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July 29

Need a flat metal surface for heat sinking - suggest melting aluminium or solder?

I have a couple of brass candelabras which I'm using in a lighting project. The light will come from high power LEDs inside the candle cups. I need a good thermal connection between the rear of each LED bead (I intend not to use the star-mounted LEDs) and the metal candle cups. In order to obtain a good connection, I need a flat surface in the bottom of each cup. To obtain a flat surface, I was thinking I should melt some metal in the bottom of each cup. Aluminium has a lower melting temperature than brass and may be a possibility. However solder has an even lower melting temperature and may be much easier to work with, although its thermal conductivity is lower. Would solders containing a flux core pose a problem for this application? — Preceding unsigned comment added by 2.97.18.184 (talk) 01:33, 29 July 2012 (UTC)

The thermal conductivity of solders varies quite a bit, with ordinary tin-lead eutectic not very good. See http://www.electronics-cooling.com/2006/08/thermal-conductivity-of-solders/. In contrast, the thermal conductivity of alauminium is about 250 W/m.K (http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html), about 5 times better than ordinary solder. Never-the-less, depending on the cup size and shape, it is probably the case that even tin-lead solder will be good enough. By mathemically modelling the volume of the metal as concentric thin cups of simple half-sphere & cylinder shape you can calculate the therml conductivity from LED to cup outside surface, and you can roughly estimate the heat conduction from cup to air with Pressman's formula: R = 7400 A^-0.7 (R in ^oC/W, A in mm²) You probably won't get a sufficiently flat surface due to surface tension, and depending on what metal the cups are made of, you may have issues with the melt disolving some of the cup material - this can significantly increase surface tension. Surface tension may force you to spot-face machine the surface to get it flat. Flux residue can be dissolved off with citrus-tpe solvents, but if you are going to machine the surface, that will get rid of teh flux as well. Keit121.215.49.33 (talk) 03:40, 29 July 2012 (UTC)

Standard practice is to use thermal paste, which makes the matter of surface machining moot. It isn't adhesive, though, so you'd likely need to use a fastener to attach the LEDs, and you would still need to have two surfaces that are roughly complimentary shapes (i.e. matching concavity/convexity). BigNate37_(T) 03:52, 29 July 2012 (UTC)

+1. I've also seen metal rods of an appropriate diameter soldered as close to the hot component (LEDs) as possible on the lead which you can ground to the fixture, and then soldered to the fixture, and then smothered in thermal ceramic/silicone paste over the solder. 207.224.43.139 (talk) 05:29, 29 July 2012 (UTC)

Note that the usual sorts of thermal paste sold for electronics heatsinking purposes is not at all thermally conductive compared to metals. It's only designed to go as a thin smear between two "mill finish" flat surfaces bolted together. My Radiospares catalog gives thermal conductivities ranging from 1 to 3 W/m.K. Compare that to aluminium (250 W/m.k). Such thermal pastes provide a small benefit because transistor/diode/etc surfaces and heatsink surfaces are normal machined surfaces and not mirror polished - this means that without the paste there is microscopic air gaps btween high spots, and even 1 W/m.k conductivity is orders of magnitude better than air. Using such pastes in other than a thin smear will not do anything useful. Keit120.145.177.174 (talk) 06:41, 29 July 2012 (UTC)

Silicone thermal compound based on aluminum nitride is better than solder at over 100 W/m*K, so you can slather it to protect the solder joint. I don't know if that's typical for heatsink compound. 207.224.43.139 (talk) 07:20, 29 July 2012 (UTC)

Do you know any trade names, product codes, manufacturers, etc, that we can use to to trach down & purchase such wondrous stuff? The link provided for silicon nitride in the Wikipedia article on thermal grease is a dud. Keit120.145.141.39 (talk) 12:09, 29 July 2012 (UTC)

Use a table spoon to melt solder over a gas stove and pour it into the light fitting if the light fitting has a watertight metal form. You may be able to epoxy shut small escape routes for the molten solder in the base of the cups, but do that outdoors for certain because the epoxy will give off even more volatile fumes than the melting solder. (Do it on a BBQ) Use a pedestal fan. Place the fan very close to the work as you are melting and pouring, with the fan facing away from the work and away from you. It will suck away the fumes without disrupting your work. I agree to take full legal responsibility for your head falling off and the city catching fire, so be sure to email this note to your lawyer first. You might also try running a led embedded in putty in the fitting, or silicone sealant, or mixing metal shavings in, Then measure the temperature of the LED after 5 minutes and see which gives the lowest reading. You can ask a local engineering shop or handyman to turn some pieces of aluminium for you and use heatsink grease for the gap. (And always remember, don't solder while naked) Penyulap ☏ 14:42, 29 Jul 2012 (UTC)

Does it matter? LEDs don't produce a lot of heat. That's what makes them so energy efficient compared to incandescent bulbs. Why isn't air cooling sufficient? --Tango (talk) 17:23, 29 July 2012 (UTC)

A few watts a piece if it is the large ones, the ones the requester says they won't use, if it is a simple 5mm or 3mm two lead package, then the power consumption is tiny and no heat sink is required. But as they are mounted flat, it seems to be a package somewhere in between, which makes sense as the small ones can't light up a room really. I think the best thing to do is to hook one up and then enclose it in the same manner it is meant to be in permanently, and measure the final temperature as I said. It's most likely there is enough conductance to keep it cool. But any high brightness led say, over 100mA can get quite hot so long as it is thermally insulated, most of the time it is not, and certainly open air cooling is enough to cool it. Keeping the heat contained is what the enclosure will or won't do. I'd say just give epoxy a go. Penyulap ☏ 17:57, 29 Jul 2012 (UTC)

For a high power LED it does matter. Since the OP isn't even putting it on a star or round heatspreader there's a good chance they will kill probably within seconds to minutes it without a good thermal connection to some heatsinking. This doesn't mean aircooling isn't sufficient, simply that it needs a good thermal connection to a resonably sized heatsink. The LED datasheet should give good info on what is required (every power LED datasheet I've looked at had a section on thermal management). Personally I'm far from convinced the solder idea is sufficient but the OP will need to look in to the requirements themselves. Also the OP hasn't exactly specified what sort of power LED they're referring to and what their target current range is. E.g. the requirements for an XM-L run at 3A (maximum rated) would be quite different from one run at 350mA (or for that matter a XB-D run at 350mA). I suspect the OP isn't considering something like a large LED array, e.g. a Bridgelux BXRA-56C9000-J-00 [1] with a typical forward voltage of 30.4V run at 3.75A (maximum rated) but who knows?

Remember that while LEDs may be fairly efficient they have a much smaller surface area and volume and also do not like to get hot losing efficiency i.e. generating more heat for less light as they get hot (which from the end user POV generally means if the designer knew what they were doing and used a good constant current driver, the LED can get visibly dimmer as it warms up) and also lowering their lifespan possibly quite significantly depending on the running temperature. And their efficiency is also helped by the low amount of non visible light (which doesn't hang around the LED). I've discussed all this in more detail with references in the past if there is still any confusion.

Nil Einne (talk) 10:44, 30 July 2012 (UTC)

Does atrioventricular block benefit the heart of athletes?

Here it is mentioned that athletes can have certain heart conditions that in non-athetes would be considered to be heart diseases:

"First degree atrioventricular block and second degree Möbitz type 1 block occurred more frequently in athletes. Atrioventricular dissociation and Möbitz type II block were not observed in controls but did occur in athletes."

So, does having an atrioventricular block benefit someone who does a lot of endurance training? Count Iblis (talk) 01:52, 29 July 2012 (UTC)

You might wish to look at our atrioventricular block article. I can't imagine that it would be beneficial for the atria and ventricles to lose their usual synchrony, but our article says that in athletes it may be "benign". Looie496 (talk) 04:13, 29 July 2012 (UTC)

Origin of HIV/AIDS

In a recent question on the humanities desk the OP repeated something I've frequently heard before that I have never been able to find a reliable source for, or even a reliable source debunking it, namely; that HIV was first transmitted from simians to humans though sexual contact. I can think of numerous reasons why this is highly unlikely (a human is unlikely to have been the receptive participant, the penetrative participant has a low chance of contracting the virus and this probably isn't something that happens regularly, the apes in question are very strong and not likely to enjoy such treatment, etc.). The scientific consensus as far as I'm aware is that it was people eating bushmeat contaminated with the virus that caused the initial transfer to humans (contracting the virus in this way is also unlikely, though I suppose this happens frequently enough to explain it). Can anyone provide references or links to discussions on this dubious hypothesis? 203.27.72.5 (talk) 01:58, 29 July 2012 (UTC)

Reading History of HIV/AIDS as well the reviews cited in the transfer section don't even mention sexual contact as a possibility. If the article accurately portrays the neutral point of view, then I would say that human-chimp sexual contact as the point of entry of HIV into our species is an extreme minority viewpoint. Someguy1221 (talk) 02:24, 29 July 2012 (UTC)

I'm sure it is an exteme minority viewpoint amongst medical professionals and anyone who has stopped to think about what they're saying, but I keep hearing it or reading it which leads me to believe it is some sort of a relatively common misconception. I'm not going to attempt a google search right now because I'm on a work computer, but I'd think there would be quite a few hits for people restating the hypothesis in forums, etc. I'd like to know where it came from and I'd really like to see where some expert in the field has debunked it. 203.27.72.5 (talk) 03:47, 29 July 2012 (UTC)

Bushmeat#Role in spread of diseases explains the much more likely vector, and [2] is the most recent review you want, citing this specific detailed primary source. Sexual contact between chimps, apes, or monkeys and humans is very rare, with bushmeat being much more common as per that source. 207.224.43.139 (talk) 05:40, 29 July 2012 (UTC)

Thanks, but neither of those mention the hypothesis I'm asking about. There is an (unsourced) mention of the the misconception at Misconceptions_about_HIV/AIDS#Origin_of_AIDS_through_Human-monkey_sexual_intercourse, so if someone finds a source I can add it to that. Apparently one Republican state senator from TN repeated it in an interview. 203.27.72.5 (talk) 09:34, 29 July 2012 (UTC)

The fact is that our data is too limited for the specific means of transmission to be anything other than a guess. However, sexual relations is a quite poor one. Either being bitten by a wild or pet monkey (which would also have a lesion of some kind or to suffer an injury, since saliva is not a viral reservoir), or having contact with a recently slaughtered monkey while having a cut (This could easily be imagined if one is preparing the monkey to be a meal) is much more likely. But if a Tennessee politician thinks he can gain votes in his district by guessing sex, it isn't impossible. There is no reason any authoritative scientific source would discuss it. Bestiality with monkeys in Africa is almost certainly rare or non-existent and other avenues are not anywhere near as implausible.173.15.152.77 (talk) 12:52, 29 July 2012 (UTC)

I'm not sure what you're looking for. It's pretty obvious where the misconception comes from - HIV is sexually transmitted in humans, it is thought to have originated in monkeys, so people put two and two together and get five. I'm sure loads of people have independently come to the same misunderstanding, so you aren't going to be able to find the origins of the misconception. --Tango (talk) 17:49, 29 July 2012 (UTC)

On a related question, if you eat the meat of a human who is infected with HIV, can you contract HIV? ScienceApe (talk) 16:22, 29 July 2012 (UTC)

Contracting HIV by giving oral sex to someone that is infected has an extremely low chance of infection (although it is increased if you have any sores or cut in and round your mouth). Eating infected flesh would presumably be similar. (Note, it being very rare to catch it this way doesn't invalidate the bushmeat hypothesis - as long as there were enough people eating enough infected bushmeat, someone would get infected sooner or later.) I can't find a reliable source for the likelihood of catching HIV from oral sex, but I'm sure I've seen one before. The best I can find is this CDC page saying it is probably less likely than from anal or vaginal sex, but it doesn't give any numbers. --Tango (talk) 17:49, 29 July 2012 (UTC)

I can't help but recall something Frank Zappa said in the early years when the monkey story came out: "So who's been screwing those monkeys?" ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:06, 29 July 2012 (UTC)

Eating is only part of it. The hunting and butchering part is the more dangerous end of the bushmeat trade. Wounds and blood galore.

Anyway I found this source: HIV/AIDS, Health and the Media in China. It closely parallels that Stacey Campfield's reasons for segregating the people who can get infected, and those who can't. In the senator's reasoning, it's a gay disease brought on by bestiality and "unnatural" sex acts. In early Chinese propaganda, it was a yuanshi (primeval) disease and the result of the Africans being "naturally" wild and uncontrolled. Both are bizarre and quite dangerously ignorant. *shakes head at the fact that this guy is a senator*

But anywho, yes. It's a common enough joke. Ricky Gervais in GTA 4 jokes about... SPOILER ALERT!... how the patient zero accedes to having received it from eating bushmeat to avoid having to admit that he had sex with an ape; and then confronts the chimpanzee who at first denies eating monkeys, but then agrees he did when the only other alternative is that he had sex with a monkey. Doesn't sound that funny when I say it like that. :P -- OBSIDIAN†SOUL 21:03, 29 July 2012 (UTC)

In his original post above, User:W203.27.72.5 claims that "the penetrative participant has a low chance of contracting the virus". Is this actually true? If so, wouldn't it imply that heterosexual men should have much lower rates of HIV than women? —SeekingAnswers (reply) 22:00, 30 July 2012 (UTC)

Check out out articles that give risks like our ones (e.g. HIV/AIDS). If it's a decent article, they nearly always give different risk estimates for penetrative/insertive and receptive intercourse, normally in the range of 1/5 and 1/10 difference although as our article shows, there tends to be fairly wide variance in estimates risk (although I think something went wrong with our insertive anal intercourse figure). However your assumption doesn't necessarily hold, it will depend on things like the frequency of high risk activity. Nil Einne (talk) 13:26, 31 July 2012 (UTC)

Your logic breaks down, SeekingAnswers, when you consider that the only reason women would have a higher rate of infection is because they contract the virus by having heterosexual intercourse i.e. with heterosexual men. If the men have a lower infection rate then the women will have a lower exposure rate. Then of course, there's the actual frequency of high risk activity as Nil Einne mentioned above. 203.27.72.5 (talk) 20:54, 31 July 2012 (UTC)

I could be wrong since I'm not an epidemiologist or even a statistician but I believe you're mistaken. I'm pretty sure that if you model an extremely simple system where you start off with an equal sex ratio of HIV infection and no HIV transmission from anything besides sex and presume only heterosexual intercourse and no difference in level of risky behaviour (beyond that due to the differences in insertive/receptive and sex ratio) and same effect of HIV and of course some degree of non-monogamy; you'd find that over time the sex ratio of HIV infection changes so that more women are infected then men. The ratio won't be as great as the difference between the risks of receptive/insertive. While the female partner may be at greater risk due to being the receptive partner, as the sex ratio of infection changes, the male will be at higher risk because a greater percentage of their putative partners have HIV; which I think is what you were referring to. But the ratio will still equilibrate at something other then 1:1. Remember not everyone with HIV is going to infect every single one of their sex partners, but if the believed difference in receptive/insertive risks are correct, the male partner has a greater chance of infecting their female partners (or will infect a greater number).

Of course such simplistic models have little relevence to the real world. A male who regularly engages with unprotected insertive anal intercourse with drug addicted sex slaves is going to have a higher risk then a female who only ever engages in protected receptive vaginal-penile intercourse in a monogamous relationship. (Ignoring other risk factors.) In fact I wonder whether a female who engages in unprotected receptive vaginal-penile intercourse in a monogamous will be at lower risk then a male who regularly engages in protected anal intercourse with drug addicted sex slaves. (And from a population standpoint, remember that if the woman is truly monogamous and doesn't engage in any other activity likely to infect someone else including childbirth and breastfeeding; she isn't going to infect anyone even if she is unknowingly infected by her sex partner who isn't as monogamous as she thought, something which does unfortunately happen.)

P.S. Hopefully none of my earlier examples offend anyone. I'm using them simply to illustrate the point rather then try to imply anything. One thing I'm pretty sure is correct is that the risk for a woman who only ever has sex with women (who similarly only ever have sex with women) is significantly lower (again ignoring other risk factors) then for a woman having sex with men for HIV and most STDs. Something which many of the anti same sex relationship groups seem to ignore when they speak of the evils of same sex relationships. But I guess many of the people in such a groups tend to be the sort that thing females don't matter so they it's not surprising if they don't care that they're asking women to put themselves at greater risk while at the same time speaking of the STD evils of men having sex with men.

