTC)[reply]
And no doubt the text was far larger than on any real screen. This is a common trope in movies and TV, as a person reading small, monochrome text on a screen, in silence, just isn't very interesting to watch. StuRat (talk) 04:32, 14 July 2012 (UTC) [reply]
From memory StuRat, no it wasn't like that because it wasn't important that the viewer actually read the text, it was just lines of text scrolling over the screen much like an old execution of autoexec.bat on a 486 running windows 3.1. 203.27.72.5 (talk) 05:46, 14 July 2012 (UTC)[reply]
I can beat the Alien example. An original Outer Limits episode featured a future video phone, with a cord, and ... wait for it ... a rotary dial. :-) StuRat (talk) 02:15, 14 July 2012 (UTC) [reply]
Ha. That's hilarious. And realistically, how much has a video phone conversation changed our lives vs wireless telecommunications and reliable buttons? But no one is going to marvel at how much CGI went into making a futuristic button. Audiences wouldn't have even understood what was going on if they saw a movie that depicted the use of a modern mobile phone back when Outer limits was on TV.203.27.72.5 (talk) 02:24, 14 July 2012 (UTC)[reply]
I think they would have. After all, the Dick Tracy two-way wrist radio (introduced January 13, 1946, with video added in 1964) had buttons, going way back. StuRat (talk) 03:15, 14 July 2012 (UTC) [reply]
Did he get spammed by Jamba!, or MMS pictures of evidence to his client using the intergrated camera? Did it have a visible antenna? Did he lose reception in underground carparks, or have no coverage in a major metropolitan area? 203.27.72.5 (talk) 03:23, 14 July 2012 (UTC)[reply]
The D'Arsonval meter movement is rather funny: [1] (at the bottom). We still use that on car speedometers and gauges, though. The speaker also looks like something from a 1960's console TV. The screen does seem to use some type of flat screen technology, at least not a CRT. StuRat (talk) 04:02, 14 July 2012 (UTC) [reply]
Can Cannabis grow in the Colorado high country?
9000+ feet, Rocky Mountains. I was walking through an open meadow near a popular golf course and noticed Cannabis looking plants growing in bunches within a large circle of area. According to the rather confusing Cannabis article, "The leaves have a peculiar and diagnostic venation pattern that enables persons poorly familiar with the plant to distinguish a Cannabis leaf from unrelated species that have confusingly similar leaves (see illustration)"—first of all, what illustration?! Okay, next, the picture to the right of the paragraph sure looks like what I saw. What "unrelated species" are there that I may be confusing this with? If this is Cannabis, does that mean someone threw some seeds there as a joke or something? Thanks! Reflectionsinglass (talk) 02:58, 14 July 2012 (UTC)[reply]
In case it's meant as a serious Q, let me take a stab at it: Cannabis grows like a weed, hence the name. Not sure if it grows at that altitude, but, if so, maybe some hippie spilled some seeds out of his baggie, and that's all it took.
The illustration they meant was the one to the right. Here's the full-sized version: [2].
Doing some web searches, it does appear to grow at high altitudes, but 8750 feet is the highest point I saw listed explicitly. Here's a couple sites I found: [3], [4]. StuRat (talk) 04:11, 14 July 2012 (UTC)[reply]
Wild cannabis isn't that rare of a weed in NA, but no one cares because the weed version is worthless to smoke, just like the vast majority of plants we eat, plant breeders have dramatically improved the quality of cannabis that is cultivated. The "hippie" bit is uncalled for, please keep your stereotyping to yourself. Unique Ubiquitous (talk) 05:03, 14 July 2012 (UTC)[reply]
The wikipedia article must need a visit from the PC police too then, since it says that the movement is known for experimentation with drugs. 203.27.72.5 (talk) 05:37, 14 July 2012 (UTC)[reply]
Sure, but it does not follow that those who use or grow the drugs are hippies. It has never been the case that only hippies smoked pot, and the vast majority of pot smokers today are not hippies. I would be more worried that someone is intentionally growing them up there — which can be a dangerous thing to interact with depending on who is growing it. When you see a stand of marijuana growing, consider that that's somebodies money growing out there. --Mr.98 (talk) 15:15, 14 July 2012 (UTC)[reply]
What's the reference to "grows like a weed, hence the name" about, Stu? The etymology has nothing to do with weeds, as far as I can see. -- ♬ Jack of Oz ♬ [your turn] 05:12, 14 July 2012 (UTC)[reply]
Do you not use the slang word "weed" in Australia, for cannabis ? StuRat (talk) 05:28, 14 July 2012 (UTC)[reply]
I'm pretty sure JoO is aware of the slang word, they're just saying the etymology of the slang word has nothing to do with cannabis growing like a weed. Whether or not this is true I can't say, I had trouble any reliable sources most appear to discuss othe things like the word marijuana or pot. Nil Einne (talk) 05:49, 14 July 2012 (UTC)[reply]
Sorry, of course I know it as "weed". I misinterpreted Stu's comment, which I read to mean that the name "cannabis" was from some presumably Latin or Greek word meaning "weed". My bad. But in checking out the etymology, I did discover it's cognate with the word "canvas". That had never occurred to me, but it makes a lot of sense. -- ♬ Jack of Oz ♬ [your turn] 06:24, 14 July 2012 (UTC)[reply]
NA = North America. What else, StuRat? OsmanRF34 (talk) 05:26, 14 July 2012 (UTC)[reply]
OK, a bit non-specific, though. I listed two possible more specific meanings. StuRat (talk) 05:28, 14 July 2012 (UTC)[reply]
Which of the three contains the region mentioned in the title of this section? —Tamfang (talk) 06:08, 14 July 2012 (UTC)[reply]
People often reply to questions on one part of the world with answers on how things work in their own part of the world. StuRat (talk) 06:30, 14 July 2012 (UTC) [reply]
In order that we may answer your questions within wwikipedia ref desk guidelines, please explain at the ref desk discussion board thread on this post why you cannot see the illustration in the article you searched to the right of the text you mentioned. Please upload an image there so we may help you identify the plant, although, do be aware that people have been shot for trespassing on someone's weed patch. Please explain there what evidence you have that someone has planted these plants as a joke so that we can evaluate it, rather than speculate and debate upon it. (Comment added by User:Medeis (μηδείς), who, by omitting their name, implies that their opinion is that of everyone here, when it is really only theirs. StuRat (talk) 05:09, 14 July 2012 (UTC))[reply]
From our article it appears that some people have described ditch weed as a separate species, though I haven't reviewed the evidence; whatever it is called, it was used fairly widely for routine purposes of landscaping and preventing erosion even during the early days of Prohibition. Apparently law enforcement still goes to great lengths to seek out and exterminate such plants, though they are suited for little but genuinely medicinal or perhaps textile use. Wnt (talk) 05:14, 14 July 2012 (UTC)[reply]
I do not believe it can grow there. Cannabis needs lots of warmth and light. OsmanRF34 (talk) 05:23, 14 July 2012 (UTC)[reply]
Light isn't a problem at elevation. If anything, they get more light, especially UV. Warmth could be a problem, though. StuRat (talk) 05:26, 14 July 2012 (UTC)[reply]
Perhaps I should have elaborated. "Ditch weed", according to our article, is Cannabis ruderalis, and is hardier than the other species. Wnt (talk) 11:10, 14 July 2012 (UTC)[reply]
How can law enforcement distinguish between wild useless cannabis and smokable cannabis? Do they look different enough? OsmanRF34 (talk) 05:33, 14 July 2012 (UTC)[reply]
I doubt if they bother, but just destroy anything that looks like it. StuRat (talk) 05:56, 14 July 2012 (UTC)[reply]
Cannabis sativa grows wild in the UK, and throughout Western Europe. According to my wild flowers book it is native and not introduced. I dare say it is a common escape from cultivation (hemp). It's said that the plants have little or no pharmacological content, not sure if that is because of the variety or because of the growing conditions. Illegal cultivators in the UK use greenhouses or artificial lighting. The UK police have no interest at all in wild hemp, as far as I know. Itsmejudith (talk) 17:08, 14 July 2012 (UTC)[reply]
Thanks to all the responses. The plant is growing on private property owned by a resort, which owns the golf course as well. So there's no fear of being shot. I also assume that a pot farm would look more like that scene in the film Without a Paddle, with lots of land dedicated to these plants than just the few bunches I found. I'll bring a plant inside and compare it to the photograph in the article. The way the sentence with the phrase "see illustration" is worded, I was looking for an illustration showing the different types of plants that can be confused with cannabis. I might post a photograph of these plants as well and post a link here. Reflectionsinglass (talk) 21:31, 14 July 2012 (UTC)[reply]
Question about Big Bang theory.
Transcluded from the Miscellaneous reference desk. 203.27.72.5 (talk) 06:05, 14 July 2012 (UTC)[reply]
the Big-Bang theory is telling that the universe was originated about 13.75 billion years ago from a tiny ball with infinite density and temperature when the ball blasted with a big bang. according to the theory the universe is expanding like a balloon. My questions are:-
1. where that 'tiny ball' was? kept over something? floating some where? or hanging over something?
2. where forom that 'tiny ball' came?
3. who had created that tiny ball?
4. how is it possible that a very 'tiny ball'had so much of matter that a universe of billion galaxies with billion stars are containing?
5. If the universe is expanding then there must be one starting point and one ending point or an edge, then what is there out of the edge?
Wouldn't the Science Desk be a better place to ask science Q's like this ? StuRat (talk) 04:46, 14 July 2012 (UTC) [reply]
4) Since matter can have an infinite density, as in the singularity in a black hole, there's no reason the entire universe couldn't fit into a tiny point. StuRat (talk) 04:48, 14 July 2012 (UTC)[reply]
There was probably never a time of infinity density and temperature; big bang cosmology doesn't require that, and it doesn't seem very likely. Cosmic inflation is the best known attempt to explain the origin of the initial very dense state, but there isn't enough evidence to be sure that it's right. It isn't necessary for the expanding region to have an edge, though it could. Other than that, the answer to the questions is "nobody knows (yet)". -- BenRG (talk) 06:31, 14 July 2012 (UTC)[reply]
Your questions make assumptions that the universe "before" the big bang and "outside" it have properties like the universe we know today. But depending on the particular theory, these assumptions may be false (which is why I have put those words in quotes). For example, one common theory about the Big Bang (famously presented by Stephen Hawking is that "before the Big Bang" is like "South of the South Pole". So our experience is that wherever we are on the planet there is something to the South of us; but if we go to the South Pole, our experience (our assumption) breaks down: there is no "South" there. In the same way, Hawking suggests, at the Big Bang there is no "before". On that theory, your questions 2 and 3 do not make sense, as they contain erroneous presumptions. --ColinFine (talk) 08:42, 14 July 2012 (UTC)[reply]
(ec) I thought the idea was that since all of space was contained within the big bang--there was no "place" outside it. So it makes no sense to ask "where" it happened. It happened "everywhere". Isn't this supposedly why the Cosmic microwave background radiation is found everywhere? And, perhaps I'm wrong, but isn't the big bang also supposed to be the origin of time itself? If so it would make no sense to ask about "before" or "what caused" it, right? Pfly (talk) 08:45, 14 July 2012 (UTC)[reply]
(5) An expansion does not imply that there will not be a contraction. In other words, the expansion may go on forever - or it may not. It may contract. It may oscillate between expansion and contraction. We simply don't know. Our universe may be a bubble in an even bigger universe - or it may not. I'm reminded of one of Haldane's quotes: "The universe is not only stranger than we imagine, it is stranger than we can imagine". We can gather information and see what that information leads us to, but to suggest that we know the answers to your questions is arrogant at this point in time. Doesn't stop us theorising, of course, and shouldn't stop you asking! --TammyMoet (talk) 08:53, 14 July 2012 (UTC)[reply]
Blood test after getting infected by HIV....
I had only oral sex with a prostitute before 3 months but now I fear that it might have infected me from HIV as I had some rashes on my genitals and perhaps she also had bleeding gums........ Now I want to clear my doubt that either I got infected or not. I heard somewhere that HIV will not show up in blood test so early after getting infected, so what is right time for blood test. — Preceding unsigned comment added by 14.140.235.82 (talk) 06:19, 14 July 2012 (UTC)[reply]
Wikipedia does not give medical advice. See a doctor, or other appropriate medical practitioner. AndyTheGrump (talk) 06:22, 14 July 2012 (UTC)[reply]
The OP has not asked for medical advice regarding us diagnosing or treating his condition. He has asked how soon a positive HIV test shows up after infection. The answer is that it may take very little time or more than a year. See HIV_test#Window_period. μηδείς (talk) 05:39, 15 July 2012 (UTC)[reply]
See a doctor as soon as possible, how long you have to wait before HIV is detectable is completely irrelavant if you are already presenting symptoms. Time is of the essence, the sooner you get yourself diagnosed and treated the better. Vespine (talk) 22:55, 15 July 2012 (UTC)[reply]
Do Sounds Played at the Same Time Add?
If you play two sounds at the same time will the resulting sound wave be the sum of the two individual ones? I'm guessing no since a sound wave that is a constant would not sound like anything and you can add two sine waves to get this. Then again, going from the graph of a sound wave to what it sounds like has always been a point of confusion for me. Thank you for any help:-) 209.252.235.206 (talk) 09:02, 14 July 2012 (UTC)[reply]
Yes, they add (the wave equation governing sounds is a linear equation). You can have cancellation of sound waves (for example when you hear a beat). —Kusma (t·c) 09:09, 14 July 2012 (UTC)[reply]
Yes, if they are exactly the same sounds, in phase with each other, and both arrive at the listener at the same time, then, as you said "the sine waves will add". However, if they are out of phase, either from being produced at slightly different times, or being at different distances from the listener, they can actually cancel each other out (see noise cancellation). Note that when they do add, twice the amplitude of sound wave does not mean it's twice as loud. See decibel. StuRat (talk) 09:13, 14 July 2012 (UTC)[reply]
You're welcome. I will mark this Q resolved. StuRat (talk) 09:59, 14 July 2012 (UTC)[reply]
Resolved
You marked it resolved prematurely, Stu. You have repeated a common fallacy. Consider two independent sound sources (meaning each has its own arbitary waveform and phase): One sound source imparts x watts of acoustic power to the environment and the other y watts. Since energy cannot be created or destoyed, there is x+y watts of acoustic power in the environment. However, the amplitude [the amount of air displacement, or the distance a freely suspended surface (a la a microphone diapham or an eardrum) will move] is proportional to the square root of the acoustic power, just as the voltage in an electric device is proportional to the square root of the power. Two sound sources being indentical in all respects except being out of phase cannot just cancel, as this would mean energy destroyed. What happens is cancellation occurs in some directions and reinforces to double strength in others, the directions being a function of the spacing and phase of the two sources. In other words, the sound becomes directional - analogous to the common use in radio broadcasting to use two or more carefully spaced antennas to provide directional coverage. This principle is also used in concert sound reinforcement - indentical loudspeakers fed with indentical program are "stacked" to beam the sound into the audience and not waste it to the sky. Complete cancellation can only occur if the two sound sources occupy the exact same point in space - a rather theoretical concept. Ratbone121.215.69.8 (talk) 10:12, 14 July 2012 (UTC)[reply]
That's consistent with what I said, where I mentioned them both adding and cancelling, listing cancelling due to "being at different distances from the listener". Obviously the two sources wouldn't be at different distances from all possible listeners, and there the sounds don't cancel. The noise cancellation article I linked to explains the details. As for the math, I linked to the decibel article, which explains the relationships between power level, volume, etc. StuRat (talk) 10:24, 14 July 2012 (UTC)[reply]
Transcluded to Ratbone's now created talk page. 203.27.72.5 (talk) 11:09, 14 July 2012 (UTC)[reply]
BTW, since you misspelled it 3 times in your post, let me point out that it's "identical" not "indentical". StuRat (talk) 10:24, 14 July 2012 (UTC)
[reply]
You should know by now, Stu, that I do lnkow how to spoll, but I am a shockinkg typist. Ratbone121.215.29.47 (talk) 12:20, 14 July 2012 (UTC)[reply]
Either there's an error in your logic or you just weren't clear on what you meant Ratbone, but where you said "Two sound sources being indentical in all respects except being out of phase cannot just cancel, as this would mean energy destroyed" it sounds like you're saying that being in phase is an intrinsic property of the two sound sources. It's not the sources, but rather the waves that are either in or out of phase, and that depends on the location i.e. they're in phase at point A, out of phase at point C, and somewhere in the middle at point B. 203.27.72.5 (talk) 10:29, 14 July 2012 (UTC)[reply]
This is probably just a comment on my english, but the wording I used is entirely standard in electronics and acoustics. Engineers talk of sources being "in phase", "out of phase" etc, without implying that waves will be the same relative phase everywhere in space, a phenomena which you have clearly appreciated. Ratbone121.215.29.47 (talk) 12:20, 14 July 2012 (UTC)[reply]
Ah, yes, well I'm not an accoustics engineer, so I wouldn't know about their standard technical jargon. Thanks for clearing that for me. 203.27.72.5 (talk) 13:06, 14 July 2012 (UTC)[reply]
"Two sound sources being indentical in all respects except being out of phase cannot just cancel, as this would mean energy destroyed": well, they'd have to be in exactly the same place, and the energy will be zero at all times since no wave is actually emitted. —Kusma (t·c) 10:33, 14 July 2012 (UTC)[reply]
Two sources producing the same sounds in phase would be indentical, 180o out of phase, outdentical. Everything else would be inbetweenical. Clarityfiend (talk) 22:37, 14 July 2012 (UTC) [reply]
If I'm not mistaken, I believe that the existence of black holes was early in the 20th century without the involvement of either dark energy or dark matter.
Likewise, the more recent 'proof' that black holes actually exist (based on the velocity of stars orbiting around the unseen black hole) is not dependent on
dark matter or energy either.
How does the existence of dark energy and dark matter effect our understanding of black holes?Honeyman2010 (talk) 11:01, 14 July 2012 (UTC)[reply]
There is theory about objects called MACHOs that could include black holes and is meant to explain dark matter. It's essentially been disproven though. Dark matter and black holes are believed to be unrelated. 203.27.72.5 (talk) 11:06, 14 July 2012 (UTC)[reply]
Agreed; there is no close relation or connection between the three concepts. Black holes were known to be a theoretical consequence of general relativity long before any evidence of their actual existence was found, and indeed the observational evidence for black holes is still somewhat indirect and not totally conclusive. Dark matter and dark energy are names for possible mechanisms explaining puzzling astronomical observations (the galaxy rotation problem and the accelerating universe respectively), but the details of these mechanisms are not completely understood. The similarity in names, each involving black/dark, is partly coincidence and partly lack of imagination on the part of physicists/cosmologists. Gandalf61 (talk) 11:23, 14 July 2012 (UTC)[reply]
Thanks for the answers, but my confusion does not stem from the similarity of the words "black" and "dark". My question seems logical since black holes represent infinite gravity, and dark matter and dark energy are thought to comprise perhaps 80% of the matter in the universe. Surely some interaction cannot be so summarily dismissed. Also, would the recent discovery of the Higgs (a scalar) and dark energy (thought to be a scalar) not suggest the possibility of a link? And, finally, if Unification is ever realized through String Theory (perhaps pushed along now with the Higgs), or some other preocess, would that bear on my question? Thanks Honeyman2010 (talk) 12:16, 14 July 2012 (UTC)[reply]
The article on MACHOs explains why it is unlikely that dark matter has anything to do with black holes. Also, you should read the article on black holes, as you seem to have some misconceptions about them. They do not have infinite gravity. According to general relativity they contain a point called a singularity that has infinite density. Their mass is finite and they may have other characteristics that define them (see no hair theorem). 203.27.72.5 (talk) 12:44, 14 July 2012 (UTC)[reply]
Your table has nothing to do with the question. Please quit spamming the link.
The original question was, "do the existence of dark energy and dark matter change the way black holes work?". The short answer is "no, not really". The long answer is, "dark matter is absorbed like any other matter, and dark energy presumably gives a repulsive force as it does in any volume of space, but one that's far too weak to be relevant". --Christopher Thomas (talk) 02:43, 17 July 2012 (UTC)[reply]
I believe that the blue lines in Figure 2 on p. L70 of Lacki and Beacom (2010) impose constraints which bear on the answer to this question, but I have been told I am not interpreting that paper correctly, although the reasons why are elusive. I welcome others' opinions. 71.212.249.178 (talk) 05:05, 17 July 2012 (UTC)[reply]
Polyvinyl fluoride and PubChem name. A little confusion.
Hello, I looked up polyvinyl fluoride in PubChem Compound and got struck. For polymers, PubChem Compound shows only the monomers. However in this case it shows fluoroacetylene instead of fluoroethylene. (i.e; fluoroethyne instead of fluoroethene). Why? And in Pubchem Substance, it is more confusing to me. Can you help me please? Your comments are always welcome. They have got it almost right for polyvinyl chloride. (For reference you may look CAS and CHEBI:)Vanischenu mTalk 12:34, 14 July 2012 (UTC)[reply]
I don't think the answer is too exciting. It looks like they're just plain old wrong. Should be an alkene, not an alkyne. 203.27.72.5 (talk) 13:01, 14 July 2012 (UTC)[reply]
It's quite unfortunate that this occurred at a trusted site. Thank you for your kind reply. I will mark this question as resolved then.
