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August 4

Farts

Not trolling—is it possible to fart in your sleep? 71.146.0.138 (talk) 01:26, 4 August 2012 (UTC)

I would assume so based on the various TV shows with characters farting in their sleep. Futurist110 (talk) 01:48, 4 August 2012 (UTC)

Does this count as original research? Yes. I've been told I do it all the time. Mingmingla (talk) 01:50, 4 August 2012 (UTC)

Thanks. 71.146.0.138 (talk) 03:49, 4 August 2012 (UTC)

Flatulence is caused by the buildup of gases in your gastrointestinal tract, usually as byproducts of secondary digestion by your gut flora. Their movement down your intestines is also controlled by the peristaltic movement of involuntary smooth muscles, which does not depend on you being conscious. So yes.-- OBSIDIAN†SOUL 03:40, 4 August 2012 (UTC)

Thanks. 71.146.0.138 (talk) 03:49, 4 August 2012 (UTC)

Thanks. 71.146.0.138 (talk) 03:49, 4 August 2012 (UTC)

The most common thing to wake me on long car trips where I am not driving is the rush of air as the windows are rolled down in panic. My grandmother's favorite story was of the woman from the next county over who, when looking for the pepper at the church kitchen while cooking pierogies on a Sunday, instead of asking, Gde póper déla? with a fixed Polonic penultimate accent asked Gde popér(-)dela? with a free Ukrainian oxytonic accent. μηδείς (talk) 05:13, 4 August 2012 (UTC)

As a non-speaker of Polish or Ukrainian (aplogies for this lamentable deficit) I'd be quite interested in understanding this semantic joke, any chance of a translation? Richard Avery (talk) 06:49, 4 August 2012 (UTC)

Certainly. The past tense of East Slavic verbs is formed by the past participle, which is declined for gender and number, with an implied form of "to be" which is usually deleted. (English retains the archaic perfect forms "Christ is risen" and "The time is come" which are parallel, except that East Slavic drops the "is" as implied. French has Elle est venue, "she is (has) come", with the feminine past participle of venir, "to come") The past participle of delati "to do, to put" for women is delala, shortened by haplology to dela. (One generally adds -la to the verb stem to form the Slavic feminine past participle.) "She put the pepper on the table" is Wona de(la)la poper na stol. The verb perdeti, "to fart", (perd-, following Grimm's Law, is cognate to the English; the root is PIE) like many verbs, takes the prefix po- to imply a single, completed action, as opposed to a continuing action: poperdeti, "to make a fart" whose feminine past participle is popérdela. Hence, the only difference between "Where did she put the pepper?" Gde póper déla and "Where did she fart?" Gde popérdela? in my grandmother's dialect is one of where the stress falls. Her friend's dialect, however, had a different stress pattern, where poper was stressed on the final syllable, as opposed to most of the ladies at the church who pronounced the word póper with initial stress. Hence their humorous reaction to her innocent question. μηδείς (talk) 07:26, 4 August 2012 (UTC)

:-) Thankyou. Richard Avery (talk) 14:10, 4 August 2012 (UTC)

Race and Running Speed?

This is a serious scientific question. I'm not trying to be offensive or racist. I've noticed that there are a lot of black people in professional (such as Olympic) running events. I have two questions:

1. Is the % of black people in professional running events disproportional to their % of the population? 2. If this is disproportional and a favorable proportion to black people, do black people have a genetic ability to run faster?

Thank you. Futurist110 (talk) 01:55, 4 August 2012 (UTC)

East Africans in particular, right? —Tamfang (talk) 02:46, 4 August 2012 (UTC)

Well, skin colour isn't going to make any difference at all. And different groups of people from many parts of the world have black skin. I doubt if the OP was thinking of Australian Aboriginals, Polynesians and south east Asians when he wrote that question. Some groups of people seem to have a higher proportion of members who can sprint faster than many (West Africans), or run longer distances better than others (East Africans), but one has to take social, geographic and economic factors into account too. If you live in a poor country, you're more likely to choose running as a sport than swimming or equestrian. If you live at high altitude, you can have an advantage in endurance sports. HiLo48 (talk) 03:04, 4 August 2012 (UTC)

See Kalenjin_people#Athletic_prowess. Members of the Kalenjin tribe of Kenya win about 40% of marathons world-wide. μηδείς (talk) 04:56, 4 August 2012 (UTC)

By black, I meant the U.S. census definition of black, meaning of Sub-Saharan African descent. Futurist110 (talk) 06:29, 4 August 2012 (UTC)

And HiLo pointed out that having black skin itself is irrelevant to running, it's probably only a chance marker (for US Americans...) for a certain genetic, cultural, geographic and economic background that is relevant. Black skin is as relevant to running as is white skin to building high skyscrapers. The two things simply have nothing to do with each other causally, they are only associated by common economic, cultural and educational traits (that for example favor "white" architects to build many skyscrapers). --TheMaster17 (talk) 07:48, 4 August 2012 (UTC)

So you're saying it has to do more with lifestyle and exercise and that it has nothing to do with race? Gotcha. Futurist110 (talk) 07:56, 4 August 2012 (UTC)

HiLo: Sources please. And scientific ones for this Science desk, not social commentary. Rmhermen (talk) 14:07, 4 August 2012 (UTC)

Sources for what? If we demanded sources for everything posted here this would be a very different place. I'm not trying to deceive anyone. I just can't be bothered hunting down sources right now. Ignore my comments if they don't fit your belief structure. HiLo48 (talk) 18:11, 4 August 2012 (UTC)

There was a BBC Horizon documentary about this issue quite some time ago about the long distance runners from Kenya and Ethiopia. The conclusion was that the most relevant factor here was that these runners have longer legs in relation to the rest of their body (or certain parts of their legs are longer), and that means that for the same effort they will go faster. It is basically the same reason that explains why bipedal motion is more efficient than walking on 4 legs. A human can outrun a horse on the long run, hunter gatherers in Africa run for hours persuing antilopes eventually catching up with them...

For the sprint the type of muscles tissue you have is important, apparantly people of West African ancestory have the right stuff. Social effects can't be of much relevance here, because of the huge gap between the best white 100 meter personal best and the average best season's best time over the last decade. Only one white athlete has ever run faster than 10 seconds and none of the athletes from East Africa or Asia, see 10-second barrier:

"Nearly all the sprinters who have beaten the 10-second barrier are of West African descent. Namibian (formerly South-West Africa) Frankie Fredericks became the first man of non-West African heritage to achieve the feat in 1991 and in 2003 Australia's Patrick Johnson (who has Irish and Indigenous Australian heritage) became the first sub-10-second runner without an African background.[5][6][7][8] Frenchman Christophe Lemaitre became the first white European under ten seconds in 2010 (although Poland's Marian Woronin had unofficially surpassed the barrier with a time of 9.992 seconds in 1984).[9] In 2011, Zimbabwean Ngonidzashe Makusha became the 76th man to break the barrier, yet only the fourth man not of West African descent.[10] No sprinter of predominantly Asian or East African descent has officially achieved this feat."

Count Iblis (talk) 15:46, 4 August 2012 (UTC)

Keep in mind as well that you are talking also about the very bleeding edge of the bell curves, here. The bell curves for all populations in terms of running performance are going to look nearly identical; where they vary are going to be maybe tiny, almost imperceivable shifts in the median, and tiny, tiny differences on the far fringes. The Olympics and whatnot are pitting the far fringe of one country against the far fringe of another. The tiniest of differences in genetics, training, and so forth make the differences in such situations. The lesson here isn't that the population genetics don't matter for these sports — they do seem to — but that you shouldn't read racing performance (or sports in general) as telling you too much about population genetics. It is not likely the case that your average Ethiopian is genetically a better long-distance runner than, say, your average Swede, but over a large population of Ethiopians and Swedes, your handful of gifted Ethiopians will be better at this sport than your handful of gifted Swedes. (It is also obviously the case that the countries that spend more time and more money on searching out talent end up with more of it. There is likely no genetic reason that Americans, Russians, and Chinese dominate gymnastics and Africans do not — finding and cultivating gymnastic talent is just a much bigger deal in the former countries, so they are able to find those who reside at the end of the bell curves and devote enough resources to them that they go to the Olympics as opposed to doing other things with their lives.) --Mr.98 (talk) 17:48, 4 August 2012 (UTC)

In terms of long distance running again certain people from East Africa have a slight advantage - hence the dominance of Ethiopeans, Somalis and Kenyans in these competitions - they tend to have longer heel bones calcaneus than most other people. This difference gives then a slight leverage advantage to the transfer of power frome their achilles tendon's to the ball of the foot - in long distance races this small advantage adds up to result in a disproportionate number of marathon champions. (The same leverage advantage comes into play with Maasai men's traditional jumping dances.) Roger (talk) 18:26, 4 August 2012 (UTC)

I missed where Futurist attributed running speed to skin color. Has anyone ever heard of the Kalenjin people, who win 40% of marathons world wide? I wonder what percentage of the world population the Kalenjin are? Something near 40%? Nothing statistically improbable going on there.... μηδείς (talk) 21:22, 4 August 2012 (UTC)

See second paragraph of first post. HiLo48 (talk) 00:14, 5 August 2012 (UTC)

The user is American, I expect he would have said races with dark skin if he had been referring to Australian Aborigines or other dark skinned races, and given his clarification, I think my expectation was correct. μηδείς (talk) 18:12, 5 August 2012 (UTC)

I guess I missed the part where anyone here claimed that the genetic and social opportunity were equally distributed. Fighting strawmen with strawmen is a waste of everyone's time. --Mr.98 (talk) 21:34, 4 August 2012 (UTC)

So your point is that the Kalenjin are pampered rich brats? This is the wikipedia reference desk. If you think this place is about arguing you are mistaken. Provide links and refs, not ideological OR and ad hominem. μηδείς (talk) 22:19, 4 August 2012 (UTC)

Are you just trolling? Because you don't seem to be addressing anything I — or anyone else here — has actually written. --Mr.98 (talk) 02:03, 5 August 2012 (UTC)

Everything you have provided above is OR, Mr.98. I'd love to see your graph of Inuit vs Kalenjin running ability. Talk about straw men, as for "social opportunity", what are you on about? The 1% and how they monopolize running shoes while the barefoot rest of us can't afford the price of running down the street, perhaps? Who brought that issue up? Was there a paragraph on it I missed in the Kalenjin article? μηδείς (talk) 18:12, 5 August 2012 (UTC)

"Social opportunity" just means the fact that they have folks who search out the talent and put them in there. It's a necessary prerequisite, obviously, to getting to any competition. Again, I don't think you're actually reading anything anyone else writes with the intention of making sense of it — which is a pretty good sign of a troll. What you get out of it, I'm not sure, but feeding you probably isn't going to help much. (My stuff isn't OR, it just isn't cited. I could awash you wish boring academic books about sensible ways for thinking about the biology and sociology of race, including books on sport and race in particular, but why bother? You aren't going to read them; you can't even be bothered to read posts on here that are contrary to your pre-held beliefs.) --Mr.98 (talk) 15:12, 6 August 2012 (UTC)

Body build is also important, for long distance running your BMI has to be very low while you can still eat 5000 Kcal/day or more. Take e.g. Mo Farah, his height is 1.75 m but he only weighs 56 kg. Many people from East Africa have this type of "walking skeleton" body build. Count Iblis (talk) 19:27, 5 August 2012 (UTC)

Usain Bolt says that the Jamaican food that he eats makes him run fast. Count Iblis (talk) 15:23, 6 August 2012 (UTC)

Neurology and music

Is there any neurological basis to the moods associated with different types of musical scales, or is it entirely cultural? --108.206.7.65 (talk) 01:59, 4 August 2012 (UTC)

See Cognitive neuroscience of music.—Wavelength (talk) 02:36, 4 August 2012 (UTC)

That article doesn't discuss my question specifically. --108.206.7.65 (talk) 17:37, 4 August 2012 (UTC)

Can you perhaps elaborate a bit on what prompted the question ? Do you think there are different moods associated with different types of musical scales and if so what are they, for example ? Sean.hoyland - talk 17:51, 4 August 2012 (UTC)

For example, major scales are associated with positive emotions while minor scales are sad. --108.206.7.65 (talk) 17:16, 5 August 2012 (UTC)

This Nature article[1] and it's sources may interest you. And there are these articles about the minor third and sadness in speech (for speakers of American English).[2][3][4] Sean.hoyland - talk 17:49, 5 August 2012 (UTC)

It certainly must have a cultural dimension, as listening to squealing Chinese music must be more pleasant for them, or they would have executing all of the musicians long ago. StuRat (talk) 03:36, 4 August 2012 (UTC)

The short answer is that yes, there are absolutely strong innate underpinnings to the emotional influence of certain tones, chords, prosody, and many other features of music, many of which are universal across cultures (in neurologically healthy individuals, anyway). Though of course culture does have some influence at the same time. If you're interested in exploring this concept in depth, but want something that is (fairly) accessible to a non-cogntive-science-expert, then I can very strongly recommended both Daniel Levitin's This is Your Brain on Music and Oliver Sacks' Musicophilia. If memory serves, Steven Pinker also treats the subject, albeit much more briefly, in his books How the Mind Works and The Blank Slate, which are great reads in any event. If you're looking for something especially light, I stumbled across a documentary sometime back called How Music Works which, from what I saw, seemed to put a good deal of examination into this subject as well, but I did not watch it at length. I believe it was a BBC production, but don't hold me to that. Snow (talk) 03:57, 5 August 2012 (UTC)

Hydrotriiodic acid

Since hydroiodic acid contains the iodide ion, I don't see why combination with elemental iodine should not produce the triiodide ion as with iodide salts.--Jasper Deng (talk) 04:10, 4 August 2012 (UTC)

http://pubs.acs.org/doi/abs/10.1021/j100810a041 207.224.43.139 (talk) 05:48, 4 August 2012 (UTC)

Involuntary Change of Sexuality?