Nil Einne (talk) 08:59, 1 August 2012 (UTC)

Actually, you're correct. I made a rudimentary model with a population that started with 10% male infection and 0% female infection and then assumed that every person had sex with a random person of the opposite sex in a iterative process. If women have a 10% chance of infection from sex with an infected male, and men have a 1% chance of infection from sex with an infected female, then by the 11th iteration the females' infection rate is higher than the males' and by the time half the men are infected, about 95% of the women are. 203.27.72.5 (talk) 20:52, 1 August 2012 (UTC)

Argon fluorohydride

Does HArF contain Ar(II) or Ar(0)? Double sharp (talk) 06:14, 29 July 2012 (UTC)

According to Argon fluorohydride it's a hydride, so that would make the Ar²⁺. 203.27.72.5 (talk) 06:18, 29 July 2012 (UTC)

Actually, no, it's Ar(0). Argon is more electronegative than hydrogen, but less electronegative than fluorine. Therefore, the oxidation number of hydrogen is +1, the oxidation number of argon is 0, and the oxidation number of fluorine is -1. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 06:28, 29 July 2012 (UTC)

Nope, from this article in Chemical and Engineering News,

"Many recent findings, including the first evidence for an argon compound, have come from matrix-isolation studies at the University of Helsinki in Finland (Markku Räsänen and coworkers). These studies have established the existence of a large variety of novel compounds, all stable up to 40 K. Included are HXeOH, HXeCCH, HKrCN, HKrCCH, and HArF. The last requires comment, because of the nonexistence of ArF2.

In all of these compounds, the vibrational spectroscopic findings indicate that the canonical form ([HNg]+Y–) contributes importantly to the binding of the molecules. The tiny proton is highly electronegative, and it bonds covalently to Ng in these molecules. The proton affinities of the noble gases are the following: He, 1.8; Ne, 2.2; Ar, 3.0; Kr, 4; and Xe, 6 eV."

So the form is [HAr]⁺F^-. Therefore the argon can only be Ar²⁺. 203.27.72.5 (talk) 06:56, 29 July 2012 (UTC)

Actually, having drawn the Lewis structures the argon must be Ar⁰ because of the relative electronegativities as Whoop said. The electronegativity of argon isn't extactly known, but the trends indicate it should be about 3.5 on the Pauling scale. 203.27.72.5 (talk) 07:56, 29 July 2012 (UTC)

Or if you want to get really technical, the oxidation number (as opposed to oxidation state) is what is denoted by Roman numerals (as in the OP question) and there the convention is for the electrons to be considered to reside with the ligands, which in this case is the H and F, so that would make the argon (II). 203.27.72.5 (talk) 08:01, 29 July 2012 (UTC)

Radon

Are any Rn(IV) and Rn(VI) compounds known to exist? If they do, could specific examples be given? Double sharp (talk) 06:19, 29 July 2012 (UTC)

From the same external article I linked to above,

"Although the easier ionization of radon leads one to expect the most extensive chemistry for that element, the high instability of even the most stable isotope has severely limited studies of it. L. Stein, of Argonne, established (in 1962) the existence of a fluoride--probably RnF2--but he and others were unable to confirm the existence of oxides or relatives of the perxenates."

So, it sounds like no, they cannot be confirmed to exist due to the instability of radon, but they do probably form. 203.27.72.5 (talk) 07:02, 29 July 2012 (UTC)

Most likely nobody tried to establish a research project on radon chemistry lately. Today there are good methods to do chemistry on instable elements, but not back in the 1960s.--Stone (talk) 12:40, 29 July 2012 (UTC)

Check out: likely yes, this one doesn't agree (an "X for dummmies" book, don't tend to trust them always)

Try a Google search: "radon RnO3"--R8R Gtrs (talk) 22:22, 3 August 2012 (UTC)

Locking car doors to prevent being thrown out

I've met a few people who always lock the car doors to prevent them from opening in case of an accident (and they try to convince me to do the same). I always thought the claim was weak for several reasons, but that's just based on my uniformed guesses. So the question is: will locking your car doors decrease the risk of you being thrown out of the car in case of an accident? Vehicle door is of no help.Sjö (talk) 08:45, 29 July 2012 (UTC)

Well, during an accident you could conceivably have something get caught on the door handle and pull it open, but this doesn't seem very likely. The better safety justification for locking doors is that it keeps a criminal with a knife from jumping in and carjacking you while stopped at a light. And, of course, kids or pets might manage to open the door while the car is in motion, and locking them makes this harder.StuRat (talk) 09:10, 29 July 2012 (UTC)

I would think that wearing a seatbelt would be a much better way of ensuring that you're not thrown from the car (or onto the steering wheel, or through the windscreen) in a crash. Mitch Ames (talk) 10:03, 29 July 2012 (UTC)

Car Talk says locking provides a small improvement in keeping the door closed in a crash, and that keeping the door closed is very important for overall protection of the occupant in ways unrelated to "staying inside".[3] DMacks (talk) 10:09, 29 July 2012 (UTC)

Bad idea. Very bad idea. Car door locks are designed in such a way that accidental opening is quite unlikely, unless the crash is so severe it becomes meaningless. And if you have at least half a brain you'll be wearing a seatbelt anyway. But locking the doors will make life more difficult for emergency crews to get you out, should you be dazed and/or confused. If they can't open the door, they'll use "jaws of life" gasoline-powered cutting tools to get you out, thereby writing off your car, which in many cases would be otherwise repairable. If your insurance company finds out you locked the door, they might pay out only the cost of the repair instead of the full replacement value. Quite apart from the risk of you being killed by fire (fires is not very likely in cars made by American manufacturers & their regional offshoots, but is something that does happen significantly often with Aisan cars). Should you be dazed/unconscious or whatever, and there is a fire in your car due to crushed wiring or whatever, you want bystanders &/or emergency guys to get you out immediately, before they get scared for themselves wrt explosions, and not be frustrated by a locked door. The exception is certain European cars eg Mercedes, that automatically unlock all doors if at least one airbag is triggered. Wickwack120.145.165.103 (talk) 12:21, 29 July 2012 (UTC)

A mild awareness of all factors is a good alternative to a rule. If you are driving a route that takes you across or beside a body of water, or into a tunnel, it is better to leave them unlocked. Escape in these situations could be a little easier (in the case of the water, it won't make a difference once the car actually enters the water, only before). Procedures for water entry are complex. The primary case for locking your door is when you don't always wear a seatbelt, in those cases, even if you don't notice it, you do lean against the door. If it is not closed properly, it can and often does, open and eject the occupant (much to their surprise) so locking the door is an added step which helps you actually check that the door is closed properly, and may indeed help stop it opening if it is faulty. Extra levels of protection are worthwhile, but fake strategies like driving with headlamps lit during the daylight hours should be avoided.

Short answer, LOCK your doors normally, UNLOCK them when approaching a waterway or tunnel and then lock them again afterwards. Probably a good idea to google some safety guidelines for tunnels as well, as Europe has a great many, and they are a whole world of hurt apart from regular roads. It is worthwhile knowing what to do, what not to do, and to generally avoid tunnels under certain circumstances. Penyulap ☏ 12:47, 29 Jul 2012 (UTC)

As you pointed out the OP is from Sweden and Daytime running lamps are required. I notice too that studies seem to say that DRL do improve safety in certain conditions. CambridgeBayWeather (talk) 15:23, 29 July 2012 (UTC)

Yes yes, and the oil companies tell countries to go to war as well, look at Tony Blair, Britain was his own personal militia to take the oil companies of Africa, so a little legislation is trivia. Headlights use electrical current from the alternator, which loads up the car's engine and uses more fuel for a given distance. The studies do not address the cause of the statistics, they only count the raw data. If you started a rumour that wearing a Poodle Hat whilst driving improved safety, then on the grounds that there are idiots who will believe anything you tell them, some idiots will take up the challenge and wear poodles whilst driving. If you then study the poodle group compared to the rest of us, you will also find they take ALL advice seriously, they always wear seat belts, always drive slow, never drink alcohol and so on. Those factors are showing through in the raw statistics and are published to perpetuate the myth. It's just another grapefruit diet sure you'll lose weight by starving yourself, it works, and the citrus co makes money. If you drive and see a RV with glaring lights you must look away from it, so how does that make it anything but invisible on this planet ? Hype. locking and unlocking must depend upon the environmental conditions and expected anomalies along the way, so computing the chance of requiring a speedy abandonment of the vehicle or the chance of car-jacking is probably sufficient to override the norm, which overall, would probably fall on the lock side so you don't fall out. (for worldwide) Penyulap ☏ 17:21, 29 Jul 2012 (UTC)

If the oncoming traffic is causing glare that is making you look away then there is something wrong with the oncoming vehicle. I've never had a problem with the lights of oncoming vehicles. How do you cope with the glare at night when all vehicles have their lights on? CambridgeBayWeather (talk) 23:11, 29 July 2012 (UTC)

As I have seen it done, drivers at night often hold their hand up to block the view of the headlights without blocking the view of the road, but I've only seen them do this in dark stretches where their eyes adjust to the darkness fully, I think you wouldn't see it as much in built up areas. Penyulap ☏ 03:30, 30 Jul 2012 (UTC)

Some very questionable advice above, about the importance of NOT locking the doors. Cars I've owned in recent years AUTOMATICALLY lock the doors when the car starts moving. Carjacking is a danger that is lessened by locking the doors. Rescue squads, firemen, and police just break the glass, rather than sending for the "jaws of life" when the car door is locked. I question the claim that the insurance company will pay less if the doors are locked. A locked door might be less likely to allow ejecting an unbelted idiot when the car flips.Edison (talk) 13:34, 29 July 2012 (UTC)

It's quite appropriate advice because I have taken into account the enquirers local conditions. They live in Sweden I believe. These factors come into account as carjacking is not universal. Insurance company rules vary widely between companies let alone countries. Penyulap ☏ 14:09, 29 Jul 2012 (UTC)

Btw, my comments on my userpage aren't about you, they are about the other Edison :) Penyulap ☏ 14:16, 29 Jul 2012 (UTC)

European cars such as Mercedes do automatically lock the doors as you start moving, but they also automatically unlock if an airbag is triggered - that is a safety requirement for the reasons I gave above. In the old days (not so old days with some brands) when cars were locked by a simple mechanical up/down button on the door sill, yes, that's what rescue chaps did - they bashed the glass, and then pulled up the lock button to open the door. But with modern cars, there's generally no such button - the deadlocks are electrically operated by either key or keypad. That may not be accesible, and an accident may cause an electrical fault disabling the unlocking (automatic unlock will happen momentarily before that happens). So, yes indeed, they will use "jaws of life" (which incidentally of course involves first smashing the glass out). Wickwack124.178.48.62 (talk) 13:52, 29 July 2012 (UTC)

"...when you don't always wear a seatbelt." With all due respect to Penyulap, but as I stated above, if you don't always wear a seatbelt, you're a half-wit. With and without accident statistics are very clear. See http://www.carrsq.qut.edu.au/publications/corporate/seat_belts_fs.pdf - not weraing a seatbelt increases the probablity of injury or death by up to a factor of 10. I owned a Ford Falcon - a very common car here in Australia. I was hit while doing 60 km/hr almost head on by another vehicle that went thru a red light at 80 km/hr - it wrote both cars off - wrecked them. I was wearing a seatbelt and walked away without a scratch. The other driver, who was in a small Japanese car, had only a slight scratch. Without a seatbelt, an 80+60 km/hr impact will seriously injure if not kill. Most folk who have been in a serious accident will tell a similar story. Wickwack124.178.48.62 (talk) 13:41, 29 July 2012 (UTC)

Again wearing seatbelts is a local variation, although cars in Australia are designed with the expectation that all occupants will wear a seatbelt, it is not the case in the United States. In the US, cars are sold with airbags that deploy with a far greater force than those in Australia, as it is every Americans right to be a moron and not wear a seatbelt. The manufacturers take that into account and make the airbag support the whole torso and head of the occupant, while in australia, it's just the ole noggin that needs attention, blimey mate get with the program. struth. Penyulap ☏ 14:16, 29 Jul 2012 (UTC)

Every state in the US has seat belt laws, only one state is lax enough to enforce the law just for minors, so I'm not sure what you are talking about when you say we have the right not to wear them...we have just as much a right to speed like a moron, meaning not at all. 71.195.84.120 (talk) 16:39, 29 July 2012 (UTC)

Cool, I wasn't aware of that, my memory must be faulty, but then, the airbag thing must point clearly to some large market where seatbelt use is lower than Japan or Australia for example. Penyulap ☏ 17:21, 29 Jul 2012 (UTC)

Airbags provide additional protection, especially in the event of a head-on collision. They used to be available only on luxury cars, but now they're pretty much standard issue in America. And just to reiterate, many states have what they call "click it or ticket" laws, meaning it is not a right to drive without a seatbelt. (In fact, driving itself is not a right - it's a privilege regulated by the government(s).) ←Baseball Bugs ^{What's up, Doc?} carrots→ 19:03, 29 July 2012 (UTC)

Airbags are not meant to be used without a seatbelt. They form part of what's known as the Supplemental Restraint System. To quote the wikpedia article; "severe or fatal injuries can occur to vehicle occupants very near an airbag or in direct contact when it deploys. Such injuries may be sustained by unconscious drivers slumped over the steering wheel, unrestrained or improperly restrained occupants who slide forward in the seat during pre-crash braking". Increasing the force of airbag deployment for unrestrained passengers just sounds like a way to smack them even harder with the thing after they've already made contact with the dash or steering wheel. 203.27.72.5 (talk) 00:07, 30 July 2012 (UTC)

I assume the thing about locking cardoors is mostly aimed at reducing the odds that kids manage to open them at the wrong time; I'm really sceptical of the carjacking issue, which seems like a very low risk indeed, and it's not like you can't be carjacked straight through a closed window, unless you have bullet proof glass. Wnt (talk) 03:33, 30 July 2012 (UTC)

A locked door can still be opened from the inside (at least in every car I've tried it) so it won't prevent accidental opening, but there are often child safety latches (don't know what they are called in English) that disengage the inside door handle.Sjö (talk) 12:56, 30 July 2012 (UTC)

It is written in the article itself, outside the US, airbags are wearer as they are based upon the idea that people wear seatbelts more often, that is how they do the testing. I'm not saying people don't usually wear seatbelts in the US, they do, I'm saying the statistics vary according to country. I'll be happy to eat my keyboard and post the pics if every country wears seatbelts as often as the other. Penyulap ☏ 03:41, 30 Jul 2012 (UTC)

Having rules against not wearing seatbelts has nothing to do with the percentage of people who do, or the manufacturers efforts to compensate appropriately for it. Copyright. they have rules against it too, doesn't mean nobody does it. Penyulap ☏ 03:43, 30 Jul 2012 (UTC)

Having rules, publicising those rules and (perhaps most importantly) enforcing those rules with penalties for non-compliance probably does affect the percentage of people who wear seatbelts. At least the Western Australian Office of Road Safety seems to think so. Mitch Ames (talk) 10:04, 30 July 2012 (UTC)

Kinky tails on asian cats

Does Wikipedia have an article on the genetic defect which cause many cats from Thailand and Malaysia to have kinky tails? -- 203.82.81.154 (talk) 12:09, 29 July 2012 (UTC)

I've not found one, but I found this article which says "Kinked tails are seen commonly in many breeds of cat, particularly Siamese, Burmese and Oriental breeds. The kinks typically result from deformities of the bone and are listed as defects by most breeding authorities. However, they are usually only of aesthetic relevance as they cause no pain or discomfort to the cat." I would suggest that because the deformity is of no real significance, there's not a lot written about it, and my searches so far have confirmed it. --TammyMoet (talk) 12:45, 29 July 2012 (UTC)

my daughter has apha thalassemia

moved from Talk:Thalassemia#my daughter has apha thalassemia

my daughter has alpha thalassemia and I'm trying to get a better understanding of this. The doctor have advise that she cannot marrie anyone who has the same trait. what will effect will it cause when thry have a child together?