Is it true that the genetic difference between two different ethnic groups in Africa like say the Hutu and the Zulu people is comparable or even greater than the genetic difference between a given black guy and a given white guy? ScienceApe (talk) 16:07, 14 July 2012 (UTC)[reply]
Interestingly, both autosomal and X-linked sequence data show higher DNA variation within Africans than between Africans and Eurasians, contrary to the general observation of lower within-population than between-population differences in population genetics. This finding implies that Africans differ on average more among themselves than from Eurasians. Thus, with the exception of many minor unique variants, the nucleotide diversity in Eurasians is essentially a subset of that in Africans, as suggested by the observation that both Y-linked and autosomal haplotypes found outside of Africa were often a subset of the collection of haplotypes found in Africa. Our finding is more in agreement with the out of Africa model of human evolution than with the multiregional model because it is consistent with the view that modern humans originated in Africa and that a smaller subset of this population later migrated to other parts of the world. During and after the migration some variants would have been lost and, as the separation time is still short, non-Africans have not yet acquired many high-frequency variants, though they might have derived some variants from indigenous archaic populations in Asia and Europe. For these reasons, the genetic differences between non-Africans and Africans are on average smaller than the genetic differences within Africans. (Yu et al. (2002). "Larger Genetic Differences Within Africans Than Between Africans and Eurasians". Genetics. 161, 269-274)
Which basically means yes. I don't know specifically about Hutu or Zulu genetic differences, but the latter study includes several Bantu peoples (of which the Hutu are genetically very close to) and the Zulu people. However, it also includes the !Kung, which belong to the Khoisan-speaking peoples; and two of the African pygymy peoples, the Aka of the Mbenga group and an unspecified member of the Mbuti group. The latter peoples are the most genetically diverse of the human populations on the planet, so depending on what you mean by "African" it can be skewed one way or another. Most people tend to separate the Khoisan group and the pygmies from other African populations, which in turn are separated from the more recent ethnic Arabs in North Africa (not included in study). Also note that "Eurasians" in this case refers to European (both Western and Eastern) and Middle Eastern human populations, though the sample group for them is composed purely of Europeans.-- OBSIDIAN†SOUL 17:29, 14 July 2012 (UTC)[reply]
This should not be surprising, under the the recent African origin of modern humans theory. (It is only surprising if you are fooled into thinking that superficial differences like skin color, hair type, and eye folds are actually indicative of deep genetic differences.) Imagine Africa as a big pool of genetic diversity. Spurs are flung out of it relatively recently in human history. These spurs migrate all over the place. But they are still just spurs of some initial African population — by and large, the initial Africans stay in Africa. So there would still be more diversity there than elsewhere. See also, Founder effect: populations that leave necessarily have less genetic diversity than the place they left. Such is my quite lay understanding of it, anyway. --Mr.98 (talk) 17:36, 14 July 2012 (UTC)[reply]
On an interesting note, given the historic trends of racism. The non-African population genetically closest to African populations are Eurasians. The farthest are the dark-skinned and curly-haired Melanesian Oceanians and Australian Aborigines. Just goes to show how phenotypes can be quite misleading.-- OBSIDIAN†SOUL 17:40, 14 July 2012 (UTC)[reply]
On the example of Hutu and Zulu, both groups have origins in the Bantu expansion, so that might not be the best example to use. Of course the genetic difference between two individuals depends on the specific individuals. "A given black guy and a given white guy" is too vague to be very meaningful. Pfly (talk) 03:34, 15 July 2012 (UTC)[reply]
Name for numbers in chemical notation?
Is there an overarching, dedicated name for the numbers in chemical notation indicating quantity of atoms in a molecule. For example it would refer to the numbers, collectively as a class, in water and ozone: the 2 in H2O, and the 3 in O3?--108.46.98.134 (talk) 16:47, 14 July 2012 (UTC)[reply]
I just looked quickly at some of our articles on formulas. They don't seem to name them though. They are just a ratio of the moles of the elements I think. Scholars may have named them at one point. If they haven't then I move that they be called 'Canoe ratio integers'.--Canoe1967 (talk) 17:50, 14 July 2012 (UTC)[reply]
Ha! It feels like they should have a name. I want to use it in a sentence in something I am writing but I can make do. However, I'll check back for further answers.--108.46.98.134 (talk) 18:02, 14 July 2012 (UTC)[reply]
Nope. That is the big number in front to count the number of molecules in a reaction.--Canoe1967 (talk) 18:09, 14 July 2012 (UTC)[reply]
Maybe not but "stoichiometric" is a great word to know.--108.46.98.134 (talk) 18:18, 14 July 2012 (UTC)[reply]
I think the numbers (and symbols) surrounding chemical symbols are informally known as "indices" (sing. "index", of course). See this. The number specifying the number of atoms of an element seems to be rather unimaginatively known as the "right subscript" from its relative position (see Chemical symbol).
Then there's also the Greek numerical prefixes (which must be differentiated from the Latin numerical prefixes used for temporarily naming new elements), mono-, di-, tri-, tetra-, penta-, etc. (e.g. H2O (water) is dihydrogen monoxide; O2 (molecular oxygen) is dioxygen; O3 (ozone) is trioxygen)
And lastly, there's the terms monatomic, diatomic, triatomic, etc. But these refer to the number of atoms in a molecule, not the number of atoms of an element in a molecule (e.g. H2O is triatomic, so is CO2)-- OBSIDIAN†SOUL 18:25, 14 July 2012 (UTC)[reply]
Could it safely be called the 'proportional integer suffix' type thing?--Canoe1967 (talk) 18:33, 14 July 2012 (UTC)[reply]
A single Oxygen atom is roughly more than twice the radius of a Hydrogen atom. And Hydrogen is 1/16th the relative atomic mass of Oxygen of course... so "proportional" doesn't exactly fit. :P How about just "number of atoms of an element in a molecule", heh.-- OBSIDIAN†SOUL 18:52, 14 July 2012 (UTC)[reply]
'quantitative integer suffix'? I am just trying to think of a ten dollar phrase for a 2 bit number is all.--Canoe1967 (talk) 19:00, 14 July 2012 (UTC)[reply]
What's wrong with just calling it the "subscript" ? StuRat (talk) 19:05, 14 July 2012 (UTC)[reply]
Even IUPAC called it just as subscripts at the very sacred Golden book, the Gold Book (online version). See empirical formula. You will be disappointed to see molecular formula. Simply, it represents the number of an atom or a species in one molecule of the compound under consideration. This is really an amazing question! Vanischenu mTalk 23:48, 14 July 2012 (UTC)[reply]
It should be noted though that there are two subscripts. The left subscript is the atomic number (number of protons), while the right subscript refers to the number of atoms of that element in a molecule.-- OBSIDIAN†SOUL 23:07, 16 July 2012 (UTC)[reply]
Making graphite out of wood
How can you make it? Is that technically too difficult? What happens to wood if you just put a lot of pressure into it? OsmanRF34 (talk) 17:35, 14 July 2012 (UTC)[reply]
Can you make graphite out of wood? You can certainly make charcoal out of wood, which is another form of carbon, but isn't strictly speaking graphite. Synthetic graphite is not made from wood. --Mr.98 (talk) 17:44, 14 July 2012 (UTC)[reply]
Graphite#Uses_of_synthetic_graphite has methods. That is a sub-section of the graphite article above. I would think it is more a matter of cost than difficulty. They may use it to get purer forms as well.--Canoe1967 (talk) 17:57, 14 July 2012 (UTC)[reply]
My reading of that section led me to conclude that synthetic graphite is made of Silicon carbide, not wood. --Mr.98 (talk) 18:20, 14 July 2012 (UTC)[reply]
The natural creation section says "....a result of the reduction of sedimentary carbon compounds during metamorphism." I would assume some of that was wood. It could possibly be made from wood in a lab but would probably involve more steps?--Canoe1967 (talk) 18:43, 14 July 2012 (UTC)[reply]
Right, but doesn't that probably take like millions of years? --Mr.98 (talk) 19:36, 14 July 2012 (UTC)[reply]
Wood is a very complex substance made largely of cellulose, a sugar, when dry. Charcoal is what is made be heating wood in a reducing environment, not graphite, which is made of sheets of carbon, not amorphous carbon. μηδείς (talk) 02:19, 15 July 2012 (UTC)[reply]
When I was about 10, I was given a chemistry set (something you don't see nowadays). This led me, as it did with a lot of boys, to figure out how to make gunpowder and other sorts of explosives. I aslo had a burner that used alchohol as a fuel, burning it via a wick. I found that placing a cold plate (thin pice of metal) in the top part of the flame produced copious quantities of very pure graphite in powder form adhering to the cold plate. It works on test tubes containing water too. Keit58.169.240.198 (talk) 02:16, 15 July 2012 (UTC)[reply]
That's called soot. It's not graphite. μηδείς (talk) 02:51, 15 July 2012 (UTC)[reply]
Well, there you go; you could make graphite from wood by first destructively distilling it to make wood alcohol, burning it and reducing the hot CO/CO2 with a metal. Not too efficient, but there you go. 203.27.72.5 (talk) 02:27, 15 July 2012 (UTC)[reply]
Hey wait, I didn't read that part about it working on (presumably glass) test tubes. Medeis is right. It was just soot. 203.27.72.5 (talk) 03:17, 15 July 2012 (UTC)[reply]
Yes, the black stuff on the cold plate is soot. But what is soot? In this case, almost entirely carbon with a bit of hydrocarbon. Not the same as soot from other sources such as wood. What's carbon precipitated when not heated to sublimation? Why, graphite! Keit121.221.5.163 (talk) 04:02, 15 July 2012 (UTC)[reply]
What is soot, you ask? Well, it's a mixture of hydrocarbons and amorphous carbon. Amorphous carbon is a bit of a misnomer because it's actually a mixture of graphitic and diamond-like carbon. There's no reason to think that the soot you made when you were 10 had a particularly high graphite content. Why do you think the hydrocarbon and diamond-like carbon content was low? 203.27.72.5 (talk) 04:49, 15 July 2012 (UTC)[reply]
Why did I think it had no significant hydrocarbon? - because it was a dry powder with no smell. While amorphous carbon produced by other means may have traces or significant amounts of diamond-like material, anything diamond like from this source doesn't sound very likely. Amorphous carbon is relatively quite reactive compared to graphite - the stuff I made behaved as I expected it to. Keit60.230.195.6 (talk) 13:44, 15 July 2012 (UTC)[reply]
You could just make charcoal as per above and then heat that to ~3000°C to make graphite, as is mentioned under Graphite#Electrodes. 203.27.72.5 (talk) 03:20, 15 July 2012 (UTC)[reply]
How to get graphite out of wood: Buy a bunch of pencils, split them open, and take out the graphite "leads". :-) StuRat (talk) 02:35, 15 July 2012 (UTC)
[reply]
Nope - that's part graphite and part clay. Keit121.221.5.163 (talk) 04:02, 15 July 2012 (UTC) [reply]
Do algae like or even need darkness once in a while?
If algae (in my case I'm very interested in growing Spirulina) are grown in a Photobioreactor using artificial light instead of direct sunlight, it seems obvious you'd have the highest yield when the light is always on. Evolutionary, though, algae are used to having at least a few hours of "rest" during the night. If you'd supply 24/7 light, could you be halting some important processes from happening? Joepnl (talk) 21:15, 14 July 2012 (UTC)[reply]
Judging by how close to the poles algae are known to thrive, I think the assumption that in nature they wouldn't be exposed to light 24/7 is incorrect. 203.27.72.5 (talk) 22:17, 14 July 2012 (UTC)[reply]
Ok, some algae (or may be all) possibly like 24/7 light. But to be more precise: I'm only referring to algae (like Spirulina) that only survive in high temperature areas and so have had millions of years of being able to "sleep" at least 6 hours a day and possibly have developed some good or even vital use for that period.
@71.212.249.178 from that article I can't see the reason why algae would or could need darkness? Joepnl (talk) 22:49, 14 July 2012 (UTC)[reply]
I was guessing yes on "like" and no on "need" for the tropical varieties you are interested in, but μηδείς's answer below is better, especially if you judge "like" strictly by growth rate. 24/7 sunlight for tropical algae isn't likely to cause enough metabolic stress on them to make their growth rate much less than twice that of 12 hours per day sunlight. 71.212.249.178 (talk) 02:25, 15 July 2012 (UTC)[reply]
Some higher plants need a period of darkness or red light to bloom. See photoperiodicity. There are photosynthetic reactions that proceed in the dark, see dark reactions. I am unaware of any metabolic need for darkness. μηδείς (talk)
dark reactions: "Despite its name, this process occurs only when light is available." photoperiodicity is about seasons whereas growing algae is about "seasons" with a duration of perhaps 24 hours or even less. What I'm looking for is research that says "Spirulina (dietary supplement) contains a lot less beta-carotene in a 24/7 light situation, compared to Spirulina that had 20 minutes / hour darkness. Joepnl (talk) 13:18, 15 July 2012 (UTC)[reply]
Are you implying that you believe this to be true because you have come across it before, and are looking for help finding a ref you know exists? μηδείς (talk) 16:42, 15 July 2012 (UTC)[reply]
Sorry, that was a bit unclear. I was trying to give an example of what kind of conclusion might come from such research, but I don't know if it has been done or did get to a conclusion like that. I can just very well imagine that algae use daylight to gather as much energy as possible, and switch to making complicated molecules during the night. If it's always "day", they might not make that switch resulting in a worse end product. My new hobby is to grow Spirulina, using artificial light, and I obviously don't want to torture the poor cells :) Joepnl (talk) 17:37, 15 July 2012 (UTC)[reply]
I doubt you would have any change in composition beyond an increased concentration of malic acid, which wouldn't change other things enough to bother turning off the lights for part of the time. But there is only one way to find out! Run an experiment. 71.212.249.178 (talk) 08:00, 16 July 2012 (UTC)[reply]
This poster from a recent conference may be relevant: [5]. Unfortunately, I can only find the abstract online. If you can track down an e-mail address for the presenter you might be able to get a copy of the poster or a preprint of the paper. --Amble (talk) 15:27, 16 July 2012 (UTC)[reply]
Thank you! I'll try to contact them. I also found a book on growing spirulina which says "Growth only takes place in light (photosynthesis), but illumination 24 hours a day is not recommended. During dark periods, chemical reactions take place within spirulina, like synthesis of proteins and respiration." That makes the results of your find extra interesting.
Well if it's your new hobby, maybe you want to start looking for labs where you can do basic assays like this. 71.212.249.178 (talk) 19:46, 16 July 2012 (UTC)[reply]
Not sure about the US, but it's not a $30 thing here to go to a lab and say "Hi, can I use your machine to test my sample for protein (or maybe something poisonous I haven't even heard of) content, and btw I'll be back every thursday with new samples". I'm happy to start playing with algae to try different lights, temperatures, agitation, alkalinity, water levels, nutritients, etc myself and I hope the real scientists, who have all the machines, may be able to tell me if 24/7 daylight is a bad idea and I should have a mechanism for 6/24 hours darkness. Or more. Or less. Or maybe 15 min/hr instead. Joepnl (talk) 00:13, 18 July 2012 (UTC)[reply]
I was suggesting labs where you can mail food samples for standard nutritional analysis assays which support agriculture. If there is a farm economy near you, there should be an assay lab for farmers which does mail work. 75.166.200.250 (talk) 06:49, 18 July 2012 (UTC)[reply]
Ok, that's true. I'll look for one. Thanks! Joepnl (talk) 21:06, 18 July 2012 (UTC)[reply]
What color skin did the earliest humans have?
I know of the theory stating that ancient humans migrated out of Africa, but there's something about it I don't quite understand. Would the earliest humans have had black or white skin? I'm just trying to figure out if Europeans descended from black humans, or if the black skin tone was something that evolved later in Africans to cope with the sunlight. I'm just trying to understand this better. Thank you for any and all information. InforManiac (talk) 23:18, 14 July 2012 (UTC)[reply]
Black skin would have come first, as this is important to living in Africa, or any place with bright sunlight, without getting skin cancer (clothes, hats, sunscreen, and spending most of our time indoors now serve that purpose). Europeans and (north) Asians later developed lighter skin, since, with less sunlight, skin cancer was less of a concern, and lack of UV light to synthesize vitamin D became more of an issue (vitamin D supplements now lessen this concern). StuRat (talk) 23:22, 14 July 2012 (UTC)[reply]
Thank you. That's kind of what I assumed, but I just wanted to double check. Thanks again. InforManiac (talk) 23:25, 14 July 2012 (UTC)[reply]
OK, I will mark this Q resolved. StuRat (talk) 23:27, 14 July 2012 (UTC)[reply]
Actually, the idea that skin color derived as an adaptation to protect against sunlight is an outdated but still common misconception held in increasingly low regard by researchers. Rather, like most phenotypical variation between the races, it is believed to have been (at least much more) the result of sexual selection, rather than natural selection. However, Stu is correct that the original Homo Sapiens sapiens were dark skinned. For the OP, I know of a couple of very good resources on this subject (and the general outwardly physical divergences of the races that are very accessible to even non-experts, if you're interested. Note: I've removed the resolved tag since I do not believe an accurate and full answer was given and expect further discussion to be forthcoming. Snow (talk) 00:28, 15 July 2012 (UTC)[reply]
I don't understand. Why would people in tropical climates prefer dark-skinned mates, people in temperate climates prefer medium-skinned mates, and people in arctic climates prefer light-skinned mates ? StuRat (talk) 00:58, 15 July 2012 (UTC)[reply]
They don't; it's an incremental process; people tend to prefer (but not necessarily to exclusion) mates who look like those they grew up around. This does not just apply to skin color; when you look at married couples, you find they tend to have very similar characteristics in the shape and relative size of many facial features which are counter-intuitive when you look at the overall span of human variation (things like the length of the earlobe, the width of the bridge of the nose, ect.). This and a whole ton of other well evidenced mechanisms have led a strong consensus that the differentiation of light-skinned people (and different phenotypes in general) started from random mutations (as all adaptions do, whether based in natural or sexual selection) which developed slowly thereafter. That's a cursory explanation that needs a lot more extension, I know, and I hate to bring it up and then dash out just when I got your curiosity up, but as I'm short on time and it will have to wait until later -- will comment further by tomorrow at latest, my apologies! Snow (talk) 01:16, 15 July 2012 (UTC)[reply]
That seems to just be saying that people with ancestors in hot climates having dark skin and those in cold climates having white skin is complete coincidence. That's not a very compelling argument. StuRat (talk) 02:14, 15 July 2012 (UTC)[reply]
No Snow, that's incorrect, StuRat is right. Melanin which is the pigment that produces dark skin, is well known to protect against UV radiation. ScienceApe (talk) 21:40, 15 July 2012 (UTC)[reply]
comment: The primary driving factor for dark skin was probably not skin cancer, which likely wouldn't affect you until after you had children, but the fact that UV destroys folic acid (vitamin B9) in the blood, leading to spinal bifida in pregnant women. That is, an inappropriate level of melanin in either direction leads to deformities in children.
Also, chimps have pale or at least blotchy skin. Black skin wouldn't be necessary as long as we had hair or lived in the forest, but the earliest common ancestor to humans most likely did not live in the forest, and was very likely much less hairy than modern Europeans. — kwami (talk) 23:53, 14 July 2012 (UTC)[reply]
Why would the earliest common ancestor to humans be "very likely much less hairy than modern Europeans" ? --Demiurge1000 (talk) 00:50, 15 July 2012 (UTC)[reply]
Europeans seem to be an outlier. Looking across the most divergent genetic lineages, most have very little body hair. The other famous outlier are the Ainu, also a northern (= cold, and not the environment of our common ancestors) people. — kwami (talk) 02:49, 15 July 2012 (UTC)[reply]
The primary driving factor for dark skin was its protective properties against UV radiation which cause skin cancer and other diseases. What you're saying is true, but it seems likely that it was a combination of factors. Suffice to say, having light skin in Africa and other sunny environments confers no benefit and is harmful, thus would be selected against. Aside from our head, human hair is too fine to provide much protection from the UV light on the rest of our bodies. Human populations in Africa lived in a multitude of environments, forests, deserts, jungles. It seems fairly obvious that they had dark skin. Our non-sapiens (homo) ancestors probably had dark skin as well. ScienceApe (talk) 22:04, 15 July 2012 (UTC)[reply]
I don't think this can be answered without speculation. No harm in that, so long as what is written comes from good scientific thinking, and preferably excellent sources. Has this been studied and written about by notable, suitably qualified anthropologists or similar? We also need to moderate the original question, and suggest that black and white are not the only, diametrically opposed options. There's a lot of other shades out there. HiLo48 (talk)
Of course there a lot of other shades out there. I'm just trying to figure out, generally speaking, how humanity's skin tone started and where along the line things changed. I mean, when humanity was starting in Africa, was skin tone dark and subsequently got lighter in other areas? Or did humanity's skin start out lighter, but got darker in Africa as time progressed? I thought StuRat provided me with a good answer, and I still think his answer maybe very good. I am a little confused by the conflicting opinions though. In regards to the other shades that you mentioned, File:Homo_heidelbergensis_(10233446).jpg is one of them. I just want to get a loose understanding of what happened. InforManiac (talk) 03:47, 15 July 2012 (UTC)[reply]
As far as accessible and widely well-regarded sources go, Jared Diamond wrote extensively on this subject matter in the The Third Chimpanzee, I seem to recall. That's an excellent book, by the way, that I recommend to anyone who is looking for a primer on early human prehistory and development, especially as regards animal precursors to our uniquely human traits and our later differentiations as a species. As for more technical sources, I will add some a bit later, as well as a deeper discussion of why the "trait that evolved to protect against sunlight" hypothesis is considered dubious by contemporary researchers -- would do it now but afraid I'm just out the door! Snow (talk) 00:54, 15 July 2012 (UTC)[reply]
One bad case of sunburn in Africa would make you lion fodder. The evolution of pale skin, blond hair, and blue eyes can be attributed to sexual selection. There is a pretty universal trend for females to be paler than males. μηδείς (talk) 02:13, 15 July 2012 (UTC)[reply]
Dark skin in a sunless climate causes rickets. That's a strong selective force. Since we tan, you wouldn't get bad sunburn in Africa with pale skin, you'd just get really leathery as you age. AFAIK, the preference for pale skin is a product of hierarchical societies, and presumably would not apply to foraging populations like our common ancestors: pale skin means you spend time indoors and therefore have not had a peasant's life of outdoor labor. (Men don't want to be dark for the same reason; ditto the preference for long fingernails.) I'd like to see a study that women are actually paler than men, accounting for time spent in the sun. — kwami (talk) 02:47, 15 July 2012 (UTC)[reply]
No kwami, dark skin in a sunless climate does not directly cause rickets, vitamin D deficiency can lead to certain diseases involving weak bones like rickets. Having dark skin means you synthesize vitamin D from the sun at a much slower rate, but if the individual is consuming a diet rich in vitamin D, it's not a problem. But yes, there was a selective force for lighter skinned individuals in Europe and northern Asia for this reason. The preponderance for getting a sunburn or a suntan for a light skinned person depends on a number of factors. Genetics is a big factor. Some light skinned individuals simply burn more easily than others. If I were to guess, light skinned people whose ancestry traces to Mediterranean countries have better protection from the sun than say... people from Poland. ScienceApe (talk) 21:51, 15 July 2012 (UTC)[reply]
@InfoManiac: Anatomically modern humans would have started out with the dark skin typical of Africans, Dravidians, Negritos, Melanesians (New Guineans) and Australian aborigines. Whites and Orientals show different mutations in the melanin genes leading to differently pale yellow and pink skins. From Race_(human_classification): "Scientists discovered a skin-lighting mutation that partially accounts for the appearance of Light skin in humans (people who migrated out of Africa northward into what is now Europe) which they estimate occurred 20,000 to 50,000 years ago. The East Asians owe their relatively light skin to different mutations.[62]"μηδείς (talk) 04:16, 15 July 2012 (UTC)[reply]
Thank you. I was just thinking about that. About a year or so ago, I was reading a news article about an African family, and a couple of the children had a certain albino mutation. I understand that there is more than one kind of albinism in humanity. But anyway, a few children of black Africans looked as European as could be. I don't remember the eye color, but instead of the hair being white, it was light blond. InforManiac (talk) 04:29, 15 July 2012 (UTC)[reply]
What color skin did the earliest humans have? arbitrary break 1
The Washington Post article cited for that claim basically backs up what StuRat said in the beginning about the vitamin D (but just makes hints about black skin being a defense from the sun). It also mentions potential sexual selection, so maybe there's not really a consensus on that part of the issue. 203.27.72.5 (talk) 04:35, 15 July 2012 (UTC)[reply]
Nautrally brown and blond hair also occurs among Melanesians and some Australian aborigines (though the allele responsible is different to that of Europeans). And both groups as well as the now mostly extinct Ainu are among the hairiest of the human populations. Same with epicanthic folds which actually also exist natively in Scandinavian, Northern Slavic, and Celtic Europeans as well as Khoisan-speakers of Africa. Nasal bridges vary considerably as well, being predominantly low in East Asians but high in most Native Americans, despite being descendants of the latter. And neanderthals were about as phenotypically varied as modern humans in terms of hair color at least.-- OBSIDIAN†SOUL 07:20, 15 July 2012 (UTC)[reply]
I'd like to see a ref that aborigines can have naturally blonde hair. I really can't imagine that. 203.27.72.5 (talk) 07:55, 15 July 2012 (UTC)[reply]
As a (white) Australian who has thru work met a large number of aborigines, I'm very skeptical of this. Meeting a full blood aboriginal with blond hair has not happened. The photo Obsidian posted is of Rowan McNamarra, a noted Australian child actor. In the movie Sampson & Delila, he appeared with blond hair, and in all movie promotional photos and movie associated pics he has blond hair. But in other photos he appears to have black or dark brown hair. Its worth noting that the film was about folk living with no hope. It is very common for such people to be mixed race. Full bloods tend to have more pride and self-worth - it may be that the film people had his hair dyed for that reason - the film, light on dialog as the character portrayed by Rowan is severely brain damaged from gasoline sniffing, is full of visual cues and symbology probably completely lost on non-Australians, and mostly lost on Australian white audiences. The text is a very old text. In my State, Western Australia, there is a group originating from the Carnarvon area amomgst whom blond hair is very common, and their facial appearance is a little different to other aboriginal groups. It was only recently (~20 years ago as I recall) that it was proved that a Dutch ship was wrecked on the coast about 300 years before white settlement, and surviving sailors were accepted by the locals and intermarried. That's where the blond hair came from. Samson & Delila, a low budget film acted, directed, and produced almost entirely by aboriginals was an absolutely excellent film by the way. Wickwack124.178.177.175 (talk) 13:17, 15 July 2012 (UTC)[reply]
Stick my IP into a geolocate site and see why I'm so sceptical of this. I'm in the middle of nowhere in the NT, I work with the indigenous here on a daily basis and I've never seen nor heard of anything like this. I won't rule out that one individual tribe in central Australia has a blonde trait, but it must be very rare. W203.27.72.5 (talk) 22:38, 15 July 2012 (UTC)[reply]
Do click the links. Like mentioned below, take a look at the frequency map of the blond hair trait. The areas where it is near universal in occurrence is in central (eastern) Western Australia, gradually tapering off to the coasts of the state. The northern areas of Western Australia and NT are excluded (0% occurrence). Also note that it's a sexually dimorphic and paedomorphic trait, i.e. it's more prevalent among women and children and will usually darken after puberty (again like European blonds as mentioned below). Besides the only other explanations really is that either the pictures are a massive photoshop conspiracy, several scientists have somehow confused Australia with Austria, or hair bleaching has just become a massive fad among Australian Aborigines of all ages. :P -- OBSIDIAN†SOUL 23:29, 15 July 2012 (UTC)[reply]
Just to clarify, I did click the links. The paper about an Aboriginal tribe that had blondism is convincing. That's why I said I won't rule out that there is one tribe like that. But it's not wide spread in the NT which is in agreement with your map. Also, Alice Springs is in the NT, so if there is a tribe near there with blondism, then there can't be 0% occurrence in the NT. And there is a bit of a fad for younger aborigines of both genders to bleach their hair (it's not restricted to them either), which I think is more likely the origin of some photos of young, blond indigenous Australians. W203.27.72.5 (talk) 02:19, 16 July 2012 (UTC)[reply]
It's a study, not anecdotes. Take that in consideration. The study records blondism in central Australian Aborigines, notably among the Warlpiri around Alice Springs (AFAIK, Rowan McNamara is Warlpiri. the movie itself was about them). As an Australian I think you already know too that hair color in Australian Aborigines darken with age, and the same is true even in Europeans where most blond-haired children grow up to be brown-haired adults. And lastly, see this map of its frequency among Australian Aborigines, and note that it's less common the nearer you are to the coast.