I know the one's sexuality is not a choice, but is it possible in extreme cases for one's sexuality to (somewhat) change over time due to factors out of this individual's control? For instance, could it be possible for a bisexual gay who initially strongly preferred women when it came to sexual attractiveness to strongly prefer men later on? Personally, I was always straight, but the characteristics and types of women that I found attractive have changed over the years. My question is if it is scientifically possible for such a change in one's view of sexual attractiveness to be much more extreme over the years, as in my example above? Futurist110 (talk) 07:35, 4 August 2012 (UTC)

That's a minefield of a topic. See Sexual orientation for a brief and extremely simplified overview; and the Kinsey Reports and the Klein Sexual Orientation Grid for two studies which have attempted to find out. But the answer is yes from the results of the Klein Grid and from personal observation.

The why, however, is problematic. It may be prison sexuality, latent bisexuality (in the traditional sense or the innate bisexuality sense), situational sexual behavior, coming out or finally accepting repressed homosexuality, self-enforced conscious rejection or adoption of an orientation (however ineffective that may be), experimentation, peer pressure, the result of personal trauma, positive or negative reinforcement over long periods, dissonance between gender and very strong emotional attraction (affectional orientation), hormonal, genetic, cultural, etc. Add to that the questions surrounding gender and sexual identity, and the religious and cultural conventions that attempt to control or classify them, and you end up with only one conclusion:

Sex is complicated.-- OBSIDIAN†SOUL 09:51, 4 August 2012 (UTC)

Tom Robinson describes himself as "a gay man, who happens to have fallen in love with a woman". Go figure. --TammyMoet (talk) 12:28, 4 August 2012 (UTC)

I am not sure about the issue of control (who would say their sweet tooth is voluntary?) but I can attest that my polarity, for lack of a better word, has varied over the years. Before I knew what sex was I had crushes on males and females. From puberty to 18 I was primarily homosexual. From 18 to 24 primarily heterosexual in action, and homosexual in dreams. (My boyfriends and girlfriends have always known I was bisexual.) Then the reverse. Then back again after some time. I must say, the most shocking development was when I dreamt of having sex with Britney Spears. (And this was even after the South Park episode.) She is not at all my type physically or musically. But it was a dream, and I don't blame myself for acts of my subconscious. (And it was fun!) I can offer no explanation. But I recommend everyone try both ways lest they never know what they are missing. μηδείς (talk) 21:19, 4 August 2012 (UTC)

The recent scholarly history on this subject has presented an interpretation of sexuality as a largely innate (and to a large degree unalterable) psychological/cognitive feature. This trend, perhaps unsurprisingly, co-evolved with increasing social tolerance for, and understanding of, LGBT drives, and the overturning of the previous reigning paradigm that gay and lesbian desires were almost entirely learned (and thus "correctable". Even more recently, however, some researchers are starting to question whether we may have over-corrected a bit might not be a bit more of a spectrum or "continuum" in which some (though certainly not all) individuals may have the propensity to slide from one category of sexual preference to another over the course of their lives, or under certain circumstances. This view is slowly gaining some traction in terms of research geared specifically towards human neurology, but it's worthwhile to note that this interpretation of sexuality in many social species has been uncontroversial for some time. All of that being said, there is at least some degree of innate preference in the vast majority of individuals and we're starting to understand the developmental mechanisms that go into forming them a bit more. For example, it's now fairly well-established fact that men who were born as the third son or on are markedly more likely to self-identify as gay upon reaching sexual maturity (even adjusting for social home life during upbringing; that is, whether they were raised along side those siblings or not). The popular explanation for this phenomena being that somehow the hormonal influence of past pregnancies somehow influences the development of these males in utero to result in children who (in our past evolutionary context) would have been able to assist their siblings in raising their progeny (who would share at least some of their genes, afterall), without further straining the demand on limited resources with their own offspring or becoming competitors for limited mates. This is just one of many small but convergent facts that point to innate biological mechanisms influencing sexual preference long before the cognitive machinery is up and running to directly make these "choices". But then there are some who, as they mature, will bounce back and forth between these preferences - Medeis' seems to be one such, from his description. Honestly, most modern researchers are not likely to be surprised by this, I would think -- the concept of malleability, but only within certain constraints, is a pretty common refrain in a number of different sub-disciplines of the cognitive sciences these days.

All of this deserves one big caveat though -- while a small proportion of people may change their predilections over the course of their life, all research on the idea of "triggering" such a change suggests that, by and large, it cannot be done; that is to say Conversion therapy and similar methodology for "forcing" a gay person straight (or, theoretically, vice-versa) will have no substantive effect (unless perhaps that person's neurobiology was already swinging them into that new state). Needless to say, many of the findings presented above are highly contentious (and as Obsidian noted, subject to interpretation via context), but I've tried to synthesize and represent the currently most common views by scholarship on the issue. As regards the concept of a sexual orientation spectrum that I opened with, there has been a fair amount of both speculation and research in the last couple of years in particular and I'll see what I can't do about re-locating some of it for you. Snow (talk) 03:42, 5 August 2012 (UTC)

I just want to take clear--the change in sexuality has to occur naturally without a person wanting it. Futurist110 (talk) 07:36, 5 August 2012 (UTC)

That is actually not clear at all. There is a difference between something that is not voluntary, and something that is against one's wishes. μηδείς (talk) 23:33, 5 August 2012 (UTC)

Just see Sexual_orientation#Fluidity_of_sexuality. 112.215.36.172 (talk) 10:09, 5 August 2012 (UTC)

Getting wet

It is raining. The rain is coming at me at 45 deg. I have no raincoat. Will I be dryer when I get home if I run through the rain or if I walk? --89.243.128.176 (talk) 14:04, 4 August 2012 (UTC)

If it's coming towards you, then running will result in less water falling on you. If its hitting your back, walk at the same speed as the rain is moving horizontally.--Gilderien Chat|List of good deeds 14:05, 4 August 2012 (UTC)

I agree with the first part, and in the second part, that strategy will indeed minimize the rain hitting you from the side, but it depends on the vertical velocity of the rain whether that is more important than minimizing the time rain is hitting you from above, which you would get from running as fast as possible. - Lindert (talk) 14:19, 4 August 2012 (UTC)

There was actually a recently released study on this in the European Journal of Physics. (See news coverage [5], [6], and freely available research article [7]). The short answer is that you'll be drier in almost all cases if you run instead of walk, although there are exceptions. -- 71.35.119.233 (talk) 18:14, 4 August 2012 (UTC)

Is it just me or has this all ignored the fact that if you run home, you spend less time in the rain? Yes, you may make complicated alterations to the raindrop-per-second rate and those are interesting deductions. But as long as rain is subject to gravity, you're going to be dryer for having spent less time in it. BigNate37_(T) 18:48, 4 August 2012 (UTC)

Indeed. I expect everyone knows from personal experience that you can avoid getting as wet by running home. If you have to be outside for a fixed period of time, then all of this might make a difference, but if you can get home in half the time, you'll be drier. It's important not to over-think problems! --Tango (talk) 19:09, 4 August 2012 (UTC)

In a first approximation, speed doesn't matter. You have a certain density of raindrops in the air, and if you cover a certain distance, you will sweep out a certain volume (cross section times the distance covered), and that volume contains a certain amount of water. Count Iblis (talk) 19:37, 4 August 2012 (UTC)

We're not ancient Greeks - we don't ignore empirical evidence in favour of pure reason. We've all been caught out in the rain and know what happens. If you run, you don't get as wet. If your reason doesn't fit with the empirical evidence, they your reason is wrong. Now, it is possible that I'm simply wrong as I get just as wet either way - there is a natural human tendency to overestimate the amount of control we have over our lives. The way to find out isn't with maths, though. It's with people running and walking in the rain and seeing what happens. --Tango (talk) 20:38, 4 August 2012 (UTC)

Actually I think Count Iblis's approach is the best way of visualizing this problem, but you need to think of it in the rest frame of the raindrops, not the rest frame of the street. If the raindrops are falling at a 45° angle downward and to the right, then with respect to their rest frame, you, the street, and the shelter you're trying to reach are all moving at a 45° angle upward and to the left:

                  .........._........
                   ........|\.........
                    .........\.........
                     .........\.........
                      ..........#........
                       .........#.........
                        ........#..........

The ### is you, the dots are (stationary) raindrops, and the dotless areas on either side are shelters. You want to sweep the # figure in any upward/sideways direction, minimizing the number of dots you intersect. If you "stand still", you're moving up and to the left and intersecting more and more drops without bound, so that's bad. If you want to reach the shelter on the left, it appears that the most efficient way of doing it is to go directly to the left, which corresponds to running as fast as possible. If you want the reach the shelter on the right, the most efficient way appears to be straight up: since you're 1/3 as wide as you are tall, you intersect about 1/3 as many raindrops that way than if you went horizontally. This corresponds to running at the horizontal speed of the rain. But if the rain were falling more vertically, the shelter edges in this picture would be closer to vertical and going straight up wouldn't look so attractive any more. Once the slope of the sides exceeds 3, you're better off running as fast as possible. This approach still works if you add a third dimension and replace the rectangle with a more accurate human shape. -- BenRG (talk) 21:28, 4 August 2012 (UTC)

I asked a slightly more complicated version of this question here at the math desk: How wet will the windshield get? μηδείς (talk) 18:59, 4 August 2012 (UTC)

It is also important not to underthink the question. A tall skinny person moving at a certain speed with his body inclined at a certain angle will only get the top of his head wet, while at a faster speed he will run into the rain in front of him. The cross section, angle of attack, and relevant speeds all matter. See the link above for the definition of the variables in the formula ρ·s·A·(u·sin(Θ)/v+cos(Θ)) μηδείς (talk) 19:32, 4 August 2012 (UTC)

Time to bring in the Ultimate Authority: Mythbusters. They tested it and found you get wetter by running (at least for the way they set it up).[8] Clarityfiend (talk) 00:34, 5 August 2012 (UTC)

• They seem to have done only one trial per configuration, and there are no error bars.
• The theoretical model predicts that when the rain is vertical the amount you absorb should be very similar whether you walk or run, but when walking a much larger fraction of it falls on your head. Their coveralls had no hoods.
• Running might splash more water from the ground onto your legs.

They seemed to have no theoretical understanding of the thing they were studying, and they made no attempt to isolate possible causes of their surprising result. Yet they pronounced the myth busted. Very poor science. -- BenRG (talk) 02:07, 5 August 2012 (UTC)

Your graphic does seem to be an excellent proof of the fact that standing still in diagonally falling rain will get you infinitely wet. Does anyone have an opinion as to the validity of the formula I reposted? μηδείς (talk) 03:12, 5 August 2012 (UTC)

It looks correct to me. It's not the same problem, though. For an arbitrary rain direction I think it would be $\rho (s/v){\vec {A}}\cdot ({\vec {u}}+v{\hat {x}})$ where ${\vec {A}}$ is the directed area (unit normal times area). For an arbitrary shape (like a human figure) you'd need to replace ${\vec {A}}$ with a function that returned the cross-sectional area. -- BenRG (talk) 04:40, 5 August 2012 (UTC)

Having seen parts of episodes of Mythbusters before, I'm not exactly surprised. I'm sure they've done some okay stuff, but whenever I've seen they often seem to be pronouncing some myth busted or confirmed on the flimisiest of evidence. The lack of repetion or real theoretical understanding of what they're doing seems to be a common problem. This shouldn't exactly be surprising, it's a TV show and a lot of the nitty-gritty of real science isn't exactly exciting. It does seem to me people give way to much credence to them, particularly in complicated cases where things could easily have gone wrong. Nil Einne (talk) 05:34, 5 August 2012 (UTC))

That's disappointing even for Mythbusters. They specifically said in their intro that walking gets you head wetter and running gets your front wetter and then they only measured the water on their front. Of course they concluded the running gets you wetter... The show is obviously intended to be entertaining rather than rigorous, but it is usually a little better than that. --Tango (talk) 11:25, 5 August 2012 (UTC)

Well at least they didn't just fake the results when the actual results weren't cool enough I guess [9] Nil Einne (talk) 19:05, 5 August 2012 (UTC)

If we're using Brainiac as our point of reference, then Mythbusters deservers a Nobel Prize! That show was ridiculous. --Tango (talk) 23:51, 5 August 2012 (UTC)

Count Iblis' approach only works if you're running at least as fast as the downward velocity of the raindrops (or even faster?) (i.e. never). When running slower, the raindrops you sweep out will be replaced by additional raindrops falling on you before you get out from underneath them.

Another consideration is how much more you will sweat when running than when walking and whether you would rather be drenched in sweat than in rain.--Wikimedes (talk) 06:50, 6 August 2012 (UTC)

Sweating only takes place if you are hot an the raindrops would nicely coole you. in addition running decreases the great differense between your speed and that of the raindrops meneing that the amount of water displaced while running is very slitely graiter then the amount of water that replaces it, if you are walking the amount of displaced water will still be very slitely greater then the amount of water that replaces it but less so. And don't forget that while the cerfase area of that portion of your body that gets wetter if you run (your front) is much greater then that of the portion of your body that gets wetter if you walk (the top of your head) remember that running gets you home much faster then walking.Aliafroz1901 (talk) 12:06, 8 August 2012 (UTC)

How many strings make up a quark?

I don't know if this question has a meaningful answer, but I'll throw it out there anyway. ScienceApe (talk) 16:21, 4 August 2012 (UTC)

String theory was originally a theory of strongly interacting quarks, in which a quark was the end of a string (thus explaining why single quarks never appear in isolation).