[Author unknown] 86.136.221.113 (talk) 11:36, 27 July 2012 (UTC)

I think this is worthwhile answering, please assume good faith. Penyulap ☏ 12:32, 29 Jul 2012 (UTC)

Genetic counseling definitely crosses into our policy of no medical advice. The original poster should find a genetic counselor to explain this in more detail. The doctor in this case was simply indicating that by classical Mendelian inheritance, someone who expresses alpha thalassemia is usually someone with a double-recessive of the gene in question. If they procreate with someone else who is also a double-recessive, 100% of their children will be double-recessive. If they procreate with someone who is merely a carrier (one copy of the thalassemia gene, which is not enough to express the disease), the children will have a 50% chance of being a double-recessive and a 50% chance of being only a carrier. If they procreate with someone who lacks the thalassemia gene altogether, their children will be 100% carriers. The probabilities of classical genetics are straightforward, but the real-life implications and the real-life complications are often not — and this is why a genetic counselor should be talked to. --Mr.98 (talk) 13:18, 29 July 2012 (UTC)

For more information on what Mr.98 is talking about, see autosomal recessive (also linked in the first sentence of thalassemia). --Tango (talk) 21:56, 29 July 2012 (UTC)

The above explanation may be applicable to beta thalassemia but is incorrect for alpha thalassemia, which results from the expression of two pairs of genes. --202.28.181.200 (talk) 09:46, 30 July 2012 (UTC)

You're right — the genetics are much more complicated than I'd realized. It actually depends quite specifically on exactly the way genome is expressing in the daughter and the potential mate -- you get very different results if you make different (legitimate) assumptions (the most common form of alpha thalassemia is either -/a -/a OR a/a -/-, and these produce very different Punnett square crosses with others of the same or the alternative form). The results can be anything from a carrier with almost no expression, to a fetus that cannot survive outside the uterus. The good news is that there is probably more flex to this than the original doctor said; the bad news is that the bad results could be even worse than I originally assumed. Again, a genetic counselor is definitely needed in this situation. --Mr.98 (talk) 15:09, 30 July 2012 (UTC)

Resources we can offer: We cannot comment specifically on your daughter's condition. However, we can suggest you read the articles Thalassemia, for a broad overview, and Alpha-thalassemia for the condition you are asking about. The external links sections at the bottom of these articles will suggest other websites, resources, and support groups you may find informative, likely more informative than we can be. Specifically the section Types in the Alpha-thalassemia article describes the concern for potential different effects on a child depending on how many copies of the affected genes it inherits from each of its parents. μηδείς (talk) 17:33, 29 July 2012 (UTC)

I certainly agree that we should not suggest whether they should marry or not. However, we are here to assist in research, even if it is not as notable as that of Augusto and Michaela Odone. I am glad you have given some guidance towards research, I would not like to see someone genuine turned away from the project if they are earnestly seeking to learn more. Penyulap ☏ 14:23, 29 Jul 2012 (UTC)

Don't forget, Kainaw's criterion is there if you're unsure about answering medical questions. BigNate37_(T) 15:12, 29 July 2012 (UTC)

My hesitation to go into any more detail comes from the fact that there can be many individual caveats to such an explanation. I attempted to answer the question in general terms as to what the doctor was probably trying to say, but even then I hesitate to put words into a doctor's mouth. Basic Mendelian genetics is relatively straightforward, but real genomes are usually much more complex, even for very simple traits. --Mr.98 (talk) 16:06, 29 July 2012 (UTC)

Oh, it wasn't my intent to call your judgment into question! Apologies if that's how it sounded. BigNate37_(T) 16:15, 29 July 2012 (UTC)

Please see http://ghr.nlm.nih.gov/condition/alpha-thalassemia, http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001613/, http://www.aafp.org/afp/2009/0815/p339.html, and http://asheducationbook.hematologylibrary.org/content/2009/1/35.long 207.224.43.139 (talk) 21:33, 29 July 2012 (UTC)

Collimated electromagnetic field

Is it possible to collimate electromagnetic field into a beam similar to a laser? ScienceApe (talk) 16:20, 29 July 2012 (UTC)

A laser beam is a collimated electromagnetic field. Do you mean a static, non-oscillating field? If so, I'm pretty sure the answer is no, except in the interior of structure such as a coil. Looie496 (talk) 16:27, 29 July 2012 (UTC)

Do the lines of force of a magnetic field count: [4] ? StuRat (talk) 19:00, 29 July 2012 (UTC)

Those are not collimated -- see collimation. Looie496 (talk) 19:17, 29 July 2012 (UTC)

A directional antenna looks different at each wavelength. A parabolic dish antenna, or a Yagi, serve to collimate an RF electromagnetic field to some extent. At optical wavelengths, we tend to use refractive optics - that is, lenses - rather than reflective optics (mirrors) - because we can conveniently build such effective, compact structures. But, if you ever look at a radio telescope, you'll see that it's just a Newtonian telescope mirror designed to focus a very large wave.

Finally, keep in mind that a laser is not just a collimated beam. It is a special type of light amplifier - and as a side effect, produces monochromatic light, which is very easy to collimate. You can collimate a beam of light even if it did not come from a laser source. So, by the same token, we can create amplifiers at other wavelengths to create strong radio or other electromagnetic waves; and we can also collimate those beams using appropriately designed "optics" suitable for the frequency. Nimur (talk) 19:28, 29 July 2012 (UTC)

No. (K.I.S.S.) Penyulap ☏ 03:50, 30 Jul 2012 (UTC)

Penyulap, while your answer was certainly succinct, it is also entirely incorrect. A laser beam is an electromagnetic wave. And, as earlier answers have explained, the concept can be extended to other electromagnetic radiation. Brevity is no substitute for accuracy. Nimur (talk) 14:28, 30 July 2012 (UTC)

de-colorized iodine

I saw something in the first aid aisle called de-colorized iodine. How do they de-colorize iodine? Does it affect its properties? --Wrk678 (talk) 18:03, 29 July 2012 (UTC)

From what I can see online, it is probably potassium iodide, but might be another iodine compound -- you will probably see exactly what it is if you look at the ingredients label. If it is indeed an iodine compound, the properties will be quite different from those of ordinary tincture of iodine. Looie496 (talk) 18:24, 29 July 2012 (UTC)

I'm not sure what that would be doing in first aid. My understanding is that the usual first-aid use of iodine is to kill bacteria (and viruses, I suppose) by oxidation; potassium iodide is not going to oxidize anything. Sometimes KI is taken orally when there are worries about iodine-131 in the environment after a nuclear mishap, but that's not a standard first-aid concern.

Tincture of iodine isn't used that much anymore because there are safer alternatives (and maybe because big brother is worried about people using it to make meth). --Trovatore (talk) 21:34, 29 July 2012 (UTC)

Sorry, I thought "tincture" was the term for the usual brown stuff. Anyway, my take from what I saw scanning the web is that "de-colorized iodine" is a product whose utility for first aid is, um, not well established. Looie496 (talk) 23:14, 29 July 2012 (UTC)

isint potassium iodide yellow? And how are the properties different?--Wrk678 (talk) 21:18, 29 July 2012 (UTC)

The article on potassium iodide explains why KI yellows due to impurity or age. BigNate37_(T) 23:21, 29 July 2012 (UTC)

There is also potassium triiodide which is likely what our OP is asking about. You make it by dissolving iodine in KI solution. Graeme Bartlett (talk) 06:58, 30 July 2012 (UTC)

But that solution is not colourless (which I assume is what is meant by "de-colorized"). See the left most testtube in the picture under "Testing for Starch" 203.27.72.5 (talk) 07:24, 30 July 2012 (UTC)

Curiously, according to this De-colorized Iodine label it's just tincture of iodine, and the active ingredient is the alcohol, with the iodine and iodide being listed as inactive. 203.27.72.5 (talk) 07:39, 30 July 2012 (UTC)

In this particular instance, this is a clear case of angel dusting, where the amount of iodine is insufficient to have any effect or change the color, but is dishonestly marketed as if the iodine was in sufficient quantities to provide an antiseptic effect, when, in fact, the alcohol does that. Their ruse is rather transparent; they must feel they can sell it for more if people think it's an iodine antiseptic than an alcohol antiseptic. StuRat (talk) 08:19, 30 July 2012 (UTC)

What is exceptional about the human body ?

...relative to other animals. Here's what I came up with so far:

1) There's our brain, obviously, although the much larger size of whale brains suggests they much have abilities we lack, like remembering every detail of their lives, perhaps. We do have the greatest division of labor among any species, I believe, as a result of our brains.

Now for ones I'm less sure of:

2) The opposable thumb does give us the ability to use tools. However, this ability is shared by other primates.

3) Our permanent bipedal motion allows us to walk long distances using little energy, see farther, and also to carry and use tools more effectively. (We do, however, pay for it with a slow sprint speed and lots of back problems.) Ostriches and other birds seem to share this ability, however, and without all the negatives.

4) Our starvation response seems to allow us to survive a month or two without food. Short of hibernation, this seems pretty decent. How does this compare with other animals ?

5) Our adaptive immune system seems able to provide us with immunity to a wide range of diseases after we've been exposed to them. How does this compare with other species ?

6) Our eyesight seems to be good overall, except for the huge percentage of us who are near-sighted or far-sighted. While other species have eyesight that can magnify more, see additional wavelengths, or see in the dark better, etc., we seem to have decent combo, especially the parts involving our brain, like motion detection and pattern recognition. How does this compare with other animals ?

7) Our omnivore abilities appear to allow us to eat a large variety of foods, with the exceptions of decomposing food, feces, grasses and wood, and foods containing various toxins. How does the wide range of foods we can eat compare with other animals, such as bears ?

8) Our lifespan seems to be near the top end of most animals.

Are there any other ways in which the human body is exceptional ? StuRat (talk) 18:56, 29 July 2012 (UTC)

I wouldn't say humans are exceptional in precise ways like that. Historically, pretty much every claim of the form "Humans are the only animal that..." has been disproven. The combination of the things you mention may be exceptional, but I expect an animal can be found for each of them that is "better" than humans. I think the most exceptional things about humans are the extent to which we use language and technology (neither of those is unique to humans, but I don't think any other animals use them as extensively and in as advanced a form). --Tango (talk) 22:14, 29 July 2012 (UTC)

The most important thing about humans ecologically is that we are the most K selected animals for body mass on the planet. This is a direct result of the success of human culture as a survival strategy, and the long period of acculturation (for things such as language acquisition which it requires. See K and r selection. Basically animals can invest a lot in a few children or invest a little in a lot of children. The latter, r selected animals, tend to live very short lives, most only a year or a season, and some only a day or a month as adults. Whales and elephants are the most K selected non-human animals, and live about as long as us, but they hugely outweigh us. Each human life is a huge biological investment so far as reproduction goes. We can't reproduce successfully on average til our late teens. We can only successfully raise one baby every two years on average. Historically, women may have had 10 or 12 babies in a lifetime, but on average they only had two or three that survived to adulthood, a fact which has not changed with modern demographics. And the presence of grandparents is a proven success strategy with humans. This means we are selected for strong immune systems, big brains, and long life in general, with the traits that support it. Other animals of our body size tend to have small litters, like big cats, or one precocious offspring like deer. They become independent in the fist year and reproductive within a few years at most. Humans are the epitome of altricial animals. No other animal takes a year to be able to walk or swim. It is the huge reproductive investment in each human that makes us unique and so successful. μηδείς (talk) 22:17, 29 July 2012 (UTC)

• Our social and communication systems are light-years more complex than that of any other animal.
• We're tool users. Creating what other animals have to evolve to.
• We have the longest childhood/adolescent dependency period of any animal by far. The second closest are orangutans and elephants, whose children stay with their parents for up to 10 years.
• We're one of the few animals where the females have concealed ovulation.
• We're one of the few animals who sweat for thermoregulation. The only other I can think of atm are horses.
• Binocular vision gives depth perception. But it's also common among other predators.
• Trichromacy makes us remarkable among mammals. But pretty average to weak in terms of other animals like birds.
• For a large mammal, we're relatively hairless. I just thought of elephants and whales! LOL
• We're one of the few animals that have recreational sex. Though admittedly other mating animals probably don't know they're reproducing either.
• Lactase persistence, we're one of the few mammals that can still derive nutrition from milk at adulthood. At least the humans who've been lucky enough to inherit the several mutations for it. Also random : don't feed your cat milk, they like it but they can't digest it and get stomachache, kthx.-- OBSIDIAN†SOUL 22:49, 29 July 2012 (UTC)

On brain size, a more useful index than raw mass of brain tissue is the ratio of brain mass to body mass — see the Encephalization quotient. Basically a lot of any brain is taken up with the motor skills and regulatory work of a large body. So animals that have big brains relative to their mass tend to be using more of their brains for being smart. Dolphins come out well in that comparison, as do chimps. Whales, not so much, but they may be an exception in any case because of their ridiculous amount of mass. Elephants are quite intelligent despite the inflated brain size because of their mass — it's still larger than average. In any case, it's pretty clear that raw brain size isn't really the trick — the trick is having certain specialized organs in the brain wired up in useful ways.

Humans are not exceptional in that we possess any one thing that other animals don't. But we are fairly tailored towards complex linguistic, social, and cerebral applications. These paired with excellent hands for tool-making has, over the long term, made us feel fairly dominant. (Whether we are dominant is an open question. Insects still have a one-up on us in terms of raw numbers and future prospects. From the point of view of krill, humans have just shown up and haven't been doing too much of interest.) --Mr.98 (talk) 23:21, 29 July 2012 (UTC)

You do realize biologists consider dolphins whales? μηδείς (talk) 00:39, 30 July 2012 (UTC)

Our dolphin article says "Dolphins are marine mammals closely related to whales and porpoises". This isn't the same as being a whale. StuRat (talk) 02:24, 30 July 2012 (UTC)

(ec)I think Looie is by far and away the most qualified to comment on this but my understanding is that whales need large brains just to control and receive feedback from their massive bodies. I don't think there's any suggestion that they have super abilities to remember everything or anything like that. 203.27.72.5 (talk) 23:22, 29 July 2012 (UTC)

I am glad you assigned winning prize in the spelling bee to the student who, because he was absent on the day of the test, didn't get any questions wrong. As for whale, I already posted the link to encephalization quotient. You might find reading it surprising, especially if you compare the size of the brains of sauropods and dolphins. μηδείς (talk) 00:37, 30 July 2012 (UTC) * 203.27.72.5 (talk) 03:25, 30 July 2012 (UTC)

When I said "Looie is by far and away the most qualified to comment on this" I was only refering to point 1) about the brain size since Looie apparently has a PhD in Neuroscience. But since you obviously feel left out, I left you a gold star :) 203.27.72.5 (talk) 03:25, 30 July 2012 (UTC)

I appreciate that star, I'll move it to my user page if you don't mind. I agree with Looie's statement below on the vagueness of the thread. But I think the answer is quite clear that our big brains, long childhoods, and longevity, making us the most K selected animal on the planet, all have to do with the success of culture and the traits it encourages the selection of. μηδείς (talk) 18:46, 30 July 2012 (UTC)

This topic is too diffuse for me. If it were only about brain size I might have something to say, but I don't like topics that are bound to meander all over the place. Looie496 (talk) 03:45, 30 July 2012 (UTC)

I think a major thing is that humans spend a huge amount of effort trying to learn and explore for the sake of interest and curiosity as opposed to simply finding out what we need to know to survive. I could be wrong about this being exclusive to us though. Juliancolton (talk) 03:01, 30 July 2012 (UTC)

We should not overlook fine motor skill. Bus stop (talk) 04:05, 30 July 2012 (UTC)

The answers seem to be going off track here. I want to know in what ways, if any, humans are PHYSICALLY superior to other animals, not all of the ways we are mentally superior. StuRat (talk) 04:07, 30 July 2012 (UTC)

How about our ability to sweat? An interesting and related article is Endurance running hypothesis. Bus stop (talk) 06:10, 30 July 2012 (UTC)

Regarding question #5 (how does our adaptive immune system compare with other species), see the article you linked to (Adaptive_immune_system#Alternative_adaptive_immune_system). All vertebrates except the most primitive ones (jawless vertebrates) have an adaptive immune system that is similar to ours. Vaccination is routine practice in fish farming, see for example this link. --NorwegianBlue ^talk 17:56, 30 July 2012 (UTC)

The ability to get scurvy (inability to synthesize vitamin C)? is fairly exceptional, though not unique. --catslash (talk) 18:48, 30 July 2012 (UTC)

Aren't humans the only animals capable of abstract thought? --146.7.96.200 (talk) 19:38, 30 July 2012 (UTC)

StuRat, this documentary video may interest you. (Warning: Some content may be objectionable to some viewers.) (Disclaimer: I do not necessarily agree or disagree with general or specific points made in the video.)

• The Superior Human? | Watch Free Documentary Online (1:13:33)

—Wavelength (talk) 20:21, 30 July 2012 (UTC)

Care to give me a summary, before I invest over an hour in watching it ? StuRat (talk) 23:05, 30 July 2012 (UTC)

The narrator discusses about 18 "alleged reasons" for the claim of human superiority, with "counterarguments" for all of them. The "alleged reasons" include: intelligence, language, culture, tool-making, opposable thumbs, bipedal locomotion, longevity, population, and position atop the food chain.

—Wavelength (talk) 23:56, 30 July 2012 (UTC)

But we're not even at the top of the food chain. 203.27.72.5 (talk) 01:34, 31 July 2012 (UTC)

Actually, we are on top of the food chain (we are an apex predator). Other animals only rarely eat humans, and we eat them more often than they eat us. So, if we aren't an apex predator, then no animals is. StuRat (talk) 05:13, 31 July 2012 (UTC)

Gustave regularly eats people. No one eats him. He's an apex predator. 203.27.72.5 (talk) 07:51, 31 July 2012 (UTC)

He may end up being eaten by people eventually, or maybe just made into belts. StuRat (talk) 09:39, 31 July 2012 (UTC)

I don't see this mentioned above, which seems surprising: an awareness of self and mortality which gives us the possibility of surving the destruction of the planet or a solar event by deliberately colonizing others, although we're not there yet; and, the imagination that we may arrive as visitors. Dru of Id (talk) 23:25, 30 July 2012 (UTC)

StuRat, you may also find this article to be interesting.

• Usain Bolt vs. The Cheetah: Olympians of the Animal Kingdom | Summer Olympics 2012 | LiveScience

—Wavelength (talk) 19:06, 31 July 2012 (UTC)

They just compare sprinting, where humans are at a distinct disadvantage. I'd expect us to to better in marathons. StuRat (talk) 03:23, 1 August 2012 (UTC)

From the original list, our eyesight is fairly average, which is in itself unusual: most animals specialize for something such as central vision, peripheral vision, low-light vision, etc. Not on the list is human endurance: there are a great many animals that can outrun us in the hundred-meter dash, very few who could keep up with us in a marathon, and most wouldn't even survive trying to complete a hundred-mile ultramarathon. --Carnildo (talk) 01:32, 2 August 2012 (UTC)

Isn't that number 3 on my list: "Our permanent bipedal motion allows us to walk long distances using little energy" ? StuRat (talk) 08:34, 2 August 2012 (UTC)

Most people couldn't survive trying a to complete a hundred-mile ultramarathon either. 203.27.72.5 (talk) 03:19, 3 August 2012 (UTC)

Melted cheese, part 2

I previously asked about why melted cheese tastes batter and got my answer, thank you.