The Carnarvon shipwreck story is also actually quite old, not 20 years ago. Though the wrecks of Batavia, Zuytdorp, and Vergulde Draeck were indeed only found in the mid-20th century, they have long been known to have sunk there. It was already a folk explanation for the occurence of blond or light-skinned Aborigines even in the 19th century in Western Australia. While intermarriage between natives and survivors is indeed quite plausible (though AFAIK, no DNA tests have proven this yet as of 2012), that does not mean that it's the cause of blondism, as it's also present elsewhere where there are no wrecked European ships, much less shipwrecked Europeans.
And I'm curious, why is it so hard to accept that blond hair is not exclusive to Europeans? Claims of European admixture as a reason for European features in natives (and vice versa, e.g Scandinavian epicanthic folds, most famously Björk's) based on hearsay accounts of shipwrecks or early intermarriages lost to history is common but unless substantiated by genetic studies, most if not all of it, is bullshit. Those kinds of explanations were very prevalent in the years of scientific racism (late 19th to early 20th century, pre-Hitler). Similar shipwreck stories were also used to explain some light-haired and blue/gray-eyed Mandan of North Dakota and "Blond Eskimos" in the same time period. And their existence has been used to "prove" everything from Greenlandic Viking settlers (despite the "Blond Eskimos" actually being in western Canada) to the Mormon lost tribes simply because Europeans colonists could not accept that such traits may be present in other human populations. It has since been genetically proven in 2003 that the fair-haired Kitlinermiut individuals are not descendants of early Viking explorers of Greenland.-- OBSIDIAN†SOUL 15:44, 15 July 2012 (UTC)[reply]
Yes, I was already aware. I myself first had blond hair, according to my parents, but it was dark brown by the time of the oldest photo of myself I have - age 3. I can recall being shown an aboriginal baby by its proud parents - she had light coloured hair. They told me they fully expected it to darken.
You are quite correct - the story is old. As I recall, Carnarvon area aborigines have always told whowever would listen that they had a partly white ancestry - but nobody of academic significance listened. I don't know about modern DNA test specifically, but it was proved about 20 years ago as follows: It happens that they have an inherited blood disease extremely rare elsewhere - in fact for a long time they were the only group in teh world known to have it. The disease isn't of much consequence for most of their life, as I understand, but does shorten their life a bit. A doctor researching it became aware, or already knew, of a closely similar disease confined to the descendents of a particular africaaner family in South Africa. Blood samples were obtained from SA and it turned out the disease was identical. Dutch ship crew records were then checked and it was found that a ship called at South Africa and took on some africaaners from that same family as repalcement crew. The ship was wrecked on the Carnarvon coast. For those who are unaware, Africaaners are people resident in South Africa since the 16th century, descended from Dutch pioneers. Wickwack58.170.163.160 (talk) 16:32, 15 July 2012 (UTC)[reply]
I'm guessing you meant the occurrence of variegate porphyria (common in Afrikaners) and Ellis-van Creveld syndrome (most notably documented among the Amish who were from Holland) in Western Australian Aborigines. The conclusions of both studies were actually negative. The three (possibly four) cases of variegate porphyria documented in Aborigines (out of six documented cases overall in Australia in the span of 20 years) were the result of different mutations from the South African one. And the Ellis-van Creveld syndrome is not exclusive to the Dutch, but is common in founder populations (particularly small groups of humans with little to no contact with other populations for long periods of time). See [6] and [7] for the actual studies.-- OBSIDIAN†SOUL 17:09, 15 July 2012 (UTC)[reply]
P.S. Please don't split your posts. :P It makes it confusing to determine who wrote what. -- OBSIDIAN†SOUL 17:11, 15 July 2012 (UTC)[reply]
What parts have been split up? I don't want to mix up who wrote what. Thanks. InforManiac (talk) 19:48, 15 July 2012 (UTC)[reply]
Sorry that was meant for 120.145.151.40. Disregard it. -- OBSIDIAN†SOUL 23:29, 15 July 2012 (UTC)[reply]
H'mmm... Your references support your statements, but as I recall, they traced it to a specific SA family - the newspaper article gave the Afikaner names. It could be that it was a different disease, or it could be that the researcher who gave the conclusion I reported simply got it wrong. Wickwack120.145.151.40 (talk) 18:06, 15 July 2012 (UTC)[reply]
I think they were actually simply reporting that Western Australian Aborigines seem to share two relatively rare genetic diseases that were also prevalent in other Dutch-descended populations. And they are quite correct in that. It was that connection, after all, that prompted the latter two studies which eventually proved that it was incorrect. Kind of a false positive in other words - seemingly damning evidence at first glance, but falls apart at closer inspection. Happens a lot in scientific hypotheses actually. -- OBSIDIAN†SOUL 18:23, 15 July 2012 (UTC)[reply]
Yes, especially in the medical field. Wickwack120.145.134.211 (talk) 02:34, 16 July 2012 (UTC)[reply]
@StuRat, Arctic dwelling people, Inuit and Eskimo are not light skinned. For the most part they are slightly darker than the average European. In the spring, for obvious reasons, the face and arms, if exposed, tend to get very dark. CambridgeBayWeather (talk) 12:10, 15 July 2012 (UTC)[reply]
They look rather light-skinned to me: [8], [9], [10]. However, if darker skinned, than, say, Nordic people, that might be explained by them having relatively recently migrated from more Southern portions of Asia. StuRat (talk) 19:57, 15 July 2012 (UTC)[reply]
And where did those in the Lake Baikal region come from ? Eventually they must have had ancestors from a more southerly climate, it's just a question of if it's far enough back to have allowed for major changes in skin color since then. StuRat (talk) 21:45, 15 July 2012 (UTC)[reply]
By your 'reasoning' here, StuRat, the fact that Eskimos evolved from reptiles far enough back explains why they are green. But you seem to have inadvertently omitted your source. μηδείς (talk) 21:58, 15 July 2012 (UTC)[reply]
Even you must realize that a few hundred million years is long enough for skin color to change, while a few thousand might not be. StuRat (talk) 02:39, 16 July 2012 (UTC)[reply]
Actually mammals did not evolve from reptiles, they evolved from therapsids. Eskimos and Inuit don't have dark skin, I suppose they have darker skin than individuals from say, Norway. I can't tell if they have skin darker than people whose ancestry is from China though. ScienceApe (talk) 22:26, 15 July 2012 (UTC)[reply]
Saying mammals evolved from therapsids, not modern reptiles is, of course, the usual gotchalism you will find on the ref desk. But therapsids have long been characterized as reptiles, it depends on how you wish to define the term, and you are quite aware of the point being made. These are the synapsids you say are not reptiles:
As for the Eskaleuts, there is no evidence whatsoever that they evolved from South Asians, if you define that as India, China, and the land between. Here is a comment from an actual source:
He had brown eyes, dark skin, thick blackish hair and type A blood.
This eskimo, who lived about 4000 years ago in Greenland, also had dry earwax, shovel-like front teeth, an increased risk of going bald and the metabolism of a person who could survive in a cold climate.
And his ancestors were, to the surprise of scientists, ancient people in east Siberia rather than neighbouring Native Americans or Inuits.
All this detailed information about the long dead man has come from a study of a small clump of his hair, preserved for thousands of years in the Arctic permafrost.
And posting massive charts to further a debate about whether mammals evolved from therapsids or reptiles in response to a question about human skin colour is of course the usual of off-topic grandstanding that is frequently found here too. W203.27.72.5 (talk) 01:19, 16 July 2012 (UTC)[reply]
In the CIE Lab color space colors are represented by three parameters - lightness (L*) and a* and b* channels (the * is there to prevent confusion with the related Hunter Lab color space). L* is restricted to between 0 and 100 but the a* and b* channels, which may be positive or negative, are more complicated. Some references state they don't have a theoretically defined minimum or maximum value but note that certain combinations do not produce reaalizable colors. Others state that the minimum and maximum values depend on the color space being worked in - for instance this really gorgeous pdf explains that in the a* and b* channels are restricted to -100 to +100 if working in the CMYK space, but states that larger values can be attained in other spaces. On the other hand, this online color converter - if you inspect the javascript "under the hood" - restricts the a* and b* channels to -128 to +127. What I've not found anywhere is an explanation of how the limits on a* and b* vary, why it's exactly ±100 for the CMYK space ("by definition" is the obvious answer, but I've not seen it stated explicitly elsewhere and it isn't in the wiki article), or in general what magnitude of value is certain to be unrealizable (it's not obvious to me why that javascript only uses about ±128, but I can understand it's intuitively pointless stretching to ±500). Where could this information be found? ManyQuestionsFewAnswers (talk) 02:28, 15 July 2012 (UTC)[reply]
The article claims that its 2nd external link has "explanations" for the parameters. I think the first page of [11] may do a better job for you. You probably know that an 8-bit byte representing a signed integer has the range [-128, 127] while humans are more likely to use [-100, 100] for familiarity reasons. 71.212.249.178 (talk) 05:13, 15 July 2012 (UTC)[reply]
Thanks that's a nice link. Yes, the -100 and +100 (or -128 and +127) are obviously not completely arbitrary. But while that document has a very clear explanation of the conversion process, better than the Wiki article, I can't see an answer to my original question about what are the a* and b* co-ordinates' theoretical and practical limits (if such a distinction is meaningful!). It is clear that the human gamut extends substantially beyond a* or b* = ±100 (you can see that on this document on the diagrams from page 27 onwards) even if the CMYK space doesn't, and there are imperceptible "colors" beyond that gamut. From the diagrams it looks like b* can go above 130 and still lie in the human gamut so long as a* is approximately -30, and I can't discern where the lower boundary for b* or the boundaries for a* would lie. ManyQuestionsFewAnswers (talk) 13:35, 15 July 2012 (UTC)[reply]
There's no contradiction here. The first document says "The range of a* and b* never exceeds −100 to 100 in the cmyk color space." That doesn't mean that CMYK covers exactly that range, just that the CMYK gamut is nested in that range, as you can see in some of the images in that document. It's not considered especially important to be able to work with highly saturated colors (the colors at the edge of the human gamut). Various tools limit the gamut in various ways for various reasons—because they only care about limited-gamut output devices or because they want to store a* and b* as integers in one byte each, for example. -- BenRG (talk) 23:23, 15 July 2012 (UTC)[reply]
Yes, that all makes a lot of sense thanks, I presume the human gamut is limited by biological features that have to be measured, rather than being capable of theoretical calculation, and that explains the highly irregular shape? And yes I meant to say that the -100 to +100 was just upper and lower bounds for the a* and b* channels under CMYK, but additional restrictions apply (as you say not every pair of a* and b* values can be realized). It was the nature of the upper and lower bounds that I was particularly interested in rather the extra level of complexity about how they interact! From what you are saying, ±100 or ±127 is normally "good enough" because colors outside that range are so highly saturated that humans are not visually sensitive to them? ManyQuestionsFewAnswers (talk) 00:48, 16 July 2012 (UTC)[reply]
Humans are not visually sensitive to their differences, because incremental value changes in those outside ranges become vanishingly smaller changes in light's spectral envelope shape. 71.212.249.178 (talk) 02:06, 16 July 2012 (UTC)[reply]
This is outside my field, but I note that carbon monoxide posioning works by cripling the function of haemoglobin in the red cells of the blood (see http://en.wikipedia.org/wiki/Carbon_monoxide_poisoning), whereas cyanide posioning works by interfering with tissue cell mitochondria, and this would immediately affect brain cells (see http://en.wikipedia.org/wiki/Hydrogen_cyanide). So the mechanisms are not similar - they are completely different. This does directly contradict what Ledgard says on pages 72, 73. So I googled. See authoritative reference: http://emedicine.medscape.com/article/832840-overview#a0104 - this agrees with Wikipedia that hydrogen cynanide stuffs up mitochondria and gives details of how it does so. It is very well known, even amongst lay people, that CO affects red cells. Ratbone121.215.146.212 (talk) 10:36, 15 July 2012 (UTC)[reply]
Outside your field, but hit the spot none the less. Thanks very much Ratbone! 203.27.72.5 (talk) 11:01, 15 July 2012 (UTC)[reply]
Resolved
Yet another Higgs question
How many percent of physicists believed, prior to the recent discovery, that the Higgs boson would not be found by the LHC? How many percent believed that it didn't exist at all? It seems to me that although testing the claims of existing theories is important in science, the Standard Model's prediction of the Higgs is kind of like me predicting that the Sun will rise tomorrow. If it doesn't rise, that will be an earth-shattering discovery, but few people seriously expect it to not rise. Is this a valid characterization of the Higgs boson, or am I way off? --140.180.5.169 (talk) 06:40, 15 July 2012 (UTC)[reply]
The Higgs is necessary if the Standard Model is correct. But we already know it's at best flawed, so there is no general theoretical requirement for the Higgs tto exist. — kwami (talk) 07:30, 15 July 2012 (UTC)[reply]
I don't get it. The particle has not been confirmed to have the behaviour expected of the Higgs, so why has Hawking admitted defeat? — kwami (talk) 07:26, 15 July 2012 (UTC)[reply]
Because he's noble in defeat. And because he's reasonably sure that if it turns out later they've discovered some unpredicted particle and the Higgs is still at large, then he will still be able to get his money back from the other guy. 203.27.72.5 (talk) 07:43, 15 July 2012 (UTC)[reply]
It has to do with Hawking's old idea about information loss due to Hawking radiation, see here. It leads to the conclusion that you can never detect any fundamental scalar particle. Count Iblis (talk) 15:34, 15 July 2012 (UTC)[reply]
We don't really have any model of the world in which the sun doesn't rise tomorrow. There are several Higgsless models. Dauto (talk) 18:41, 15 July 2012 (UTC)[reply]
At least some of these "Higgsless" models have a spin-0 particle that behaves like the Higgs. It's just not a fundamental particle, but some kind of composite or weird non-particle state. The article claims "All of the alternative mechanisms use strongly interacting dynamics to produce a vacuum expectation value that breaks electroweak symmetry", which (if it's true) means that they all have a field like the Higgs field. Given that, I'd think it would be hard to prevent perturbations in that field behaving like a Higgs boson, though it might be easier to make the mass of the quasi-Higgs high enough that it couldn't be found at the LHC.
As for Hawking, even if he was confident in the correctness of that paper (which I doubt) it only applies to a fundamental Higgs, so he could still lose to a composite Higgs. I think he probably bet against the Higgs because it's the more interesting outcome, and didn't really expect to win. -- BenRG (talk) 23:47, 15 July 2012 (UTC)[reply]
Preserving body part for future genetic sequencing
How do I preserve a part of myself as of today so that it can be genetically sequenced when technologies become cheaper, more available, and more reliable? Also, is it possible to sequence the skeletal remains of a person? Many thanks. 180.254.88.42 (talk) 08:00, 15 July 2012 (UTC)[reply]
The bone marrow could be sequenced, until decayed, which, depending on conditions, could be under a year or up to several thousand years. The easiest way to preserve your DNA would be to pull a hair, with the root, seal it in a sterile container, and freeze it. Be sure to label it. StuRat (talk) 08:46, 15 July 2012 (UTC)[reply]
A researcher in my lab stores stuff in an ethanol water mixture on the field and in the lab for Later DNA sequencing. Don't know the ratio though.Staticd (talk) 11:02, 15 July 2012 (UTC)[reply]
Collecting a sample with a buccal swab (basically rubbing the inside of your cheek with a Q-tip) is another non-invasive technique, that according to this page, at least, is generally considered preferable to collecting a hair sample. If you're willing to spend a little bit of money, there are companies that are set up to help you preserve a DNA sample. Some will do things like save your sample for you at -80° C, which will presumably make the sample last longer than in a home freezer, and some companies sell chemicals for preserving the DNA sample at room temperature. To find those companies, the link above is a good place to start, or just google "DNA sample preservation". Red Act (talk) 19:01, 15 July 2012 (UTC)[reply]
The simplest way, as StuRat says, is a few strands of hair. But let me point out that your DNA sequence as of today is the same as your DNA was when you were born and will be when you die. It could in principle be used to clone you, but it does not contain any information about who you have become since you were born. Looie496 (talk) 04:07, 16 July 2012 (UTC)[reply]
The problem with hair is that it can be unreliable. If you do go with hair samples, you have to be careful to collect hairs that still have the root attached, i.e., the hairs have to have been plucked out of the scalp. Hair shafts alone will not do, so the hair found in your hairbrush will probably not be adequate, unless there happen to have been a few hairs that have been plucked out from aggressive brushing. About 40% of hair samples submitted for DNA paternity testing, for example, fail to be adequate for that purpose.[12] Rubbing a Q-tip on the inside of your cheek is also quite simple, it doesn't hurt like plucking a hair out of your head does, and it's a more reliable way of collecting a usable DNA sample. Red Act (talk) 18:41, 16 July 2012 (UTC)[reply]
I considered suggestion that, but was concerned that the bacteria also collected in that manner would lead to decomposition of the DNA over the years. Freezing would help, but, between crappy frost-free refrigerators that thaw the food frequently, and power failures, significant decomp could still occur. This seems less likely with a dry, freshly plucked hair, with the root intact. StuRat (talk) 21:01, 16 July 2012 (UTC)[reply]
Sticky robots
My son has got a bathtub toy which consists of robot shaped parts that stick to the tiles when wet. The parts are very lightweight and made of some foamy material. I was wondering about the physics behind it. Explanations can be as technical as necessary. Thanks. bamse (talk) 08:03, 15 July 2012 (UTC)[reply]
Can you provide more details? Maybe the brand so we can google it and see what you're refering to? I'm just having a hard time imagining it looks like, not having any kids (or their toys) myself. 203.27.72.5 (talk) 08:23, 15 July 2012 (UTC)[reply]
Could it contain tiny suction cups ? They tend to work much better when wet. StuRat (talk) 08:42, 15 July 2012 (UTC)[reply]
I guess these are robot-shaped versions of the more common foam bathtub letters (sample ad). The adhesion mechanism is probably a mixture of static cling (as used in vinyl decals) and soap residue. Unfortunately our article on static cling is poor, and doesn't even attempt to explain how static cling decals work. --Heron (talk) 09:39, 15 July 2012 (UTC)[reply]
Does static cling work on wet objects ? StuRat (talk) 09:41, 15 July 2012 (UTC)[reply]
Cling wrap certainly does work with wet food products, so I guess it might. 203.27.72.5 (talk) 09:50, 15 July 2012 (UTC)[reply]
Be careful not to confuse cling wrap with static cling. Cling wrap sticks by means of adhesive additives (see madsci.org [13] and [14]), while static cling is a purely electrostatic effect. --Heron (talk) 11:17, 15 July 2012 (UTC)[reply]
Hmmm...my physics lecturer said once that cling wrap was the only example of a useful purpose of static electricity in everyday life. Looks like he was confused. 203.27.72.5 (talk) 11:24, 15 July 2012 (UTC)[reply]
Pretty sure it's just adhesion due to the thin film of water, which is highly cohesive with itself, and also adheres to the foam (due to high surface area), as well as the tile. Water is actually a good adhesive, if the right material properties are met (high surface area, small forces). Here's the same phenomenon: put a toothpick on a surface, put three small drops of water on the toothpick, then another toothpick on top. If you are careful, you should be able to pick up the top toothpick, and the bottom one will stick to it via water adhesion. Further links on water adhesion here: [15] and here [16]. (I would not personally use "static cling" to refer to this effect, even though the adhesive/cohesive forces in water have to do with electrostatic forces on the molecular level...) SemanticMantis (talk) 15:48, 15 July 2012 (UTC)[reply]
Thanks for all the replies. Indeed these seem to be like the bathtub letter mentioned by Heron. No suction cups (unless they are microscopic), they stick both on the bathroom tiles and on the bathtub and work with plain water and soapy water. If they get dry, they fall off the wall, but can be reused if made wet. The adhesion/cohesion explanation sounds very plausible to me. bamse (talk) 19:01, 15 July 2012 (UTC)[reply]
Lightning captured in nuclear explosion photograph
I came across this popular image shown in many topics related to nuclear weapons. I have noticed there is wierd lightning on the center of the picture, connecting ground and skies, and I can't manage to find out what caused it. What is that lightning ?