In superstring theory as a theory of quantum gravity, I think a quark would be "one string". Quarks are complicated even in the standard model, though, so take this with a grain of salt. -- BenRG (talk) 16:30, 4 August 2012 (UTC)

August 5

botox and spoiled food

okay, let's say i a come across some improperly stored food that has become contaminated by botulism toxin. can i harvest it from the can of food and use it to reduce the appearance of wrinkles in my face.

note that the question is not SHOULD i do that but can i, in theory, do that? or is the kind you put in your face a *different* type of botulism. — Preceding unsigned comment added by 24.228.83.134 (talk) 01:36, 5 August 2012 (UTC)

There are seven different types of botulinum toxin, and the one used to reduce wrinkles (along with treating many conditions) is naturally found in improperly canned food. Someguy1221 (talk) 01:51, 5 August 2012 (UTC)

But as far as harvesting the toxin, the preparation you find in a cosmetic surgeon's office was purified from a bacterial culture, and not from spoiled food. Purifying it out of food would likely be extremely difficult, and purification is necessary to prevent allergic reactions that would result from injecting random crap under your skin. Someguy1221 (talk) 01:56, 5 August 2012 (UTC)

Organic group abbreviations

I can't seem to find any information (on WP nor on the wider Internet) about abbreviations for organic groups. Our article methyl group mentions that that group is often abbreviated as "Me". I see other abbreviations from time to time (for example, "Pr" for the propyl group). Is there any commonly-accepted list of these abbreviations, or are they simply ad-hoc shortenings? — This, that, and the other (talk) 03:11, 5 August 2012 (UTC)

We have a (probably incomplete) list at Symbol_(chemical_element)#Other_symbols_that_look_like_element_symbols. That list is sadly unreferenced, so I'm left with no clue as to whether there is an accepted standard or if people just make them up as desired. Someguy1221 (talk) 04:01, 5 August 2012 (UTC)

Thanks :) — This, that, and the other (talk) 05:40, 5 August 2012 (UTC)

Here is a list of commonly used abreviations. I don't know who the authority is on this though. IUPAC doesn't seem to have much to say on the topic. 112.215.36.172 (talk) 10:18, 5 August 2012 (UTC)

Please explain electricity consumer earthing

In the multiple earth neutral system Keit described in response to an earlier question, how many of these household ground rods with "several hundreds of ohms" resistance each are typically combined in parallel? Is it only to the neutral from the local transformer, or are the secondary neutrals of multiple transformers connected? Are metal cold water pipes not also used as grounds (granted some places use nonmetallic pipe, and the US lately seems to require a driven ground rod in addition to and water pipe ground))? Is a secondary neutral carried all the way back to the substation? Ive seen lots of installations (US) where there is a ground rod at the transformer and one at each house served by the transformer, without a "lighting secondary main" of phases and a neutral connected to other transformers along the line. It is all too common for there to be a fault in the transformer or external to it from the primary to a secondary conductor. If such a fault from the primary to secondary occurred and there were tenor 20 houses with 200 ohms ground resistance each, all the wiring in the houses would be elevated to quite a high voltage, until the primary fuse blew. Recent US code called for a supplemental ground if the first driven ground has over 25 ohms resistance. Common US practice is to bury the rod and the connection of the wire to it, making the "wiggle test" difficult. Also it is common for the connectors in the neutral line to develop a loose or high impedance condition, with normal load current having to flow to earth through the ground rod or water pipe at the house, until the problem is fixed. In a loose neutral condition, the remote grounds would not help much. Edison (talk) 20:17, 4 August 2012 (UTC).

As Edison's question requires an answer that covers several related topics that will be off-tack for the OP of the earlier question, I have moved his query to here - I hope Edison and everbody else does not mind. Edison has asked so many questions in his lengthy paragraph above that an answer must also be pretty long. So I intend to answer it all, but different parts of the answer will come over the next day or so - I do have lots of other commitments. As it appears that Edison has some misconceptions about what house/dwelling earth stakes/electrodes are supposed to do, and what they are not intended to do, I shall include an explanation on that, as well as answering Edison's specific questions & comments. Keit60.230.207.82 (talk) 04:11, 5 August 2012 (UTC)

I applaud your moving my questions to a separate topic and welcome your enlightenment on the topic of earthing practices. Grounding/earthing problems are a frequent root cause of power quality complaints. Edison (talk) 00:38, 6 August 2012 (UTC)

• The discussion below is divided according to the following topics:-

• Terminology
• Number of paralleled earths in a typical MEN area
• Connection of MEN neutral runs together
• Connection of utility water pipes in earthing
• Use of extra neutrals
• Risk to comsumers from HV faults
• Issues with burying earthing components
• Loss of supply neutral to consumer premises
• What consumer earths are intended to do
• What consumer earths are NOT intended to do
• Principal risk in HV faults - Earth Potemtial Rise & Step & Touch Hazard
• What Power Companies do about EPR & S&T
• Need for Power Coordination, what is Power Coordination
• What Power Companies do about Power Coordination - impact on earthing
• Summary / Conclusions.

• Terminology

As in any technical field, using the correct terminology aids considerable in understanding the topic. The following terms are used in the following text (text by Keit):

Multiple Earth Neutral (MEN) system: A system of local electricity distribution at Low Voltage comprising 4 conductors/wires - one for each of three phases (the "active" conductors) and a neutral conductor/wire that carries return current. The neutral is nominally at zero volts tension. At each metered customer connection, the neutral is earthed by a customer supplied earth electrode - a short (1.5 m typical) metal stake driven into the ground.

Common Multiple Earth Neutral (CMEN) system: The connection of the neutrals of more than one MEN system together.

Ground: That dirty stuff we walk on when outside in the sunshine. In USA it means something diffrent - see below.

Earth: A system of at least one electrode driven into the ground and it connecting wire(s) intended to sink electric current and thereby minimise the voltage on whatever is connected.

Great Body Of Earth: That big round thing all and all the animals live on, and used as a reference point by electrical Engineers. The great body of earth provides a very low electrical resistance between any two points - measurement and theoretical studies have shown that it provides 0.049 ohm/km (known as the Carson Resistance, named after an American telephone engineer who first proved its' magnitude) between any two points, regardless of geology. However connection must be made by earth electrodes, and due to the concentration of current near each earth electrode, the resistance at each electrode is very high and dependent on local soil resistivity unless multiple electrodes are driven to considerable depth. Great Body of Earth is not an officially recognised term, but I have used here to make the following text clearer for non-electrical engineer people.

Low Voltage (LV): A voltage used at power company customer premises and distributed in a MEN system. Low voltage is defined as over 32 V AC and below 600 V AC. Typically 115/120 V phase to neutral (North & South America, Japan) and 230/240V in almost all other countries.

High Voltage (HV): A voltage over 600V and equal or below 132 kV AC. In most of the world, HV is standardised at 6.6 kV, 11 kV, 22 kV, 66 kV, and 132 kV phase to phase.

Extra High Voltage (EHV): any voltage higher than 132 kV.

Transformer: A device that convert from one voltage to another. In particular, used to convert HV into LV for ditribution to customers

Transmission Line: An infrastructure of wires or cables used to carry large amounts of power at HV or EHV to large substations.

Feeder: An infrastructure of wires or cables used to carry electrical power at HV from a substation to another or to an trasnformer.

Ring Main Unit (RMU) A three way switch carrying HV. The power company can use it to isolate the incomming feeder, the outgoing feeder, or the local load as may be required to isolate faults or "deaden" a feeder or load so that linesman can make repairs.

Substation: A substation is a facility for isolating and connecting transmission lines , feeders, and transformers to meet operating requirments vis-a-vis changes in load and/or system faults. Substations can range from just an RMU plus a transformer, up to large installations covering thousands of square meters of space. Substations usually incorporate protection - automatic devices such as circuit breakers that isolate faults in order to minimise damage to power company infrastructure.

Earth Potential Rise: The local rise in ground voltage around an earth electrode system.

NOTE: USA terminology varies from the above. In particular, USA uses the term ground and grounded to mean, in this context, an electrical earth, and electrically earthed. The meaning varies with context, whereas the non-USA terms are constant in meaning - they do not vary with context. Unfortunately, due to the wide availability of American textbooks, the terms ground and grounded have crept in everywhere, causing some confusion and the need for more convoluted techical wording.

Keit124.182.53.95 (talk) 13:02, 7 August 2012 (UTC)

• In the multiple earth neutral (MEN) system, how many of these household ground rods are typically combined in parallel?

It varies considerably.

In accordance with standards enforced by the Authority, each property that has a consumer's meter (for electricity charging) must have ONE earth electrode. The electrode must provide a standard buried depth (which is not varied, regardless of soil conductivity or any other factor). The electrode is connected by a wire (known as the earthing conductor) to the meter box neutral bar (a copper bar to which all the house wiring neutrals are connected). The neutral bar has the neutral wire from the supply authority's street distribution connected to it. The supply authority/power company's neutral condutor running down the street thus connects all the house/consumer earth electrodes in parallel. The number connected in parallel in the MEN system may range up to several hundred or more.

The supply authority MUST ensure that the system is safe in all cicumstances. In a well developed street with a hundred or more consumer earths paralleled, there is no problem. However, in a new land development, the first house completed may, for a while, be the only house completed. There are some mitigating factors, but with only one functioning comsumer earth, the supply authority must install a good enough earth electrode system at the distribution feed point (transformer, transformer & ring main unit, or whatever), and may, if soil conditions are not favorable, install additional spaced earth electrodes, AND/OR, interconnect the neutral with that of an adjacent distribution area with a good number of installed consumer earths i.e., implement a CMEN. What is a "good enough" earth system? That is a complex issue of its' own. It is clear that Edison has some misconceptions. If you want to know more about this sub-topic, post a new question.

• Is a MEN only to the neutral from the local transformer, or are the secondary neutrals of multiple transformers connected?

Often, the neutral, and thus the earthing system, for a distribution (240V supply for a street or small area) is isolated from the neutral & earths of other areas. However, the supply authority/power company may elect to electrically tie the neutrals of two or more distribution areas together, either directly, or via the high voltage (6.6 kV and higher) neutral and earthing system. This is known as the CMEN system (Commoned Multiple Earth Neutral). Again, the reasons for tieing MEN systems together or not tieing them together are a complex subject on its own, but reasons for a CMEN may include: a) insuficient consumer earths in a particular MEN area, b) poor soil conductivity, c) high voltage system configuration, to name a few. There are both pros and cons, depending on circumstances, regarding implementing a CMEN or just having seperate MEN runs.

Keit60.230.207.82 (talk) 04:43, 5 August 2012 (UTC)

• Are metal cold water pipes not also used as grounds?

The basic answer is "No, but...". They have been used in the distant past, and it is possible that one could find an old house that still has as its consumer earth as metal water pipe.

Regardless of the presence of any "in ground" metal, an earth electrode of prescibed length MUST be provided. However, the principle is that the house earthing system must present the people in and around it with the lowest available voltage (i.e., closest to the potential of "great body of earth"). If fortuitously earthed metalwork is available, e.g., metal water pipe, gas pipe, the steel of a steel framed building etc, and due to high local soil resistivity such metal work could be a "better earth" than the prescibed length stake, and as such offer a lower voltage, then the house earth shall be electrically connected to this metal work. Rules on connecting to water pipes vary regionally, as it has some definite disadvantages - it can present a risk to plumbers and can "export" voltage to other properties/consumers - but in no case shall metal work be relied upon for electrical earthing. If a building is multi-storey or surmounts a hill top, it may be subject to lightning strikes as defined by relavent standards. In such cases, there will be lightning ariels (pointy rods on the roof that provide the most attractive place for a strike), down-conductors, and a lightning drain earth system. Lightning drain earthing systems will gnerally comprise multiple deep electrode systems to provide a specified low electrical impedance to "great body of earth" and as such far outperform any earth stake provided as part of the building electricity system. Again, you still have to provide the regulation prescribed short length electricity consumer earth electrode, and the lightning drain earth is connected to it (at one point only), and both earth systems must be clearly labelled as to which one they are. Keit121.215.143.169 (talk) 10:06, 5 August 2012 (UTC)

• Is a secondary neutral carried all the way back to the substation?

Essentially, No. There is only one neutral in principle. In open wire street distribution (i.e., unisulated wires strung on poles), there are four conductors comming from the transformer - one for each of the three phases, and the neutral wire. However, in underground distribution, or bundled aerial cable, the cable may be screened, and may be steel wire armoured. Some power authorities earth the armouring at one end only (this avoids heting due to current in the armour and thus maximises the current carrying capacity of the phase conductors. Others earth the armour at all connection points - experience has shown this to minimise lightning-caused faults and is becoming standard practice with all administrations.

In high voltage transmission lines, there is normally no neutral wire at all, but there will be an earth conductor of some sort. In open wire practice, there is normally an earthed wire above the phase wires to provide a more advantaguous place for lightning to strike, and for power cordination purposes. In HV underground transmission, each phase conductor will be surrounded by a coaxial copper screen, and the whole surrounded by steel wire armour. The screens and armour will be earthed at both ends, and thus will provide a return path for current. Mutual inductance between the phase conductors and the screens and armour will force most of the return current to go in the screens and armour and not the great body of earth, regardless of the relative impedances.

See discussion on CMEN above.

Keit121.215.143.169 (talk) 10:39, 5 August 2012 (UTC)

• It is all too common for there to be a fault in the transformer or external to it from the primary to a secondary conductor. If such a fault from the primary to secondary occurred and there were ten or 20 houses with 200 ohms ground resistance each, would not all the wiring in the houses be elevated to quite a high voltage, until the primary fuse blew?