I'm surprised more businesses don't sell previously melted cheese, considering how it makes a mess to melt it yourself, and you can't always melt it when on the road. Those portable string cheese containers, for example, could contain previously melted cheeses, which you could squeeze out like with Go-Gurt. It does seem to be potentially more messy than unmelted cheese, but we do eat plenty of other potentially messy foods, like grape jelly, and, in Wisconsin, at least, cheese curds. So, is there another problem with it ? Does it decay more quickly ? StuRat (talk) 19:40, 29 July 2012 (UTC)

Have you ever actually tried melting cheese and leaving it to sit for a day? The oil separates from the rest, and you get something approximating rubber coated with oil. It's not anything I would want to eat. It seems like what you are searching for here is Cheez Whiz. Looie496 (talk) 19:47, 29 July 2012 (UTC)

If you melt real cheese while somehow keeping the fat from separating from the protein matrix (with emulsifiers or melting salts usually or... dunno, very very slowly?), it will solidify into something else - processed cheese! :P -- OBSIDIAN†SOUL 20:09, 29 July 2012 (UTC)

Yes, processed cheese#Advantages sums it up. "...extended shelf-life, resistance to separation when cooked, and uniformity of product." The big clincher is that real cheese changes flavour and texture rather unpredictably when partially melted, which is not optimal from a convenience food standpoint. BigNate37_(T) 20:15, 29 July 2012 (UTC)

July 30

Explain how ducks & chickens stay alive without their heads.

Warning: The videos show slaughter of ducks and chickens for their food. The channel is "TheTimeToHunt," and they are filmed by farm hands who also specialize in hunting. The video about the ducks is also age-restricted. If you don't wish to view the slaughter of farm animals, please don't watch.

• Duck slaughter
• Chicken slaughter

As you can see, after the slaughter, their bodies move around without their heads, for a relatively long while. The chicken, particularly, seems to flail around as if in sheer anger, toward the end of its video. (What is it trying to do?)

Also, I believe it seems to bawk furiously, but how would it without its head?

Anyways, without a brain to control bodily movements, how exactly would their bodies move anyhow?

And have there ever been incidences of decapitated human bodies moving around in a similar fashion? How long did the longest post-decapitation movement last? Thanks. --70.179.170.114 (talk) 00:11, 30 July 2012 (UTC)

Well, http://www.damninteresting.com/lucid-decapitation/ cites some literature on the topic of human decapitation if you're interested in tracking down non-anecdotal information. BigNate37_(T) 00:19, 30 July 2012 (UTC)

(edit conflict) A simple way to think about it is that not all your brains are in your brain. Many basic bodily movements and reflexes — like your instinctual reaction to being burned — are governed by your spinal cord (in the case of being burned, this has an obvious evolutionary advantage — the spinal cord burn reflex is much faster because it skips the brain until after the fact). Presumably many bird motor functions are handled by non-brain nervous connections. As for people, I don't know about bodies moving after decapitation in anything but very uninteresting ways (and the amount of blood lost in decapitating a human would be immense due to the importance of the jugular veins which would kill the body off very quickly), but two things come to mind: 1. brain death, whereby your body can stay quite alive provided that certain basic needs are met for it, despite the upper functions of your brain being decidedly dead; 2. the opposite question, whether a decapitated severed head can survive long outside the body, has been studied. The answer is not long — again, the key factor here being the sudden change in blood pressure and lack of fresh oxygen, which is quickly fatal to humans and probably all animals above a certain mass. --Mr.98 (talk) 00:24, 30 July 2012 (UTC)

Also, the brain stem is the most vital part of the brain, and is below the rest, so can be left after a "decapitation". In one case, a chicken survived for years with only it's brain stem. StuRat (talk) 00:37, 30 July 2012 (UTC)

See also Mike the Headless Chicken. 207.224.43.139 (talk) 01:14, 30 July 2012 (UTC)

Surgeons with serious ego problems have a fetish for killing siamese twins because they figure it looks good on a resume. One such case comes to mind, where the co-joined twin was not fully formed, I can't recall the name of that condition, but it is quite common. One twin had only fully developed down to their neck, and no further. They lived for their whole life dependent upon their sibling for life support, and lived a good life by their own standards, being sentient, emotional, basically everything any generic quadriplegic mute would be. However surgeons always overlook the fact that twins can live quite happily together forever in their mad rush for fame and the spotlight. The child was murdered by the surgeons in the eyes of the local religious leaders and any reasonable human being, and a funeral took place. So as for the brain living without a body, that can go on for quite some time. As for a body living with no brain, I believe the surgeons are still alive today doing this kind of thing.

I haven't watched any videos, but have read about chickens kept alive for a long time spoon fed after their brains were sliced in a particular way. But you can also study brain death. Penyulap ☏ 04:02, 30 Jul 2012 (UTC)

How is this relevant to the question? Either way, I think you should be careful making those kind of accusations. There are significant medical, ethical and legal questions surrounding the separation of conjoined twins and it is not remotely as simple as you make out. These days, separation is normally done only if both twins stand a good chance of surviving, or if there is a good chance that both will die if they don't separate them (and that at least one will live if they do). Quality of life is not generally a significant concern - what they think about is whether they will live at all. (This was not always true - separations were performed in the past with lives lost where they wouldn't have been today. There will also be some differences from country to country, but I think the basic goal is the same everywhere, there are just differences in judgement.) --Tango (talk) 13:14, 30 July 2012 (UTC)

And I guess the chicken flails around furiously towards the end of the video to cope with the sudden shooting pain, correct? If it's got nothing to do with that, then why would it flail around instead of trod around the yard like usual? --70.179.170.114 (talk) 20:42, 31 July 2012 (UTC)

How does flailing around help cope with pain? 203.27.72.5 (talk) 03:46, 1 August 2012 (UTC)

Names of a couple of extremely hazardous chemicals

Looking at List of extremely hazardous substances, I noticed that one of the entries was Phosphonothioic acid, methyl-,. Wanting to know what it was, I put it into Google and was pointed to Phosphonothioic acid, methyl-, s-(2-(bis(1-methylethyl)amino)ethyl)O-ethyl ester, but I didn't learn anything about the first compound. This prompted a series of questions in my mind:

• What's the significance of ", methyl-," at the end of the first one? Does it have an extra methyl group somewhere? And regardless of why it's included, why is it tacked onto the end with commas and a concluding hyphen?
• All of those nested parentheses on the second one (VX nerve gas) confused me, because I can't remember seeing parentheses in a compound name before. What do they signify? IUPAC discusses compound naming only very quickly and doesn't mention nested parentheses. Nyttend (talk) 01:51, 30 July 2012 (UTC)

If you look at the first intermediate product in the image to the right, it looks like it's analagous to your "phosphonothioic acid, methyl-", and it's called methyl phosphonous dichloride. I think your compound should be written "methyl-phosphonothioic acid" but they wanted to make it appear in alphabetical order next to Phosphonothioic acid, methyl-, s-(2-(bis(1-methylethyl)amino)ethyl)O-ethyl ester. 203.27.72.5 (talk) 02:13, 30 July 2012 (UTC)

See the Blue Book Online for examples of parenthese in organic compound names with explanations. 203.27.72.5 (talk) 02:29, 30 July 2012 (UTC)

Let's go through in this case. 1-methylethyl means that you have a side-chain of the molecule with two carbons (ethyl) with a one-carbon branch from the root (1) carbon. AKA isopropyl (note that the "diisopropylamino" version of the name handles the same thing with far fewer parentheses). bis means you have two of them attached to one spot. That spot is the 2-position of a different ethyl, to which they are attached via an amino, i.e. a nitrogen. If we momentarily chop off the nitrogen and all attached to it, what's left is phosphonothioic acid labelled according to the three different bits coming off of it - the 1-methyl, the S-(2-ethyl), and the O-ethyl ester. (Which O isn't specified, because the two would be mirror images; the formula as written is racemic) I'm not actually sure why it's 1-methyl and not "P-methyl", or if they're going to use a 1 for phosphorus, why the O and S don't have standard numbered positions also (except that would suck) but that's not how they do it. Wnt (talk) 13:51, 1 August 2012 (UTC)

The list gives the source for its information, http://ehs.uark.edu/DocumentPages/ExtremelyHazardousChemicals.pdf, and a look at that source shows that two of the entries for Phosphonothoic acid variants have been truncated in the table. That particular one should be Phosphonothioic Acid, Methyl-, O-(4-Nitrophenyl) O-Phenyl Ester. Looie496 (talk) 02:15, 30 July 2012 (UTC)

I find myself wondering if some of these listings are motivated by political rather than toxicological factors, i.e. use as precursors to something, e.g. piperidine and aniline, which don't AFAIK rate as particularly deadly. (Not really sure why aniline rates even by this explanation, actually...) Of course, the list has a particularly heavy emphasis on nerve gasses and precursors thereof. Wnt (talk) 03:22, 30 July 2012 (UTC)

I don't understand the point of the list at all. It has things as common place as ammonia but neglects things as hazardous as nitroglycerin and TNT. About half of the listed chemicals don't even rank as a High Hazard according to my ChemAlert database. It doesn't list any of the toxic lead compounds, some of which are very hazardous (lead sulfate, nitrate, acetate, bromide, chloride, fluoride, iodide, oxide, thiocyanate, chromate, etc.). And as the amount of red ink on the page testifies, a lot of it is ridiculously obscure. 203.27.72.5 (talk) 04:09, 30 July 2012 (UTC)

That's a valid point. It should probably be moved to another title, one that reflects its legislated nature. I've been following this section and it wasn't until you made that remark that I opened the article and realized that list is based on some American law. I would have assumed it was based on something more quantitative, or at least something more academically authoritative. BigNate37_(T) 04:27, 30 July 2012 (UTC)

As for piperidine and aniline; piperidine is considered highly hazardous with an LD₅₀ of 30 mg/kg (mouse, ingested) plus high flammability and causes burns; aniline is considered moderately hazardous with an LD₅₀ of 195 mg/kg (dog, ingested), though humans have a much greater tolerance for it (TD_Lo (ingestion): 3125 mg/kg (child)). It's also a possible carcinogen. 203.27.72.5 (talk) 04:35, 30 July 2012 (UTC)

If you're still interested in finding out about methylphosphonothioic acid, the PubChem article might be what you're looking for. 203.27.72.5 (talk) 05:15, 30 July 2012 (UTC)

The answer to this puzzle is actually pretty banal. Those chemicals are there because they appear explicitly in the text of the Emergency Planning and Community Right-to-Know Act, which requires them to be handled in a specific way. Looie496 (talk) 05:19, 30 July 2012 (UTC)

It's not even a puzzle, it's explicitly stated in the first two sentences of the page! One could certainly propose renaming it to a more clear title, but you can't say the page itself is at all unclear about the listing/inclusion criteria. DMacks (talk) 05:28, 30 July 2012 (UTC)

My problem wasn't so much with the article, but rather with the list as written by the legislators. Why would you title the list "extemely hazardous substances" when some of the things aren't really that hazardous? Why does the list name some very obscure substances while totally missing out more common and much more dangerous ones? Presumably, other legislation will refer to this list for various purposes. It seems like this list ought to a least be named in a way that makes it a bit clearer what exactly it lists, and better would be word or two as to the criteria for inclusion. 203.27.72.5 (talk) 06:01, 30 July 2012 (UTC)

Actually the current list is managed by the EPA through the CFR. I'm not looking at the text of the original bill... but even when congress itself writes technical lists like this there's usually input from committees and relevant science. I'm sure they have their own internal criteria for what goes on the list at the EPA. Shadowjams (talk) 09:00, 30 July 2012 (UTC)

Other agencies and other countries may have different priorities and different lists (yes yes, risk knows no language, but priorities do vary in reality). We shouldn't have an article which presents the EPA's list as though it's a global or agency-independent list of the most hazardous substances. A list which drew together items from different sources might be better; either that or rename the article. No? bobrayner (talk) 12:49, 31 July 2012 (UTC)

Sustainable athletics

Watching the Olympics, it seems like it's more often than not that the athletes are trying to recover from some injury - ACL tear, Achilles tear, etc. Often they're going in with visible signs of injury - it's amazing how many of the volleyball players have two fingers taped together for some reason, for example. Question: is it possible, if people wanted, to arrange the competition not to be a bloodsport, to come up with a way to design things so that the athletes have a lower lifetime risk of injury? Is anyone trying to do that practically? Wnt (talk) 03:50, 30 July 2012 (UTC)

As an athletic trainer of some years, I can tell you that many tapings are preventative. Many healthy football and basketball players get wrists and ankles taped before each game. Much like compression stockings and compression sportswear, this tape tension applied to joints can give the muscles a tighter "skin" in which to operate; this has the effect of preventing injuries. In the case of volleyball players, multiple fingers are taped together because the paired taping protects the fingers without impairing control of the ball surface. The tape itself can have a positive effect on ball contact. Boxers use a specific taping/wrapping technique which prevents injury of the hands despite constant pounding. Often athletes of Olympic caliber are pressing the body to feats few can achieve. Occasional injuries are often unavoidable. The use of compression taping is one legal and practical method of preventing injuries which otherwise might occur. BusterD (talk) 05:01, 30 July 2012 (UTC)

Well, they could wear protective gear, like helmets and pads, but who would want to watch a gymnast wearing all that ? They could add more springiness to the ground or equipment, but any substantial change like this makes comparison of new records with old records difficult. StuRat (talk) 08:29, 30 July 2012 (UTC)

That doesn't help. Statistics show that injuries don't change when protective gear is introduced. People just take more risks. --Tango (talk) 13:18, 30 July 2012 (UTC)

I'd like to see those statistics. If true, why do American football players wear so much of it ? StuRat (talk) 19:48, 30 July 2012 (UTC)

Because it's a spectator sport and the crowd loves to see the players take risks....and to see them not pay off. 203.27.72.5 (talk) 19:59, 30 July 2012 (UTC)

No. Atheletes will always push themselves to the limits in order to maximise their performance. When you do that, there is always a risk that you will go slightly beyond your limits and injure yourself. --Tango (talk) 13:18, 30 July 2012 (UTC)

Malcolm Gladwell wrote an interesting portrait of a long-distance runner in the New Yorker recently. Basically this guy is one of the best in the world because he can disconnect the part of him that says, "hey, you are at your limit" and will more or less run until he is very nearly dead. He's almost died on numerous occasions. That seems to be what it takes to be one of the great athletes. I'll pass, personally... --Mr.98 (talk) 14:16, 30 July 2012 (UTC)

In most sports, people are working constantly to better protect players, through rule changes, education and training, better equipment, more severe punishments for offenders, etc, particularly in more dangerous sports like American football[5][6]. I'm unclear if the question is asking specifically about rules to protect volleyball players, but even in volleyball there have been efforts to improve the safety of volleyball players[7][8]. --Colapeninsula (talk) 16:18, 30 July 2012 (UTC)

That first link is remarkable - not being a sports fan, I didn't have any idea the rules had been changed much for this purpose, let alone so often! It's interesting. Though the page doesn't really say how much all this accomplished. Wnt (talk) 02:37, 31 July 2012 (UTC)

• There can also be superstition around various kinds of tape or special garment; athletes may believe that it helps their performance even if there's no solid evidence to support this belief. Of course, a placebo can still cause a real performance improvement - and something which looks more drastic and medical may have a bigger placebo effect. I don't know whether power bracelet type stuff is allowed in olympic competition (it might be banned for advertising rather than performance-enhancing reasons) but that kind of thing is very popular in various sports. So, some of the visible stuff you see might not be a way of repairing an existing injury, or preventing a future injury, but simply a lucky rabbit's foot.
• Also, there will be some observation bias because these athletes are in the spotlight and generally wearing uniform garments which don't cover all their bodies, so anything on their skin will really catch the eye. Sometimes it's just a bit of tape; no biggie. I used to tape my toes to reduce chafing when I trained intensively; chafing from a single event wouldn't be a crisis, but the cumulative effect would be uncomfortable, and tape is cheap. bobrayner (talk) 12:45, 31 July 2012 (UTC)

I have concluded that the more/better the pading and protective gear in american football the more numerous and severe the injuries based on observing the helmet to helmet and body charging especially when you can support the helmet with the shoulder pads so that there is almost no risk of damage to tackler from a spear-type tackle. Rugby has just as much if not more contact and they seem to have the same injury rate. When you don't have all the protection you reconsider how bezerk you will go on the opponent.165.212.189.187 (talk) 13:42, 31 July 2012 (UTC)

Rough food

While reading the article Halitosis, I found a term rough food in Management section under point 2. Can you provide me some examples of rough food? Sunny Singh (DAV) (talk) 13:55, 30 July 2012 (UTC)

It would seem that this refers to the texture of the food, so maybe toast or cereals. I conclude this because the section refers to the scraping action on the back of the throat. --TammyMoet (talk) 14:24, 30 July 2012 (UTC)

See "Roughage" (—> "Dietary fiber") and wikt:roughage.