What is the English word for this office lamp with a "swan neck" backbone (you can move it in any direction - and it stays). Grey Geezer 09:30, 15 July 2012 (UTC) — Preceding unsigned comment added by Grey Geezer (talk • contribs)
The bendy bit is called a gooseneck, so the lamp is called a gooseneck lamp. --Heron (talk) 09:34, 15 July 2012 (UTC)[reply]
I have a floor lamp like that, and just call it the "adjustable lamp". StuRat (talk) 09:35, 15 July 2012 (UTC)[reply]
I'd call it a gooseneck lamp as well. Though I'm not sure what this has to do with science. Dismas|(talk) 09:45, 15 July 2012 (UTC)[reply]
Gooseneck - sure! Thanks! Case closed. Grey Geezer 10:39, 15 July 2012 (UTC) — Preceding unsigned comment added by Grey Geezer (talk • contribs)
follow-up question from someone else What is the most common manufacturing technique used to make a lamp like this possible? What's in the shaft? 69.243.220.115 (talk) 13:38, 15 July 2012 (UTC)[reply]
The stem of the lamp consists of a series of rings that act as little joints which allow each ring to articulate and move a small amount, say a millimeter. With lots of little joints on lots of little rings, the whole thing bends and twists. --Jayron32 19:39, 15 July 2012 (UTC)[reply]
(edit conflict) One common construction is to have a spiral of metal (or sometimes plastic) in which each winding overlaps and links (but is not rigidly attached) to the adjacent ones. The whole thing can flex because the amount of overlap can change a little at each winding. DMacks (talk) 19:40, 15 July 2012 (UTC)[reply]
Looking at mine, it seems to use rings, not a spiral. There must be some type of catch on the inside of each ring to keep it from sliding completely off the adjacent ring. StuRat (talk) 20:55, 15 July 2012 (UTC)[reply]
Mine appears to use double rings, one set on the outside, and one on the inside, like so:
Or maybe the outer rings and inner rings are combined into one, like so:
______
\ /____\
______ CROSS SECTION
/____\ /
I do find myself wondering how they assemble such a thing, though (must involve folding down some flaps, forcing rings together, then folding the flaps back up, like in a molly bolt):
______
\ /___/\ <- Fold down flaps
______
/____\ \/ <- Fold down flaps
What are the advantages and disadvantages of classic weights/resistance training with cardio vs circuit training? 176.27.222.99 (talk) 13:03, 15 July 2012 (UTC)[reply]
We can't give medical advice, and this is a perfect example why. The answer depends strictly on several separate results of a physical examination. Ask a professional trainer certified in exercise planning. 71.212.249.178 (talk) 19:41, 15 July 2012 (UTC)[reply]
Im not asking for medical advice. Im asking for a scientific answer to my question which is purely academic. Its up to the person answering to give an academic answer rather than medical advice, which cant be hard since im asking a very generic question. A question asking for medical advice would be alot more specific. 176.27.222.99 (talk) 20:16, 15 July 2012 (UTC)[reply]
This is hardly a medical advice question... although the usual caveats about checking with your doctor before starting an exercise regimen... There's a lot of discussion and debate about cardio versus strength training. Generally strength training is going to help build fast twitch muscle and from an aesthetic standpoint, create more definition and possibly (depending on a lot of things) size. Cardio will improve other aspects of your fitness.
There's a lot of dogma around exercise and nutrition and so you may hear people who are absolutist about their particular position. Ultimately you have to decide for yourself. Shadowjams (talk) 20:33, 15 July 2012 (UTC)[reply]
What amount of the alcohol in mouthwash is absorbed by the mucosal membranes etc in your mouth? Assume the mouthwash is 20% a.b.v. and that the mouthwash is swirled around your mouth for 30 seconds (or show that these are unreasonable assumptions)— Preceding unsigned comment added by Egg Centric (talk • contribs)
I'll assume this is not a medical question and not a homework question. I found no useful links at Google search. Wikipedia's info in the buccal membrane inside the mouth seems very sketchy, with only a passing reference in Oral mucosa, which is a very short and uninformative article. Someone studying dentistry or oral surgery could perform a real service by improving our coverage of the buccal membrane and oral mucosa in general. Caffeine gets readily absorbed through the oral mucosa, and sugar is also absorbed slowly. As for alcohol, all I found on the web was that drinking alcohol regularly for a long time can lead to cancer of the oral mucosa, as can using a high alcohol mouthwash, even without swallowing alcohol. Edison (talk) 17:43, 15 July 2012 (UTC)[reply]
It depends on the proportion swallowed. 71.212.249.178 (talk) 19:47, 15 July 2012 (UTC)[reply]
At least in the United States where I live, any mass-produced mouthwash uses denatured alcohol, so you can't get drunk off of it without poisoning yourself. --M@rēino 21:09, 16 July 2012 (UTC)[reply]
Is aging slowing as life expectancy increases?
Life expectancy has increased greatly over the last century. However, has aging slowed down at all? I know in the middle ages for example people were considered grown and ready for marraige at around 15 years of age. Were these 15 years olds more developed than modern 15 year olds? Has puberty and growth slowed down at all?
Has menpopause got any later? What are the reasons for this? Is people in developed countries having children later an evolutionary pressure, and how do you expect this will affect evolution of H. sapiens in the near future?--178.167.159.126 (talk) 16:51, 15 July 2012 (UTC)[reply]
This is based on hearsay, but people are apparently reaching puberty faster now than before. 109.97.146.146 (talk) 17:39, 15 July 2012 (UTC)[reply]
There is evidence that women reach menarche (age of first period) earlier by 2 - 3 months per decade. This page has some interesting cross-cultural graphs. As to why this should be, I would speculate that it is a combination of factors: improved nutrition and healthcare being a large factor, and possibly oestrogenic chemical environmental residues, whose impact is still unknown. --TammyMoet (talk) 17:55, 15 July 2012 (UTC)[reply]
I can't access your article: do they control for quality of nutrition? I came across a study a while back that showed that, among upper-class girls (ie. those who can be assumed to have reliable access to quality food), the age of menarche hasn't changed in the past 400 years. --Carnildo (talk) 01:28, 18 July 2012 (UTC)[reply]
(ec) Yes, puberty is getting earlier. The biggest factor causing this is apparently less starvation, as one of our starvation responses is to delay the onset of puberty. StuRat (talk) 17:56, 15 July 2012 (UTC)[reply]
One of the things about life expectancy that is a bit of a fallacy is that people used to die in their 40s and 50s, and only recently began living into their 80s and 90s. This is true to a point, that is people do live longer, a bit more than they used to, but it isn't as simple as that. Much of the increase in life expectency in modern developed nations actually comes from two situations:
a) Children living to maturity
b) Women surving childbirth
In his book A Little Commonwealth, John Putnam Demos did a detailed demographic study of Plymouth Colony. Now, this was a 17th century colony of people, mostly first generation imigrants, living in a society without modern medicine and modern nutrition and the like. What he found was that males who reached their teens lived nearly as long in the 1600s as they do today, as did women who made it to their 50s. That is, if a man could make it out of childhood, or a woman could make it to menopause, their was not a dramatic difference in lifespan 400 years ago than today. It turns out the risks to long life are mostly childhood disease and pregnancy complications. If you made it through those landmark events, you stood as good of a chance of living just as long then as now. So when you see lifespan figures from the past, understand that the numbers are skewed a lot by those issues. Seeing that, at some point in history the average lifespan was, say, 50 years old doesn't mean that lots of people died in their 40s. What it means is that lots of people died as young children and it dragged the average down a lot. Now, there is a big caveat in Demos's study and that is that the situation is very different in cities, where sanitation really lowered lifespans of people. Plymouth was a small, agrarian society where the problems of urban sanitation don't create the close proximity necessary to spread epidemic disease like black plague, cholera, typhus, and the like. If there are three things which have raised life expetency more than any other in the modern world it has probably been, in order a) vaccinations against childhood disease b) prenatal care and c) urban sanitation. Everything else has made small, incremental advances, but those are the three biggies. As far as directly answering the question regarding age of maturity at both ends of life (puberty and old age); a lot of that is cultural as much as anything else. As others have noted, for health reasons it seems people are reaching puberty earlier than before, but for nearly all of history 15 years old has been an age when a person has reached biological sexual maturity. That does not mean that a person is emotionally or culturally considered ready for adulthood, parenthood, or sexual activity. Many of those things are determined by one's culture: in one place and time, 15 year olds are considered full adults, while in other places and times the age may be younger or older. --Jayron32 18:43, 15 July 2012 (UTC)[reply]
Specifically, water treatment and sewage treatment seemed to be absolutely critical to increasing the average lifespan, by stopping the spread of water-borne diseases.
I believe many measures of life expectancy also exclude infant mortality. StuRat (talk) 20:37, 15 July 2012 (UTC)[reply]
They do. But that only removes people who die before their first birthday. 5 year-olds are not infants, and many of them died of things like measles and scarlet fever and polio, diseases that in the modern developed world have been essentially eradicated by vaccines. --Jayron32 03:07, 16 July 2012 (UTC)[reply]
This is certainly the argument of e.g. Ivan Illich, who felt that improvements in sanitation were a larger factor in improved human life expectancy and wellbeing than the medical profession had provided. (Not saying I agree with him, am curious why he didn't rate progress in things like vaccination so highly, but that what StuRat and Jayron say is sensible.) ManyQuestionsFewAnswers (talk) 00:38, 16 July 2012 (UTC)[reply]
There are some specific aspects of aging which now seem to happen more slowly:
1) Skin aging. Due to spending less time in the sun, wearing more clothes, using sunscreen, moisturizers, etc.
2) Dental wear (distinct from other dental problems). Food used to contain bits of sand and such, which wore down the teeth, but with modern processing, our food doesn't contain this. Also, people formerly used their teeth as general tools, for cutting materials and such, but now we use external tools (although I have to admit to occasionally biting open a blister pack/clamshell, like the one containing the scissors needed to open blister packs/clamshells :-) ). StuRat (talk) 20:46, 15 July 2012 (UTC)[reply]
I'm pretty skeptical of number 2 — do you have a source for that?
To add my own speculation on top of speculation, I think a lot of people show less "visible signs of aging" than you see in movies of people of the same age in, say, 1940 or 1950, in large part because most people now don't smoke. But I don't have a source for that (would be interested to know if someone does). --Trovatore (talk) 22:18, 15 July 2012 (UTC)[reply]
"Foragers tend to have a lot of wear at a young age, while later agriculturalists have less wear." [17]. StuRat (talk) 01:29, 16 July 2012 (UTC)[reply]
"This type of wear may have resulted from using the teeth to soften cedar bark fibres for the weaving of blankets." [18]. StuRat (talk) 01:32, 16 July 2012 (UTC)[reply]
The question was about trends "over the last century". There weren't many foragers left by then, at least in the developed world. --Trovatore (talk) 01:31, 16 July 2012 (UTC)[reply]
The OP didn't ask us to limit our responses to the developed world (they did mention it in one question, but I took that to mean they are only asking about the developed world with respect to age at childbirth). StuRat (talk) 01:34, 16 July 2012 (UTC)[reply]
I think there were very few foragers left anywhere in the world, at least percentage-wise. The hunter-gatherer lifestyle does not support large populations. --Trovatore (talk) 01:37, 16 July 2012 (UTC)[reply]
Chimmney-like thing in boats
How is called this chimmney-like thing that are found in many boats?--90.165.112.194 (talk) 18:12, 15 July 2012 (UTC)[reply]
It's called a "Dorade box", and it's for allowing air in below deck while making sure no water gets in. Dominus Vobisdu (talk) 18:27, 15 July 2012 (UTC)[reply]
Why is it such a boat cliche to have the tube bend over to protect from rain when chimneys on land often a little hat over it? (though Essex House does do the flue turned over thing) Do they ever put a jog in the flue so the rain lands in a sump? I thought of that when I was ~13. Sagittarian Milky Way (talk) 23:57, 16 July 2012 (UTC)[reply]
The 90-degree bend is so that the forward motion of the ship will force air into the intake, not to keep rain out. --Carnildo (talk) 01:36, 18 July 2012 (UTC)[reply]
How long does it take for wind turbines to pay for themselves?
That first link also doesn't seem to include the land purchase price, which can be significant for a large wind farm (especially if they need a buffer zone, as neighbors probably don't want massive windmills right on their fence). StuRat (talk) 20:32, 15 July 2012 (UTC)[reply]
I hope only the footprints of the turbines take land area economically, e.g. from agriculture. 71.212.249.178 (talk) 22:27, 15 July 2012 (UTC)[reply]
Your question doesn't make sense to me. Don't they pay for themselves by generating profits? W203.27.72.5 (talk) 22:19, 15 July 2012 (UTC)[reply]
Yes, but in how much time? Can you get the spreadsheet to work? I better fire up windoze. 71.212.249.178 (talk) 22:27, 15 July 2012 (UTC)[reply]
The House of Lords document is not about dollar terms. Building anything requires energy, energy for melting aluminum, mining the metals, shipping parts, etc. The document tells the reader how much energy is required to build each type of plant, and how long the then built plant would have to operate to create the amount of energy required to have built it in the first place. Unique Ubiquitous (talk) 22:39, 15 July 2012 (UTC)[reply]
That document is looking at it in a really useless way. For a start, you get that energy back in the future, so it's worth less to someone now than the energy that's all going into it. W203.27.72.5 (talk) 01:06, 16 July 2012 (UTC)[reply]
Also, if that's the case, then taxes, salaries and profits don't cost any energy (though they may be used to spend on things that do). W203.27.72.5 (talk) 01:08, 16 July 2012 (UTC)[reply]
Agreed, the given statistics would only be of importance where energy was very scarce and needed to be direly mananged. And to Sturat, wind turbine land is available for dual purposes, though even if it weren't a wind farm would only consume as much land as an equally productive coal plant - and thats excluding the land required for the mining. Unique Ubiquitous (talk) 01:21, 16 July 2012 (UTC)[reply]
I've been to a wind farm and they told me each turbine lasts about 20 years, and the first 10 years are spent paying for itself.--92.251.194.63 (talk) 02:01, 16 July 2012 (UTC)[reply]
Hm, I got two years for a $1,000,000 2MW turbine from the NREL spreadsheet above, but this windustry.org spreadsheet suggests that a pair of GE-financed 1.5 MW turbines costing $6,300,000 pay for themselves as soon as the contracts are signed.
"a standard two-megawatt turbine costs about 2.75 million euros to build and earns about 275,000 euros a year for the sale of electricity at the market rate. But that revenue can rise to about 500,000 euros with special state-mandated incentives paid by utilities as a premium for renewable energies. In many countries, wind producers are receiving feed-in tariffs -- premiums above the market rate as a bonus for renewable energy." (NYT, 2009)
"A turbine with a feed-in tariff contract receives 13.5 cents a kilowatt hour, or $135 a megawatt hour for its output. (One megawatt is 1,000 kilowatts.) A two-megawatt turbine running at full speed, 24 hours a day for a year, would therefore produce 17,520 megawatt hours of power. Assuming it operates at 35 per cent capacity, in the real world it will produce about 6,132 megawatt hours. At $135 a megawatt hour, that means revenue of $827,820 annually. Assuming a more conservative capacity of 27 per cent, it would generate revenue of $638,604. Offsetting the revenue are very high capital costs. The cost of purchasing, erecting, financing and connecting a turbine runs at about $2,500 a kilowatt of capacity, although prices are declining and in some cases are now below $2,000 a kilowatt, according to CanWEA. That means a two-megawatt turbine costs $4 million to $5 million to install. Included in the cost is rent of more than $19,000 a megawatt — paid to the landowner where the turbine is erected. That works out to about $38,000 annually for a two-megawatt turbine." (Toronto Star, 2011)
http://bloomberg.com/energy suggests $135/megawatt-hour is way too high even in Canadian dollars. I haven't seen electricity over 35 USD/megawatt-hour all summer, even in Houston. Perhaps the much more expensive Canadian turbines produce high grade electricity. 71.212.249.178 (talk) 04:48, 16 July 2012 (UTC)[reply]
Not sure what those Bloomberg numbers mean as the average residential price of electricity in the US is $119.50/mWh [19]. Unique Ubiquitous (talk) 05:35, 16 July 2012 (UTC)[reply]
Ah, that's the difference between wholesale and retail, and explains the Canadian figures. Thank you. The mark-up supposedly pays for grid transmission, local distribution, maintenance, and customer service. The Canadians probably pass the retail along as a subsidy after taxing the heck out of the turbines. I'm guessing there could be quite a bit more competition in the turbine marketplace, but they are being installed as fast as manufacturers can make them. 71.212.249.178 (talk) 05:57, 16 July 2012 (UTC)[reply]
The House of Lords report is based on energy return on energy invested: ie. it takes 1.1 years for the average windmill to generate as much energy as went into producing it. --Carnildo (talk) 01:42, 18 July 2012 (UTC)[reply]
Hydrogen critique?
Even liquid hydrogen has less than a third the energy density of gasoline.