Such primary to secondary faults certainly do occur. However, in a correctly implemented MEN (or CMEN) system there is no dangerous rise in voltage in the houses etc. The MEN consumer earth system is not intended to deal with such faults and quite normally will not be capable of sinking the current. It would be prohibitive in cost to make consumer's earths capable of sinking HV-sourced fault current - especially in many areas of Australia, where the ground is essentially dry sand and/or rock to great depths and the electrical resistivity very high. Power authorities/companies provide other means for managing and sinking fault currents originating in the primary/HV side. I will explain this in another paragraph or 2, or 3.

Keit121.215.143.169 (talk) 11:20, 5 August 2012 (UTC)

• Common US practice is to bury the rod and the connection of the wire to it, making the "wiggle test" difficult.

In my answer to the OP in Ref Desk http://en.wikipedia.org/wiki/Wikipedia:Reference_desk/Science#Earthing, I intentionally omitted some factors he didn't need to know.

At one time in Australia, for instance, it was sufficient, in terms of regulations, to drive the house earth stake into the ground near the meter box, and attach a green earth wire of the prescribed gauge, one end to the neutral bar in tehg meter box, and the other end to the earth stake with a clamp. As part of their electricity supply contract with the power company, consumers/householders were required to maintain the wire, clamp and stake in good order and condition (not actually themselves - they should hire an electrician when required). Installing electricians commonly left some excess lenghth in the wire, coiled up, to facilitate re-terminating should it become necessary. However, because the wires were exposed, they tended to occaisonally get damaged. I myself once stripped one such earth wire right off accidentally while operating a large lawnmower. Most folk would eventually notice damage and call an electrician, but some might not. Current regulations require the wire and its attachment to be "protected against damage from reasonably expected events" - this means running the entire wire length in conduit. Commonly, nowadays, the entire setup is buried, but in this case there must be a small pit housing the top of the stake and its' connection, so that it can be easily located and checked. In such cases, the wrigle test is still possible. The lids of the pits are inscribed "MAIN EARTH". Any other earth present, such as a lightning drain earth, ham radio earth, etc must NOT be labelled "MAIN EARTH". Completely hiding it by burying it in soil without a pit is very bad practice and not acceptable. It must be possible to visually inspect it. Keit124.182.149.216 (talk) 12:23, 5 August 2012 (UTC)

• It is common for the connectors in the neutral line to develop a loose or high impedance condition, with normal load current having to flow to earth through the ground rod or water pipe at the house, until the problem is fixed.

Edison's claim that this is common is very surprising - it would only be common if installation practices are very poor and/or the installing electricians incompetent. Never the less, such a fault is obviously possible.

However, perhaps conter-intuitively, a relatively high house earth is actually safer. Remember that the purpose of a house earth (consumer's earth) is to ensure that appliance metal work is at the lowest available voltage, and NOT to ensure the actual voltage is minimal. It matters not a whit if the appliance user, touching exposed metal of the appliance, is at (say) 100 V above true earth, so long as he can't touch anything at a lower voltage. See other paragraphs on this. However, if the house earth, and therefore the house neutral, is, say, 50V above true earth due to high earth system resistance, then that is 50V less to run the appliances. Lamps will be very dim and flicker badly, and power appliances and electronics will not work properly, if at all. This will make the householder immediately contact an electrician to get it fixed. If a house earth was good enough to sink the load current and keep the neutral voltage low, then lamps and appliances will still work ok - so the householder in ignorance will not call an electrician. The open or high impedance neutral connection to the street wiring/cabling may become a residual fire risk. Keit120.145.32.129 (talk) 14:16, 5 August 2012 (UTC)

. Please note that the correct spelling is "neutral" not "nuetral." In the US, at least, overhead or underground connections from a transformer or a lighting secondary main are typically made by crimped connections, which can develop a higher than desired resistance over time. This may be in a phase or a neutral. A "loose neutral" has undesired effects, such as the side of 120/240 distribution with a high load having a low voltage while the other side has a high voltage. It is painfully common. Edison (talk) 00:36, 6 August 2012 (UTC)

I have corrected the spelling. Crimped connections are used here in Australia too. However, connection trouble is very rare. I have been in the electronics and electrical game for many years and have never experienced it, only heard about it. Of course, as we use double the voltage, the effect of any connection resistance will be a lot less. For instance, a 1 ohm resistance in a circuit feeding a 240 V 1 kW resistive load will drop the load voltage by 2% - hardly noticeable. In a 120 V 1 kW circuit, the load voltage will drop 9.4%. Even so, I think you must be mis-informed, either that or crimping practices in your area are poor. The practice of splitting a phase into two, with 120 V (one side earthed) used for lighting and domestic appliances, and 240 V (balanced to earth) for heavy draw items and industrial equipment is pecular to the USA and certain other "110/120 V" countries. We use 240V (single phase) and 415 V (3 phase) for all consumer equipment. However a dropped neutral will still result in a similar problem at reduced degree - a heavy load on one phase will increase the voltage on the other 2 phases. Keit58.169.250.192 (talk) 02:12, 6 August 2012 (UTC)

Texts on power quality and my own utility experience negate your claims I am "misinformed" with regard to the incidence of high resistance connections in the conductors from the utility to the consumer, and I doubt that workers are peculiarly careless in North America. Edison (talk) 03:43, 7 August 2012 (UTC)

Where I have used the term "misinformed", I meant in connection with what you appear to believe is the function and performance of the various sorts of earthing used. However I do find your claim that supply neutrals are commonly high resistance or open surprising. It certainly is a rare problem in Australia. I too doubt that elecrical workers are especially careless in North America - in fact over the years the USA has, among professionals in the electricity supply field, a reputation of having a safe and reliable system - at least until the US Govt started interfering with pricing policy and wholesale regulation. So perhaps you are misinformed or have misunderstood what you have seen. Just what is your utility experince? Keit124.182.53.95 (talk) 13:19, 7 August 2012 (UTC)

What the consumer earths in an MEN (or CMEN) system are intended to do:

The consumer earths are principally there to ensure that a person who is holding or touching exposed metal-work of an appliance, and thereby has his body at the neutral voltage, is at a voltage low enough in comparison to any other conductive thing (water tap, damp floor, gas stove, or whatever) he/she could simulataneously touch, that he/she will not percieve an electric shock and is not at risk of electrocution.

An example should make this clear:- Let us say that, due to a certain resistance in the supply authorities earthing system, together with the load current on the street distribution or fault condition existing in the absence of consumer earths, an appliance metal work is at 35 V with respect to the great body of earth. If the consumer (in bare feet perhaps) is standing on a bare damp concrete floor, or is simultaneously touching a gas-main fed oven, then he will get a shock, as the floor or oven will be at zero potential. There is in this case 35 V potential difference across him.

Now, assume each house has its earth stake. If the soil in the area is low in resistivity, small currents will flow to great body of earth via these stakes, thereby forcing the neutral voltage down - making it safe.

Let's now say the area is like many areas in Australia, essentially a thin layer of top soil, and under that dry sand to a depth of 30 m or more, overlaying bedrock. In such a case, the geology is high resistivity and even many parallled consumer earths won't do a terrific job of bringing down the neutral voltage. The consumers, though, are still safe - why? Because everything conductive they can touch is either fully insulated, or is in contact with topsoil, which has all these earth stakes poked into it. If the nuetral is 35 V above true earth, then everything else is nearly the same. If everything the consumer can touch is at the same 35 V, 100V, or even an impossible 350 V, it doesn't matter. There is no potential diffrence across him and he can't get a shock.

Keit58.169.250.192 (talk) 02:59, 6 August 2012 (UTC)

What the consumer earths in an MEN (or CMEN) system are NOT intended to do:

1. Consumer earths are not intended to carry significant current. For both normal loads and fault conditions in street distribution, house wiring, and appliances, the current in the earth stakes is very low. The bulk of load and fault currents is carried back to the transformer in the supply authority/power company's neutral wire. This is only partially dependent on the electrical resistance of stakes to great body of earth vis-a-vis the lower resistance of the neutral. The return current is largely forced into the neutral by mutual inductance between the active (phase) conductors and the neutral. Essentially, this means that the active wire, being very close to and physically in parallel with the neutral, forms a transformer with the neutral, so that whatever current flows in the active wire causes a more or less equal return current in the neutral. In general, a current of more than a few milliamps in the earth stake is an indicator of incorrect or faulty installation.

2. Consumer earths are not intended to sink current due to faults to the High Voltage side of the transformer. Such fault currents are up to 3000 Amps, and to expect any consumer to pay for an earth to handle that would be utterly prohibitive. The power company must provide other means to manage and sink HV fault currents - this will be described below. In practice, the paralleled consumer earths in a well developed MEN or CMEN area can assist in sinking fault currents arising from HV to LV breakdown.

3. Consumer earths are not intended to sink significant load current should the supply neutral be high resistance or broken/open circuit. To provide consumer earths do so would in many, if not most, areas would be expensive, and would mask a neutral fault. With the prescribed single short earth stake, failure of the supply neutral will result in lights and appliances not working properly, and, usually, not working at all, resulting in the consumer/householder urgently seeking an electrician, as mentioned elsewhere. Keit60.230.199.55 (talk) 05:35, 6 August 2012 (UTC)

Principal risk in fault currents from High Voltage transmission lines & feeders - Earth Potential Rise

Each MEN area providing low voltage (115/120/230/240 V) to consumers is feed via a step down transformer from a high voltage (between 6 kV and 132 kV) line or feeder. The principal interest here with faults on HV lines or faults in substations/RMU's/transformers fed from HV is what is called "Step and Touch hazard". When there is a HV fault causing a current to flow to earth via the substation/RMU/transformer earth electrodes, the current leaves the electrode(s), passing through the soil, locally radiating out in all directions, prior to finally heading downwards into the great body of earth. The soil has an electrical resistance - this means that the soil current causes the earth electrode(s) to raise in voltage above the deep earth level. As the current leaves the electrode(s) and spreads out to lower and lower current density, on the surface of the ground there is a contour of decreasing voltage.

A given electrode might (say) be raised to 1200 V above deep earth level, and at 1 meter away the soil surface be at 1000V, at 2 m away 500 V, and so on, until at a large distance the voltage is negligible. This is called Earth Potential Rise. Due to the high voltage available on HV lines, the current into earth electrodes can be substantial, and so Earth Potential Rise can be substantial.

In my example just given, a person standing with one foot 2 m from the electrode, and the other foot 1 m away from the electrode, would have a voltage difference between his feet of 1000 - 500 ie 500 V. Unless he has dry shoes with very good insulation properties, that 500 V difference, known as the step voltage, will result in hazardous current to flow thru his body and may very well kill him.

In my example above, let's say the substation has a metal/wire fence around it, or a brick or concrete wall around it. Brick and concrete must be regardled as conductive. Due to the voltage contour on the ground/soil surface, if a person touches the fence or wall, his hand will be at a higher voltage with respect to his feet - this is known as "Touch Voltage". Touch voltage can be more dangerous than an equal step voltage.

When Engineers design a substation, RMU, or transformer installation, they calculate the gound surface contour of voltage, and calculate the step and touch voltages, and then take action to ensure the step and touch voltages are within safe limits (which assume a 2m high human) regardles of worst case fault conditions.

For any given substation/RMU/transformer. one can draw a more or less circular line, on the ground surface, around the substation/RMU/transformer which is the closest distance a human can safely stand. For a small street trnansformer of RMU, the safe distance can be zero. For a major substation fed from a major HV or EHV transmission line, it can be 50 m or more.

Earth potential rise in LV (120/240 V) distribution due to faults to an LV conductor are a non-issue as the available voltage is not high enough to hurt anyone before a circuit breaker or other protection trips.

Keit124.182.38.215 (talk) 11:34, 6 August 2012 (UTC)

What power companies do in order to reduce Earth Potential Rise & hazardous Step & Touch voltages

There are a multitude of methods, all with their own pros & cons, but the main methods are:-

(a) Reducing the HV fault current by inserting an impedance in the earth connection at the source end of the HV line/feeder - either a resistance or inductance.

(b) In underground HV cabling, utilising the screens and steel wire armouring to carry the return current. As stated elsewhere, mutual inductance between the phase conductors and their screens and steel wire armour forces most fault current to return via the screens and steel wire armour. The ferromagnetic properties of the steel wire armour usefully enhances the mutual inductance effect. Open wire (ie wires slung on poles or towers) trasnmission can use the lighning protection conductor or power coordination conductor for this purpose.

(c) Install an effective earth electrode system at the substation/RMU/transformer to sink the fault current not returned in the screens & armouring. This "left over" current can be hundreds of amps or more, requiring a resistance to earth as low as an ohm or even less. so such earth systems can be very substantial, comprising multiple deep driven electrodes. I have acted as consulting Engineer on projects where substation earthing has cost over $1 million - much more than the substation hardware.

(d) Install a fence or wall at a safe distance, so that humans cannot approach within a Step & Touch hazardous area.