—Wavelength (talk) 20:58, 30 July 2012 (UTC)

Energy density of springs and the like

What is the energy density of springs, elastics and other mechanical devices for the storage of energy? OsmanRF34 (talk) 17:13, 30 July 2012 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know.

We have an entire section in our article on Hooke's law - the thermodynamics of elastic materials. However, in most basic physics texts, you'll see this question come up as a standard example problem for calculating conservative work. Depending on what you're doing, you may be able to get by with simple algebra. Nimur (talk) 18:03, 30 July 2012 (UTC)

Human interaction

Often a male assumes that if a female smiles at them a lot, then the female is attracted to the male. However in human interaction, the majority of people will smile after making eye contact regardless of gender. So why do so many males have this false predisposition. 176.250.151.7 (talk) 18:49, 30 July 2012 (UTC)

Wishful thinking. thx1138 (talk) 19:09, 30 July 2012 (UTC)

It depends on the context. If the receptionist smiles at you, you understand it's just her job. If a woman sitting at the bar keeps looking at you and smiling, it means she is attracted to you, or you are funny looking. :-) StuRat (talk) 19:52, 30 July 2012 (UTC)

True but other than a bar, generally most people will smile, unless they are in a bad mood. I think smiling is more of a friendly gesture than one that suggests attraction. 176.250.151.7 (talk) 20:22, 30 July 2012 (UTC)

It's more the eye contact than the smile. A woman who doesn't want attention from a man will carefully avoid making eye contact with him. Looie496 (talk) 20:33, 30 July 2012 (UTC)

(edit conflict) Most people can tell the difference between an initial eye-contact followed by a friendly smile, and repeated non-accidental eye-contact (with or without the smile) that indicates special interest of some kind -- not necessarily sexual, but usually taken to be, especially in a bar. Most females make similar assumptions. Dbfirs 20:35, 30 July 2012 (UTC)

This is very much a cultural phenomenon. I remember when I was living in (the former East) Germany, the people there thought Americans were strange because they always smile during general interaction. They didn't find it unpleasant, just odd. Javanese that live in Bali often point out how Balinese people never smile, but foreign tourists there often talk about the glowing receptions they receive from Balinese everywhere they go. How men interpret the smiles they receive from women is entirely dependent on their own background, experiences and predispositions. 203.27.72.5 (talk) 22:50, 30 July 2012 (UTC)

If the male assumes the smiling female is smiling at him because she is attracted to him, and he is wrong, then he might end up suffering some social embarassment, but no other negative consequences. If, on the other hand, he is right, he might end up mating with her and producing offspring. If the male does not assume the female is attracted to him, then whether she actually is or not, he will not be mating and producing offspring with her. Therefore, natural selection favors males who assume that smiling females are attracted to them, since there is very little cost to him being wrong and much to gain if he is right, so the answer to your question "why do so many males have this false predisposition" is evolution. —SeekingAnswers (reply) 01:34, 31 July 2012 (UTC)

Except that "some social embarrassment" can mean "comes off as that creepy guy who doesn't read body language or respect boundaries, and treats the slightest friendliness as a sign of sexual attraction: alarming" which can strongly negatively affect future prospects. Even if you're assuming the usual strange world proposed by the typical evolutionary psychologist, it is likely to get the guy beaten up by the men that the women are actually attracted to, and possibly shunned. See also: Schroedinger's rapist, which should really be required reading for all pleasant but slightly awkward men who are attracted to women [9]. 86.161.208.94 (talk) 14:33, 31 July 2012 (UTC)

There must indeed be cultural differences between regions if Looie496 is correct in his region. I (an Australian male) find that virtually all females smile and look me in the eye - its just natural friendliness and means nothing. I can normally distinguish without any difficulty or even needing to think about it, three situations: (1) Smiling, eye contact, & general friendliness as part of their job, cf StuRat's receptionists, (2) Smiling etc in just being friendly, eg neighbors, someone met while waiting for a train, and the like, and (3) Smiling etc as part of sexual attraction. I don't go on smiles or eye contact - I go on body language and what she does. For example, if she leans forward to you while talking, it may mean she wants you. If you notice that she's slighly (or more than slightly) more vivacious with you than with other males, that is a strong hint she wants you. If she laughs at your weak jokes, that's a good sign. If she fiddles with her clothing, or asks you about her clothing, that's a strong sign. If you pay her a compliment (eg "that dress looks good on you") and she just says "thank you", she's just friendly - but if she responds extra brightly and straightens her back or rotates, that's a good sign. But just a smile, no matter how warm - means nothing. Eye contact - means nothing.

I think SeekingAnswers is on very shaky ground in asserting males taking friendly smiles as come-ons is due to evolution. In the "cave-man" days, folk lived in small groups and tribes. In such cases, specialisation was most desirable (some made good spear points, others good at spearing animals, still others good at first aid & herbal remedies etc), teamwork essential, and no-one could survive on their own. So friendship and bonding with all tribe members was essential, and distinct from sexual pairings to raise children. A male who imposes himself on a female that doesn't want him has always been a disruptive thing that threatens the team/tribe. This means that evolution may have meant some pressure against propagating males who misread the friendship of females.

So, what's the answer to the OP's question? It assumes that many males do misread - is this true? If it is, maybe its social inexperience. Perhaps some males haven't found the right girl yet, and have lowered their filtering criteria. Perhaps an artifact of modern western living, which does not involve small tribes. Or chaps who went to all-boy schools and not co-ed schools. Some males spend their early working life in jobs where they don't have any female work-mates. Those that do can practice their social skills.

Wickwack124.178.41.15 (talk) 02:59, 31 July 2012 (UTC)

7 billion pieces of paper

(This topic could possibly be posted to the Mathematics of Entertainment desk, but since it involves applied math and possibly the behavior of falling objects I've chosen Science.)

After Team GB entered the stadium during the Olympic opening ceremony, the commentators (both BBC and NBC) claimed that 7 billion pieces of paper were released. I presume this figure was part of the press package. Starting with an conservative estimate of one square inch per slip (say 1/2 inch by 2 inches), 144 slips per square foot, and a rough interior stadium area of 500,000 square feet, I calculate that the resulting accumulation would be on the order of 100 slips deep. The actual results appeared to be only fractional coverage of the track and other areas of the stadium. Am I missing something or has the LOCOG stretched reality a bit? -- Tom N (tcncv) talk/contrib 18:50, 30 July 2012 (UTC)

In case anyone wonders whether you misheard billion for million, that 7 billion number is reiterated by The Telegraph, Dallas Morning news, and ESPN - the wording of each so similar it does sound like it's from the same source. Each says the pieces were "tiny" but not how big. One thing we do know - they were all dropped from a single helicopter. This says the paper-drop copter was an AgustaWestland AW101, which says it can take an internal cargo of about 3000 kg or an external (hooked) cargo of about 5500 kg; I can't find a photo of the drop (showing the helicopter) so lets run with 5500 kg. I'm too busy to do the arithmetic, but if you take that and paper density you can figure out the area of paper (given different candidate paper densities) that it would cover, and so how big a 7 billionth of that would be. Given that it's just one helicoper and not an armada of them, I'd guess the fragment size is of the order of 1 square mm. -- Finlay McWalterჷTalk 19:47, 30 July 2012 (UTC)

That 7 billion sounded too high to me, too, at the time. I don't think a square millimeter would work, it would just look like you were dropping powder on the field from a camera far away. You want it large enough so you can see individual flashes as each piece turns into and out of the light, from any camera in the stadium. StuRat (talk) 19:56, 30 July 2012 (UTC)

Standard office paper is 80g/m² - I would expect thin confetti to be half that (or even less). A m² has a million mm². Since the 7 billion slips of paper represent the 7 billion people on earth, we talk about a short scale billion - i.e. a thousand million. 40 g times 7000 is only 280 kg, so the paper slips can be up to about 20 mm² without too much trouble. --Stephan Schulz (talk) 20:03, 30 July 2012 (UTC)

I think the 7 billion figure was supposed to represent the global human population. As for the paper size, my impression from the video feed (where several slips could be seen momentarily landing on the athletes and stirring around near their feet) was that the slips were roughly finger-sized, much bigger than 20 mm² - more like in the 1000s of mm². That would seem to eliminate the possibility of a helicopter drop if these figures are correct. -- Tom N (tcncv) talk/contrib 21:19, 30 July 2012 (UTC)

I just checked - apparently, one can get paper with as little as 7 g/m². That gives us another factor of 5 or so compared to my computation, i.e. 100 mm² per slip, or e.g. 4 mm times 25 mm - still small, but not extremely tiny. --Stephan Schulz (talk) 21:54, 30 July 2012 (UTC)

After another look at the video and noting several slips riding the girls behind the British flag bearer, I would put my best guess at 15 mm x 60 mm. Using the 7 g/m², I get about 44 tonnes of paper. Also a few shots of video appear to show multiple sources, possibly ground-based blowers, rather than a single overhead drop. Back to the end-result - I only see somewhere between 1% and 10% ground coverage, which is about 1/1000 to 1/10000 of what I would expect from 7 billion pieces. Should we call this an extreme case of embellishment or is there some other explanation? -- Tom N (tcncv) talk/contrib 23:36, 30 July 2012 (UTC)

So far we've just assumed that all the pieces are the same as one another. They could quite reasonably be dropping 100,000 larger ones and the rest be 3mm chads. -- Finlay McWalterჷTalk 23:48, 30 July 2012 (UTC)

I'd just like point out that so far all answers have assumed that the pieces are of equal size. That is almost certainly wrong and if you assume a broad size distribution all that is essential is that the average is very small for the weight to be signifiantly reduced. With a small average size it's still possible that the particular pieces for which their size can be estimated are from the larger end of the distribution. 203.27.72.5 (talk) 00:23, 31 July 2012 (UTC)

And interesting point based on the two answers above. Assuming the 7 g/m², 63 million pieces of paper sized 15 mm x 60 mm would be 396.9 kilograms kilograms. That leaves 5103.1 left of the 5500kg. So the other 6,937,000,000 pieces of paper could be about 736 micrograms each or still ~105 square milimetres each. Nil Einne (talk) 08:29, 31 July 2012 (UTC)

That would make a plausible theory but for the fact that I see no evidence of a "dusting" of the arena, for which I calculate an expected average depth of about 10 1-cm² particles over an area 60,000 m². Confetti of that size would also be evident in people's hair. -- Tom N (tcncv) talk/contrib 13:32, 31 July 2012 (UTC)

Maybe in keeping with the symbolism of the 7 billion human inhabitants of Earth, a few million priviledged individuals of prominent standing were given a position in the grand ceremony, while the rest were dropped in the garbage out back. 203.27.72.5 (talk) 02:29, 1 August 2012 (UTC)

Isn't there a difference between US billion and UK billion? Which one is the press release using? There might be another factor of 1000 to account for. RudolfRed (talk) 03:33, 31 July 2012 (UTC)

As noted by Stephan above, it's short scale (i.e. US) billions. 203.27.72.5 (talk) 04:12, 31 July 2012 (UTC)

If it was long scale, that would be 7 trillion (short scale), and the people on the field would be buried alive. StuRat (talk) 05:03, 31 July 2012 (UTC)

Note that as the article mentions, there's little difference any more as the short scale is very rarely used in English (as the article also notes, usage in other languages is more variable). (Also as hinted at by StS the human population of the earth is the same (estimated figure), whatever you call the number.) Nil Einne (talk) 07:42, 31 July 2012 (UTC)

Don't you mean the long scale is rarely used in English ? StuRat (talk) 08:40, 31 July 2012 (UTC)

Ooops yes sorry for any confusion. Nil Einne (talk) 09:57, 31 July 2012 (UTC)

Foraging worker ant behavior

Some questions about foraging worker ant behavior:

1. Do foraging worker ants eat any of the food they find while they're out foraging, or do they bring all of it back to the colony first?
2. After bringing food back to the colony, do the worker ants eat any of the food, or do they just starve and give the food to other castes like queens, drones, larvae, and pupae?
3. If a foraging worker ant is separated from its colony and unable to find its way back, does it attempt to survive on its own, or does it just run around aimlessly looking for the colony until it dies?

—SeekingAnswers (reply) 21:48, 30 July 2012 (UTC)

In most cases, the foragers do not eat the food directly. As with soldier castes, many of them lack the mouthparts to feed themselves. Helper ants within the colony feed the soldiers and foragers. A good example are the leaf-cutter ants; the foragers are collecting leaves, while the ants eat only the mold grown on those leaves, so it must be processed within the mound before being fed to anyone. Foragers would usually have no way of surviving on its own and would soon starve. Matt Deres (talk) 00:43, 31 July 2012 (UTC)

July 31

Very specific spider question

I guess you can phrase this question in one of two ways: What is the smallest spider, in proportion to the web it weaves? OR What spider produces the largest web, in proportion to its own size? Evanh2008 ^{(talk|contribs)} 03:23, 31 July 2012 (UTC)

Apparently, it's the Darwin's bark spider [10] [11]. 203.27.72.5 (talk) 03:29, 31 July 2012 (UTC)

Cool! Thanks! Evanh2008 ^{(talk|contribs)} 04:03, 31 July 2012 (UTC)

What Do Women and Gay Men Find Attractive in Men?

This is a serious question. I am a straight male but I was wondering what others who are attracted to men see in men. Most men are hairy, stinky, and overweight/obese. Also, a lot of men are very aggressive. All of these seem to be serious turn-offs, so I'm wondering if there have been any scientific studies done showing what people find sexually attractive about men? Futurist110 (talk) 06:04, 31 July 2012 (UTC)

Muscles are attractive to many, as is height, and a deep voice. And even the attributes you list as unattractive are desired by some. StuRat (talk) 06:11, 31 July 2012 (UTC)

I don't think that anyone finds stinkiness attractive. Futurist110 (talk) 06:17, 31 July 2012 (UTC)

They do. There is a Greek dance where the men put handkerchiefs in their armpits to get them good and sweaty, then present them to their woman, who sniff it approvingly. It's only our culture where body odor is considered unpleasant (excluding the French, of course). :-) StuRat (talk) 06:33, 31 July 2012 (UTC)

Yep stinkiness is attractive. LOL. Futurist110, you underestimate the range of human fetishes. Smell is actually very important in human sexuality - pheromones. See

• "Sexy" Smells Different for Gay, Straight Men, Study Says (National Geographic)
• Pheromone attracts straight women and gay men (New Scientist)
• Do Pheromones Play a Role In Our Sex Lives? (Scientific American)
• How the Nose Can Control Human Sexuality (Mental Floss Magazine)

As for the visual and behavioral stimuli, the same things men find attractive in women: lots of different stuff. Some men like blondes, some brunettes, some like them scrawny, some like them big, some like them assertive, some like them shy, adventurous/conservative, smart/innocent, etc. I bet if I asked you what you find attractive in women your list will be very different from the next guy. Except the criteria will be different for men of course.

If it consoles you, "gold star" (exclusively homosexual) gay men can't understand why men find women attractive as well. I can appreciate feminine beauty quite easily, but there's zero sexual attraction. Same thing with smell. Women smell pleasant enough, male sweat however is sexy. See Sexual attraction and Neuroscience and sexual orientation.-- OBSIDIAN†SOUL 06:41, 31 July 2012 (UTC)

What school did you go to where they gave out gold stars for that ? :-) StuRat (talk) 06:44, 31 July 2012 (UTC)

Not a school. The Gay Mafia! lulz. They send it by mail, and you get discounts at gyms and salons with it.-- OBSIDIAN†SOUL 06:54, 31 July 2012 (UTC)

Just curious--are you into bears? Futurist110 (talk) 07:22, 31 July 2012 (UTC)

LOL, that's a bit personal. If you're asking if body hair or size also factors into attraction. Yes. As I said, different criteria. In the same way that men have idealized archetypes of women they find attractive; so do women and gay men. i.e. the criteria is not just "must have penis". And body hair and size are some of those criteria in the same way that breasts and long legs are for straight men.

I do notice something though. Gay men tend to be more into the idealized rugged alpha male. While women tend to be more into bishōnen-types (the success of boy bands for example) or supermodel-sh guys (what one blogger describes as the Johnny Depp factor). Not always, but often enough to be notable. Some researches link this with the economic environment and the perceived parenting skills. i.e. Women in richer countries tend to prefer the "feminized" men; while women in poorer or more dangerous places tend to be attracted to the macho men. I guess the "dangerous" part of the latter applies to gay men as well, even in rich countries. Others just link it with an innate finickiness in each gender.

• Why women now prefer Johnny Depp to Sean Connery (The Telegraph)
• Why Women Don't Want Macho Men (The Wall Street Journal)
• Gay Men Prefer Masculine-Faced Men, Study Suggests (Science Daily)

To quote from the last article:

"Our work showed that gay men found highly masculine male faces to be significantly more attractive than feminine male faces. Also, the types of male faces that gay men found attractive generally did not mirror the types of faces that straight women found attractive on average," says Glassenberg. "Men, gay or straight, prefer high sexual dimorphism in the faces of the sex that they are attracted to. Gay men and straight men did not agree on the types of male faces they considered attractive."