So, I've been really interested in hydrogen vehicles recently, and if one day in the future I can afford one, I hope to buy one (which might be a challenge living in Canada, but one step at a time). One thing I've noticed though, in the criticism section of our Wikipedia article is that critics claim that "hydrogen vehicles will emit more carbon than gasoline vehicles (in their lifetime)". How is this so? Is it because the number one way that companies produce hydrogen is through using fossil fuels? Electric cars face the same thing, except worse, considering the source of their electricity mainly comes from fossil fuels too. But wouldn't a simple solution to harnessing hydrogen be electrolysis, perhaps using solar electricity (which can even easily be done at home)? And what other problems (besides cost) could the hydrogen car face? Thanks, 64.229.5.242 (talk) 19:59, 15 July 2012 (UTC)[reply]
Storage for hydrogen is remarkably difficult. It embrittles metals in which it is stored or pressurized. There are some ceramics virtually impervious to damage from this, and systems to compensate for it, but they are fragile, heavy, and bulky and thus unsuitable for transportation. Hydrogen also has a colorless flame which is often considered a safety hazard. You may be interested in http://windfuels.com, http://airfuelsynthesis.com, page 28 here and the conclusions of this paper. 71.212.249.178 (talk) 20:24, 15 July 2012 (UTC)[reply]
As far as creating hydrogen at home using solar power, this wouldn't be practical. A huge array of solar panels would be needed, since solar cells are rather inefficient. StuRat (talk) 20:18, 15 July 2012 (UTC)[reply]
Solar is expected to be competitive with wind after 2020, depending on how well Makani Power does. 71.212.249.178 (talk) 20:24, 15 July 2012 (UTC)[reply]
One man a few years ago had an array of solar panels on his roof, and it could easily power his house. I doubt that a "large array" would be needed to split water, which only needs at least 1.23V. 64.229.5.242 (talk) 20:54, 15 July 2012 (UTC)[reply]
Voltage has nothing to do with it. You can get any voltage you want out of an arbitrarily small array of solar panels, but then the current is so low that won't generate hydrogen at a sufficient rate to do anything with it. There's also the problem of liquifing the hydrogen once you generate it. If you're burning the hydrogen as the BMW Hydrogen 7 does, you will only get something like 30% of the generated solar power back as kinetic energy in the movment of your car. If it uses hydrogen fuel cells, then it should be about the same efficency as an electric car (since you're basically just using the generated hydrogen as a battery. The solar panels themselves take huge amounts of energy to create (due to the zone refining required to get pure silicon), which is almost always sourced from fossil fuels. Electric cars that use batteries also have the advantage of storing the waste energy from braking, which even your hydrogen fuel cell car won't do. W203.27.72.5 (talk) 22:13, 15 July 2012 (UTC)[reply]
A house uses less electrical energy than a car in use, unless it has electrical A/C or electrical heating on, in which case solar panels on the roof aren't likely to get the job done. (The fact that everybody doesn't already power their houses entirely with roof solar panels is evidence enough that this isn't practical.) StuRat (talk) 21:24, 15 July 2012 (UTC)[reply]
Spot on. I wish greenies would understand that. Wickwack121.221.217.187 (talk) 11:04, 16 July 2012 (UTC)[reply]
I guess solar is already technically competitive with wind in the middle of the day peak during the summer, but not enough to make investing in solar a better idea than investing in wind for probably at least a decade. 71.212.249.178 (talk) 21:31, 15 July 2012 (UTC)[reply]
Also, any new technology could be responsible for lots of carbon emissions, if it results in us dumping our current fleet of vehicles in junkyards. We should wait until each vehicle is due for replacement, before switching to a new technology, or, where possible, modify our current vehicles now, to use more efficient technology. StuRat (talk) 20:22, 15 July 2012 (UTC)[reply]
Well, no - carbon in fuel used until scrapping has already been emitted, carbon emitted during manufacture (eg in powewr stations powering the factories) has already been emitted. However it is right to keep them in use until worn out, as making new stuff causes more emissions, as others have said. Wickwack121.221.217.187 (talk) 11:02, 16 July 2012 (UTC)[reply]
That's exactly what I meant. I didn't think it necessary to explain it all explicitly. StuRat (talk) 20:51, 16 July 2012 (UTC)[reply]
Curently, the vast majority of hydrogen is produced by steam reforming of methane, a process that emits carbon dioxide: to be precise, exactly as much carbon dioxide as if you'd burned the methane. Since the hydrogen produced has a lower energy content than the source methane, a hydrogen-burning car consumes more methane to go a given distance than an equivalent methane-burning car. A car powered by a hydrogen fuel cell may be different, as the increased efficiency of the fuel cell may offset the energy lost in producing the hydrogen. --Carnildo (talk) 01:52, 18 July 2012 (UTC)[reply]
The efficiency of hydrogen electrolysis from water has increased from about 35% to almost 80% in the past decade, due mostly to an iron-ruthenium catalytic anode plating developed by Schrodinger equation-based simulations of catalytic properties. Since, several additional improvements have occurred. 75.166.200.250 (talk) 19:57, 18 July 2012 (UTC)[reply]
Science disciplines
Are Biology and Chemistry subsets of Physics or are they completely different but have overlaps?176.27.222.99 (talk) 20:13, 15 July 2012 (UTC)[reply]
I'd call them separate, and biologists and chemists would likely agree, but a physicist might disagree. StuRat (talk) 20:16, 15 July 2012 (UTC)[reply]
Biology is a separate subject. Chemistry really is a branch of physics. Dauto (talk) 20:22, 15 July 2012 (UTC)[reply]
Yes, they overlap. The difference is that chemistry not only overlaps with physics, it is pretty much completely covered by the definition of physics (which studies the basic property of matter including its chemical properties). Dauto (talk) 20:37, 15 July 2012 (UTC)[reply]
The gas cloud that collapsed to give rise to our Sun, the Earth and the othe planets also gave rise to you and me. One can, in principle, formulate any biological question in terms of only the fundamental laws of physics, as a summation over the initial conditions of that gas cloud. Count Iblis (talk) 22:52, 15 July 2012 (UTC)[reply]
You won't have to go that far to defend the point that biology is chemistry constrained by existing living beings. You can rest assured that everything that's within a living being is explained by chemistry/physical/mathematical concepts. What else could someone expect? OsmanRF34 (talk) 23:47, 15 July 2012 (UTC)[reply]
Then do it or show where it has been done. "What can be asserted without proof can be dismissed without proof" - Hitchens. μηδείς (talk) 23:21, 15 July 2012 (UTC)[reply]
I don't know if the question is whether or not one can be derived from the other so much as whether they are considered separate sciences. When I studied chemistry, it was taught by the School of Physical and Chemical Sciences. It's since become the School of Physics, Chemistry and Technolgy, and includes IT subjects. Biology was always taught by the School of Life Sciences. W203.27.72.5 (talk) 23:12, 15 July 2012 (UTC)[reply]
@OsmanRF34: Assuming I understand your comment, can you please explain to me the meaning of sexual selection using only chemical terms? (Forgive me if I misunderstand you.) The issue here is not that nothing in biology contradicts chemistry. The issue is that the concepts of chemistry are insufficient to express the truths of biology. Again, I refer to supervenience. μηδείς (talk) 04:04, 16 July 2012 (UTC)[reply]
Well, when one collection of genetic molecules loves another collection of genetic molecules very much, and the enzymes are right and they have been to a sanctuary to witness to their friends and families that they sincerely believe they might belong to organisms in at least the same genera, then they may react in such a way as to replicate in disjoint pairwise parts, and if they are lucky, the replica might be pH-balanced and otherwise viable within the host organism's cytoplasm.... 71.212.249.178 (talk) 04:55, 16 July 2012 (UTC)[reply]
David Goodstein referred to biology, chemistry and physics as being "decoupled" from one another (this idea is probably not original to him). Point is, there is plenty that can be done in biology without any knowledge of chemistry, and plenty that can be done in chemistry without any knowledge of physics. The three basic, hard sciences absolutely overlap, but parts of them can be separated. With regard to what Medeis mentioned about the genetic code, I think the more important lesson about it is that biologists were able to do a tremendous amount of new science once the genetic code was deciphered, but most of the new discoveries required no understanding of the chemical nature of Watson-Crick base pairing. It's the same way a programmer can write software for your computer without knowing why a transistor works, or how a mechanic can tell that you need a new car battery even though he couldn't build one from scratch. Although I guess these are all just more advanced versions of "how does a pencil know to fall if it doesn't understand gravity?" Regardless, I'm still waiting for the complete formulation of biological laws starting from the standard model of quantum physics. Someguy1221 (talk) 05:17, 16 July 2012 (UTC)[reply]
I agree with Someguy1221 and disagree with μηδείς. Fundamental laws can give rise to effective laws in some regime and it is then possible that some phenomena are fully described by these effective laws. What then happens is that in a counterfactual situation where the fundamental laws would have been slightly diffent, the old effective laws still exist but it is located at a slightly different scale. So, in the programmer example of Someguy1221, if the fine structure constant were slightly different, electrodynamics would have been affected, but you could still have slightly different people writing the same computer programs on slightly different computers. The program would still be the same, so to understand the properties of the program, why it did get written etc. etc., it seems that the fundamental laws don't play any role at all.
But, of course, the existence of the effective laws and is properties can in principle be derived from the fundamental laws. Within physics itself one frequently encounters this, e.g. a lot of thermodynamics is independent of statistical physics in the sense that the laws of thermodynamics don't depend on the underlying miscoscopic model of the substance. Also, while the value of thermodynamical variables obviously do depend on the microscopic model, at the critical point they can behave in a singular way, and that singular behaviour is to leading order the same for many different materials (e.g. the heat capacity of water at its critical temperature diverges in exactly the same way as nitrogen near its critical temperature). The explanation for this universal behavior is that the different materals at their different critical temperatures are described by the exactly same effective model. Count Iblis (talk) 16:05, 16 July 2012 (UTC)[reply]
Perhaps you are confusing the history of the universe itself regardless of our knowledge of it with science as a body of knowledge. No one is claiming that something that is not chemical or physical occurs in biology. The OP's question, however, was whether biology is a separate science from physics. It is. It is a separate set of concepts which cannot be derived a priori from physics. I see you have studiously ignored that point entirely, making unsupported assertions about biology while speaking of thermodynamics. Again, I challenge anyone to show where any concept like ecological niche or sexual selection has been defined in the terms of chemistry or physics, or contradict the fundamental and striking fact that the genetic code is chemically arbitrary. μηδείς (talk) 19:13, 16 July 2012 (UTC)[reply]
"Randomness in quantum theory not only here to stay, it is apparently the way to go. 'Its appeal is its fundamental nature and broad range of implications: knowing the precise configuration of the universe at the big bang would not be sufficient to predict its entire evolution, for example, in contrast to classical theory,' says Tittel."
Terence E. Stuart, Joshua A. Slater, Roger Colbeck, Renato Renner and Wolfgang Tittel, 'Experimental Bound on the Maximum Predictive Power of Physical Theories', Phys. Rev. Lett. Volume 109 Issue 2 DOI:10.1103/PhysRevLett.109.020402 cited in Does Play Dice With The Universeμηδείς (talk) 17:53, 17 July 2012 (UTC)[reply]
Mathematical Formulation of the Standard Model
From a mathematical point of view(I am a mathematician). Looking at the description of the Standard Model (mathematical formulation), it looks quite ugly. Compared to lets say the Maxwell equations or Einstein's field equations which look mathematically aesthetic, the formulation of the standard model seems to be a huge mess. Is there a simpler formulation than in the article available or has there been any research related to simplifying the formulation (lets say by basing the theory on the fewest possible "simple" axioms)? I noticed that physicist do most calculations and derivations much more sloppy (eg. Renormalization) than it is done in mathematics (this is also mentioned in the article Yang–Mills existence and mass gap). Is there any research on a mathematical rigorous formulation of a theory (standard model or something different)? --helohe(talk) 23:57, 15 July 2012 (UTC)[reply]
Yes, but none of them come anywhere near the predictive power of the Standard Model, especially now. See unified field theory. You might be more interested in studying electroweak interactions, where there is still a rich opportunity for theory being tested by experiment. 71.212.249.178 (talk) 01:15, 16 July 2012 (UTC)[reply]
Isn't the OP just talking about if you had the same theory but just formulated it in a neater, more rigourous way? I can't see how that would make it less predictive. W203.27.72.5 (talk) 01:41, 16 July 2012 (UTC)[reply]
The Standard Model (with neutrino mass) consists of relativistic quantum field theory plus:
Some "extra dimensions" (perhaps not literally) that are curled up into a shape whose symmetry group is the group of (3×3, 2×2) block-diagonal unitary 5×5 matrices, called the SM gauge group.
A fermionic field that is chiral (only one of the two circular polarization directions exists) and transforms in the 16-component representation of SO(10), considered as a supergroup of the gauge group in the obvious way (i.e., it occupies those "orbitals" in the "extra dimensions"). Also, two more copies of the same field, and the CPT duals of all three.
A scalar field in a particular two-component rep of the gauge group, and its CPT dual.
All possible renormalizable symmetry-respecting interactions between those components, with seemingly random strengths.
From that, after a fair amount of manipulation, you get all the usual particles with their weird charges and interactions.
Although the strengths looks kind of random, they aren't totally random. The particle masses vary over a much wider range than you'd expect (the masslessness of the photon and gluons is a prediction, though). The strong force CP-violating angle is consistent with zero, for no apparent reason. It's not clear why the gauge symmetry is what it is, or why there are three copies of the fermions, or why they seem to only exist in those orbitals. And that scalar field seems kind of out of place.
No rigorous axiomatic formulation of the Standard Model has been found, and it's not for lack of trying. That's probably because it genuinely doesn't have one. -- BenRG (talk) 02:02, 16 July 2012 (UTC)[reply]
July 16
How long can you thrive/survive on water and calories?
My understanding is:
Without water you can survive a day or two.
With water but no food you can survive maybe a month or two.
With water, calories, and protein, you can thrive for about a month before symptoms of scurvy. It's not clear from the article how long you could survive (in ill health).
So I wonder:
What about the intermediate case of water and calories but no protein, e.g. sugar water but nothing else?
This depends on the initial body mass index. Fat will be converted to calories. Protiens (e.g. muscle) will be recycled (to e.g. bile ducts) but lost over time without replenishment. The correct answer depends on the body mass index distribution and fat proportion of the population. 71.212.249.178 (talk) 01:11, 16 July 2012 (UTC)[reply]
Well, what I meant was, that there would be no caloric deficit. Or are you saying protein deficit would still trigger depletion of fat? --174.118.1.24 (talk) 01:24, 16 July 2012 (UTC)[reply]
Yes, thanks, they are relevant but as you say, no timelines. --174.118.1.24 (talk) 03:43, 16 July 2012 (UTC)[reply]
Don't forget salt. That becomes a problem long before protein does. --Tango (talk) 02:41, 16 July 2012 (UTC)[reply]
I see! Thanks for pointing that out. I should also then wonder if there is any other deficiency that I haven't considered that manifests before protein? --174.118.1.24 (talk) 03:43, 16 July 2012 (UTC)[reply]
The list of deficiencies that you will suffer from in a very short time would be very long. Since I can't find any examples of people who have tried to live on that diet, I can't say how all of those issues interact, but I agree with Tango that the most serious is Hyponatremia. Sodium (and also potassium) are very important in your nervous system and are constantly flushed from the body as they're highly water soluble. They're almost never in short supply, but with the constraints you've placed, your neuron function would be impaired very quickly. 203.27.72.5 (talk) 04:03, 16 July 2012 (UTC)[reply]
The OP suggestion that you will not survive beyond two days without water is untrue, see this for just one example. As for surviving on water with no food, 2 months seems about right as (unfortunately) seen in Bobby Sands self imposed hunger strike. Richard Avery (talk) 09:50, 16 July 2012 (UTC)[reply]
Sands and the other hunger strikers ingested water and salt. They were young men in good health until their hunger strike, so probably able to live as long as anyone could from the general population. They generally died in the tenth week of the strike; the seventh week was the worst. They certainly would have lasted shorter periods, and had a more unpleasant time, but for the salt. John M Baker (talk) 18:35, 16 July 2012 (UTC)[reply]
This also implies that, if he is a young man in good health, someone ingesting only sugar water and salt could survive for more than 10 weeks, maybe quite a bit more, although presumably he would start to suffer health effects from the lack of essential nutrients prior to that time (maybe in that difficult seventh week). I don't know how long someone ingesting only sugar water without salt could last, but I suspect less than 10 weeks, and it sucks to be that person. John M Baker (talk) 19:29, 16 July 2012 (UTC)[reply]
Water, salt, sugar
So my question was based on several mistaken assumptions. Water and salt is what gets you a couple of months. Salt is actually a limiting factor even before sugar, let alone protein! So what about water, salt, and sugar then? For that matter is it even correct to put sugar immediately after water and salt, or is there a more immediate concern? --OP 174.118.1.24 (talk) 04:46, 17 July 2012 (UTC)[reply]
Well, oxygen comes first but that goes without saying. I think water, salt, and sugar would get an average person several months. There could be some other water soluble minerals or vitamins which come before protein. 71.212.249.178 (talk) 05:23, 17 July 2012 (UTC)[reply]
You may find the article Kwashiorkor to be informative. It is a syndrome caused by inadequate nutrient intake (especially protein) among people who get adequate calorie intake. That pretty much describes your water-salt-sugar diet to a T. People live for years with the syndrome, but can suffer serious physical and mental health and other quality of life issues, which can be life-long and debilitating even if their diet is eventually corrected. The issue is especially acute in children, who can suffer developmental disorders as a result. The condition does not appear to be itself directly fatal, but it does result in many sorts of oportunistic causes of death (i.e. weakened imune system leading to more infectious disease). There are also articles on other malnutrition issues, such as marasmus (which is calorie deficiency) and Cachexia, which is a general "wasting away", but is more a symptom of other diseases than a disease unto itself. For micronutrient (vitamin and mineral deficiencies) you'll want to research those individually; things like scurvy or goiter or rickets, but many of those are chronic conditions not known to reliably cause death on their own, excepting perhaps scurvy. --Jayron32 05:39, 17 July 2012 (UTC)[reply]
I expect, however, that people suffering from kwashiorkor do receive at least some micronutrients, which people on a water-sugar-salt diet would not (unless you consider salt a micronutrient), and I don't think it would be possible to live for years without micronutrients. In particular, I would expect that the lack of potassium would lead to a fatal case of hypokalemia at some point. I don't know to what extent other micronutrient deficiencies would be fatal. John M Baker (talk) 14:21, 17 July 2012 (UTC)[reply]
We can interpret "salt" pretty broadly. If you drink oral rehydration solution (which is water, sugar and various different salts) then things like potassium aren't a problem. I'm not sure if vitamins and minerals would get you first or if it would be essential amino acids. Can anyone find a source for that? If it's the vitamins and minerals, then it wouldn't be much of a stretch to add a one-a-day multivitamin to the water-salt-sugar diet. After that, I'm pretty sure it would be essential amino acids that would get you. You do need some fat in your diet as well, but I think you could go a long time without that. (This is all assuming you're an adult - children need different nutrients because they are still growing and babies need quite a lot of fat to support brain development.) --Tango (talk) 20:33, 17 July 2012 (UTC)[reply]
I don't know where the IRA hunger strikers got their salt, but it seems most likely that it was table salt, which does not include potassium. John M Baker (talk) 22:56, 17 July 2012 (UTC)[reply]
Also note this 1998 article in which a more recent hunger striker, 61 days into his strike, was expected to die soon due to his low potassium levels. In the event, Barry Horne ended his strike a few days later; his death three years afterward, from liver failure, is thought to have derived from his multiple hunger strikes. John M Baker (talk) 23:11, 17 July 2012 (UTC)[reply]
Is it unhealthy to smoke tea?
My friend is putting tea in his tobacco to give it flavor. Is this bad? I really care about him. --50.13.107.190 (talk) 06:27, 16 July 2012 (UTC)[reply]
Well, smoking tobacco is itself unhealthy enough that you should discourage him from doing that in the first place. Also note that the phrase "smoking tea" is slang for smoking cannabis/marijuana, so it is unclear when you say "smoke tea" if your friend is smoking earl grey or is toking the refer, as the kids today say. --Jayron32 06:34, 16 July 2012 (UTC)[reply]
Smoking camellia sinensis is not unheard of. I don't see any kind of harm it could cause, but I'm also not a chemist. Regardless, I'd be willing to wager that the tobacco smoke is doing far more damage to your friend than the tea ever could. Evanh2008(talk|contribs) 06:36, 16 July 2012 (UTC)[reply]
I don't see why inhaling the product of the incomplete combustion of one clump of plant matter is any better than another, additives from the production process not withstanding. 203.27.72.5 (talk) 06:55, 16 July 2012 (UTC)[reply]
Nicotine does not naturally occur in camellia sinensis, so there is that. Evanh2008(talk|contribs) 07:06, 16 July 2012 (UTC)[reply]
Nicotine, in the very small doses that you get in tobacco smoke, has a vanishingly small effect on your health. It's a stimulant, and that's about all. That's why nicotine inhalers, gums, patches, etc. are used to wean people off smoking cigarettes. The long term effects of smoking cigarettes has been widely studied. The effects of smoking tea leaves has not. They are going to contain a huge number of essential oils and other complex organic molecules for which the long term effects of volatilising and inhaling are unknown. At least with cigarettes you have some idea what you're doing to yourself. 203.27.72.5 (talk) 07:31, 16 July 2012 (UTC)[reply]
Just to clarify, the nicotine makes tobacco addictive, and the tar makes it harmful. I've never understood why cigarette companies don't go to nicotine inhalers as a permanent replacement for cigarettes, rather than just to wean people off tobacco. That way, the customers could get their nicotine fix without the tar, and the tobacco companies would still make their profit, by selling the nicotine they extract from the tobacco, in inhaler form. StuRat (talk) 07:54, 16 July 2012 (UTC)[reply]
Yeah, that way they would also have a surer income source, since their customer base wouldn't keep dying. I think the major hurdle to that is the fact that nicotine inhalers and what not are dealt with as medications from a legal perspective, whereas cigarettes, cigars, pipe tobacco, etc. are dealt with as tobacco procucts. I've heard smokers complain that they would like to try those methods for getting off the cigarettes, but they all cost so much more even with the high sin taxes on cigarettes, and some have the added inconvenience of needing a doctor's prescription. 203.27.72.5 (talk) 08:03, 16 July 2012 (UTC)[reply]
What Stu said. The tar is the primary harmful ingredient in cigarette smoke, sure, but the nicotine is what makes it addictive. The addictive properties of nicotine are what encourage people to smoke, and very often to smoke in larger and larger quantities. Even if tea smoke produces as much tar and/or other harmful substances as cigarettes do, there isn't going to be the same level of physiological dependence that comes with nicotine. If you roll yourself a tea cigarette, the most addictive thing you're likely to get is... caffeine, maybe? Evanh2008 (talk|contribs) 08:05, 16 July 2012 (UTC)[reply]
It sounds like we could save millions of lives just by changing the regulatory and tax structure of nicotine inhalers. You'd think this would be a major campaign issue, in a US Presidential election year. StuRat (talk) 08:11, 16 July 2012 (UTC)[reply]
Between a sitting President who smokes and generally believes in taxation, and an opposing candidate who generally doesn't believe in taxation but also has a moral proscription against smoking, it's not likely to come up. ←Baseball BugsWhat's up, Doc?carrots→ 13:46, 17 July 2012 (UTC)[reply]
Also, generally speaking, as per Cigarette taxes in the United States, most of the tobacco taxation is at the state level, which is beyond the reach of the Presidential candidates. In fact, it's a pretty low-level issue, as it's considered a "sin tax" by some, and from the libertarian standpoint it's a "voluntary" tax, in that tobacco is strictly recreational. ←Baseball BugsWhat's up, Doc?carrots→ 13:55, 17 July 2012 (UTC)[reply]
There's nothing "voluntary" about that; voluntary status has nothing to do with why you want the good being taxed. The notion of a "voluntary tax" is usually applied to things that considered are user fees in disguise, like the tax on gasoline, provided it's genuinely earmarked for highway improvement — you pay it to use the public highways, and if you don't want to pay it you can find a way not to use them. Of course it's not a perfect example, because maybe you want the gasoline for other purposes and you'd still have to pay the tax, but it's as close as the concept gets to making actual sense. --Trovatore (talk) 08:06, 18 July 2012 (UTC)[reply]
Right, but high taxes on cigarettes and low taxes on nicotine inhalers is exactly what we need to improve the health of millions. So what makes the inhalers cost more ? It seems to be a result of them requiring a prescription, so why do we require that ? I think I will break this off as a new Q. StuRat (talk) 19:23, 17 July 2012 (UTC)[reply]
If you listen really carefully you can already hear the screams of "School kids will think it's candy!" and other assorted nonsense red herrings. 203.27.72.5 (talk) 08:26, 16 July 2012 (UTC)[reply]
Smoking anything is harmful, as the small particles inhaled when you smoke ("tar") are a lung irritant, and can cause inflammation or more serious problems. StuRat (talk) 06:47, 16 July 2012 (UTC)[reply]
You could always slap a swingeing tax on tea leaves - or has that been tried before? Alansplodge (talk) 18:53, 16 July 2012 (UTC)[reply]
Why do nicotine inhalers cost more than cigarettes ?