Common industry practice when planning a new HV route is to calculate the phase conductor current under worst case fault conditions (a Phase to neutral short in the substation/RMU/transformer). The maximum fault current in HV lines, due to protection coordination (ie ensuring that any circuit breaker trip due to a fault is the circuit breaker that causes power to be cut only in the system portion whewre the fault is) requirements, is of the order 18,000 Amps. However, normally, if it is 3000 Amps or less, fine. If over 3000 A, take action to reduce it to 3000 A, such as Method (a) above. Then, calculate what portion of that 3000 A or whatever it may be, will flow into the substation earth system, worst case. Then, use a suitable (ie, is economic, fits on the site, etc) combination of methods (b), (c), and (d) to get Step and Touch safety. Keit120.145.61.75 (talk) 02:42, 7 August 2012 (UTC)

Gosh, Keit, are you going for a record? So far you have used 8 different IP addresses in answering one question. Are you on the road? Edison (talk) 03:52, 7 August 2012 (UTC)

I've probably set a record as far as length of answer goes. But you asked a good question, and a good question deserves a good answer. The reason while my IP address keeps changing is 2 reasons: 1. My ISP uses dynamic IP - that is, they allocate an IP from a pool each time my PC boots up &/or connects. 2. I am developing certain software - when I want to test it, I disconnect from the public network and re-connect on a private network - otherwise via bug I could be a right pain to everyone. Sometimes, due to other software I've been testing, my PC crashes and has to be rebooted - dang, another different IP address. Keit124.182.16.69 (talk) 05:42, 7 August 2012 (UTC)

Need for Power Coordination

Energy from electricity infrastructure, especially HV and EHV transmission lines, can be trasnfer to other nearby conductors, including telephone company cabling, metal water pipes, metal sewage pipes, town gas pipes, railway lines, and even, in some cases, the steel structures of large area commercial buildings. Energy gets trasnfered in the following ways: If (say) a HV power company line, and a telephone company cable run physically parallel along a street for some distance, there will be mutual inductance between the two - in effect they form an elongated transformer - fortunately not a very efficient one. Fault currents due to substation short circuits and the like can, if the Engineers did not address the issue, cause voltages in the telephone cabling (which normally carry speech signals measured in mV, plus low voltage DC to power the phones) that can be lethal to telephone company linesmen & technicians. As insulation on telephones is designed to a reasonable price and appearance, bad cases can even be lethal to telephone users. Similarly, HV fault currents can casue voltages in pipes etc lethal to plumbers. As well as this, and even if lethal conditions do not exist, normal load currents in EHV, HV, and LV power company lines can cause "hum" in telephone company cables.

Earth potential rise in a substation can in some cases cause power frequency energy to get into the earthing system of a nearby telephone exchange (via the electricity supply cabling to the exchange - a large exchange may be fed with HV direct from the substation, for essential service reliability) - this can also cause hazardous voltages for both telephone company technicians and telephone company customers, because the phone cables radiating out from the exchange "export" the earth potential rise to all phone customer's premises. ("Exporting" of earth potential rise is one reason why in most countries it is not permitted to supply AC utility power to another metered property - e.g., an electicity customer can use an extention cord to power tools etc in his own yard, but may not use an extention cord to power devices in a neighbour's yard)

There are things power companies can do to remove the problem, or inadvertantly make it worse, and things that telephone, water and sewage, and railway companies can do to remove the problem, or make it worse. Thus there is a need for power companies and the other utilities to co-operate and co-ordinate their activities - this is called Power Coordination - and is a highly specialised branch of electrical engineering, and very rewarding, as I can tell you from personal experience. Keit124.182.16.69 (talk) 07:18, 7 August 2012 (UTC)

What power companies do as part of Power Coordination

The best and cheapest power codination is done at the planning stages - Since a problem arises by running power company lines and telephone/water/gas lines right beside each other for long distances down the same street, then try not to do it - or at least put the power company stuff on one side of the street, and the other ultilities on the other side. However, this is not always possible, and not always cost effective (e.g., if there is only one road/access to a community). There are many ways of solving the problem - below are the most common methods.

The power company can install a "shield conductor", earthed at each end, on its power line poles/towers, or in the same trench as its' power cables. Mutual inductance wil cause a current to flow in this extra conductor, and the magnetic field from this extra conductor will cancel out most of the field from the other conductors - in effect it acts as a shield for the other utilities. Shield conductors also, by carrying return current assist in mitigating earth potential rise during HV faults. The other utilities can also choose to install shield conductors, however this would be unusual.

It is possible that a substation/RMU/trasnformer earth system, although good enough to ensure Step and Touch is not a hazard, from a Power Coordination point of view, there is still a problem. If so, either the power company can install an extra low-resistance substation/RMU/transformer earthing system, or the other utilities can install earthing. Telephone companies often install enhanced earthing systems for power coordination purposes. It depends on who was first in the street (and who has the best negotiators).

Summary/conclusions

Hopefully, Edison has managed to wade thru all this, and it is of help/interest to Edison and other Ref Desk readers.

Hopefully, from all the above, it has become clear that:-

• The MEN and CMEN systems provide a sound, safe, cost effiective. electricity distribution that caters for all types of geology.
• The earth system at customer premises, need only, and should be, a prescribed short length single electrode - these electrodes carry only very small currents under both normal load and fault conditions. Their purpose is only to ensure that consumers touching exposed metal are thereby at the lowest available voltage at the site.
• The earth systems at power company substations/RMUs/transformers are designed to sink large fault currents and are intended to mitigate HV fault Step and Touch hazards and solve power coordination issues.
• Substation/RMU/transformer earthing systems are therefore typically substantial, and are individually on a case by case basis designed for specific perfomance ie a specified low resistance to great body of earth.

I have written all the above from a working knowlege of Australian standards, and practices, in particular AS 3000 Electrical Installations (formerly known as The Wiring Rules), EG-1 Substation Earthing Guide, and WA Electrical Requirements. Other standards apply. European standards are similar. The corresponding publications in the USA that cover some of the topics include the National Electrical Code (NEC), and IEEE STD-80 Guide For Safety in AC Substation Grounding. USA practice varies in detail. I have minimal knowlege of US practice although the technical libraies of employers I have worked/consulted for have copies of the NEC in their libraries. I do know that US standards can be seen as not as tight safety-wise as European and Australian standards. But it must be noted that: a) Large scale distribution of AC power occurred earlier in the USA. Those who come later can avoid early mistakes before it's too late to change. b) It's a lot harder to kill yourself with 120 V than it is with 240 V. However, basic fundamentals are just that - fundamental - they apply to everybody. So I think Edison was misinformed on some aspects, or perhaps misinterpreted local practice.

• Enjoy! Keit124.178.169.148 (talk) 08:36, 7 August 2012 (UTC)

Various minor typing errors and the like fixed. Keit120.145.72.208 (talk) 10:07, 8 August 2012 (UTC)

science/physics

Q1)an object of mass 1kg is tied with a 2m thread and it is rotated by velocity 5 m/s.calculate the centripetal force?

Q2)an object is having velocity 5m/s in east direction,now it turns to the north direction with a same speed and it takes 10sec.calculate the centripetal acceleration?

Q3)a rocket launcher launches a rocket of mass point 325 ton with velocity 50m/s and the launcher experiences a instant velocity of 3.25m/s.derive the mass of the launcher?

Q4)a bullet and a gun having velocity after shooting 500m/s and 8m/s respectively.derive the ratios of the masses?

Q5)two object of same mass,the ratio of there velocity is 1:3and ratioof there rotating radius is 3:1.derive the ratio of centripetal force? — Preceding unsigned comment added by Ekknoorkaur (talk • contribs) 04:37, 5 August 2012 (UTC)

Q6)Will we do your homework for you? I'll answer Q6. No. Looie496 (talk) 04:56, 5 August 2012 (UTC)

Genetically Modified Corn Cell

Ok so, the process of gene splicing has been used to create a recombinant plasmid. Then, this recombinant plasmid has been successfully inserted into a corn cell via a transformation method. From there, how does this genetically modified cell affect or create an entirely new crop, to carry out the newly desired functions? Any help would be GREATLY appreciated!! 220.233.20.37 (talk) 07:13, 5 August 2012 (UTC)

Presumably they don't just put it into any old corn cell, but into a reproductive cell. The corn plants produced from this reproductive cell would then contain that gene, and they would then pass it on to at least some of their offspring. As to how a gene changes the cell function, it's often accomplished by coding proteins, which then do the actual work. StuRat (talk) 07:51, 5 August 2012 (UTC)

Looking at [10], the popular methods seem to involve carrying out any of several transformation protocols on entire suspended embryos, at a very young stage. Someguy1221 (talk) 09:17, 5 August 2012 (UTC)

In theory, one can use any plant tissue [11] as plant cells can regress to regain their totipotentcy and from there can form a callus than roots and shoots and so on. That you don't need an embryo to genetically engineer in important as many crops produce worthless seed, ex Granny Smith apple trees are all descendant from a single branch through cuttings as their genetics are so heterozygous that any sexually derived offspring would be quite different from the parents. 65.95.22.16 (talk) 13:32, 5 August 2012 (UTC)

Grains like commercial wheat and corn seed are created differently from apples, though. There are intentionally out-bred. See hybrid vigor and Hybrid_(biology)#Hybrid_plants. (although neither is a very good explanation). Rmhermen (talk) 17:01, 5 August 2012 (UTC)

As 65.95.22.16 indicates, the transformation isn't usually done on reproductive cells, but rather on vegetative tissue or plant tissue culture callus. You then typically propagate the cells in cell culture (usually under selection so that only the transformed cells grow). At a certain point you can treat the callus with hormones which causes it to sprout roots and leaves, at which point you can transfer it to soil, grow it up, pollinate and collect seeds like a regular plant. This is for most plants. Occasionally you'll find other techniques, e.g. for the model organism Arabidopsis thaliana the easiest transformation method is in planta Agrobacterium transformation, where you basically dunk the whole flowering plants in the transformation solution and some of the seeds they then produce are transgenic. -- 71.35.119.233 (talk) 17:33, 5 August 2012 (UTC)

Priority of Köppen classification

My question is about the Köppen climate classification system. I am trying to determine the priority of calculation. For example, if an area is very dry and also very warm, it may well satisfy the conditions of being in Group A and Group B. The Sahara is mostly classified as Group B, hence B > A. Places in Antarctica, though, could be dry enough to satisfy Group B, but are classified Group E, hence E > B > A. Is this true? And where do C and D fit in? Thelb4^(talk) 16:23, 5 August 2012 (UTC)

It's not a question of priority. The groups are, at least in principle, non-overlapping. An area that is very dry (for the whole year) can't be in group A. It can be extremely dry for part of the year, as with savanna, but then it would have to be wet for another part of the year. Generally speaking A is hot and wet; B is dry all year and not too cold; C is temperate and not too dry; D is cold; E is polar. Looie496 (talk) 17:40, 5 August 2012 (UTC)

Because this will be archived, let me recalibrate that a bit. The basic point is valid, but here is a better description of the categories: A is hot and humid; B is dry (whether hot or cold); C is humid temperate; D is cold and humid; E is polar. Looie496 (talk) 15:36, 6 August 2012 (UTC)

HERBS in lab

hello Can you please explain the difference between oil and extract? Is oil a kind of extract? which one is the ethanolic yield from the seed? Thanks Simagoulou (talk) 18:43, 5 August 2012 (UTC)

An oil is usually taken to mean a lipid that is in the liquid phase, or more broadly any hydrophobic liquid. An extract is, IIRC, an alcohol soluble scent or flavoring element from a food product. Many extracts contain what are called essential oils, which are usually the primary aroma components. To state it another way, the "extract" is all of the stuff you get when you soak the plant in alcohol. The "essential oils" are specific compounds which provide the scents for a foodstuff. Most extracts contain a mixture of essential oils, as many plants contain more than one specific essential oil. For example, many mint plants contain menthol, but they also contain other essential oils that give each a distinct flavor, which is why peppermint is not identical in flavor to spearmint, and thus while both extracts will contain a lot of menthol, they will also contain different things as well. --Jayron32 18:55, 5 August 2012 (UTC)

Are all extracts obtained by soaking in alcohol ? If so, I'd expect the result to be mostly alcohol. Do they then remove the alcohol in some way ? StuRat (talk) 19:12, 5 August 2012 (UTC)

Our article about Extracts mentions that some are used as the alcohol (or similar-solvent) solution whereas others are produced by other processes or somehow lead to the "pure" essence rather than a solution. Some of the terminology in this field is a bit convoluted (or not quite matching the standard modern scientific meanings) because the terms were used in this field well before there was a more specific understanding of the chemistry involved. DMacks (talk) 19:25, 5 August 2012 (UTC)

As DMacks notes, the terminology is a bit fuzzy, but usually when you buy something at the grocery store called "XXX extract" whether it is vanilla extract, peppermint extract, almond extract, etc. it is an alcohol extract, and yes it is more alcohol than essential oils. You can make water-based extracts as well, I suppose; Tabasco Sauce is basically a water extract of chili peppers. However, essential oils are strong juju; pure essential oils are rediculously pungent to the point of being unusable in pure form (from the pepper example, capsaicin, the essential oil of chili peppers, will blister your skin in pure form). Things get whacky when you start dealing with extracts and essential oils in pseudoscientific "new age medicine" bullshit like aeromatherapy and stuff like that; since they're just making it up as they go along the terminology gets contaminated from those fields. --Jayron32 19:34, 5 August 2012 (UTC)

The methods of extraction of essential oils from plant matter vary: steam distillation, or solvent extraction (where the solvent is removed prior to use), or use of carbon dioxide to extract the oils from the plant matter. Jayron, if you don't think essential oils work, then please don't use menthol or Olbas oil next time you have a cold: or peppermint oil if you have an acid stomach (Colpermin to give it its OTC name): or Friar's Balsam for a bad chest. Obviously none of these remedies work because, well, it's all pseudoscience isn't it. Actually the scientific study of essential oils is growing year by year. --TammyMoet (talk) 20:11, 5 August 2012 (UTC)

The issue is not with compounds that have medically verified theraputic effects. I am quite sure that many compounds which are essential oils also have theraputic effects. The issue is that, in the popular media, the real science is contaminated with bullshit. I'm all for double-blind placebo-controlled medical studies which show theraputic effects of any compound. That's fine. I use many compounds which are extracted from plants, and remedies which have a basis in such compounds. But the fact that there is good science sadly doesn't make the bullshit disappear. After all, my local pharmacy carries homeopathic remedies on the same shelves as the actual medicine. As long as that bullshit continues then we haven't won the war... --Jayron32 04:34, 6 August 2012 (UTC)

The usual result of pseudoscience is a core of products which actually work (mints are proven to have anesthetic properties, for example), accompanied by unsubstantiated claims far what can be proven. StuRat (talk) 20:17, 5 August 2012 (UTC)

Austrian window-box plant; ID, please

Could someone ID this plant, please: http://twitpic.com/afxhtc It was seen in many window-boxes in the Salzburg area of Austria in the last couple of weeks. The flowers are about half/ three-quarters of an inch in diameter. Andy Mabbett (Pigsonthewing); Talk to Andy; Andy's edits 21:04, 5 August 2012 (UTC)

Perhaps a Sanvitalia? Andy Mabbett (Pigsonthewing); Talk to Andy; Andy's edits 21:34, 5 August 2012 (UTC)

Or a Doronicum? Andy Mabbett (Pigsonthewing); Talk to Andy; Andy's edits 21:48, 5 August 2012 (UTC)

Sanvitalia seems correct. Likely Sanvitalia procumbens, which is widely cultivated and seems to have dozens of cultivars.-- OBSIDIAN†SOUL 09:45, 6 August 2012 (UTC)

Can mosquitos breed indoors ?