Weird, huh. :P-- OBSIDIAN†SOUL 09:06, 31 July 2012 (UTC)

Let's be very clear that the 'attractive' sort of smell is typically a fresh sweat smell, rather than a stale sweat smell. So, if you want to attract women, you do typically need to wash regularly. If you're a particularly sweaty person, or going to a particularly sweaty situation, antiperspirant will reduce the unpleasant dampness while not completely impeding fresh sweat. Spraying yourself with throat-catchingly stinky bodyspray/aftershave is a typical teenage mistake that few find actually attractive, and will mask the useful smells. Going without a shower and then spraying with boy-perfume is just unpleasant. 86.161.208.94 (talk) 14:25, 31 July 2012 (UTC)

Word.-- OBSIDIAN†SOUL 15:18, 31 July 2012 (UTC)

My subjective experience strongly matches the notion that response to pheromones determines sexual orientation; moreover, it is my personal belief that exposure to pheromones continues to reshape notions of sexual attractiveness throughout life (such as tolerance for gray hair or different ethnicity). I would very much like to see a study of whether exposure to concentrated pheromones can help those with sexual disorders, most notably pedophilia, to adjust and adapt their desires to more practicable goals. But I'm unaware of any such research, and don't have the appropriate position/training to conduct it. Wnt (talk) 06:14, 1 August 2012 (UTC)

I don't think pheromones have much effect in humans. We are mostly attracted based on visual and audio stimuli. If not, we wouldn't get turned on by magazine pics, porno flicks, and phone sex, but would be attracted to ugly people with the right pheromones. StuRat (talk) 06:20, 1 August 2012 (UTC)

My crazy notion is that the pheromone is not so much a signal to cause immediate sexual attraction as a signal that teaches sexually attractive characteristics (sort of like a positive-reinforcement electrode in a brain, which is not so much a source of direct pleasure as a means of reinforcing changes in behavior). Generally speaking, sexually attractive features tend to be average in nature; this could be seen as the aggregate outcome of someone being exposed to pheromones in the presence of many different individuals. My anecdotal observation was that exposure to the intense pheromones of a colony of breeding mice for 10-15 minutes made me start to have a quite distracting degree of sexual thought about two unquestionably unattractive women I worked with there at different times (I mean, one of them had severe acne scarring, and the other was of an ethnic group which at that time I perceived to be ugly), and while much of the effect wore off within an hour after leaving the environment, after several exposures they continued to seem moderately attractive to me even years later. Wnt (talk) 13:15, 1 August 2012 (UTC)

And don't forget, to put it scientifically, that many are attracted to the twig and berries. StuRat (talk) 06:35, 31 July 2012 (UTC)

Twig and berries? Futurist110 (talk) 07:49, 31 July 2012 (UTC)

This pic should make my meaning explicit: [12]. :-) StuRat (talk) 08:25, 31 July 2012 (UTC)

Oh yes, the package. Yeah, that's the one thing that most women find attractive in men. Futurist110 (talk) 19:13, 31 July 2012 (UTC)

Also, consider the things men don't do, which many find unattractive in women, like menstruation/PMS/menopause/bloating/cramps and crying (well, most men don't). StuRat (talk) 06:38, 31 July 2012 (UTC)

Women aren't too keen on most of those things either. As to the things men do that women generally don't find attractive, I don't even know where to start. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:16, 31 July 2012 (UTC)

Sexual attraction has evolved such that in the absense of natural selection pressure leading to survival of the fittest, sexual selection will prevent degeneration. Therefore women find those features attractive that indicate fitness, men find those features attactive that indicate fertility. Count Iblis (talk) 16:20, 31 July 2012 (UTC)

I'm going right back to the start, and calling a huge "Citation required" on "Most men are hairy, stinky, and overweight/obese". -- ♬ Jack of Oz ♬ ^{[your turn]} 07:54, 1 August 2012 (UTC)

The OP is from the USA where;

• • 72.3% of men are overweight or obese,
  • every person has body odour
  • men normally have thick body hair on their face, chest, armpits and groin

101.172.42.144 (talk) 09:32, 1 August 2012 (UTC)

Thanks for that. So, if the last 2 factors, which are common to all men, are the turn-offs (? turns-off) the OP claims them to be, why would women be any less repelled by them than other men are? -- ♬ Jack of Oz ♬ ^{[your turn]} 10:49, 1 August 2012 (UTC)

You made the distinction between straight and gay men in your title, but not straight and gay women. It should be; "What Do Straight Women and Gay Men Find Attractive in Men?" 92.233.64.26 (talk) 10:35, 1 August 2012 (UTC)

You also forgot bisexual women, men who have sex with men, men who rate 2 on the Kinsey scale, transgendered people and hermaphrodites. 101.172.42.143 (talk) 11:15, 1 August 2012 (UTC)

Does Occam's Razor Make the Existence of Gods Unlikely?

• Occam's Razor = The hypothesis/theory that makes the fewest assumptions is the best.
• Hypothesis 1 = Since everything is (or can/will be) explained by natural/scientific forces, God doesn't exist.
• Hypothesis 2 = There is an invisible, undetectable, walk-through, see-through, very powerful immortal being out there.

Futurist110 (talk) 07:35, 31 July 2012 (UTC)

• Well, Occam's Razor is that the simplest scientific hypothesis which explains everything should be used, and, while "God did it" is a very simple explanation for everything, it's by no means scientific. Since God isn't science, Occam's Razor doesn't apply. StuRat (talk) 08:43, 31 July 2012 (UTC)

(EC) the application of Occam's Razor is mentioned in the article you linked and also briefly mentioned in Existence of God and also given how often it's something that's brought up in plenty of other sources e.g. [13] [14] (there must be more total discussion then the entire RD archives combined). It may be helpful if you explain what parts are still confusing you. Nil Einne (talk) 08:50, 31 July 2012 (UTC)

Just looking at the original wording "that entities be not multiplied save of necessity" tends to suggest the answer to the question is yes. --TammyMoet (talk) 09:47, 31 July 2012 (UTC)

Before reaching any conclusions, define "God". ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:13, 31 July 2012 (UTC)

Occam's razor is a principle for deciding between competing theories. It doesn't actually say anything about the likelihood of those theories. --Tango (talk) 12:25, 31 July 2012 (UTC)

Actually, I was under the impression that Occam's razor does try to determine which theory is more likely based on our current knowledge and concepts. Futurist110 (talk) 00:21, 1 August 2012 (UTC)

Read our article - there is nothing about likelihood. It's just about what theory one should chose, not which is more likely to be true. --Tango (talk) 00:35, 1 August 2012 (UTC)

Occam's Razor itself is just one model (admittedly, a very widely adopted model, but still only one model) of how to think about things. It is not some Eternal Truth Set in Stone for All Time. You don't use it, for example, to work out which of those two cute girls you prefer. -- ♬ Jack of Oz ♬ ^{[your turn]} 02:51, 1 August 2012 (UTC)

There's a difference between likelihood and truth. For instance, many scientists considered the existence of the Higgs boson to be very likely, but it wasn't proven as truth until this year. Likewise, it is very likely right now that Besse Cooper will reach age 116, but it is not truth until she actually does reach age 116 later this month. Occam's razor deals with likelihood, not absolute truth/fact. http://math.ucr.edu/home/baez/physics/General/occam.html And actually, I do use a variant of Occam's razor to determine which of two cute girls I prefer. If I know a lot about one cute girl but I know very little about another cute girl other than her name, I would prefer to date the first cute girl since I think that she would be a better match for me based on my current knowledge (which could obviously change in the future). Also, with the first cute girl, there would be less odds of me later finding out something very unappealing about her than with the second cute girl about whom I know much less about. Also, excluding the hair and the eyebrows, I generally tend to find girls more attractive by the frequency and amount of room on their bodies that they use a razor on. ;) Futurist110 (talk) 02:09, 2 August 2012 (UTC)

The problem with Occam's razor is that 1. a lot of real-world things are pretty complicated, and 2. it can be quite arbitrary to decide which of two theories is the most simple. So let's say our two theories are, "there is a God" and "there is not a God." Which of those is simplest? Superficially you can count up the number of Gods in each and proclaim "not a God" the winner, but that's naive. Adding a God radically simplifies certain aspects of cosmology, biology, and morality. Getting rid of the God requires also developing elaborate and complex theories of where we came from, why the universe exists rather than doesn't, and so forth. It's not at all clear to me which is simpler — they're both pretty complex, when you start hashing out the implications. Even then, Occam's razor is, at best, a heuristic — a philosophical short-cut — and not a proof or even theory whatsoever. So I really don't see it getting one out of this sort of bind with any kind of straightforward action, if one is intellectually honest. (I say this as a subscriber to the no-omniscient-God theory, but for different reasons.) --Mr.98 (talk) 13:06, 31 July 2012 (UTC)

Adding a god doesn't really simplify anything - the question "Where did the universe come from?" just becomes "Where did the god come from?" and you haven't actually made any progress. You've just shifted the problem back a step. --Tango (talk) 19:55, 31 July 2012 (UTC)

Very poorly worded - I would say that everyday more and more scientists are saying things like Hypothesis #2: "There is an invisible, undetectable, walk-through, see-through, very powerful immortal (being[something]) out there." Aand less and less are saying things like Hypothesis #1 because they realize that it might be immpossible for them to actually "explain everything". 165.212.189.187 (talk) 13:29, 31 July 2012 (UTC)

Furthermore, to say everything WILL BE explained by natural/scientific forces is the same as "believing in God" i.e. it requires faith.165.212.189.187 (talk) 18:21, 31 July 2012 (UTC)

It's not the same thing. One is faith in extrapolation of an known and measurable method, the other is a faith in the existence of a supernatural entity. Not all faith has equivalent truth status. (I can have faith that someone will probably be elected as the US President in November. It is not the same thing as me having faith that the world is going to end in 2012.) --Mr.98 (talk) 19:37, 31 July 2012 (UTC)

define super-natural and entity. all faith is based on probability. there are risks of being wrong in each example. i have faith that one day i will throw a stack of papers in the air and they will disperse then come back together and land on the ground in the same exact ordered stack that i threw up.68.83.98.40 (talk) 06:10, 1 August 2012 (UTC)

Exactly. Also, I think I saw or read somewhere that 93% of scientists are skeptical about the existence of gods. I'll need to find the source, though. Futurist110 (talk) 00:24, 1 August 2012 (UTC)

That sounds a little high. Scientists are certainly less likely to be believers than the general population, but I doubt it is so overwhelming, especially in the less physical sciences (religion tends to contradict physics quite a lot, it doesn't contradict biology anywhere near as much). There is also a general trend for better educated people to be less religious, and scientists are very well educated (see Religiosity and intelligence), so pulling out an effect that is purely sure to them being scientists may actually be quite difficult. --Tango (talk) 00:35, 1 August 2012 (UTC)

Why do you say religion contradicts physics more than it does biology? 203.27.72.5 (talk) 02:32, 1 August 2012 (UTC)

I think the issue is that it's difficult to be scientifically curious about the very core laws of the universe, as a physicist is, while accepting on faith that the very core workings of the universe are governed by an active god who you can never hope to fully understand. There's less difficulty accepting the principles of a more specialized field like biology while maintaining that god is what's going on under the hood. While you most often hear about religious fundamentalists denying evolution, I think it's safe to say that most scientists who believe in god don't take the bible (or whatever religious text) that literally. Rckrone (talk) 04:58, 1 August 2012 (UTC)

Well not all of physics deals with "the very core workings of the universe". There's a lot of areas like ballistics and fluid dynamics. And not all religions even have a concept of God, let alone an active one who cannot be understood (Buddhism, some forms of Hinduism, Scientology). In the USA anyway, as I understand it, the traditional battleground in the war of science vs religion was the biology classroom. You don't really hear of fundamentalist types refuting Einstein's theory of relativity, or arguing that Newton's Laws of Motion shouldn't be taught to their kids. But I don't think that it makes much sense to generalize and say that religion in and of itself conflicts more with physics than biology or vica versa. There are religions that were specifically designed not to conflict with science. 203.27.72.5 (talk) 07:30, 1 August 2012 (UTC)

I think that's more a consequence of a lack of 20th century physics in the classroom until your second or third year of university. You can learn about the animal kingdom a lot earlier in life than you can learn about quantum mechanics. Frankly I agree with Rckrone, that biology is the easier pill to swallow; I don't see why evolution is objectionable. From a purely theological point of view, I do not understand why the supposition of an omnipotent deity precludes the possibility that said deity effected theistic evolution. Trying to invalidate religious tenets on scientific grounds is as easy as invalidating scientific principles on faith-based grounds, and the sheer absurdity of that artificial dilemma seems to be lost on most people. BigNate37_(T) 07:47, 1 August 2012 (UTC)

http://www.stephenjaygould.org/ctrl/news/file002.html - Here's the source about 93% of scientists being religious skeptics. For the record, though, even a biologist would probably have a basic grasp of physics and how it works from college. Futurist110 (talk) 07:00, 1 August 2012 (UTC)

In the US, maybe. In the UK, you can be a professional biologist without haven't studied physics past age 16. We specialise a lot earlier in the UK. --Tango (talk) 11:39, 1 August 2012 (UTC)

Oh, all right. Yeah here in the U.S., at least among science professors and teachers I found more skeptics than believers among those with whom I talked about religion. For the record, it's very possible to have a belief in gods that does not conflict with science (including physics), but these gods would need to be a Deistic-kind of gods in the sense of not interfering in our lives or our (pre-afterlife) affairs. Futurist110 (talk) 02:17, 2 August 2012 (UTC)

Why??68.83.98.40 (talk) 03:04, 2 August 2012 (UTC)

Why what? Futurist110 (talk) 03:41, 2 August 2012 (UTC)

...these gods would need to be a Deistic-kind of gods in the sense of not interfering in our lives or our (pre-afterlife) affairs. Oh, I guess you mean like how gravity doesnt interfere w our lives.68.83.98.40 (talk) 04:36, 2 August 2012 (UTC)

God doesn't have to be deistic, but Deism is the easiest spiritual belief to coexist with a scientific mindset. In all seriousness, the Flying Spaghetti Monster is also perfectly consistent with science. You assume either that God does not interfere in our experiences, or that we can't tell. There is also secret option 3, which is to assume we can tell, and that everyone else is denying the obvious, even though you have no understanding of science to begin with. Someguy1221 (talk) 04:50, 2 August 2012 (UTC)