This was discussed briefly above, but I'm still not quite understanding what causes the high prices on nicotine inhalers. Also, are there places where they cost less ? StuRat (talk) 19:27, 17 July 2012 (UTC)[reply]
Well, Health Canada Advises Canadians Not to Use Electronic Cigarettes. I can't speak for your countries, but here the solution would seem to be addressing Health Canada's issues with the technology. At the very least, that would require studies and lobbying in direct opposition to tobacco companies' interests. It may also require more R&D, should independent studies find serious side-effects to the use of those technologies (though it seems unlikely). BigNate37(T) 19:32, 17 July 2012 (UTC)[reply]
See supply and demand. Concepts like value and the cost you pay for something are only very tentatively connected. In our minds, we have a sense of "price justice"; that the cost you pay for an item should be somehow connected to the cost necessary to produce that item. This is so far from economic reality to be laughably wrong, and yet most people believe that if item A costs twice what item B does, it must have cost twice as much to produce, etc. etc. That isn't how it works, in any way. If it was, it wouldn't explain why I can buy a 16 ounce bottle of soda at the front of a grocery story for $1.69 and get a 2 liter bottle of the same brand of soda at the back of the store for $0.99. The only contributing factor to what you pay for an item is what the market will bear. You have to pay high prices on the inhalers because that's what people will pay for them. --Jayron32 19:49, 17 July 2012 (UTC)[reply]
So long as competition exists, then the price for which an item is sold should be closely related to all of the costs of producing and selling that item. That is, if it costs $1 to make, market, and sell an item, then you won't be able to sell it for long at $10, as a competitor will come along and undercut you on price and steal your customers. There are, of course, various ways that competition can be prevented, such as price fixing (illegal) or patents (legal). StuRat (talk) 20:57, 18 July 2012 (UTC)[reply]
Where are 2 liter bottles of Coke/Pepsi produced sodas $0.99? We're only slightly gentrified and it's $1.99, rarely $1.25 on sale. And we still have to pay bottle deposit and 8.875% tax. Though I remember a wholesaler let you buy single 2 liters for $0.69 in '97. 12.196.0.56 (talk) 00:43, 18 July 2012 (UTC)[reply]
I can regularly get one brand or the other (Usually Pepsi, owing to where I live, but sometimes Coke) at $1.25 per 2 liter on any given day, and about once a month I can find it discounted at $0.99. That's American dollars. --Jayron32 02:22, 18 July 2012 (UTC)[reply]
Jayron, you ought to click that link you just suggested yourself. The reason for the price discrepency between small and large bottles of soda is production costs, but you have to take into account all production costs inluding transport, labour stocking the shelves, refrigerated space being consumed in the retail outlet and the inconvenience imposed on the customer by having the product further away (i.e. The most visible locations in a store are themselves a scarce resource that must be expended on the shelving of different products) and so on so forth. Market information as a scarce resource also comes into play. The theory of marginal utility and the resulting supply and demand curves shows that in normal market conditions the amount supplied approaches the point of breaking even for both of these products. You just have to factor in all of the costs. 112.215.36.171 (talk) 23:29, 17 July 2012 (UTC)[reply]
You know what is strange, is when you agree with me, but take a tone that indicates you would be disagreeing with me. Every statement you made is illustrative of the exact point I was trying to make (that the real price and cost of an item is complex, and can't be estimated simply by comparing relative amounts) and yet you phrased it as though you were disagreeing with me. I thank you greatly for providing additional evidence and support for my point, but am perplexed by the tone of the post that indicates you wouldn't be doing that. Odd. --Jayron32 00:27, 18 July 2012 (UTC)[reply]
Well in that case, I think you're just missing the point of StuRat's question; why don't the tobacco companies lobby for a change in the regulatory structure so they can cheaply sell mass produced nicotine inhalers that don't have the same health effects as cigarette smoke? Do they like killing people? 112.215.36.171 (talk) 04:21, 18 July 2012 (UTC)[reply]
There's a huge supply infrastructure to producing cigarettes, beyond simply the companys that make and market the final product. A complicated (and arcane) system of tobacco growers and warehouses and auction systems still exist to this day, and have a vested interest in not upsetting the applecart, as it were. Living in a state where tobacco is king myself (North Carolina), the tobacco industry still has a huge political clout, and tends to be resistant to easy change. For various political reasons, tobacco has been one of the few crops to resist corporitized farming; large amounts of tobacco are still grown on small family farms, and for many small farmers tobacco is the most lucrative thing they can grow. That's what needs to be overcome in order to cause any revolutioary change in the nicotine consumption industry. And that's probably not going anywhere, as that lobby is still huge where it counts, especially on the state level. --Jayron32 04:37, 18 July 2012 (UTC)[reply]
But why would any of that change ? The tobacco companies would still need to grow, buy, and warehouse tobacco, from which they would then extract the nicotine to put in the nicotine inhalers. Unless there's some cheaper way to obtain nicotine I'm unaware of ? StuRat (talk) 04:51, 18 July 2012 (UTC)[reply]
I realize that "other factors" contribute to the final cost, beyond the raw materials. I'm asking which other factors those are, in the case of nicotine inhalers. Dramatically lowering the cost and eliminating the prescription requirement would seem to help the cigarette companies, who could then sell more nicotine, and stop killing off their customer base. And, since customers can use them just about anywhere, they might consume more nicotine that way. Cigarettes seem like a bad business model, to me, between of the terrible PR and lawsuits and shrinking customer base, at least in the US. StuRat (talk) 04:15, 18 July 2012 (UTC)[reply]
But Stu, your reasoning implies that the existing cigarette companies would be able to control the market on nicotine inhalers. If the companies themselves don't believe that, they will absolutely resist changing the system. And even if they could, there is no rule that the executives of a company have anything approximating functioning brains. At least here in the US, corporations are notorious for resisting even wildly profitable changes to their business models. Someguy1221 (talk) 04:32, 18 July 2012 (UTC)[reply]
Unless there's some other cheaper way to obtain nicotine than from tobacco, the tobacco companies would seem to have an advantage there. StuRat (talk) 04:53, 18 July 2012 (UTC)[reply]
So you are correct! Synthetic nicotine is more expensive than plant-derived nicotine [20]. Is it possible that e-cigarettes are less addictive than the real thing? Someguy1221 (talk) 05:27, 18 July 2012 (UTC)[reply]
Well, since nicotine isn't itself detectable by smokers, they do tend to associate the nicotine high with the tar in a ciggy, which can be a problem when trying to get smokers to switch to nicotine inhalers. They just don't seem "right". But, if a new generation of nicotine addicts were started out on nicotine inhalers, this wouldn't be an issue. However, to do this, the whole concept of only prescribing nicotine inhalers to cigarette smokers trying to quit has got to go. StuRat (talk) 05:52, 18 July 2012 (UTC)[reply]
UPDATE: I'd still like to see some type of breakdown of the cost of nicotine inhalers, say by raw materials, manufacturing costs, regulatory costs, lawsuit insurance, taxes, profit, etc. StuRat (talk) 20:53, 18 July 2012 (UTC)[reply]
Experience of submariners ascending from USS Tang?
According to the article, USS Tang was hit by its own torpedo and ended up heavily damaged in 55m of water. 13 seamen evacuated the forward compartment and swam to the surface, 9 actually making it, and only 5 of those managing to survive until pick-up the next day. My question is, what did these guys experience from the moment they left the submarine until surfacing? Were they wearing any sort of survival gear? Did they just take the biggest breaths they could and then slip through a hatch and swim like mad for the surface? Were they wearing buoyant gear that pulled them upwards faster than someone could swim? How quickly can a human swim 55m under water? I assume they suffered horribly from decompression sickness? The Masked Booby (talk) 08:35, 16 July 2012 (UTC)[reply]
As for whether they free dived or used an escape apparatus; the article cites a reference that they used a Momsen lung. 203.27.72.5 (talk) 08:40, 16 July 2012 (UTC)[reply]
(ec) I'd normally expect them each to have a Mae West (life preserver), but, from the description, it doesn't sound like they had them. Decompression sickness only applies if you are exposed to depths for enough time for your body to adjust, then decompressed rapidly. I would expect more rapid pressurization damage, like burst eardrums, in their case. StuRat (talk) 08:47, 16 July 2012 (UTC)[reply]
British seamen of that era used the blow and go technique to try to avoid some of the effects of rapid decompression. Don't know about US sailors though. 203.27.72.5 (talk) 08:48, 16 July 2012 (UTC)[reply]
Recent examination of the wreck of the Royal Navy submarine HMS M1 suggests that at least some of the crew attempted to swim to the surface from a depth of 73 metres, but none survived. The pioneering Davis Submerged Escape Apparatus was introduced to RN subs four years later in 1929. Alansplodge (talk) 18:30, 16 July 2012 (UTC)[reply]
A rapid ascent while holding one's breath will result in Pulmonary barotrauma or burst lung, resulting in gas embolism (air bubbles in the circulatory system). Not very good for you. Alansplodge (talk) 18:45, 16 July 2012 (UTC)[reply]
hot and sneezy
I've read somewhere that it is not possible to sneeze when you get hot. Am I living proof that this statement is wrong? Why do I sneeze when I become hot? Difficultly north (talk) 09:58, 16 July 2012 (UTC)[reply]
What do you mean by "hot"? One person's hot is another's cold. It has been in the news later that the USA has had a heat wave and people died. With a temperature that in Australia would cause us to put a coat on. 45 C can kill an Englishman, but a Saudi Arab would think nothing of it. Do you mean just hot enough to sweat noticeably? Or hot enough to cause distress and/or risk to your safety? I sneeze at the height of our summer here in Western Australia, where daily max temperatures run at around 42 C (average for hottest month about 39 C). Not because I'm hot though. Ratbone121.221.41.113 (talk) 10:53, 16 July 2012 (UTC)[reply]
Those U.S. temperatures causing deaths have actually been 40 - 43 C. And in our desert, where most of us don't live, it hit over 49 C. While the low in the mountains was -4 C the same week (24 F to 121 F in the continental U.S., July 4-10).[21]. Rmhermen (talk) 13:20, 16 July 2012 (UTC)[reply]
Our article Sneeze says (without a source) that a sneeze can sometimes be caused by a cold draught or a drop in temperature, but says nothing about sneezing being suppressed when you're hot. As I've seen many people with hay fever sneezing at the height of summer, I doubt that's the case. Rojomoke (talk) 16:57, 16 July 2012 (UTC)[reply]
OR Warning You can sneeze when you are hot, but that's not a story I will tell here. Bielle (talk) 23:39, 17 July 2012 (UTC)[reply]
Hahaha! Missed this. My father once microwaved some jalapeños and almost killed himself, my mom, and her mother. That story is retold every year on cinco de mayo.μηδείς (talk) 04:53, 18 July 2012 (UTC)[reply]
I was referring to when you suddenly warm up. After stress or on a hot British day (sat 20s-30s) or doing activity or have a hot flush. I can't comment on the first one. Difficultly north (talk) 11:16, 18 July 2012 (UTC)[reply]
Horticulture question
What is the best way to go about growing tropical fruit and veg in a damp, cool climate? Do I need to get a greenhouse? — Preceding unsigned comment added by 86.135.65.250 (talk) 14:45, 16 July 2012 (UTC)[reply]
I think one of the main problems is the roots not handling frost. You could try heat trace on them or some other method to monitor the temperature and then heat them above the survival temperatures. Anything above ground would effect the plants as well but not as badly as root damage I would think. You could 'bag' the tops and somehow keep those warm as well. They would probably still grow slower and produce less in cooler climates.--Canoe1967 (talk) 15:43, 16 July 2012 (UTC)[reply]
In Britain, where the OP geolocates, you really need a greenhouse. The San Francisco bay area, where I live, is a cool damp climate, but it rarely freezes and almost never snows, and a few tropical fruits, such as lemons and some other citrus, manage to grow okay. Looie496 (talk) 16:35, 16 July 2012 (UTC)[reply]
Not all "tropical" fruits have the same hardiness, let alone all varieties. For instance, this kiwi could almost certainly be grown in Britain with little special care (it was developed for Michigan) [22]. Other plants can grow outside their natural zones with special care. Historically, espalier technique was used to improve fruit yield in Europe. I've heard of some crazy people who manage to "lay down" entire fruit trees for the winter, so that they can be mulched and protected, but I wouldn't recommend it. Lastly, many passiflora species are hardy to cold climates, and even the tropical ones can bear fruit if brought in to the house over winter. SemanticMantis (talk) 20:16, 16 July 2012 (UTC)[reply]
Are you saying that growing passionfruit should not pose a problem? Also, do I need a special soil for this? — Preceding unsigned comment added by 86.135.65.250 (talk) 13:30, 17 July 2012 (UTC)[reply]
I'm sure it is possible in the sense that one could describe a mathematics which would explain it. Tripartate symmetries like this are known in our own universe, though not in magnetism specifically (i.e. the three color charges from Quantum chromodynamics. Not being a mathematician, a phycist, nor particularly imaginitive, I'm not sure I can conceive of what a magnetic tripole would look like, but I suspect that the geometry of a magnetic tripole mapped onto a universe with four spatial dimensions would obey similar mathematical rules as our current universe, which has a magnetic dipole mapped onto a universe with three spatial dimensions. --Jayron32 18:36, 16 July 2012 (UTC)[reply]
Given that opposite poles attract and like poles repel, I was trying to think how it could work if there were 3 poles instead of 2. The closest I can imagine is some electromagnetic equivalent of "rock-paper-scissors". ←Baseball BugsWhat's up, Doc?carrots→ 13:49, 17 July 2012 (UTC)[reply]
Changing "opposite" to "different" gives a less complicated way it would work, but maybe not as much fun.--Wikimedes (talk) 18:02, 17 July 2012 (UTC)[reply]
You may find the mathematics of multipole expansion enlightening. It is not possible to construct a field whose multipole expansion contains nonzero odd terms, and that is also consistent with the experimentally-observed behavior of magnetic fields. But, it's certainly possible to define a hypothetical field - in the mathematical sense - with arbitrary properties. Strictly, there's a very significant qualitative difference between having three "poles" and having three valid values for the magnitude (or "charge") of a pole; so the above comments about color charge should be interpreted very carefully. Nimur (talk) 18:24, 17 July 2012 (UTC)[reply]
The large sugar crystals dissolve more slowly than those of standard granulated sugar and do not settle in the bottom of the pot or rise up as froth to the surface. This reduces the risk of burning and the consequent need for stirring. It also allows impurities to rise for easier skimming. Because it minimises scum, it helps to make jams (UK) / jellies (USA) clearer.
This strikes me as odd. Larger crystals do settle more easily than small ones (I speak as someone who has grown innumerable crystals in a professional capacity over the years). And, surely it's the fact that they do settle that allows impurities (rather than sugar crystals) to float to the surface. But, conversely, if they do settle then the risk of burning increases, as does the need for stirring. Thoughts, anybody? Chris (talk) 19:08, 16 July 2012 (UTC)[reply]
It's a relatively short article stub, with an uncontroversial history. It's been years since any information was added to the article. It sounds as though you have some insight that could be helpful to other readers, so this is a case where being bold is the best course of action. BigNate37(T) 19:51, 16 July 2012 (UTC)[reply]
OK so what you've observed applies to the crystals you've worked with. But does it apply to preserving sugar crystals in a fruit/sugar/water solution? If so, amend the article. If you don't know, maybe someone who does can confirm or deny it. --TammyMoet (talk) 20:35, 16 July 2012 (UTC)[reply]
For what it's worth the words "The large sugar crystals … clearer" may be from my increasingly dodgy memory a verbatim copyvio from the back of a sugar packet. Whitworths, I think. I'll have a look down the supermarket tomorrow. I happen to remember it because I remember thinking "What?" when I read it (on the sugar packet) – "surely if they settle more rapidly they'd increase the risk of burning and need more stirring". My practical experience (as an occasional amateur maker of jam) is that preserving sugar behaves in exactly the same way as bog-standard granulated sugar for high pectin fruit, for instance gooseberries. For low-pectin fruit such as strawberries jam sugar does the job. TonywaltonTalk 23:35, 16 July 2012 (UTC)[reply]
"The large sugar crystals dissolve more slowly than those of standard granulated sugar and do not settle in the bottom of the pot or rise up as froth to the surface"
The first part of this sentence suggests that dissolving more slowly is an advantage. If so, it should be explained why it is. I suspect it is nonsense. (I realize that I'm going out on a limb suggesting it is nonsense. I may be way off base.) Wanderer57 (talk) 14:29, 17 July 2012 (UTC)[reply]
Shock wave faster than the speed of sound?
Can someone clarify this passage from me about a nuclear explosion effects:
At this point a shock wave forms at the surface of the fireball as the kinetic energy of the fast moving ions starts transferring energy to the surrounding air. This phenomenon, known as "hydrodynamic separation", occurs for a 20 kt explosion about 100 microseconds after the explosion, when the fireball is some 13 meters across. A shock wave internal to the fireball caused by the rapidly expanding bomb debris may overtake and reinforce the fireball surface shock wave a few hundred microseconds later. The shock wave initially moves at some 30 km/sec, a hundred times the speed of sound in normal air.
I get that shock waves from, say, a supersonic jet are caused by the jet moving faster than the speed of sound. I get that the expansion of an atomic fireball might be moving faster than the speed of sound, thus creating a shock wave.
But can the shock wave itself actually move faster than the speed of sound? This seems contradictory to me, but I am not a physicist. How does that work, if it does? I thought the shock wave was more or less a sound wave, and would be thus limited to the speed of sound? --Mr.98 (talk) 20:34, 16 July 2012 (UTC)[reply]
There may be a vague definition of a shock wave here. Your definition, a compression wave which does not actually move the air, and what they might be talking about, perhaps more properly called a "blast wave", where the air itself is blown away, potentially at much higher speeds. One complication is that the blast wave also generates sound along it's front, so, in that sense, the sound is moving faster than the speed of sound. StuRat (talk) 20:42, 16 July 2012 (UTC)[reply]
"it's front?" μηδείς (talk) 21:32, 16 July 2012 (UTC)[reply]
The outside edge of the blast wave, similar to a front in war or a storm front. StuRat (talk) 21:37, 16 July 2012 (UTC)[reply]
Pssst, I think she was pointing out the errant apostrophe in "it's". See pedant. Jerk182 (talk) 23:44, 16 July 2012 (UTC) [reply]
There's a bit of a trick in the way that the quote is worded; it's given away when they talk about the speed of sound in normal air. The air around a nuclear detonation is far from anything we'd call 'normal'. In an ideal gas under equilibrium conditions, the speed of sound is roughly proportional to the square root of the absolute temperature; at hundreds of thousands or millions of degrees, the speed of sound is quite a bit higher, as the individual molecules in the gas are on average moving at much higher speeds. In reality, the system isn't ideal, nor is it under equilibrium conditions, but you get the idea—the air heated by a nuclear detonation is going to be a lot hotter – and therefore faster – than 'normal'. The RMS velocity of an oxygen molecule at room temperature is about 500 m/s; the RMS velocity at 300,000 K is about 15,000 m/s: thirty-fold higher. TenOfAllTrades(talk) 21:27, 16 July 2012 (UTC)[reply]
related question: in this photo (from shock wave), does the leading edge of the shock wave (near the nose) not propagate with a speed nearly equal to that of the plane (e.g. mach 2)? I know the propagation of the wave must quickly slow down as distance from the plane increases, but this seems like it could be an obvious example of a shock wave traveling faster than the speed of sound. SemanticMantis (talk) 21:37, 16 July 2012 (UTC)[reply]
There is – perhaps appropriately – something of a semantic issue. The nose of the aircraft is certainly travelling at mach 2, therefore the tip of the shockwave would travel at the same speed. On the other hand, from one moment to the next, it isn't the same air molecules next to the nose of the aircraft; as far as the air is concerned, the shock wave really is only moving at the speed of sound. The leading edge of the shock wave at the aircraft's nose isn't a physical 'thing'. TenOfAllTrades(talk) 21:57, 16 July 2012 (UTC)[reply]
Shock wave: "Shock waves form when the speed of a gas changes by more than the speed of sound." Rmhermen (talk) 22:07, 16 July 2012 (UTC)[reply]
If you do the computations you find what TenOfAllTrades explained above. In case of a shock wave moving throug a medium, it is conventional to define the speed of sound to be that in the ambient state of the medium. The shock wave then moves "faster than sound", and the ratio of the speed of the shock wave and the speed of sound is called the mach number of the shock wave.
The reason why a shock wave can form at all is precisely because in a hot medium the speed of sound is larger than in a colder medium. So, if you start with a strong pressure wave, then in the compression phase the wave moves a bit faster than in the decompression phase. So, the compression phase will start to overtake the decompression phase and that eventually leads to the formation of a discontinuity in the pressure and density, which is precisely what an ideal shock wave is. In reality, there are also dissipative effects which smooths out the discontinuity. Also this will prevent small pressure from developing into shock waves. Count Iblis (talk) 22:10, 16 July 2012 (UTC)[reply]
Huh? Isn't there a missing angle in the above? A shock wave which is constant strength travels along its normal line which is not the direction of the plane. The shock wave has to be travelling faster than the plane to have a component equal to the plane in that direction... --BozMotalk 19:26, 17 July 2012 (UTC)[reply]
A secondary question (on shock waves)
Thanks for the above, it has clarified it a bit, though I am still a little confused. Here's a question that might get me out of my confusion: in the situation above, would the blast pressure wave hit you before the formal "sound" of the explosion hit you? Or at they one and the same (as I had assumed before reading about the shock wave being faster than the speed of sound)? --Mr.98 (talk) 01:46, 17 July 2012 (UTC)[reply]
They are the same until the speed of the blast wave slows below the speed of sound. 71.212.249.178 (talk) 03:08, 17 July 2012 (UTC)[reply]
I added to the title to make it more descriptive. StuRat (talk) 03:16, 17 July 2012 (UTC) [reply]
organic chemistry
Arrange in increasing order of basicity- furan,thiophene, pyridine. — Preceding unsigned comment added by Subimal giri (talk • contribs) 20:50, 16 July 2012 (UTC)[reply]
Arrange in increasing order of slackerdom: "students who post Q's online, expecting others to do their homework for them", "students who don't do their homework at all", "students who do their homework themselves, as intended". StuRat (talk) 22:35, 16 July 2012 (UTC)[reply]
Actually, checking the articles, I'm not sure we give enough information to actually answer the question (or at least not for someone like me, who was never much good at chemistry, and has forgotten what little he learned), though one would assume that if this is a homework question, the student should have already been given sufficient information to answer it. AndyTheGrump (talk) 23:20, 16 July 2012 (UTC)[reply]
Pyridine has a pKa of ~5.2, furan -> 35.6, Thiophene -> 33. Source.Smallman12q (talk) 02:17, 17 July 2012 (UTC)[reply]
You're comparing different types of values that you shouldn't- the furan and thiophene values are for deprotonating the neutral compound, while the pyridine number is for the acidity of the conjugate acid (the number that you actually want to determine basicity of the neutral species). Buddy431 (talk) 10:38, 17 July 2012 (UTC)[reply]
The answer lies in the relative basicities of ethers, thioethers and amines, while being careful to take into account the contributions of the various resonance structures. I doubt the marking academic would be impressed by simply looking up the pKa values. 112.215.36.171 (talk) 00:11, 18 July 2012 (UTC)[reply]
Is there a "how long you've been asleep"/awake calculator?