I have a spare bathroom I only use for the shower, and it tends to stay humid in there. Over the course of a week I killed a dozen mosquitoes in the bathroom, and only a couple in the rest of the house. Could they be breeding down the (rarely used) sink drain or in the toilet bowl ? I wouldn't think there would be any food for the larva there, but I might have rinsed out a bowl in there and left some food residue in the drain. I flushed the toilet several times, and ran the water in the sink for a bit, then poured bleach in both, and haven't had the problem since. Any thoughts ? StuRat (talk) 23:49, 5 August 2012 (UTC)

Googling suggests mosquito larvae in unused toilet bowls is a relatively common problem. E.g. Scrub all the fixtures with bleach. 70.59.11.32 (talk) 00:07, 6 August 2012 (UTC)

It doesn't take much. Mosquito larvae can make do on nutritionally weak food sources and, in some species, subsist entirely on algae. I wouldn't be surprised if the scummy water left in a drain might harbor enough bacteria to bring a handful of larvae to adulthood. Someguy1221 (talk) 05:13, 6 August 2012 (UTC)

Thanks. I was wondering how else they could all have gotten in. StuRat (talk) 19:17, 6 August 2012 (UTC)

Resolved

August 6

Question about the plutonium in the curiosity rover

On the talk page for the Mars Science Laboratory, I posted a question about the plutonium generator in the Curiosity rover. Please take a look, thanks. 67.182.25.41 (talk) 08:03, 6 August 2012 (UTC)

It was an easy mistake to make. The figure given for the beginning of the mission is the total thermal energy produced by the fuel, whereas the figure given for the end of the mission specifically refers to the electrical output. It should also be noted that the relationship between remaining fuel and electrical output is not linear but is defined by the Seebeck effect, which is itself dependent on the temperature of the two nodes of the thermocouples used. So you actually expect a greater-than-exponential loss of power as the mission goes on. But anyway, the actual figures are 125 watts at the start of the mission, and 100 at the end. Although the RTG is actually designed to output 285. Someguy1221 (talk) 08:27, 6 August 2012 (UTC)

Oh, I take that back. I see simply read the passage too fast, and the distinction is made clear. Someguy1221 (talk) 08:28, 6 August 2012 (UTC)

Landing on Mars and coming back

Did some rover, or anything similar, ever landed on Mars and came back? Or is the Curiosity rover and its predecessors just meant to land, perform their work there and report the data to Earth? — Preceding unsigned comment added by 79.155.237.76 (talk) 11:34, 6 August 2012 (UTC)

No, no spacecraft has yet landed on Mars and returned, but there are plans for such a mission, see Mars sample return mission. - Lindert (talk) 12:08, 6 August 2012 (UTC)

I'm surprised they would even consider a return mission. For much less extra fuel and rocket size I'd expect they would be able to just include more analysis equipment. The one advantage I could see is that it might be preparation for a human mission, in which case they should send an exact replica of the human capsule, with either empty seats or maybe a monkey or two (hopefully trained to use the toilet facilities). StuRat (talk) 19:15, 6 August 2012 (UTC)

One advantage of doing the analysis on Earth is that you can analyse things you didn't think of before you started. With in-situ analysis, you only have the equipment you thought of in advance. You can't spot something interesting and then come up with a new experiement to analyse it further. There are also things you can learn that would be useful for a human mission without the return capsule accurating simulating a manned one. --Tango (talk) 11:27, 7 August 2012 (UTC)

And why wasn't it done yet? Why is it easier to transport the scientific equipment to Mars than to enhance the rover with a return device? 79.155.237.76 (talk) 12:31, 6 August 2012 (UTC)

Seems pretty obvious, doesn't it? A two-way trip would mean equipping the rover to somehow blast off of Mars. That means shipping a lot of fuel, an extra rocket, etc. Make no mistake: sending something on a rocket to Mars from Earth is hard. Sending something to Earth from Mars is no easier. --Mr.98 (talk) 13:05, 6 August 2012 (UTC)

But, the escape velocity of Mars is smaller than of the Earth, and the way Earth-Mars-Earth is almost for 'free' (I believe).

It's still obviously a lot more work to make a lander that can autonomously blast off again than it is to make one that just stays there. --Mr.98 (talk) 15:05, 6 August 2012 (UTC)

The escape velocity of Mars is indeed lower, but the latter bit is entirely wrong -- you don't subtract the energy load when making the return trip; rather, you add further requirements. And while comparatively less fuel is needed for Mars -> Earth than Earth -> Mars, you have to use a lot more fuel on the (less efficient) Earth -> Mars leg to get your return rocket to Mars in the first place. Also consider: Curiosity (mass approx 1000 kg) was delivered to Mars by an Atlas V rocket, and we'll assume that 1000 kg is functionally the most mass that could have been so delivered by that platform. 1000 kg probably isn't enough to return anything from Mars to Earth. The Atlas itself weighs 340000 kg, so that's a 340:1 mass-to-payload ratio for the Earth -> Mars trip. You'd have (even granting the lesser escape velocity from Mars) less than 10 kg of total science package plus Earth-return package plus payload to play with, and that has to include all the stuff you need to survive re-entry at Earth. So why not use a bigger rocket? Because the Atlas is functionally the heaviest operational rocket available currently (+/- 10% or so). — Lomn 15:06, 6 August 2012 (UTC)

On the other hand, there was also the (failed) Russian Phobos-grunt probe, which would have attempted to return about 200 g of soil from Mars' moon Phobos. You get around the problem of getting off Mars, though the fuel then required for the return trip is similar. It was launched on a Zenit-2M, a somewhat less-powerful rocket than the Atlas 541 that launched the MSL. It's unclear how big the actual return-rocket of the Phobos-grunt probe was. Buddy431 (talk) 18:22, 6 August 2012 (UTC)

Updates To Darwin's Theory of Evolution by Natural Selection

Sorry if this is a somewhat common question; when you search the web and the reference desk archives, there's a lot of junk to filter through.

Does anyone know of a reasonably comprehensive list (for the layman) of modifications which have been made to Darwin's theory since he first proposed it? By this, I don't mean updated knowledge of the details of the events that occurred or the underlying chemical processes; I only mean modifications in the understanding of the principle. I'm no biologist, and the only example of an update that I'm familiar with is the selfish gene theory, but I'm sure there are many others.

Thanks. --75.102.79.215 (talk) 16:47, 6 August 2012 (UTC)

Have you seen the modern evolutionary synthesis article ? There's the history of evolutionary thought article too. Sean.hoyland - talk 17:05, 6 August 2012 (UTC)

History of evolutionary thought#Alternatives to natural selection onwards gives an overview with links to more detailed articles, if you want a book then Bowler, Peter J. (2003). Evolution: The History of an Idea (3rd ed.). University of California Press. ISBN 0-520-23693-9. {{cite book}}: Invalid |ref=harv (help) (or the more recent edition) gives pretty good coverage. . `dave souza, talk

The most significant modification seems to be that evolution doesn't happen at a slow, steady pace, but in jumps and starts, like growth spurts in a teenager. The causes are complex, such as a changing environment (or introduction to a new one), or the addition, loss or change of an interacting species (a predator, prey/food, competitor, or symbiont). We have also discovered the mechanisms of inheritance (DNA) and mutation, but that doesn't modify Darwin so much as add detail. StuRat (talk) 19:03, 6 August 2012 (UTC)

See Punctuated equilibrium. I think your explaination is misleading. Both the PE and Phyletic gradualism models appear to be legitimate models for understanding historic evolutionary patterns [12]. The question of the frequency of each model is an unresolved issue and besides, looking at it as a dichotomy is usually seen as flawed anyway. I also suspect you will find that many evolutionary biologists do not agree with your view that it's the most significant modification, in fact I think many would even question whether it's really a significant modification at all, see our article or [13] [14] [15] [16]. Nil Einne (talk) 21:16, 6 August 2012 (UTC)

I am a fan of Gould's but Nil is correct here. μηδείς (talk) 23:16, 6 August 2012 (UTC)

And he's entirely wrong that the mechanisms of inheritance don't modify Darwin — they have profound effects on making sense of evolution. --Mr.98 (talk) 22:31, 6 August 2012 (UTC)

No, if it modified Darwin it would prove that something he said was wrong. It just adds detail. StuRat (talk) 22:58, 6 August 2012 (UTC)

Have you actually read Darwin, much less his discussion of heredity in his theory? Much of it is not correct. --Mr.98 (talk) 16:49, 7 August 2012 (UTC)

What portion of Darwin was proven wrong by "the mechanisms of inheritance (DNA) and mutation" ? StuRat (talk) 22:39, 7 August 2012 (UTC)

Anything related to Pangenesis, for one thing. --Mr.98 (talk) 23:01, 7 August 2012 (UTC)

The most important modification is known as the modern evolutionary synthesis. Basically what this means, in lay terms, is the merging of Darwinian natural selection with modern understandings of population genetics. This took a lot of work and happened relatively recently (the 1930s or so) — before then was a sea of competing theories torn between the neo-Darwinians (like August Weismann) and the biometricians (like Karl Pearson). (It is amazing to many in retrospect that Darwin was not seen as particularly correct in the period between his death and the creation of the MES.) The MES is basically a version of evolutionary theory that takes the best of both of those worlds and makes them into one coherent theory. Aspects of it would be recognizable to Darwin but much would be new to him, as he had by modern standards a quite poor understanding of how heredity worked and that has big implications for making sense of the theory. As for other sub-theories (like selfish gene), there are tons... Category:Selection is a nice place to start for much "smaller" topics. --Mr.98 (talk) 22:31, 6 August 2012 (UTC)

The answer, given twice above, is the modern evolutionary synthesis. Part of that, and the most important, is Mendelian genetics followed by the elucidation of the nature and function of DNA by Watson and Crick. There is also the mathematicalization of population genetics by Dobzhansky, et al., and the biological species concept of Ernst Mayr. Most importantly, these are all elucidations. Nothing contradicts Darwin's theory of evolution by natural and sexual selection. μηδείς (talk) 23:14, 6 August 2012 (UTC)

Well, unless you count all of the other modes of selection Darwin never thought about, and ignore all of the parts of Darwin that are, err, contradicted by later research (like Darwin's own theory of how heredity worked in evolution). --Mr.98 (talk) 16:50, 7 August 2012 (UTC)

Thomson jumping ring

In a Thomson jumping ring experiment, how do you derive the relationship between the mass/current/temperature of the ring and its jump height?--150.203.114.14 (talk) 17:44, 6 August 2012 (UTC)

It is worked out in an article from The Physics Teacher, available at http://physicsed.buffalostate.edu/wnypta/meetings/2004-05/02-05-05/Hall1997TPT35p80-83.pdf. Looie496 (talk) 18:30, 6 August 2012 (UTC)

WP:WHAAOE has failed! Thomson jumping ring is a redlink... Roger (talk) 16:33, 7 August 2012 (UTC)

Point it to Electrodynamic suspension? DMacks (talk) 16:39, 7 August 2012 (UTC)

Sci Fi Movie Another Earth

In the movie Another Earth, a second Earth appears in our horizon, which looks as far away as our moon. Due to it's proxmity, what would be the physical consequences of earth in the movie Another Earth? Reticuli88 (talk) 18:09, 6 August 2012 (UTC)

Greater magnitude of (due to more mass in close proximity) and variability of (due to varying orbital periods) tidal effects, nighttime reflected sunlight, and solar eclipses. — Lomn 18:28, 6 August 2012 (UTC)

Specifically, I ballpark the tidal influence of Earth2 as being about 5 times that of the moon: Earth2 sits at 4x lunar orbital radius (as Earth is about 4x the radius of the moon), and is 81 times as massive. 81/4² = 5. — Lomn 18:33, 6 August 2012 (UTC)

More importantly, if I recall correctly that's an unstable configuration. In a short period of time the moon would either hit one of the planets or (more likely) be ejected from the system. The two planets would then either drift together or drift apart. Looie496 (talk) 18:37, 6 August 2012 (UTC)

Tide is proportional to the inverse cube of distance; 81/4³≈5/4 —Tamfang (talk) 20:05, 6 August 2012 (UTC)

The second Earth doesn't looks as far as the moon. It looks as big as out moon. Since the earth is bigger, it would be much far away than the moon. Comploose (talk) 18:52, 6 August 2012 (UTC)

I based my numbers on "Earth2 has the same angular size (looks as big) as the moon". However, looking at the pictures in our article, Earth2 is in fact pictured by the film as being far closer than the moon's orbit, which would easily result in immediately catastrophic consequences. — Lomn 19:16, 6 August 2012 (UTC)

In the productions notes in the wiki article:

"The DVD/Blu-ray deleted scenes feature reveals that the filmmakers did intend to illustrate some of the consequences to gravity by filming a scene in which Rhoda encounters flowers floating in mid-air, but the scene was cut from the final film."