Please continue your massive walls of opinion and debate some where more appropriate. 1.125.255.254 (talk) 09:56, 2 August 2012 (UTC)
The following discussion has been closed. Please do not modify it.
My response as to why a Deistic God or gods would best fit into a modern understanding of science is this--you don't see God making any appearances in public or possessing anyone. Everything in our lives can be explained by science, such as the pain you feel when you touch something hot or the injury that you sustain if you fall from your bike. Even the complicated things in our universe have a scientific explanation, such as the creation of the universe. Science has led to many new discoveries over the years and centuries about how things and the world works, even for things that were previously deemed unexplainable or caused by gods (such as earthquakes, plagues, and other natural disasters). I see no reason why science will not eventually discover answers to other questions about our world and universe that we are now unsure about. For the record, using God or gods to fill in the gaps in our current knowledge is an argument from ignorance, which is a logical fallacy. I do not see gods interfering in my life when I go to the supermarket, for instance. Maybe they're there and they're invisible, undetectable, and walk-through, but they still don't appear to anyone to do anything that even remotely interferes with or impacts someone's shopping. This is in contrast to gravity, which does have an impact on our daily lives, considering that when I jump, I always fall back down. Futurist110 (talk) 05:55, 2 August 2012 (UTC) I'm not the IP above. Short Reply: There's a a lot of definitions of what count as a god, so that seems to be more an assumption than something proven, do your arguments honestly rule out every nondeistic concept of a god that can be thought up? There's a lot of pretty basic things about science we still don't know and a lot of the universe we know nothing about, so it seems unreasonable to start declaring exactly what types of gods can or cannot be on the basis of science (not that I'm saying you should believe them, just that you can't really limit them). I think you are blurring the line between science and philosophy a little here. Longish Answer: Who cares about the opinion of scientists on the existence of god? If 85% of psychologists find Gears of War 3 a more entertaining game than Bioshock 2, should I care? No, just because entertainment and psychology are related in some fashion doesn't mean I should care about what they find entertaining. Now, if scientists start publishing in science journals about god, then we should care, but they aren't so we shouldn't. Another example: Particle physicists use lots of heavy mathematics, should we care about their opinions on the existence of large cardinals? Nope.,br /> As for the Occam's Razor stuff, it doesn't give you any guidance to what is true, unless you believe in some sort of design that prefers the theory with less assumptions...which is getting a little too "Intelligent Design"ish for me. As for your assumption 2, why all those properties? Why must a god be all of those things? Or do you just assume that since we haven't found some god at this point with our nascent understanding of the universe and slight exploration of it? While bitching, your hyp 1 doesn't hold much weight either. Describe what physics will be like in 300 years. You can't, can you? So how do you arrive at the contradiction between every possible god and all science ever? Please don't say that you can extrapolate from current science since physicists 300 yrs ago couldn't have guessed at what we have today, or that everything they had was false/wrong. How do you feel about consciousness, morality, free will, qualia, etc. All of these things suffer from a lot of the same problems as gods (in general, not in specific). Not that I'm saying you need believe in anything, or have any reason to (I surely didn't provide one), but I don't think you've presented anything nearly sophisticated enough to rule anything out or limit anything. Or are you perhaps disproving a biblical based concept of God as presented by people whose theological education is going to church on the weekend? I don't mean that offensively, but this is usually what everyone seems to be discussing, which is a shame, really. Anyways, sorry if I seem vitriolic, I just get really annoyed with the arguments on both sides of the debate and the narrowness of their focus, and the etc. Honestly, I'm just grumpy on this topic (with both theist and atheist alike). :-) Phoenixia1177 (talk) 05:20, 2 August 2012 (UTC) I define gods as anyone else would define them, minus the personality traits (since we honestly have no idea about which personalities gods might have) and the infinite power (having infinite power is a paradox, but one can still have overwhelming power). You're right that just because many people believe in something doesn't mean it's a fact (read argumentum ad populum). However, God/gods does/do have to do with science, since many religious people use God/gods to explain something which science can explain much better. Read what I wrote about Occam's razor again--it talks about something's likelihood of being true based on our current knowledge, not about absolute truth/fact. If you have a different definition of god/Gods, go ahead, but my definition is generally the one used in religions and popular culture. In regards to physics in 300 years, the things that we have proven so far will remain a part of physics in 300 years. Thus, what is conclusively scientifically proven remains a part of our scientific framework, foundation, and knowledge forever. I suppose that if gods exist, they could choose to intervene in our daily lives eventually, such as by starting to make public appearances. However, this has not happened for at least the last 1,500 years (but in all likelihood throughout all of human history), and thus I see no reason for the gods to suddenly starting intervening in our lives now. You can expect the gods to show up into our lives for 100 years, or have your great-great grandchildren wait for the gods to show up into our lives for the next 200-300 years, but I'm pretty confident that no gods will show up and start intervening in our lives in the future as well. If I'll be around in 50 or 100 years, I'll be there to tell you that my conclusions right now were correct. What exactly is flawed with consciousness and free will? Science can explain that pretty well nowadays. As for morality, this is not a scientific topic, but a political and philosophical one, so I don't see what this had to do with this discussion. In fact, it's a red herring fallacy. I don't know what qualia is, so let me look that up. If you claim that God or the gods intervene in our lives somewhere, you'll need to tell and show me where, and either I or someone else will provide you with a scientific explanation for it--maybe now, maybe in 10 years, maybe in 100 years, maybe in 1,000 years, maybe in 10,000 years, but eventually, in all likelihood a scientific explanation will be provided. Technically speaking, science didn't disprove the Abrahamic God either, at least not yet. Science only disprove what the Bible says he did, such as creating the Earth in seven days. Forgive me for asking, but are you an atheist, agnostic, or theist? And for the record, my arguments are as open-minded and as rational as possible. I'm an atheist right now, but I was a believer (albeit a Deist) up until two years ago, when I realized and acknowledged that in all likelihood I was deluding myself with my belief in God and the afterlife. Anyway, it's very nice chatting with you. Futurist110 (talk) 05:55, 2 August 2012 (UTC) "I define gods as anyone else would define them". Interesting since this a point of much contention among philosophers. "However, God/gods does/do have to do with science, since many religious people use God/gods to explain something which science can explain much better." I don't care what many people do with their beliefs, that's up to them. We're discussing the existence of something not human stupidity. A lot of people use a bunches of pop sci terms to give their spiritualism a more mysterious appearance, does science have something to do with spiritualism now? Nope. "Read what I wrote about Occam's razor again--it talks about something's likelihood of being true based on our current knowledge, not about absolute truth/fact." Sorry, Occam's razor doesn't talk about the truth at all, not the first to point this out. The only way Occam's razor can talk about truth would be if one of your competing theories was a subset of the other, not the case here. But even if you were right about Occam's razor it wouldn't mean much, it would just be a reason to call bullshit on Occam's razor. "In regards to physics in 300 years, the things that we have proven so far will remain a part of physics in 300 years. Thus, what is conclusively scientifically proven remains a part of our scientific framework, foundation, and knowledge forever." What? This is absolutely 100% false as it stands! Quick, which is right: QED or Maxwell? Newton or Special Relativity? Epicycles or Kepler? I could go on and on and on and on. Science is all about disproving itself and moving on! Sure it builds on the past, but it doesn't keep the past... As for your whole gods intervening thing, what does this have to do with anything? Do gods need to get involved with humans directly by popping up with bags of miracles to not be deist? If so, it's the first I've heard about it! "If I'll be around in 50 or 100 years, I'll be there to tell you that my conclusions right now were correct." Nice straw man:-) I don't need mythical beings pulling rabbits out of hats to tell you that you're arguments are bogus. Bottom line, your argument isn't good, it doesn't matter if there is a god of any type, or no, you haven't established anything with what you've said. "What exactly is flawed with consciousness and free will? Science can explain that pretty well nowadays." Nope, sorry, I don't even know what to say here. Science is struggling really really hard to come up with a good explanation of consciousness, it is one of the major modern problems of science and is no where near finished; not even kind of. As for free will, what are you talking about? Science has explained this!? Please point me to the journals where this takes place...sorry for seeming rude, but that's absolute rubbish. "As for morality, this is not a scientific topic, but a political and philosophical one, so I don't see what this had to do with this discussion. In fact, it's a red herring fallacy." God is a science topic, but not morality! Seriously, though, you should read a few text books on social psychology, or just psychology in general, morality has some connection to science (though, I agree it is primarily philosophy) And since I've seen more papers on moral stuff than on God in science journals, I'm going to have to say you've got what you said backwards there. "If you claim that God or the gods intervene in our lives somewhere, you'll need to tell and show me where," I didn't say gods intervene directly in human lives; I didn't even kind of imply that. In fact, what I said, in a nut shell, was that your argument is no good. I didn't say this because blah blah blah god, I said this because it doesn't work; even if you're right, you still haven't shown it. "Technically speaking, science didn't disprove the Abrahamic God either, at least not yet. " Who cares? I specifically bitched about everyone whining on about some narrow understanding of one specific religion as the problem with most such discussions. Are you talking about gods or some specifically defined entity based around Bible stuff. If the latter, you should say so. Also, why the "not yet"? That's got to be the funniest thing I've seen all week, I was starting to feel like I was being overly rude, but then, there it is: "not yet." Tell me, do you think there are some scientists out there, right now, putting together research on this topic, working hard at disproving god? What experiments are underway that will disprove this one specific god? "Forgive me for asking, but are you an atheist, agnostic, or theist?" Why? Does it matter some how? Also, agnostic isn't the same type of thing as the other two. "And for the record, my arguments are as open-minded and as rational as possible. I'm an atheist right now, but I was a believer (albeit a Deist) up until two years ago, when I realized and acknowledged that in all likelihood I was deluding myself with my belief in God and the afterlife." No, they aren't. I'm sorry, but all of my rude behaviour aside, you could stand to do a lot more studying on a lot of the mentioned topics. I mean you seem to think you've done something magical with a 3 line argument, an argument that's been had a thousand boring times before. Also, a lot of what you seem to say about science makes it seem like you don't know a lot of actual science, which is fine, but makes all your talk about science and god look weak. "Anyway, it's very nice chatting with you." And now I feel like a giant jerk. But, like I said, this topic just aggravates me to no end. Seriously, I get fired up with theist, atheist, whatever. Mainly because everyone sits around talking about general things with their own personal pet view lurking beneath the surface while they go on and on about what other subjects say like they've extensively studied them. So, my general nastiness aside, nice chatting with you too:-)Phoenixia1177 (talk) 07:03, 2 August 2012 (UTC)

Well damn, I really like massive walls of debate in questions about the disproving of god...next time I'll just go with a "I disagree." Anyways, if anyone cares to respond in anyway, please do so on my talk page:-)Phoenixia1177 (talk) 10:14, 2 August 2012 (UTC)

Why would the heat shield fly forward and not go back into the parachute?

I'm talking about time 3:03 of the video in the Landing section of Curiosity rover. This big thing is hurtling toward the surface, and even if for a moment pyrotechnics on board blow it forward, I'm not seeing how that big disc, once it's free of the payload and therefore much lower mass by itself, but essentially a big frisbee, isn't getting thrown back by the wind resistance (even if Mars' atmosphere is really thin, the thing's going incredibly fast) and into that very huge parachute that is right behind it. Of all the parts of that video, that disc nicely speeding out and away in front of the craft is the strangest part to me. Can someone explain why it's acceptable to believe that that disc would behave as it does in the video from 3:03 to about 3:10 and not flit back into the parachute? 20.137.18.53 (talk) 15:37, 31 July 2012 (UTC)

(For the benefit of others, this is the video in question: [15] AndyTheGrump (talk) 15:45, 31 July 2012 (UTC) )

The parachute attached to the lander is causing it to decelerate. Once the heat shield detaches from the lander, it is no longer decelerating with the lander, so it falls faster. — Preceding unsigned comment added by 148.177.1.210 (talk) 15:50, 31 July 2012 (UTC)

(ec)The huge parachute is slowing down the lander much more rapidly than the released heat shield is slowing down. Nothing is moving "back" or upwards - the downward movement of different pieces are just slowing at different rates. Roger (talk) 15:50, 31 July 2012 (UTC)

Even if you ignore the parachute, the explosive charge that removes the shield will push in all directions, so the probe is pushed up (i.e. it's rate of descent is slowed) and the plate is pushed down (it's rate of descent is accelerated). Only if the plate was at or very close to terminal velocity before the charge detonated would it then slow down and make contact with the probe again. Also, the shield is designed to be aerodynamic, so it will have a higher terminal velocity than the probe, which is not particularly aerodynamic. Even without the parachute the probe would slow considerably once it was outside the eddy currents in the wake of the shield. 203.27.72.5 (talk) 23:25, 31 July 2012 (UTC)

The heat shield isn't supposed to be aerodynamic - it's entire purpose is to slow the craft down with air resistance (while not allowing it to burn up). --Tango (talk) 00:39, 1 August 2012 (UTC)

The craft still has a far lower drag coefficient with it on than with it off. It might not be designed to cut through the air like the nose of a rocket, but it is designed to be at least aerodynamic enough to maintain stability. 203.27.72.5 (talk) 02:10, 1 August 2012 (UTC)

Keep in mind that at the point of separation, the two bodies have the same speed. So any deceleration (parachute) applied to the following body will necessarily separate it from the accelerated (explosively jettisoned) leading body. μηδείς (talk) 03:16, 2 August 2012 (UTC)

How much space and time is required to compute a simple weather model?

I recently ran into the problem where computing 23 recurrence plots (for a time process of about 8000 intervals) took a prohibitive amount of time and space (because I had to deal with 23 8000x8000 matrices). This made me wonder, how much time and space is required for simpler weather models? I imagine a simple resolution of 5000 intervals for experiment would require at least (5000)^4 * 32 bytes = 18 million GB of disk space. Then there are other multidimensional computational problems involving tensors, such as stress calculations.

Also, how are 9-dimensional, 11-dimensional string theory models processed for a simple particle-particle interaction ? 76.104.28.221 (talk) 15:39, 31 July 2012 (UTC)

I don't see where your numbers come from, especially that fourth power. In a weather simulation, nodes only interact directly with their neighbors, so the memory demand is only quadratic as a function of the spatial resolution. Weather simulations are certainly demanding and are generally run on supercomputers. However the range of useful models is so broad that the term "simple weather model" does not have any concrete meaning. Looie496 (talk) 16:10, 31 July 2012 (UTC)

Typically weather models have time steps of a few minutes or even seconds, but only produce output every 1-6 hours (depending on the application). This greatly reduces the amount of disk space needed. With parallel-processing to reduce the load on individual processors, it's quite easy to run weather models in a timely fashion. Also 8000x8000 is much larger than any domains I've seen used, what sort of dimensions/resolution are you attempting?

As a side note, I can run moderate-resolution real-time forecasts using the Weather Research and Forecasting model and its associated data assimilation system (WRFDA) on my laptop (8GB RAM, dual-core 2.2GHz processor). You can try it if you have a Macintosh or Linux system, it's free, open-source, and public domain, and the online tutorial makes it quite easy, IMHO. -RunningOnBrains^(talk) 16:25, 31 July 2012 (UTC)

To expound further, I'll look at a typical model run: the North American Mesoscale Model (this is a regional model; most global models these days are spectral models (unlikely red link, I'll have to remedy that) which is more complicated as far as calculating space needed). The NAM is currently run at a resolution of 1337x1165x60 (sources; you need an account but it's free to sign up: [16][17]) with output every 3 hours out to 84 hours, which means our total resolution (with time included) is 1337x1165x60x28. To complicate this calculation a bit further, they use an Arakawa E grid for the diagnostic equations, so in reality the resolution is only 669x583x60x28. This means that for each output variable (assuming 32-bit floating-point numbers), you need only 2.6 GB of space; and I believe the number of vertical levels on the output is reduced, so this number is probably much lower.

As far as computing power, the NAM is run on 30 nodes of 32 4.7GHz processors (sources; sorry, powerpoints: [18] [19]) and takes only 1669 seconds (about 28 minutes). I hope this info sheds some nice light on the issue for you! -RunningOnBrains^(talk) 20:29, 31 July 2012 (UTC)

Oh I'm running recurrence plots of an 8000-frame time series of Drosophila movement and I'm trying to pick out potential order in their seemingly random movements (velocities); a single experiment might have ~20 tracks. I ran into memory issues quite quickly. This caused me to wonder about weather models, which I imagine run in 4D space, not 2D!

Also, does the (kind of) coarse spatial resolution cause issues, especially with convergence (or divergence) of a discrete numeric solution from a continuous/analytic solution as resolution is increased? "12 km horizontal resolution and with 1 hour temporal resolution" might be a feat of human computer science achievement, but from a differential equation POV, it does seem kinda coarse. 128.143.1.46 (talk) 22:22, 31 July 2012 (UTC)

Could you be kind to the clueless and explain this a little more? Am I right to think that you have a two/three?-dimensional position for a labelled fly at each of 8000 time points, and you want to find resemblances between this track anywhere during the time sequence? And you've done this for 20 different flies in the same container? a) are you looking only for when the fly goes through the same exact spot in the same direction twice, or when it moves in the same direction regardless of its position, or when it's at the same spot regardless of direction? b) getting to the point, can't you 'window' this dataset somehow? I mean, this sounds more like a DNA alignment program than a weather forecaster, and that's what they do; you take some frame, maybe 100 time points, and run it against the whole dataset, and repeat with another offset from that a little bit and so forth. But I'm not a bioinformatics person. Wnt (talk) 13:28, 1 August 2012 (UTC)

The flies are confined to a 2D arena, and I measure the magnitude of velocity and acceleration and other one-dimensional parameters, so I want to find resemblances between similar velocities at anywhere during the time sequence. I would make a recurrence plot for each fly. The time resolution between t and t+1 is at 1/15 of a second. 76.104.28.221 (talk) 21:12, 1 August 2012 (UTC)

To answer your question about coarse spatial resolution, it is an extremely complicated issue. First off, as I mentioned, the actual timesteps of the calculation are much shorter than the output timesteps (on the order of seconds) because they must meet the CFL condition or the calculations will blow up. The actual outputs are only written to an output file every 1-6 hours because writing the output into an external file takes additional computing time, and no one really needs to see a second-by-second state of the atmosphere except for some research purposes. Second, spatial resolution is kept especially course because A) reducing the spatial resolution means decreasing the time steps as well, per the aforementioned CFL condition, which means that decreasing the grid spacing by half in 3 dimensions increases the computation time by a factor of 16, not 8, and B) in a non-hydrostatic model (i.e. one that explicitly calculates vertical pressure gradients instead of assuming vertical balance; most models these days are non-hydrostatic because it yields much better results at smaller scales) atmospheric convection becomes explicitly resolved at spatial scales approaching a few kilometers. This requires more explanation:

In models with larger grid spacing, (say, 10+ km) convection is parametrized, i.e. treated heuristically with various calculation rules that aren't necessarily related to the physical equations in the model. As the grid spacing is reduced, convection starts to be explicitly resolved in the model; i.e. the equations of motion lead to actual localized updrafts and downdrafts which cause rain/thunderstorms. However, until the grid spacing gets down to about 0.5 km or less, this convection is not resolved in a physically realistic way, since thunderstorms are only on the order of 10-20km across. When attempting to parameterize convection while it is also being explicitly resolved (in an extremely rough and often non-physical way) it can lead to poor results at these intermediate scales (grid-spacing of 1-10km). For this reason, these smaller-scale models almost always give comparable if not poorer results than those with grid spacings around 12 km.