Or a graph by age? I can't seem to find one on Google. Shouldn't be too hard with sleep giving hours per night at certain ages, a curve fitting and an integration.
Yes, I have just programmed one. Count Iblis (talk) 22:55, 16 July 2012 (UTC)[reply]
Are you going to share it? Proportion of age asleep does vary by age, but why would you need anything more accurate than dividing age by three? 71.212.249.178 (talk) 05:17, 17 July 2012 (UTC)[reply]
They're many calculators that ask health questions and spit out how many minutes, months, years, seconds and Plutonian years you'll live and even one that just says "You will die!", so why not one that takes your birthdate and gives how long you've been awake? Maybe I want to know how many "8 year old me" lives I've had? Though I don't know how much to cut off for early-life amnesia so I'll just cut off realistic minimum/maximum amounts and get bounds. 12.196.0.56 (talk) 00:59, 18 July 2012 (UTC)[reply]
Could they DNA test athletes and their pee so they don't try to cheat by giving other peoples' urine?
A saliva swab should be enough for the first part, right? Is there enough DNA in urine? Maybe they'll give their own urine from a clean year instead. So they'll test for signs of chemical degradation/aging in the pee, unless very well preserved urine is required for/would be detected in the normal course of drug testing. But then athletes will cryogenically freeze their urine in liquid nitrogen, and reconstitute it later for giving while they're doping. Uh, we could take their blood, right?, but that's apparently too invasive of their rights as they don't do so now. And I guess they need all the blood they can take to beat 9.58 seconds. How long after the athletic performance can they test and it still works? Maybe if they test for the last event on the athlete's calendar to save him all of his blood he could've doped on the earlier races? Allow the drug tester to take the blood sampling amount out before the Olympics and put it back in after they take the drug testing sample out?
Radioactive dating of the urine with a fast-decaying isotope? And also, would Usain Bolt run 9.59 seconds or more if he didn't pee before the race, avoid chains over circa 0.1% of his body weight, or evacuate his bowels? Will they eventually wear suits with golf ball-like dimples designed in supercomputers and the bib information printed on? Amputate their ears to save weight while racing and use stem cell-grown pinnae when not? Sagittarian Milky Way (talk) 23:38, 16 July 2012 (UTC)[reply]
I don't think there really is any DNA in urine. There are lots of things you could do to make drug screening more effective, but you have to balance a lot of factors, efficiency, practicality, cost, etc.. In situations like this, I default to the team of experts that has been paid to work this stuff out, instead of assuming my uninformed musings might come up with a method significantly better then what they have in place now. Vespine (talk) 00:46, 17 July 2012 (UTC)[reply]
Often you're right Vespine. But they managed to avoid NFL (USA's #1 sports league) drug testing till last year didn't they? 12.196.0.56 (talk) 01:52, 17 July 2012 (UTC) I'm OP on public computer.[reply]
Wouldn't assigning someone to watch them pee into the cup be far easier? A8875 (talk) 01:10, 17 July 2012 (UTC)[reply]
Apparently 20% of the population can't pee when people are watching them. They could use a camera I guess but if I were a girl I would not want videos of urine coming out of my pee hole anywhere. They have Whizzinators so testers would actually have to view the pee coming out of the urethra. And which gender watches them if they're bisexual? Would the female Muslim athletes like any of this nonsense? Or, the final word, Good grief, some sort of near future airport scanner style very quick spectroscopy scan I saw in a science magazine that only detects explosives but can be set to see urea molecules ensuring that there are no supernumary urine reservoirs. They'll use this one day. 2040 Olympics. Unless they stop using urine testing. 12.196.0.56 (talk) 01:52, 17 July 2012 (UTC)[reply]
I think sexual orientation is mostly irrelavant in a case like this. Some people feel more comfortable going to a male or female doctor, so I don't see why an athelete couldn't choose the gender of the preson doing the "watching". But i don't think people chose the gender of their doctor because they think the doctor is going to get a sexual thrill out of the experience. If anything it might be because they're worried they'll get a sexual thrill when it's innapropriate. Or I wouldn't be surprised if some people, like exhibitionists make their choice based on the fact that they LIKE showing their private parts to people of their preffered gender. Vespine (talk) 04:07, 17 July 2012 (UTC)[reply]
urine needs some serious work. There is DNA in urine. Cell-free DNA in urine has been the subject of modern research as well as how to best preserve that DNA. See:
Such aids have been banned in swimming after a spate of broken world records. See LZR Racer. --TammyMoet (talk) 09:05, 17 July 2012 (UTC)[reply]
There are a number of confusing claims above. While urine tests are more commonly used particularly in out of season testing, and generally preferred because they're less invasive, blood tests (in addition to urine tests) are used in the olympics. See [23], Use of performance-enhancing drugs in the Olympic Games, [24]. I'm doubt it will be possible to detect autlogous blood doping via transfusion using urine (not that it's easy with blood). (Generally blood in the urine is taken as a bad sign, but I won't if enough normally end up in the blood that technically it may be possible to detect homologous blood doping via urine online.) A blood passport as recently in the media in relation to the Tour de France obviously requires blood. I don't think it's uncommon that it's easier or considered more reliable to detect certain things in the blood (or in the blood in addition ot urine), according to [25], it was done with EPO in the past although as our blood doping article and the source mentions, urine alone is now considered sufficient albeit somewhat controversially (but I'm not sure that blood helps the controversy since it appears to be about the ability to distinguish natural EPO from recombinant EPO). People mentioned Paruresis, but it's worth noting AFAIK there is no real provision for this in the olympics, see World Anti-Doping Agency. Urine collection is monitored, I've heard to the extent they athelete doesn't even hold their own penis (if male). I seem to recall there was a recent case I think at the olympics or just before (but not this olympics) where a participant failed to provide urine and it was suggest paruresis may be a factor, the WADA or someone said it's wasn't something they'd even encountered before. (Can't seem to find the case.) Some people were surprised by this since it isn't an uncommon condition, but others pointed out anyone with the condition would generally have failed to advance to the olympics because urine testing is widely used at earlier levels. Also while providing fake urine is a concern, I even seem to recall there was someone disqualified from the olympics for allegedly doing this a few years back, I don't think it's really that much of a concern compared to many of the other possibilities of cheating using drugs without detection given the level of observation done, see for example [26]. I mean if someone started physically implanting something to provide fake urine, it wouldn't surprise me if ultrasounds started being used to detect that. The whizzinator may work in some contexts but perhaps not the olympics. (Edit: Forgot to mention I'm primarily thinking of male atheletes, there may be avenues for a female athelete whike under strict observation although I haven't looked in to it.) Nil Einne (talk) 06:47, 17 July 2012 (UTC)[reply]
According to [27], DNA tests on urine have been used to confirm who the urine belong to, but this appears to be primarily when officials are complicit in the cheating. It wouldn't surprise me if they're now a regular part of test since it probably doesn't add much to the cost, but I still suspect it isn't really that important in terms of in-olympics testing for the reasons mentioned above. Nil Einne(talk) 07:57, 17 July 2012 (UTC)[reply]
Found [28] which describes collection observation in some US sports, I presume the olympics is the same or stricter. It also mentions ways atheletes have attempted to cheat in the olympics on urine collection including the method that is probably used in the case I mentioned remembering above. It sounds to me like only those who have perhaps never gone thru a normal olympics style observed testing would think they have a chance of using them. More sophisticated cheats know they won't work. I guess the catherisation method mentioned in the source above and [29] can't be detected via observation, but this would be difficult if you can suddenly called up for drug testing at any moment and aren't given any time alone once you're called up. And rejecting the first sample of urine as the earlier source mentioned also sort of kills the catherisation idea. In other words, DNA testing may have its merits, but the low tech solutions are likely the best methods to ensure you get what you want, a recent urine sample from the athlete.
DNA testing also opens up other complications, e.g. for a female finding foreign DNA in their urine stream may suggest they are careless, but perhaps not that surprising [30]. The ClinChem link above also mentions other ways foreign DNA can end up in the urine stream. And of course adding your own DNA to some other sample of urine can't be that hard. You could seperate these out, but relying on them adds complications. Then there is the problem of the athelete using a clean sample of their own urine and trying to test if they're doing that. All in all, best to rely primarily on low tech. (To be fair, it sounds like I was correct above that foreign DNA can be used to detect the possibility of autologous blood doping so it may be something important to look in to.)
Ive tried to calculate and got an answer for a seemingly simple problem yet I don't think it's correct. I have a cylindrical container with a radius of 0.05m which has a vertical frictionless piston of mass 10kg. Air is trapped inside. I want to know what the change in internal energy is when 300J of heat is transferred to the air causing te piston to move upwards by 0.2m. As this is a closed system, I'm assuming there's no mass flow and I'm quite confident that the change in heat energy is 300J so that leaves the change in work done. My initial guess was that this is 10kg x 0.2m but I don't think this is correct. Where an I going wrong? I'm sure that once I have the correct change in work done, I need too add this to the change in heat energy to get the change in internal energy. 82.132.249.136 (talk) 12:25, 17 July 2012 (UTC)[reply]
Because the air is doing work on the piston, the resulting change in its internal energy (without the heat) is negative. Meanwhile, check your units: mass times distance isn't energy. --Tardis (talk) 12:42, 17 July 2012 (UTC)[reply]
Thanks according to how I've interpreted what you've said, the answer should be -[(10x9.81)x0.1]+ 300. However, I still don't think this is correct. I think it may be to do with pressure but I'm not sure how to apply this. Thanks. 82.132.249.125 (talk) 15:18, 17 July 2012 (UTC)[reply]
I don't quite understand the question. Are you asking how much energy you need to add to the system in order to increase the heat energy of the air by 300J (which will be greater than 300J, due to some of the energy going to lifting the piston)? In which case, you were almost there, it's 300J+10kg*9.81m/s*0.2m. --Tango (talk) 20:40, 17 July 2012 (UTC)[reply]
Damselfly identification
I photographed a damselfly this morning in Liaoning Province, NE China Imgur Link. If someone can help me identify it, I will gladly add it to Commons and the related article (if one exists). I figure the white leggings should make for easy identification? Those are pretty unusual... The Masked Booby (talk) 15:28, 17 July 2012 (UTC)[reply]
There is a White-legged Damselfly(Platycnemis pennipes), already but it doesn't look like your beautiful capture. I think yours is more the Seriously White-legged Damselfly. Sorry I can't be more helpful. Richard Avery (talk) 15:49, 17 July 2012 (UTC)[reply]
Wow, based on the description that's definitely it! That article already has a few good photos but they might appreciate a clearer look at the namesake legs... Great job, Richard! The Masked Booby (talk) 21:51, 17 July 2012 (UTC)[reply]
I've gone ahead and added it to Commmons. Thanks again. The Masked Booby (talk) 01:11, 18 July 2012 (UTC)[reply]
Please check my maths
Hello. I've calculated the amount of energy spent by holding 9 kg in your arms for a minute. I calculated it as follows.
But the result seems quite low to me. Am I getting it wrong somewhere? If so, where? Thanks. Leptictidium (mt) 15:34, 17 July 2012 (UTC)[reply]
You need to check the dimensions of energy. Holding a mass does not expend any energy. If you lifted the mass thru a certain height, you will have then added some potential energy to the mass. If this does not make it clear, imagine youself holding that 9kg for 1 hour. Your arms might then feel sore from having to maintain the force required, but force is not energy, and you'll still be breathing normally. Now, imagine yourself lifting 9 kg weights from the floor to a table top every second for an hour. Bet you can imagine yourself getting puffed out - heck you won't last an hour. That's because your muscles had to release some chemical energy, consuming oxygen to do so, and converting that chemical energy into mechanical energy to transfer as potential energy in the weights. Wickwack58.167.241.156 (talk) 15:47, 17 July 2012 (UTC)[reply]
Muscle usage is a strange duck, and analysis of it more rightly belongs with biology than "assume-a-spherical-cow" physics. While you're correct in that there is no additional energy imparted to the 9 kg mass by holding it in a fixed location, (and certainly a table or a mannequin will not expend any energy doing so), you're incorrect that holding something in your flexed arms doesn't expend any energy. If your muscles are in tension, you're expending energy to keep them that way, even if by a rough, entry-level-physics calculation you wouldn't be. The reason for this is that on a microscopic level your muscles have little bits that are constantly grabbing and releasing to maintain that tension, constantly burning chemical energy to do so. (Much like if you start and end with a mass at the same place on a table you don't impart any net energy to the mass, even if you expend much energy raising and lowering the mass repeatedly while the mass is temporarily hidden behind a curtain.) This is why it's often misleading to use muscle-based intuition to judge how much energy or force is required to do something. -- 71.217.5.199 (talk) 16:02, 17 July 2012 (UTC)[reply]
Well, yes, my original aim was to find out how many calories you burn by holding 9 kg for 1 minute.Leptictidium (mt) 16:34, 17 July 2012 (UTC)[reply]
Clue: the concept in question is isometric exercise. If you Google "isometric exercise calories" then you will find various numbers, but not much information on how they were obtained. I expect they were obtained empirically by measuring CO2 and H2O output from human subjects, since physics won't tell you the answer. As Wickwack said, step 2 is wrong and there's no way to make it right, since the two sides of the equation are related by an unknown function that describes how muscles work. --Heron (talk) 19:03, 17 July 2012 (UTC)[reply]
When googling as suggested by Heron, I found that the top sites returned are hardly definitive, but most confirm that isometics burn very little calories. While 71.217.5.199 is certainly correct in what he said, there's the matter of scale. Certainly just holding 9 kg, although making you muscles sore if you hold it long enough, will not alter your breathing rate one iota (try it and see!)- confirming that the additional energy consumed is just about negligible compared to the calories you burn anyway just by being alive, warm, and awake. Wickwack124.178.145.103 (talk) 02:46, 18 July 2012 (UTC)[reply]
The way the OP set out his question strongly suggests he's seeking to understand the physics and needs to understand the difference between force, power, and energy - round cow physics if you like, rather than trying to undertstand muscle efficiency and physiology. It's up to Leptictidium to come back to us and let us know which it is - then if he still needs some help, we can tailor it accordingly. Wickwack124.178.145.103 (talk) 02:46, 18 July 2012 (UTC)[reply]
Um the OP already came back and said "Well, yes, my original aim was to find out how many calories you burn by holding 9 kg for 1 minute" which suggests he's much more interested in the biological answer (not necessarily how the answer is derived) rather then trying to understand the physics. Nil Einne (talk) 14:31, 18 July 2012 (UTC)[reply]
If you say so. It's virtually identical to his original question - no new points in it. I think it neither confirms nor denies he has no understanding of the physics. It neither confirm nor denies he understands that muscles, being an imperfect machine, actually burn calories to exert a force, but those calories are very small in quantity and he wants to estimate them neverthless. Wickwack58.170.181.203 (talk) 15:32, 18 July 2012 (UTC)[reply]
What flower is this? (Seen in Chihuly Garden)
The poster of this photo on Flickr wants to know: what flower is it? (I've saved it as a .jpg file but don't know how to paste it here; advice welcome :-) -- Deborahjay (talk) 17:27, 17 July 2012 (UTC)[reply]
(edit conflict) It's a false purple thistle also known as "sea hollies", belonging to the genus Eryngium. That's likely to be an amethyst sea holly (Eryngium amethystinum), though like most cultivated ornamental plants that's difficult to tell as it could be a cultivar of another species.-- OBSIDIAN†SOUL 17:54, 17 July 2012 (UTC)[reply]
Satellites
In a stable orbit, acceleration remains tangent to velocity
If they are in orbit around Earth and are subject to its gravitational pull, why aren't they continuously accelerating at 9.81m/s2? Is there drag or a terminal velocity for satellites? Ankh.Morpork 21:09, 17 July 2012 (UTC)[reply]
Because in a stable orbit, the acceleration is always tangent to the velocity vector, so the magnitude of the velocity does not change. BigNate37(T) 21:41, 17 July 2012 (UTC)[reply]
Great simulation! I forgot that a change in direction counts as an acceleration. Thanks. Ankh.Morpork 21:52, 17 July 2012 (UTC)[reply]
In a circular orbit, the acceleration is perpendicular to the velocity. —Tamfang (talk) 04:57, 18 July 2012 (UTC)[reply]
Well their velocity changes it's speed does not changeDja1979 (talk) 21:50, 17 July 2012 (UTC)[reply]
They accelerate at slightly less than 9.81m/s2 because they are further away from the Earth, but they are constantly accelerating towards the Earth. They are moving sideways as well, though, which means they keep missing the Earth (the direction that is towards the Earth changes as they move, so gravity causes them to go in a circle). It's just like when you have a weight on a string and swing it around your head really fast. You're constantly pulling on the string, pulling the weight towards you, but if never hits you (until you stop spinning!). --Tango (talk) 21:51, 17 July 2012 (UTC)[reply]
Presumably the larger the diameter of the orbit, the faster a satellite travels if they all have similar orbital periods. Is this the case or can two satellites at different heights travel at the same speed, just the lower one has a quicker time of orbit? Ankh.Morpork 22:06, 17 July 2012 (UTC)[reply]
Intuitively, the further a satellite is from the mass it orbits, the weaker the force exerted by gravity. A weaker centrifugal force implies less centrifugal acceleration, so I would assert that velocity must also be lower to maintain the orbit. If I understood Kepler's Third Law better, I would explain the exact relationship between radius and speed of an orbit, but I don't and I can't. BigNate37(T) 22:22, 17 July 2012 (UTC)[reply]
We have Orbital speed. It states low earth orbit satellites travel roughly 7-8km/s, the moon only travels 1km/s. Vespine (talk) 23:43, 17 July 2012 (UTC)[reply]
You are correct, objects in higher orbits move slower. Kepler's Third Law says that the square of the period is proportional to the cube of the semi-major axis, ie. where is the orbital period of the planet and is the semi-major axis of the orbit (for a circular orbit, that's just the radius). You might find it easier to think of it as . Put another way, if you double the size of the orbit, you multiply the period by . --Tango (talk) 23:47, 17 July 2012 (UTC)[reply]
quaternary ammonium compounds
I recently read a study saying that 70% of all hospitals use quaternary ammonium compounds to clean the hospital beds. Personal experience in a hospital by myself has proven this to be correct. They use a dilute bleach solution to clean Most items in the Room except for the bed which they use a quandary ammonium compounds such as Lysol to clean. Why is this? My understanding is that quaternary ammonium compounds do not kill spores, such as Clostridium difficille or ringworm spores. Wouldn't it make sense to clean the bed with a product that kills such spores?--64.38.226.90 (talk) 21:16, 17 July 2012 (UTC)[reply]
Many disinfectants can cause skin irritation and are therefore not used when they are likely to come in contact with the patient's skin. Ankh.Morpork 21:32, 17 July 2012 (UTC)[reply]
why don't they just use the dilute bleach solution to clean the beds with?--64.38.226.81 (talk) 21:56, 17 July 2012 (UTC)[reply]
Bleach can cause metals to corrode, stainless steel can turn rusty with bleach as it contains chloride ion and an oxidiser. Graeme Bartlett (talk) 22:06, 18 July 2012 (UTC)[reply]
yeast
Is there a list of different types of yeast Human beings can become infected with Besides candida yeast? — Preceding unsigned comment added by 64.38.226.81 (talk) 21:55, 17 July 2012 (UTC)[reply]
The Candida article is rather incomplete though. I understand that Candida growing inside the eyeball in otherwise healthy people is almost always from "cutting their junk" with lemon juice before injecting. Closet addicts are always shocked when their ophthalmologist diagnoses the condition... --BozMotalk 06:50, 18 July 2012 (UTC)[reply]
The first half dozen turned up by google scholar [31] all look reasonable. "Candida endophthalmitis after intravenous drug abuse" is notable enough to be worth its own article if anyone can take time out from Linux articles to write it. --BozMotalk 17:07, 18 July 2012 (UTC)[reply]
July 18
were the apollo missions classified
if not, why not open source all the designs. — Preceding unsigned comment added by 84.3.160.86 (talk) 00:34, 18 July 2012 (UTC)[reply]
Seems to me this issue came up some years back at the Moon Hoax page, and some editors there discovered that the designs weren't necessary kept in perpetuity. ←Baseball BugsWhat's up, Doc?carrots→ 01:34, 18 July 2012 (UTC)[reply]
Certainly some aspects of the Apollo missions were classified, but that's not the only reason why any particular aspect of the missions, like the designs, might not be made available to the public. Another reason might simply be that it isn't in their interet. Why would they make the designs available to the public? Vespine (talk) 01:38, 18 July 2012 (UTC)[reply]
There is an urban legend that the plans for the Saturn V rocket no longer exist. The paper copies were destroyed when they were no longer needed but they still exist on microfilm. As far as the other Apollo hardware, I don't know what happened to the blueprints. They might have been destroyed when they were no longer needed. Bubba73You talkin' to me? 01:56, 18 July 2012 (UTC)[reply]
"Because it's the law"? The article linked seems to refer to copyright. Even if NASA was covered under this (which is by no means self-evident from the linked article), all it would amount to saying would be that if anyone got hold of the relevant details, it wouldn't be a breach of copyright to publish them - or presumably to use them to build your own Saturn rocket. How would this non-copyright status amount to an obligation to actually provide the details to anyone in the first place - assuming that they still have them? AndyTheGrump (talk) 02:14, 18 July 2012 (UTC)[reply]
Works by NASA are in the public domain, but that doesn't mean they need to go out of their way to make everything publicly available on the internet. No one has those kind of resources. -RunningOnBrains(talk) 15:43, 18 July 2012 (UTC)[reply]
I don't know anything about the mechanical aspects, but I do know something about the electronics that have been used in the space program, and if they are typical, then there wouldn't be anything worth open-sourcing. NASA has been so conservative in its engineering that components were generally ten years out of date by the time a mission flew. Given how long it's been since the Saturn V missions, I shudder to think what you would see there. It would be like open-sourcing stone tools from the Neolithic. Looie496 (talk) 02:25, 18 July 2012 (UTC)[reply]
And following on from that, much of the hardware might simply no longer be available. Certainly the electronics, but I'd suspect much else besides. I don't think that there is much that is actually 'non-public-domain' in terms of the information you'd need to build a new 'Saturn equivalent' design from scratch - and it would probably be simpler than trying to reproduce the original technology exactly. I suspect that more modern technology would make a better system anyway: lighter/more powerful electronics, composite materials, and all the advances in CAD/CAM manufacturing would surely improve performance a little - though perhaps not a great deal, since basically a Saturn rocket before launch is mostly fuel and oxidiser by mass, and that won't change. AndyTheGrump (talk) 02:43, 18 July 2012 (UTC)[reply]
Not saying directly whether or not the designs are or are not classified, but if they were, one could certainly understand why they would be, and why they would still be, and it has nothing to do with covering up a moon hoax. The Saturn family of rockets were designed for putting people into orbit, but it would take much modification to make them into a perfectly functional ICBM, capable of reaching any place on Earth. The U.S. government has a vested interest in keeping such information on the QT. --Jayron32 03:31, 18 July 2012 (UTC)[reply]
Are you saying the Apollo/Saturn plans are not open-sourced? Just my opinion, but I tend to believe if you sought out plans, you could obtain them. Plenty of people have built working replicas of the Apollo CM guidance computer, possibly the most sophisticated piece of equipment on the spacecraft. The computer plans are easily found online. (see here) The rest of the technology used on the spacecraft is far less advanced, and in the 21st century almost all of it is obsolete. → Michael JⓉⒸⓂ 03:44, 18 July 2012 (UTC)[reply]
It was impossible to obtain some specifications of the Saturn V and related guidance systems at the time, and a few of those are probably still classified, but pretty much everything else was out in the open. You can certainly obtain blueprints which are very accurate but omit avionics -- that was one of NASA's most popular FOIA requests for years. You can obtain the Moon landing computer design and program, but not the launch avionics computer programs (digital and analog) for the Saturn V Instrument Unit's computers. The astronauts were often consulted as to how much of their private lives (i.e., medical and duty condition) would be shared with the press, and of course they all wanted pretty much everything out in the open, too. 75.166.200.250 (talk) 04:03, 18 July 2012 (UTC)[reply]
You can find source code from the Apollo missions here. -- BenRG (talk) 05:49, 18 July 2012 (UTC)[reply]
ITAR will make it complicated to gain access to the technical stuff which is not already available. Every drawing or schematic for hardware used in space is now ITAR restricted. Even giving the name and the type of plug used to connect Mars Science Laboratory parts is only allowed after checking with if it violates ITAR. The WWW is international and therefore putting the drawings onto the net will make you a target for homeland security.--Stone (talk) 10:09, 18 July 2012 (UTC)[reply]
The Apollo Guidance Computer is well-documented. Not just the source code listed above, but the whole system. People have built replicas. 209.131.76.183 (talk) 11:41, 18 July 2012 (UTC)[reply]
How does ITAR apply to the Apollo program? NASA is a civilian agency, not military. → Michael JⓉⒸⓂ 11:59, 18 July 2012 (UTC)[reply]
ITAR is a list of things. Dual use items are on that list too. The classification of all material used in space as significant military equipment is written in the documents. It does not make sense but it is fact. Talk with people from Mars Science Laboratory is very annoying because at that time no TAA (Technical Assistance Agreement) was in place and therefore the only things presented were things already published or general knowledge. The point is different for US Citizens, but the rest of the world is not allowed to get access. --Stone (talk) 12:53, 18 July 2012 (UTC)[reply]
[32] is a little story within NASA about ITAR. --Stone (talk) 12:56, 18 July 2012 (UTC)[reply]
Was the technology classified? Yes, but not to a very high grade. A brief perusal of NASA Apollo documents shows that many of them have classification stamps on them: a CONFIDENTIAL description of the spacecraft from 1963; CONFIDENTIAL mission description from 1961; CONFIDENTIAL report of some kind from 1961; CONFIDENTIAL mission directive from 1961; CONFIDENTIAL study of moon landing modes from 1962; and so on. I haven't seen anything higher than CONFIDENTIAL, which is the lowest official ranking of classification you can have (it goes CONFIDENTIAL, SECRET, TOP SECRET, more or less; OFFICIAL USE ONLY is a rung below CONFIDENTIAL but is not really a legal classification category).