...would floating flowers really be possible? What other things would we observe happening if such a thing occured? Reticuli88 (talk) 19:42, 6 August 2012 (UTC)

No. The change in gravity even on the near-Earth2 side of the Earth would be undetectable over small scales. Someguy1221 (talk) 20:05, 6 August 2012 (UTC)

Changes of gravity don't only affect light things. Consider that gravity, besides holding flowers down, holds the ground down. —Tamfang (talk) 20:08, 6 August 2012 (UTC)

Yeah that would have been a terrible gaff. Vespine (talk) 22:21, 6 August 2012 (UTC)

Silviring Analogues for other Metals

I know that you can coat something with a thin layer of silver just by putting it in a hot mixture of Tollens' reagent and sugar, but are there other similar reactions that can be used on non-metallic surfaces but using other metals? I am specifically thinking about possible use for coating something to make it conductive enough to electroplate, so the metal doesn't matter as long as it is cheaper than silver. Bakmoon (talk) 22:21, 6 August 2012 (UTC)

In the electronics industry, there is a need for ceap arbitarily or odd shaped "shield boxes", Over the years, a number of processes for giving molded plastic boxes a conductive surfacehave been developed. A common one is the Pearlstein process: First, "sensitising" is done with a bath of SnCl₂ solution. Next, it is "activated" in a bath of PdCl₂ solution. The result is a reliable but thin conductive surface that can be built up by electroplating. Electonic parts are mounted in printed circuit boards. These boards comprise an insulator substrate, eg fibreglas or phenolic, about 1.6 mm thick, on which copper tracks are manufactured. Often, tracks are on both sides, and plated through holes (PTH) connect from one side to the other, and provide places where the wire end of the parts are soldered. At first the Pearstein process was used to make PTH's conductive after drilling the substrate. Since then better methods have been developed - you might like to research the Atkinson & Wein process and CU-EDTA. You could do a patent search on PTH. You could also consider "aquadag", which is a "paint" comprising fine carbon particles mixed in a water soluble binder. Once somthing has been "dagged" it can be electroplated. This may be acceptable for hobby use or one off's - it is a bit too slow and fussy for production use. Keit121.221.208.142 (talk) 23:05, 6 August 2012 (UTC)

One can chrome plate plastics. There are many ways to make a mirror on various non-metallic substrates, for example using elemental mercury (not sure the process for depositing it) or aluminium (vacuum deposition probably the most common). I've made some really cool-looking metal-film mirrors on various glass objects by precipitation of metallic lithium or sodium, but obviously those are a bit hard to handle (and probably not suitable for most electrochemical cells). DMacks (talk) 23:10, 6 August 2012 (UTC)

Such methods are either difficult, or use hazardous materials though. The advantage of electronics industry methods such as Pearlstein, Cu-EDTA, and aquadag is that they don't require exotic methods, are easy to use (though cleanliness is key) and the chemicals are not particularly hazardous. Keit120.145.61.75 (talk) 02:06, 7 August 2012 (UTC)

What makes Curiosity so special?

Hi all, What makes the Curiosity rover so special compared to previous Mars rovers? There seems to be more excitement over this one than previous landings (if I recall correctly). - Akamad (talk) 22:45, 6 August 2012 (UTC)

It's the most advanced to date. Shadowjams (talk) 22:51, 6 August 2012 (UTC)

The Curiosity rover has an incredibly complex landing system, so people might just be amazed that anything that complex can actually work. StuRat (talk) 22:54, 6 August 2012 (UTC)

It's a tremendous boost for ailurophobes. Clarityfiend (talk) 23:03, 6 August 2012 (UTC)

Thanks. I also ended up finding some information here. - Akamad (talk) 23:05, 6 August 2012 (UTC)

I'll also add that the previous rovers were pretty much limited to looking at things, although in addition to regular cameras they could look with spectrometers, microscopes, X-rays, and even the result of blasting a rock with gamma rays. But the Curiosity can do real chemistry on Martian rocks and soil, and let us learn a lot more than we could in the past. Someguy1221 (talk) 23:10, 6 August 2012 (UTC)

The Curiosity is a huge advancement in the Planetory Exploration process that is so very vital to the Success to the human race and maybe the discovery of new life forms even if it is the dead ancester of some Microbe. -concerned Life form

Like something from space!

• For mac cultists or UK fans, its computing power as supplied by BAE is essentially the G3 as used in the original iMac G3,[17] with the same operating system as the AirPort Extreme.[18] . . So that makes it kinda special! . . dave souza, talk 22:52, 7 August 2012 (UTC)

How close would an alien species have to be to detect us if they had our current level of technology?

If an alien species had our current level of technology and they were to focus detection efforts on our portion of their celestial view looking for alien (to them) signals, how close would they need to be to detect us given our output of signals--light, television, radio—whatever we broadcast that they might detect)? One premise: let's ignore time delay. What I mean is that a species forty light years away, if they could detect our electromagnetic output, would only be able to detect what was put out forty years ago. I don't want to limit it in this way. So at any time. Signals spread out and get weaker over distance so I assume it's pretty limited. To state it backwards, if there were aliens on a planet orbiting proxima centauri with our current level of technology, would they be able to detect us given what we output? Barnard's star? and so on, growing more distant.--108.54.25.10 (talk) 23:12, 6 August 2012 (UTC)

I suspect that the answer very much depends on directional transmissions and receivers. If we put all our technology to work to send a powerful signal to a specific planet, and they happened to have put all their technology to aiming a powerful directional telescope right at Earth (or where Earth was) when the signal comes in, then they could be far more distant than if they just try to detect signals when only random radio and TV signals arrive. In the later case, I'd think they would need to be within our own solar system. Of course, the aliens would also need to avoid looking toward Earth when we are behind the Sun or in front of it, as interference from the Sun would make our signals hard to pick out. So, the answer might come down to how close they would need to be to detect Earth, since that's a prereq for them to point a powerful antenna at Earth. StuRat (talk) 23:23, 6 August 2012 (UTC)

This is discussed on our article on the Fermi paradox. Dominus Vobisdu (talk) 23:27, 6 August 2012 (UTC)

I'm just gonna copy my comment from last time this was asked, since I was the only one to respond:

In the best case scenario, the Arecibo message is received at another planet while that planet has its own Arecibo-sized dish pointed directly at Earth. In this case, even a pessimistic estimate gives the Arecibo a detectable range of 10,000 light years [19]. In that same page, it is noted that Frank Drake claims the technology exists to boost this range ten-fold. It's hard to imagine, however, that we'd manage to land the message right on an equivalent detector. I recall seeing a calculation (but I can't recall where), that a modern radio receiver without a directional dish like Arecibo would detect the message from ~400 light years at most. A non-directional emitter and a non-directional detector would have a drastically reduced range, and with modern equipment (I'm told), you may have trouble communicating with Alpha Centauri. Someguy1221 (talk) 04:09, 19 March 2012 (UTC)

If Aliens were pointing their version of the Arecibo Observatory at us, they should be able to detect us easily from a few hundred light years away. All of this is answering based on what has already been built. We have the technology to build, if we so desired but it would be very expensive, intergalactic radio transmitters. Not that we would get any use out of them in our lifetime. But as mentioned in the article linked by Dominus, if the aliens aren't listening to the stars, they won't hear us, unless we happen to nail them directly with Arecibo, and from relatively nearby. Someguy1221 (talk) 23:33, 6 August 2012 (UTC)

• Given that the speed of light is a limitation, they'd have to be no more than about a light century away to detect our radio broadcasts, likely much closer. The fact that we have an oxygen-rich atmosphere almost mandates the presence of photosynthetic, if not intelligent life. Detecting oxygen from other planets' atmospheres is at just about our level of skill now; although we have not done it yet, we do know how. μηδείς (talk) 23:41, 6 August 2012 (UTC)

• The OP specifically asked us to ignore the speed of light delay. StuRat (talk) 23:45, 6 August 2012 (UTC)

In that case my points are false. μηδείς (talk) 02:46, 7 August 2012 (UTC)

If you mean our technological ability, we could build space VLBI telescopes which could detect city lights and radar signals tens of thousands of light years away, and campfires on an Earth-like planet hundreds of light years away, given the necessary budget and clearances. However, only the military uses the formation flight technology enabling large synthetic apertures, and they keep it secret and actively dissuade astronomers from using it. So our actual passive detection capabilities of city lights are presently limited to the few earth like planets within a few dozen light years. Write your congresspeople. 70.59.11.32 (talk) 03:07, 7 August 2012 (UTC)

If you simplify the problem to that of being able to detect some transmitter that transmit some signal at some power at some frequency using a given receiver with some given antenna, then the distance at which you can detect that signal depends on the noise and the integration time. Now, you can estimate the noise, but the integration time is arbitrary, it is bounded by the time the transmitter is going to transmit the signal.

Then if there are a large number of transmitters that transmit on various frequencies for different time periods, you could still extract this fact without being able to resolve the individual transmitters, if the (unknown) formal description of the set of the transmitters is simple enough compared to the number of transmitters. Count Iblis (talk) 16:19, 7 August 2012 (UTC)

• There is no way to shield a planet's atmosphere from being analyzed spectroscopically. Given that the presence of advanced life on a planet is likely to drive its atmosphere away from equilibrium, one should search for planets withg oxygen-rich or other non-stable atmospheres. Such planets having been identified, one can scan them intensively for radio or other unexpected transmissions. I apologize for repeating myself. μηδείς (talk) 22:23, 7 August 2012 (UTC)

August 7

Scientific article self-criticism

Hello. I was wondering what the standard procedure is for including a discussion of the limitations or possible flaws of a scientific study (in chemistry in this case, though I doubt it matters) within the paper itself. DOes one generally put an independent section at the end, or what? thank you 134.48.233.92 (talk) 01:50, 7 August 2012 (UTC)

The standard structure of a scientific paper is Introduction-Methods-Results-Discussion, and that would be part of the Discussion section. Looie496 (talk) 02:28, 7 August 2012 (UTC)

It does vary.

I suggest that you go to the library of a nearby university and look at a range of scientific journals, and/or look online for scientific papers now available free, such as those put on the Web by the British Royal Society (http://rspa.royalsocietypublishing.org/). Most universities have guideline booklets - try a university bookshop. Some academic circles like the structure given above by Looie496, others prefer a structure such as Executive Summary - Conclusion - Methods & Results - Discussion - Appendicies (if appropriate).

The structure given by Louie496 is favoured by high school and college teachers, and some univesities. The structure I gave is especially favoured in industry - as it allows management, who normally don't have the time nor the expertise to understand the details (that's what they hired YOU for) to quickly decide a) your worth, and b) the commercial value of what you came up with.

If you have identified minor flaws or limitations in work you have done yourself, that do not invalidate your conclusions, you should normally include details in your discussion section. If you have identfied flaws that prevent a conclusion (sometimes an experiment you've designed fails to work due to unexpected reasons), you would include details in your discussion, and summarise it in the Executive Summary. If you are reporting on your own work, and sincerely believe you have done good work and your conclusions are valid, but you are aware that another researcher/worker/group has drawn opposing conclusions, the professional thing to do is to summarise the opposing view in an Appendix, ending with your critique of it. You don't need to copy their entire paper, you just need to reference and summarise it.

In writing any scientific paper, you should keep uppermost in your mind three fundamental things:-

1. Write for your target audience.

2. A good scientific paper does not just describe youy findings and what you did to get them. A good paper gives just sufficient (and only just sufficient) information so that (a) another competent worker can duplicate your experiment or research, and (b) allows a competent reader to spot any mistakes or omissions in your work. This can be harder to do that to describe, but it is the mark of a good paper. For example: "I tested the melting point of an xyz lead alloy by heating it until it melted. The experiment was repeated a few times and the result averaged." That's no good. "I tested the melting point of an xyz lead alloy by heating a 100g sample in a steel crucible with a gas flame. I repeated the test 6 times, allowing it to cool each time, and averaged the result" That's much better - other folk reading your paper might suspect you forgot the effect of the lead dissolving some of the iron, and they can either take into account the inaccuracy, or repeat the test with a better crucible.

3. Just because a good structure is Summary-Conclusion-Method&Results-Discussion, or whatever, it dosen't necesarily means that's what the headings must be, but the structure should be obvious.

Keit120.145.61.75 (talk) 03:29, 7 August 2012 (UTC)

I would be very surprised to see the outline(s) described by 120.145 used in a paper presenting primary research in a peer-reviewed scientific journal, which I strongly suspect is the type of situation considered by the original poster. The Abstract - Introduction - Materials & Methods - Results - Discussion - References outline is pretty much standard for academic journals (with the occasional publication that slots the Materials & Methods in after the Discussion) presenting peer-reviewed papers that are written by scientists, for other scientists—as opposed to papers written for executives, managers, politicians, or the lay public.

The limitations of a study (along with contradictory results in the published literature) are almost always addressed in the Discussion section, though there is often some connection to points brought up in the Introduction. TenOfAllTrades(talk) 04:18, 7 August 2012 (UTC)

I did say that the Summary-Conclusion-Method&Results-Discussion format is favoured in industry, and the Introduction-Methods-Results-Discussion format is more favoured in academia. Abstract is just another name for summary, though the term abstract does suggests a summary that may employ language at a specialist level, whereas the term executive summary suggests that a more lay style of language should be used. I do agree that the Abstract - Introduction - Materials & Methods - Results - Discussion - References format is very common to peer-reviewed journals. I see no evidence that the OP is in an academic environment or a commercial environment, but note that if he/she is ready to submit to a peer-reviewed journal, it is unlikely that he/she hasn't already had exposure to such journals, and should already be familiar with common formats, and indeed the "house style" of any target journal. I had considerable research & development experience, and had written many papers, while working in the research department of a large company, long before I went to university (on company sponsorship). None of those papers were published in external journals (most of them were commercially sensitive), but that does not mean they were not legitimate. They all conformed to Summary-Conclusion-Method&Results-Discussion format. A format without a single paragraph Executive Summary and a Conclusion right at the front would not have been accepted. Keit124.182.16.69 (talk) 05:33, 7 August 2012 (UTC)

I admit that I'm reading something into the OP's use of the word 'paper'. A private-sector document that was not intended for external publication is more likely to be termed a 'report', whereas 'paper' tends to be used to refer to written works that come from the academic side of the fence. (It's not a 100% hard-and-fast rule, of course.)

I'm also guessing academic (and relatively inexperienced, at that) because this question is being asked. Someone with years of experience would know the answer to the question already because of their extensive exposure to the literature; I suspect that we're dealing with a fairly young individual: perhaps an undergraduate doing a critique of a paper, or a summer student or younger grad student preparing one of his first manuscripts for publication.

Finally, of course, the OP's IP address is assigned to Marquette University—which I think is rather suggestive. TenOfAllTrades(talk) 15:57, 7 August 2012 (UTC)

Sodium triphosphate alkalinity?

How can I convert sodium triphosphate solution molarity into pH? Ideally I'd like a general formula, not just a pH of specific molarities. 70.59.11.32 (talk) 02:56, 7 August 2012 (UTC)

You'll need the 5 K_a values for triphosphoric acid. From those you can calculate [H⁺] and thus the pH.--Jasper Deng (talk) 03:08, 7 August 2012 (UTC)

"The first two pK_a values are small, pK_a3 is 2.30, pK_a4 is 6.50, and pK_a5 is 9.24."[20] I don't understand how to use these values for acidity to get alkalinity, and am hoping there is an article explaining the [H⁺] formula. 70.59.11.32 (talk) 09:14, 7 August 2012 (UTC)

In this case, then, it may be valid to assume that there is negligible disassociation after the first two protonations, so you only have to consider the last three. Depending on the amount of precision you want, though, this calculation can be arduous. See acid disassociation constant for what I'm talking about.--Jasper Deng (talk) 16:14, 7 August 2012 (UTC)

Acid dissociation constant. DMacks (talk) 17:03, 7 August 2012 (UTC)

Oh, it's coming back to me now. I repressed all this (which seems like a reasonable coping mechanism.) So for B + H₂O ⇌ HB⁺ + OH⁻, K_b is going to be K_w (which depends on temperature) divided by K_a. The temperature is going to vary unpredictably over a wide range for the underlying question, but it seems like subtracting from 14 is the accepted thing, accurate to a few percent at 25 Celsius. 70.59.11.32 (talk) 20:28, 7 August 2012 (UTC)

H2o2

We musn't give advice in situations where a wrong answer could be fatal. Looie496 (talk) 15:54, 7 August 2012 (UTC)
The following discussion has been closed. Please do not modify it.
What would be the fastest way to breakdown a liter of h2o2 from local pharmacy (i think concentration is 3%) to regular h2o in case of emergency? How long would it take?GeeBIGS (talk) 07:29, 7 August 2012 (UTC) If you are trying to get drinking water, wouldn't it be easier to store drinking water ? (Store it in glass bottles, so it won't absorb chemicals from plastic.) If, for some strange reason, you find yourself with just hydrogen peroxide, how about pouring it into a blender and turning it on, to increase the reaction rate ? StuRat (talk) 07:39, 7 August 2012 (UTC) Yes. But when all the water is gone and the filters are spent and there is no electricity for the blender for like a year and for some reason surprisingly I still have like a half bottle of peroxide left .....What would be the fastest way to breakdown a liter of h2o2 from local pharmacy (i think concentration is 3%) to regular h2o in case of emergency? How long would it take?GeeBIGS (talk) 07:46, 7 August 2012 (UTC) Considering that people regularly gargle with 3% H2O2, it's apparently not all that bad in it's initial form. However, if you've lost electricity, how about pouring it into a bowl and stirring with a whisk ? StuRat (talk) 08:00, 7 August 2012 (UTC) Even just 3% hydrogen peroxide can kill rats if swallowed, and our own article mentions some human consequences of ingesting it. I don't think it would be appropriate for anyone here to tell you how to turn H2O2 into drinking water lest you actually try it. Someguy1221 (talk) 08:07, 7 August 2012 (UTC) Your link labeled "can kill rats" is the MSDS, which says nothing about it killing rats. StuRat (talk) 09:26, 7 August 2012 (UTC) Are you sure? "Hydrogen Peroxide: ORAL (LD50): Acute: 2000 mg/kg [Mouse]"[21]A8875 (talk) 10:40, 7 August 2012 (UTC) That explains it then. I did a search on "rat" and didn't find it. A mouse isn't quite the same. StuRat (talk) 22:36, 7 August 2012 (UTC) Give me a break. All this desk talks about is crazy chemical reactions noxious explosive radioactive substances and you don't tell the op to try it. Did you just tell me to blend peroxide and drink it. Ok here goes....thanks.GeeBIGS (talk) 08:17, 7 August 2012 (UTC) Have you read Hydrogen_peroxide#Decomposition? Throw in your silver. (Not sure how long it would take.) --Colapeninsula (talk) 09:20, 7 August 2012 (UTC) I seem to recall that crushing a mammals liver and throwing in an extract does it pretty well, due to traces of peroxidase.--Gilderien Chat|List of good deeds 13:30, 7 August 2012 (UTC) Potassium iodide is commonly used as a catalyst for decomposition in the Elephant toothpaste demonstration. It is also the iodizing agent in iodized salt. I don't know how well table salt would work, and in the end I suppose you would end up with salt water, which probably isn't what you're looking for... KI is also distributed for radiation emergencies to limit the uptake of radioactive iodine isotopes. If your theoretical emergency shelter has a stockpile of KI pills in case of nuclear attack, then maybe you could use one of those to catalyze it. 209.131.76.183 (talk) 15:07, 7 August 2012 (UTC)

This is not settled policy, if the poster requires more information he should feel free to ask for it. μηδείς (talk) 22:18, 7 August 2012 (UTC)

bug identification

Resolved

Can anyone identify this bug for me, please?—msh210℠ 17:44, 7 August 2012 (UTC)

It's definitely not a bug, it looks like a type of fly. What size is it? Roger (talk) 18:01, 7 August 2012 (UTC)

I was using bug colloquially. It's about an inch and a half long (ignoring the wings and feet).—msh210℠ 18:47, 7 August 2012 (UTC)

From the mouthparts and the general shape, it's either a robber fly or (less likelier) a mydas fly. That's about as far as identification can go without going to an expert and getting clearer photographs.-- OBSIDIAN†SOUL 18:12, 7 August 2012 (UTC)

It looks redder than any of our pictures of the Mydas fly, and than most of our pictures of the robber fly. Hard to tell (as you noted, Obsidian Soul) in my pictures, but this was reddish throughout: a sort of burnt sienna (or so) in some places and a sort of burgundy (or so) in others. (Except the wings, which were pale.)—msh210℠ 18:47, 7 August 2012 (UTC)

If it helps for identification, I found this bug in St. Louis County, Missouri. Thanks for the answerers' help thus far.—msh210℠ 18:47, 7 August 2012 (UTC)

It looks almost certainly to be "Hanging Thief" of some sort to me (which is in fact a type a robber fly of the genus Diogmites). Missouri would certainly be smack in the middle of their usual range. Specifically it seems likely to be a specimen of Diogmites ternatus, but the level of resolution in the photos leaves some doubt. That site is a great resource for entomological identification, btw, and you can always upload the images there for further (somewhat expert) opinions. Snow (talk) 19:24, 7 August 2012 (UTC)

Yes, that is, indeed, what it looks like. Thanks so much!—msh210℠ 19:39, 7 August 2012 (UTC)

Happy to be of help. :) Snow (talk) 19:41, 7 August 2012 (UTC)

Proof crosswords help with any objective cognitive function

I've seen a few critique articles of "brain game" (such as lumosity) garbage claims (which I'm not defending) that show evidence that doing such things only makes you good at those games with no transferable benefits, and more than one of the articles end with the same "you're better off playing a crossword puzzle." But is there objective evidence that that does anything other than make you good at crossword puzzles? 20.137.18.53 (talk) 18:42, 7 August 2012 (UTC)

You're right to be skeptical; there are a lot of non-empirical claims thrown about suggesting very precise correlations between various "brain teasers" and benefits to various cognitive functions and these are often untested (and even, to varying degrees, untestable, given the complexities of the mental functions involved). All of that being said, crosswords, being as popular and enduring as they are, have gotten a little bit more exposure to genuine structured inquiry (1, 2, 3). All of that being said, there's very little doubt that crossword puzzle does stimulate some amount of cognitive function in the area of memory recall, both in terms of maintaining the general robustness of those areas and in committing specific facts to memory (or reaffirming and strengthening those already there). But of course that's clearly obvious; making any more substantive claim than this general assumption is problematic, however. No mental task exists in a vacuum of course, and any activity which requires your focus is adapting your brain to process certain types of information, but as to which puzzle is likely to lead to a quantifiable uptake in which variety of cognitive performance (other than, as you say, repeating that exact task), I'd beware of any highly specific claims. Snow (talk) 20:17, 7 August 2012 (UTC)

This reminds me of my experience in selecting and hiring new employees (for technical roles). A current fad amongst human resource people is to have potential new empoyees do a so called aptitude test, such as Raven's Progressive Matrices (http://en.wikipedia.org/wiki/Raven%27s_Progressive_Matrices). In my experience, there is NO correlation between how well new employees turn out and their raven score. Doing well in a Raven test just proves you can do well in a Raven test. It is well known in the engineering game that occaisonally you get a new chap who has an outstanding academic record, honours, high exam marks, etc, but is fairly hopeless on the job. It seems that some folk are just good at passing exams. So yes, I think playing games alleged to improve cognitive ability probably just only improves your ability to play those games. Our local newspaper started printing a certain type of game in each Saturday issue. At first I found them very difficult and did not solve many of them. Now, after a year's practice, I solve them consistently in seconds. Does this make me a smarter perosn? I really don't think so. Wickwack124.178.171.30 (talk) 22:54, 7 August 2012 (UTC)

effect of exercise on cholesterol blood testing

Does exercising vigorously before taking a blood test for cholesterol levels affect the results of the test? — Preceding unsigned comment added by 98.207.213.14 (talk) 21:05, 7 August 2012 (UTC)

I think it could, yes. In any case, multiple tests are required, since any one test isn't that useful of an indicator. StuRat (talk) 22:33, 7 August 2012 (UTC)

It can. See [[22]]. Dominus Vobisdu (talk) 23:23, 7 August 2012 (UTC)

mars rover

How will the mars Rover get off of mars?

-wikifriend — Preceding unsigned comment added by 205.142.178.36 (talk) 21:39, 7 August 2012 (UTC)

Well how would you figure the Rover would get off of the red Planet? I just want to know what the plan is.— Preceding unsigned comment added by 205.142.178.36 (talk • contribs)

There is no plan. When the curiosity's nuclear battery finally dies, it will simply sit there forever. Perhaps one day future Mars explorers will recover it to send it to a museum on Earth, but there are no plans for that. Someguy1221 (talk) 22:11, 7 August 2012 (UTC)

Remember that forever's a long time. Assuming no further human or post-human intervention once it becomes kaput it will eventually either be eroded into dust by dust storms or buried by them in situ. The only thing we send back to Earth is the data. SkyMachine ⁽⁺⁺⁾ 22:43, 7 August 2012 (UTC)

Perhaps you are thinking of the Russion Fobos-Grunt mission launched in late 2011. That mission was to land on one of Mars's moons (Phobos or course) to collect and return a soil sample. The Mission Plan section briefly describes the return plan. Unfortunately, the Fobos-Grunt joined the ranks of many other failed Mars missions when contact was lost and it failed to leave earth orbit. -- Tom N (tcncv) talk/contrib 23:22, 7 August 2012 (UTC)

Don't read this unless you can handle a little sadness right now: http://xkcd.com/695/ --Trovatore (talk) 02:05, 8 August 2012 (UTC)

August 8

Mars Science Laboratory average speed

The news mentioned a total trip of around 567 million kilometers for NASA rover Curiosity and duration of about 36 weeks. One can conclude an average velocity of about 93750 kilometers per hour; however I couldn't find any details discussing this except that speed reduced from around 20,000km/h before entering Mars's atmosphere. Does anyone have some clue about the velocity profile and if an gravity assist was conducted during the trip?--Almuhammedi (talk) 01:23, 8 August 2012 (UTC)

Mars has a mean orbital velocity of 24.13 km/s around the Sun, so just catch up to it from behind. 88.112.47.131 (talk) 05:16, 8 August 2012 (UTC)

What is happening to me?

We cannot offer medical advice. Please see the medical disclaimer, and contact an appropriate medical professional. BigNate37_(T) 02:33, 8 August 2012 (UTC)