So that's pretty weak classification for mission-related things. The rocket technology itself was no doubt classified higher than that, because, as others have mentioned, it was (and is) dual-use technology, and because the US was, you know, engaged in a big Space Race with the ol' USSR. Mission details were likely CONFIDENTIAL just to avoid the possibility of sabotage, or giving away programmatic information on the US space effort. The low level of classification is meant to signal that even if they got out, it wouldn't be that big a deal; it also meant that the information could be widely shared within the NASA organization.
As for open-sourcing at the time, the reason you wouldn't do that is because the Cold War US model was "buy all the experts and give them gobs of resources," which gets rid of the need for open-sourcing. (Plus, this is rocket science. It's actually hard. Even when you do the "throw everything at it with the most brilliant people at your disposal" approach, your rockets still blow up on the launch pads half the time.) As to whether you could do it today, sure! In theory. But it takes a lot more to build a moon shot in theory than a bunch of people editing a Wiki. It's a Big Project, much harder in terms of technical accomplishment than, say, designing an atomic bomb or something like that. --Mr.98 (talk) 13:42, 18 July 2012 (UTC)[reply]
Pluto / Charon satellites
If one considers Pluto and Charon to be binary planets (rather than Charon being a satellite of Pluto), then how do the satellites Hydra, Nix, P4 and P5 relate to the double system? Do they orbit the same barycenter, or are they satellites of just one or both of the planets, or what? (Yes, I know what the IAUruled in 2006; I simply disagree.) → Michael JⓉⒸⓂ 07:34, 18 July 2012 (UTC)[reply]
They all appear to orbit it's barycenter. I don't think it would be possible to orbit just one or the other, and have it be a stable orbit, unless, perhaps, the orbit was in a Lagrange point (and, even then, it's technically orbiting both). StuRat (talk) 07:38, 18 July 2012 (UTC)[reply]
I can't see how this question would be any different for the orbit of all the planets about the Sun. It too is affected by the other planets, and wobbles for each one. The wobbles must all be added up and come to one rather complex wobble. Myles325a (talk) 07:47, 18 July 2012 (UTC)[reply]
True, but then every object in the universe could also be said to be wobbling due to in orbit about every other object. The difference is, in the case of Pluto and Charon, it's visually obvious that they are orbiting the barycenter. StuRat (talk) 07:50, 18 July 2012 (UTC)[reply]
Are the galaxies orbiting around anything, or are they flying away from wherever the Big Bang supposedly occurred? ←Baseball BugsWhat's up, Doc?carrots→ 11:23, 18 July 2012 (UTC)[reply]
The Big Bang occurred everywhere. And Stu's statement is not usefully true, but only trivially. So yes, any galaxy is 'in orbit' around any other - but most of the orbits are wildly unstable! AlexTiefling (talk) 11:34, 18 July 2012 (UTC)[reply]
The three body problem is notoriously complicated. To give a simple example, suppose Pluto had the Earth's Moon revolving around it in the opposite direction, and one of those little satellites tried to sneak past five meters from its surface. Would the rock still be orbiting the barycenter? Nope - it'd go ass over teakettle in some odd direction and probably never be heard from again. It can't be modelled simply, except in roughest approximation. Wnt (talk) 17:25, 18 July 2012 (UTC)[reply]
Note that Pluto and Charon don't have any close-in satellites orbiting the pair. I suspect this is because any such orbit would be unstable, again with the possible exception of an orbit at a Lagrange point. StuRat (talk) 20:47, 18 July 2012 (UTC)[reply]
Creationist time line refuted by Neandertal DNA
Scientists figure that the last Neanderthals were about 26000 years ago. Creationists reckon that must have been less than 6000 because the world was created on 4004 BC. And they argue that the presence of Junk DNA in the human chromosome is the result of man's degeneracy over the interim time, as his sinful nature corrupts what was originally a perfect system in the Garden of Eden.
But they DO agree that there are no Neanderthals now, and that they must have died out thousands of years ago. I would thus argue that in that scenario, the DNA of preserved human bodies thousands of years old, Neanderthal or some other variant, should then show much less "corruption" by embedded viruses and so on. If the world is only 6000 years old, and our current DNA has been progressively corrupted over that time, then DNA from even two thousand years ago should show a much smaller degree of such corruption.
But I gather they don't. I am interested to see if there is any difference at all in such junk DNA effects between us and them, and if that difference can lead to a callibration of how different they were to us, and how long ago they died out. Myles325a (talk) 07:42, 18 July 2012 (UTC)[reply]
But radiocarbon dating seems like a much easier and more accurate way to accurately date those fossils. Of course, creationists will ignore that, but they can also ignore DNA evidence and all of geology, astrophysics, and every other branch of science that disproves their world view. StuRat (talk) 07:54, 18 July 2012 (UTC)[reply]
It's a simplification to say that all creationists, or even all young-earth creationists, believe the world began in 4004 BC. That's just the Ussher chronology. But StuRat is right: some beliefs can be reinforced by science (such as the intuition that humans and apes have something in common), some are intrinsically unprovable (such as Deism's model of God - which can arguably ignored as irrelevant, but not specifically disproved), and some (like Creationism) are held by their believers directly in the teeth of overwhelming scientific evidence to the contrary. Something as sophisticated as junk DNA analysis isn't on the radar for these people, because they treat rigorous scientific methods as intrinsically suspect. AlexTiefling (talk) 08:07, 18 July 2012 (UTC)[reply]
The creationists are not very good at expressing themselves, so they get too little credit. Their typical retort to such things is to say "Were you there?". When we apply the tools of natural science, we assume that the consistent timeline we see in our experiments, which seems consistent with our own, is the only timeline. That if we go back generation after generation, the clock on the wall matches the time people experienced, and the circumstances we live under are those which our examination of historical sites supports. It is, however, definitely true that human experience can misperceive the world, that the timeline as we recall it is not what the facts indicate. Can we rule out, with certainty, that over time there is not some systematic bias - that indeed, our past, as sentient consciousness, is in what we could call one parallel universe, and our future in another? Creationism involves a very deep rejection of the materialistic certainties (faith?) of the secular perspective, and it may not be one that is satisfactorily redressed merely by more facts showing the consistency of the natural science timeline. We can argue to the consistency, clear immediate usefulness, and tremendous beauty of the natural science perspective; but to argue that our perception of the world is truly, absolutely real and not at all a matter of imagination or misperception? That is beyond our kingdom. Wnt (talk) 12:22, 18 July 2012 (UTC)[reply]
Wnt's words seem to be a long way of stating that the rate of time could have changed without our knowing it because we don't know everything and cannot be certain there isn't some aspect of physics that we've missed or not yet discovered. As such, it is true in logic, but does not seem very likely, given the weight of evidence in all manner of science fields of study, from geology, study of dinosaurs, radio isotope dating, you name it. I have actually had Christian creationists and Islamic people state this same argument to me. Wickwack124.178.177.30 (talk) 13:30, 18 July 2012 (UTC)[reply]
Actually, that's not what I meant. What I mean is more that you could be sitting there, typing away at the computer, and the next moment you look up and out at an audience around some futuristic zoo enclosure neatly labelled: "Day In the Life of an Earthling: Reconstructing the Century of the Anthropocene Extinction". Or many, many other things, some, one can hope, guided by a perfect hand, and possessing a greater level of reality. Wnt (talk) 16:34, 18 July 2012 (UTC)[reply]
The logical argument that we cannot know that the world/universe, etc, is real orginated with ancient Greek philosophers, but is it anything more than a perceptive exercise in logic? Wickwack124.178.177.30 (talk) 13:30, 18 July 2012 (UTC)[reply]
Although I think creationists are foolish in being such, I don't see that neandertals having a goodly amount of junk DNA proves anything. A Creationist might argue that they were an abombination, extremely degenerate. Further, evidence is coming to light that so called junk DNA is not so much junk after all - recent issues of the magazine Scientific American have elucidated research into this aspect. Wickwack124.178.177.30 (talk) 13:39, 18 July 2012 (UTC)[reply]
Even with such evidence, I doubt it will change anything. When faced with the harsh reality that the natural world does not resemble the world described in the Bible, literal creationists will always rather assert that the world is wrong because the Bible is always right. They can not see what is because they're too caught up with what should be. Good luck with making them see that.-- OBSIDIAN†SOUL 17:40, 18 July 2012 (UTC)[reply]
Another line I've heard from creationists is that their god deliberately made the world with evidence that seemingly contradicts the Bible simply to test their faith. Once they take that position, no evidence will prove anything to them. HiLo48 (talk) 19:48, 18 July 2012 (UTC)[reply]
I want everyone to memorize this aphorism. Right now. Commit this to memory: "You cannot reason someone out of a position they did not arrive at via reason." Learn it. Know it. Live it. It doesn't matter what evidence you present to the YEC crowd: They evaluate the evidence through the filter of their predetermined conclusion, so there's no sense in trying to talk them out of it. Its a lost cause. --Jayron32 20:07, 18 July 2012 (UTC)[reply]
airlifting a diver to hospital
So i was in vanuatu scuba diving the other day, a group of islands only one of which has a hyperbaric chamber to treat sombody with the bends. How might a diver with the bends be moved with haste to the chamber, is airlifting possible since increased altitude would worsen his problem. Can the cabin pressure of conventional planes be maintained at 1 atmosphere, or perhaps airlift by helicopter where the helicopter stays close to sea level? 110.175.191.101 (talk) 12:37, 18 July 2012 (UTC)[reply]
For airframe cost reasons, aircraft are presurised to the equivalent of 2000 m (or a little above for older aircraft), ie 80% of sea level pressure (ref http://en.wikipedia.org/wiki/Cabin_pressurization#cite_note-1), this is beacuse it is a good safety margin below the altitude (~2500 - 3000 m) where some pasengers may experience discomfort with certain medical conditions. A helicopter is not necessary for low level flight - all types of powered aircraft are required to be above the same minimum height when not actually landing or taking off - typically 1000 feet, and may be higher in built-up areas. Perhaps pilots undergoing rescue can get authorisation to fly lower, but 1000 Ft /300 m altitude has 95% of sea level pressure and should have negligible additional medical risk. Airfarme structural safety means you will not find an aircraft that can maintain sea level presure. Wickwack124.178.177.30 (talk) 13:15, 18 July 2012 (UTC)[reply]
It's more like 98% at 1000 feet. And try flying at 1000 feet in Dubai. Or Shanghai or Manhattan. There's at least 18 things at 1000 feet to fly into in Dubai. Sagittarian Milky Way (talk) 21:47, 18 July 2012 (UTC)[reply]
If pressure is an issue for transporting ill passengers, it would be easier to transport a hyperbaric chamber. Ochson (talk) 14:39, 18 July 2012 (UTC)[reply]
I believe that the helicopters typically used to transport people to a hospital aren't normally pressurized at all. Thus, they can't fly very high. However, I seem to recall hearing about one rigged for mountain rescue, where low air pressure might cause the pilots to pass out, having a pressurized compartment for the crew, and 2 separate rescue nacelles which were independently pressurized, so the patient(s) in them can be slowly returned to sea level pressure. I'd think the same strategy could work, in reverse, for divers. However, this is likely to be cost prohibitive except in areas with lots of divers. Also, one disadvantage to this system is that medical personnel can't tend to the patient during the flight, but, if they are likely to die without it, it's worth that risk. StuRat (talk) 20:22, 18 July 2012 (UTC)[reply]
I grew up a short distance from Whipps Cross Hospital in London, which at the time had one of only two hyperbaric chambers in the country. There were fairly regular visits from RAF and RN air-sea rescue helicopters carrying customers for it. I'm fairly sure the Westland Whirlwind didn't have a pressurised cabin. Alansplodge (talk) 22:21, 18 July 2012 (UTC)[reply]
Circles, flares around sun in photography.
I'm not sure this is the right section for asking about it
In photography sometimes when the sun is around the corner, strange circles appear in the photography. Something like this you can see the bright behind the tree.
What are those? How are they generated?, (How can I shoot those?) 65.49.68.173 (talk) 14:43, 18 July 2012 (UTC)[reply]
Those are lens flares, caused by internal reflections within the camera lens. You can photograph them by taking pictures with very bright objects in or near the frame. That process is easier if you a camera where you look through the lens (such as an SLR camera or, I suppose, any digital camera with a viewscreen on the back) rather than through an independent viewfinder. Various lens filters can further enhance the effect. — Lomn 14:51, 18 July 2012 (UTC)[reply]
I'm not 100% sure, but perhaps Bokeh is related to this. Bus stop (talk) 14:59, 18 July 2012 (UTC)[reply]
Bokeh is not related to this. Lens flares are internal reflections of light which cause light to appear in front of foreground objects, bokeh is just differences in focal length; foreground objects will not be impacted. -RunningOnBrains(talk) 15:34, 18 July 2012 (UTC)[reply]
Camera on a timer in 1850?
Coaz and the Tscharner brothers on the summit of Piz Bernina during the first ascent, 13 September 1850
I'm writing an article on Johann Coaz and am a little suspicious of a photo I've put in the article. This photo (right) purports to show Coaz and two others on the first ascent of Piz Bernina (according to its description in the Commons). Given that there was no one else around, could this photo have been taken on a timer with the technology available at the time (I'm hoping it could have been), or is it a shot from a different ascent that has been mislabelled? The rockiness of the summit could certainly be Piz Bernina. The source (naturfreunde-maiengruen.ch) is not very helpful at all... Ericoides (talk) 16:02, 18 July 2012 (UTC)[reply]
Here's a little history of the camera shutter for some background. This suggests that in 1850 the photographer would not have been using a shutter as we would recognise it, so also wouldn't be able to use a release timer. It seems that they would have come in about 1880. Having said that, I think that if the camera did have a shutter, the technology existed (Clockwork) to enable a delayed shutter release. However, looking at camera technology, this page tells us that Wet plate photography didn't come in until 1851. This photo (if it was taken in 1850) must, therefore, be a Daguerreotype. Here you can see the process involved in taking such a photo, with exposure times from 10 seconds to 30 minutes(!). A reasonably long exposure (maybe over 30 seconds or so) might be enough for the photographer to quickly skip round in front of the camera and arrange himself in an 'I've been here all along' pose. What do you think? - Cucumber Mike (talk) 16:15, 18 July 2012 (UTC)[reply]
An ingenious reply, thanks, but would there not be a trace of his movement on the image? Ericoides (talk) 16:31, 18 July 2012 (UTC)[reply]
At low sensibility film, there wouldn't be any traces. The sensitive material just register up a certain threshold. If the exposure time is several minutes, then things in the ball park of some seconds won't show up. Apparently, it was not unusual for photographers in the XIX century to portrait themselves: [[33]]. OsmanRF34 (talk) 16:36, 18 July 2012 (UTC)[reply]
OK, that sounds sensible, thanks. Two further questions: which one is Coaz, and which one took the photo? My hunch is that Coaz is on the right, looking at the camera, and the fleet-footed photographer is the man standing on the left (who might well also be Coaz). Ericoides (talk) 17:19, 18 July 2012 (UTC)[reply]
Looking more closely at the photo, the standing man and the man sitting on our left are holding things that look a little like posing stands. Could it be, therefore, that the man sitting on the right looking directly at the camera is the photographer? Also, you labelled the photo 'Coaz and the Tscharner brothers'; the two men who look most like brothers are the one standing and the one on the right (the potential photographer) - they seem to have similar facial features. If I've got that right, my bet for Coaz would be the man sitting on the left. Admittedly, I'm getting into rather serious guessing now! - Cucumber Mike (talk) 21:37, 18 July 2012 (UTC)[reply]
Also we seem to be looking down on the summit. When was the helicopter invented? ;-) Alansplodge (talk) 22:16, 18 July 2012 (UTC)[reply]
Noise reduction
Given a mainstream PC (with a mainstream microphone and mainstream loud speakers/headphones), can a program running on it actively cancel noise? I don't mean any noise reduction filter, that can be applied on a file on the computer, just reducing the environmental noise for the user. OsmanRF34 (talk) 17:48, 18 July 2012 (UTC)[reply]
Yes. Start by reading Noise-cancelling headphones. You can get them for a few quid on Amazon these days but the bottom line depends a bit on how white the noise is--BozMotalk 17:53, 18 July 2012 (UTC)[reply]
Read carefully: I said with mainstream headphones, not with noise-cancelling headphones. I want to know if a PC (with a mainstream microphone and mainstream loud speakers/headphones) can cancel noise, not if there are noise cancelling headphones at Amazon for a few quid. OsmanRF34 (talk) 18:06, 18 July 2012 (UTC)[reply]
Ok/ What software are you proposing to use? It is technically okay if you fix the distance between the microphone and headphones and resign yourself to it only working for wavelengths a lot longer than that (so say two octaves below middle C) but it would be a real faf to program versus the buy a cheap set of phones with a microphone inbuilt which does it better. I think the answer is probably "not with mainstream software". --BozMotalk 18:40, 18 July 2012 (UTC)[reply]
Wouldn't latency be a problem (amongst other things)? Even with ASIO, I'm just not sure PCs can achieve the latencies required for such purposes compared to dedicated hardware although I guess with highly predictable noise it may still work slightly. Note that both our article and [34] mention it only really works for low frequencies and placement of the mics are important. Nil Einne (talk) 19:08, 18 July 2012 (UTC)[reply]
This depends on the characteristics of the noise and the signal channel. If you are talking about reducing non-speech noise, try running the signal through a vocodec like Speex and see if that makes it more ineligible. If you can characterize the noise spectrally and the channel in more detail, then I can give you a better answer. 75.166.200.250 (talk) 20:22, 18 July 2012 (UTC)[reply]
Meowing bird sound in western Montana
In western Montana while camping next to the Clark Fork River I heard a bird that made a MRRREEEOOOW MRRREEEOOOW MRRREEEOOOW type sound. Any idea what it was? (It was not a cat. I know this.) Whoop whoop pull upBitching Betty | Averted crashes 17:54, 18 July 2012 (UTC)[reply]
A Google search for "meowing bird sound" leads immediately to the Gray Catbird. Our article contains a sound sample; you can see if it sounds like what you heard. Looie496 (talk) 18:06, 18 July 2012 (UTC)[reply]
I was in the audience of the recording of a BBC radio comedy the other day. Musing about it since I was wondering whether the left channel of audience noise was the audience's left or stage left (actor's left, audience's right)? 10.64.0.169 (talk) 18:55, 18 July 2012 (UTC)[reply]
Call the show's producer's office and ask for the sound stage technician. It might not be something they try to keep constant all the time. 75.166.200.250 (talk) 20:24, 18 July 2012 (UTC)[reply]
Ideally, since when you view it at home, you "become" the audience, then they should have the left channel be audience left. That way, if an actor looked to the left (or on radio, said "Hey, you on the left in the funny hat...") and asked somebody on the left side of the audience a question, the answer would seem to come from the correct place. However, in shows where there's no interaction with the audience, it wouldn't much matter. StuRat (talk) 20:39, 18 July 2012 (UTC)[reply]
Why biologist know so little mathematics? Why are they less refined that, say, physicist
Both fields can be equally demanding, but biologist seem to be less 'deep'. μηδείς (talk) 21:26, 18 July 2012 (UTC)[reply]
Resolved
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