As a further tidbit, there are literally dozens of processes that need to be parameterized because they will always be below the spatial scale of even the finest-resolution models. Thinks like boundary layer turbulence, surface roughness and friction, cloud processes, rain/snow/hailfall, snow cover and sea ice, soil moisture, and human processes like chemical emission and land use changes (i.e. farming areas have different albedo, soil moisture, and surface friction at different times of the year) all fit this bill.

Sorry if this has become overly technical, I will gladly answer any questions to clear up confusion about the above summary. -RunningOnBrains^(talk) 20:38, 1 August 2012 (UTC)

Should I trust these kinds of websites?

I was researching about what were the false assumptions of Bohr's model and why is it accurate despite being, well, wrong, and I reached this: http://www7b.biglobe.ne.jp/~kcy05t/index.html . Well it seems to say that Bohr's model is right, and there was a section down there "reasons why quantum mechanics is wrong" which made me even more suspicious than before. I'd like to know your opinion about this site but aside from that, considering the fact that I still don't know enough about these topics to know why quantum mechanics (or any other highly sophisticated topic) is right(?) in the first place, is it prejudice to dismiss the whole thing just because it contradicts theories that are more widely accepted in the scientific community? I mean at least in this example the website seems to have a lot of content, and at least some mathematical descriptions (not saying that these things are good criteria for good ideas!)--Irrational number (talk) 21:15, 31 July 2012 (UTC)

It's not wrong to dismiss a theory only because it's rejected by the wider scientific community if you don't know enough about the topic (or don't have the resources) to judge it on its scientific merits. It's impossible to be an expert in all areas, and in the areas where you aren't an expert the best you can do is trust that the people who are experts have done their jobs correctly. When there's consensus among most experts, chances are much higher that they are correct compared to the dissenters. That's not to say that the consensus is never wrong, but when you have to trust in the results of others you should put your money on the best bet. Rckrone (talk) 21:38, 31 July 2012 (UTC)

(edit conflict)Without analyzing the contents (as I am getting older and forgetting much of my quantum mechanics), anyone who claims to have proved some scientific field "wrong" is just blowing smoke. Science is not a courtroom, where a case can be dismissed on a technicality. Science is evidence for explanations and explanations for evidence, all woven into an intricate, inter-dependent non-contradictory web. If current scientific theories can't explain some isolated observation, either our assumptions about the observation was wrong (see Faster-than-light neutrino anomaly, Pioneer anomaly, or any number of sensational media stories about "new science" which are constantly proving to have mundane explanations) or our theory needs to be tweaked slightly (see Quasar#History_of_observation, Galaxy rotation curve). -RunningOnBrains^(talk) 21:56, 31 July 2012 (UTC)

One of the mose common media cliches is the "Einstein was wrong" headline. It gets dragged out every few years when some new discovery is made and completely misunderstood by the mainstream media. I groan every time I see it. Most recently for that faster then light neutrino story mentioned above. At least now you now get responses like this. Vespine (talk) 22:35, 31 July 2012 (UTC)

We're not supposed to answer requests for opinions, but as for the other question, the reason quantum theory is considered "right" is because it makes accurate predictions. The Bohr model also made accurate predictions, (and it was the first quantized model of the atom), but modern quantum theory predicts a lot more things a lot more accurately. 203.27.72.5 (talk) 23:11, 31 July 2012 (UTC)

August 1

Blood relations

i was marry with my mothers elder brothers daughter <request for medical advice removed> are we first cousins or second cousins? — Preceding unsigned comment added by Nalaka88 (talk • contribs) 06:40, 1 August 2012 (UTC)

We cannot give medical advice, so it would be best for you to seek guidance from a medical professional. Evanh2008 ^{(talk|contribs)} 06:43, 1 August 2012 (UTC)

Please see our medical disclaimer. BigNate37_(T) 06:48, 1 August 2012 (UTC)

We can answer the non-medical question. Your father in law also being your uncle makes you and your wife first cousins. See Cousin#Basic_definitions. 203.27.72.5 (talk) 08:31, 1 August 2012 (UTC)

While we can't give medical advice, I can give you a link to Cousin marriage#Biological aspects. If you wish to know how that information relates to you, then you'll need to speak to a doctor or genetic counsellor. --Tango (talk) 11:47, 1 August 2012 (UTC)

This is far more a political or cultural issue than a medical one. A small detail not mentioned in the cousin marriage article is that in the traditionally more widely favored cross cousin arrangement, which this exemplifies, one greatgrandfather contributes his X to a daughter and his Y to a son, the third generation (opposite sexes of either variety) then marry; in this case no part of the greatgrandfather's X can meet up with itself in the fourth generation. (Of course, recessive sex-linked traits only matter to women anyway) Wnt (talk) 14:23, 1 August 2012 (UTC)

Chromosomes don't stay together. See chromosomal crossover. Also, you are ignoring all the non-sex chromosomes. --Tango (talk) 23:01, 1 August 2012 (UTC)

Vitamin C in raw meat

Where does the vitamin C in raw meat come from? Madifrop (talk) 15:43, 1 August 2012 (UTC)

From the animal's food of course. Roger (talk) 15:48, 1 August 2012 (UTC)

(ec) Most animals can produce vitamin C in their bodies (see Vitamin C), and of course animals can also gain vitamin C from their food, as we humans do. - Lindert (talk) 15:49, 1 August 2012 (UTC)

The ability to synthesize Vitamin C, a rather simple compound with a similar chemical structure to glucose, was lost in the ancestry of the haplorrhines,

the primate group including the monkeys, apes, and tarsiers. This was possible because these animals received enough ascorbic acid in their diets (from fruits like figs), that they did not need to synthesize it, so losing the gene for the enzyme that catalysed its synthesis was no handicap. μηδείς (talk) 03:03, 2 August 2012 (UTC)

Shovel-shaped incisors

Why were Shovel-shaped incisors developed in humans and why are they prevalent in the Mongoloid races? What do people with non Shovel-shaped incisors have instead? Reticuli88 (talk) 15:57, 1 August 2012 (UTC)

According to [20], the crown shapes of maxillary central incisors in Caucasians is ovoid, square, or triangular. StuRat (talk) 21:58, 1 August 2012 (UTC)

See Sinodonty and Sundadonty. Dental patterns in humans go from generalized to specialized. "Proto-Sundadonty" is believed to be the ancestral dental pattern of all late Pleistocene human populations. Isolated populations that underwent the least amount of genetic drift like the Ainu, the prehistoric Jomon, modern Papua New Guineans, and Australian Aborigines still resemble Proto-Sundadonts closely. Dental patterns of South Asians, Indochinese, Austronesians, southern Chinese, Arctic Native Americans (Aleut, Inuit, etc.), and some other Native Americans are predominantly the less generalized Sundadont dental pattern (which do not exhibit shoveled incisors). Not sure about modern European, western and central Asian, and African dental patterns, but I think they are also generalized and resemble Sundadonty. On the other hand, East Asians, Northeast Siberians, and the rest of the Native Americans who underwent the most amount of genetic drift from the original human migrants out of Africa are predominantly the more derived Sinodonts. There is no whys about it, though.-- OBSIDIAN†SOUL 23:47, 1 August 2012 (UTC)

Extracting multiple regression lines from a single data set

Return maps of velocity and acceleration respectively, of Drosophila wandering in an arena.

I was inspired by the discussion here on how to extract nonlinear order from chaos in seemingly random time series such as the logistic map by using something called a "(Poincare) return map" (a little different from the Poincare map described here on Wikipedia). I used the same idea to look at the time series variables of my Drosophila, where I had tracked things like velocity, acceleration, angular velocity, etc.

I've shown two examples of the return maps I have gotten for all my Drosophila populations (more or less in the same form) to the right, though the acceleration plots and the velocity plots are from different populations. These are just examples of the plots I'm getting-- all the velocity and acceleration plots have the same basic form as these plots, although slopes and spread/distribution might differ.

I created the return maps by plotting f(t+1) on the y-axis versus f(t) on the x-axis, where f is either velocity or acceleration as appropriate. (The time difference between time t and t+1 is 1/15 of a second, i.e. time-series measurements are sampled at 15 Hz.) It reveals intriguing semidiscrete stochastic decision-making on the part of Drosophila, but how do I even statistically analyse the multiple trendlines, especially so I can detect differences between genetically-different populations? My normal approach (line/curve fitting) is useless here. I think extracting things like slopes, angle difference (maybe as a function of probability), spread from the trendlines but I wouldn't know how to begin. Can someone introduce me to "multiple trendline" analysis methods? (How would you pick out the main sequence from a Hertzsprung-Russell diagram for example?) Nothing gold can stay (talk) 21:28, 1 August 2012 (UTC)

"It reveals intriguing semidiscrete stochastic decision-making on the part of Drosophila..." ... or, it reveals aliasing due to quantization noise. You're sampling a continuous trajectory; your resolution in time is band-limited by your video frame-rate; and your samples in space are band-limited by your camera's optical/digital resolution (number of millimeters per pixel). You're aliasing like crazy in three dimensions! (x,y, and t). All data derived from the measurements should be carefully processed to avoid creating spurious signals. But, if you're certain that you believe these charts, and simply want to fit equations to the scatter-plots, you should start by reading Statistical classification. There are many different types of classifier algorithms; these types of mathematical algorithms can be used to distinguish one "blob" from another "blob" in a scatter-plot or a point-cloud. Once you separate the data into separate "blobs," (rather, "once you classify the data into disjoint sets"), you can fit a linear equation, or any other sort of statistical parameterization, for each set. Nimur (talk) 21:40, 1 August 2012 (UTC)

However I observe the discretization only happens at fast speeds or fast accelerations, where the fly moves or accelerates a lot between frames. If it was due to quantization noise, you would expect the quantization to increase as speed or acceleration decreased. If the fly is moving or accelerating quickly, there is a greater spectrum of values that it could "land" on. My spatial resolution is roughly ~6.3 pixels per mm and temporal resolution at 15 Hz, thus my velocity resolution is at least 2.4 mm/s and acceleration resolution at least 36 mm/s^2. Nothing gold can stay (talk) 22:19, 1 August 2012 (UTC)

...You're not making a very convincing case. You've computed the derivative numerically, correct? Are you familiar with the noise problem introduced by applying the finite difference operator to approximate the derivative? In other words, solving for velocity v(t) by computing the difference in position x(t+1) - x(t) is a very great way to amplify noise and amplify the error in your measurement. You don't think it's a strange coincidence that the data seems clustered around a line with slope of 1/2, 1, and 2? What you're proposing is that statistically, a fly who is buzzing around at 42.5mm/s for 1/15 of a second is very likely to decide that during the next 1/15 second, it should fly at 21.25 mm/s. This doesn't strike you as a procedural error? Nimur (talk) 23:52, 1 August 2012 (UTC)

I have a good reason to suspect my tracking problem superlocalises so the resolution is in fact better than 2.4 mm/s. I don't think it's that likely to jump from 42.5 to 21.25 mm/s because the biggest steps would be in 2.4 mm/s, if not smaller. I do note that separation increases as a function of speed/acceleration. Also, I would think error in measurement in one frame is unlikely to propagate to another because the video samples at every frame and doesn't do any sort of dead reckoning. Correct me if I'm wrong? Nothing gold can stay (talk) 00:08, 2 August 2012 (UTC)

(Also, for both aesthetic and scientific reasons, may I suggest that you use squared axes when plotting velocity-vs-velocity, or any other case when you create a scatter-plot of dimensionally-identical quantities? It helps make the interpretation easier. If you used MATLAB to create the plots, use axis equal. Nimur (talk) 21:51, 1 August 2012 (UTC)

As far as writing a program to handle the top graph, it should only compute distance from each line to those points closer to that line than the other two. You would have to specify that it needs to look for 3 lines, though. You could expect such a program to take far longer to run than if you manually separated the data into 3 blobs. StuRat (talk) 22:05, 1 August 2012 (UTC)

Okay, but how would it find the lines once I've specified the number of lines? Nothing gold can stay (talk) 22:32, 1 August 2012 (UTC)

It would initially place all the lines, say, along the X axis, then use a hill-climbing method to change the angle and elevation of each line, until it found the best location for each. If you could specify an initial guess for the placement of each line, that would certainly speed things up. If you can provide a CSV file with the data in that top graph, I could take a shot at writing a program for it. StuRat (talk) 22:49, 1 August 2012 (UTC)

Thanks a lot for your offer! :) I'll see if I can package it online. Maybe I'll upload it to my university web page. Nothing gold can stay (talk) 00:08, 2 August 2012 (UTC)

(update) Okay, I have my csv files at http://people.virginia.edu/~jrs5fg/returnvelo.csv and http://people.virginia.edu/~jrs5fg/returnaccel.csv; they both correspond to the same raw experimental data set. Basically, there are two columns in each file, the first being f(t) and the second being f(t+1). Nothing gold can stay (talk) 03:58, 2 August 2012 (UTC)

StuRat, that will only work if you're planning to fit the data to a strictly convex model. "Hill climbing" algorithms also have a nasty tendency of finding numerical instabilities and local minima. Do you know the characteristics of this data-set inside and out? Are you an expert in the field of trajectory modeling in drosophila? If so, why don't you offer up some reliable sources for best practices and techniques? And if you aren't... that's why we don't offer to conduct research. I think our O.P. ought to get in touch with their P.I. for a little more guidance and direction. Nimur (talk) 23:43, 1 August 2012 (UTC)

Geez, what's with the vitriol ? I just offered to curve fit a graph, and it shouldn't matter what the data is. It's up to the researcher to decide what it means, not the curve fitting program, or programmer. Hill-climbing doesn't always work, but, looking at the top graph, hill climbing should work fairly well here, and is likely the only option that could fit this amount of data with three lines in a reasonable time frame. The only problem I see is where the data overlaps, but I don't see any solution for that problem. I'd restrict the curve fitting to the point where the data diverges. StuRat (talk) 23:56, 1 August 2012 (UTC)

The No Original Research policy applies to Wikipedia articles. This is not an article, it's a Ref Desk question. What on earth is wrong with an answer that contains original research, significant research even, as well as just a simple calculation or graph, if the provider of the articles is happy to do provide it? Doing so may mean that the poster gets no official credit, but that's his problem. The NOR policy is appropriate to WP articles, as they comprise an encyclopedia (=collection of known facts), but here the sole criteria should be does it help the OP? As with any sort of answer on Ref Desk, it is up to the OP to assess the merits of any OR provided Wickwack120.145.176.119 (talk) 00:52, 2 August 2012 (UTC)

I'm exhausting all available options here-- I've contacted other people in my department but they are away teaching at a mountain lake this summer, so I'm trying other options. Also my PI says I have to seek outside help to solve my problem, because he doesn't know the techniques to solve this problem himself. Nothing gold can stay (talk) 00:08, 2 August 2012 (UTC)

Just curious, do drosophila have three different modes of locomotion, like a horse has a trot, gallop, etc. ? StuRat (talk) 00:14, 2 August 2012 (UTC)

I don't think so...? (I haven't heard of it, at least...) From other papers I've seen where they looked at behavior through return maps, discrete locomotion behaviors (trot, gallop, etc.) would correspond to spherical'ish clusters on a return map, not lines. i.e. at f(t) there would be discrete clusters a, b, c ... (corresponding to the different velocity modes), and at f(t+1) a, b, c, and the return map would simply imply switching between discrete modes. This is opposed to the lines bx +c... also if measured velocity was in fact discretised, wouldn't the return map break up into such clusters? Instead, the lines are fairly continuous. Nothing gold can stay (talk) 00:30, 2 August 2012 (UTC)

Did you choose 1/15th of a second because that's the time frame that makes the lines have slopes of .5, 1 and 2, or did it just work out that way the first time you plugged in the data? It just seems incredibly suspicious to me. I showed your graph to my own lab's tracking expert, and he simply refused to believe the lines are real. Someguy1221 (talk) 00:36, 2 August 2012 (UTC)

It's 1/15 second because it seems to be the maximum sampling rate from VirtualDub (I can't seem to change it, I think my camera is capable of 1/29.97). Also I believe the slopes are closer to 0.4, 1 and 2.5....what's so suspicious about the lines? Again the structure of the return map suggests possible velocity is continuous, not discrete, just that change in velocity can follow three modes, and once the fly has "chosen" a mode, there is wide continuum within that mode in which to choose. Also, why is everyone ignoring the acceleration graph? Acceleration ranges from -500 to 500 mm/s^2 (and the resolution would be at least 36 mm/s^2). When a fly is at 0 mm/s, its pdf for the next frame ranges from 0 to 500 mm/s^2-- once such a positive acceleration is chosen in that frame, a negative acceleration is likely in the frame after that, proportional to the positive acceleration "chosen". And once a negative acceleration is chosen, there is a tendency to return to zero acceleration in the next next frame. Thus, a fly's acceleration plot wanders all over from -500 to 500 mm/s^2 over time, in a seemingly random fashion. If the plots suffered from quantization error I would expect the acceleration return map (as well as the velocity return map) to look a lot different, breaking up into clusters rather than lines. Can someone check my logic? Nothing gold can stay (talk) 00:45, 2 August 2012 (UTC)

A note on using both return maps together

Return maps again, just so people don't have to scroll-up to follow this section.

Suppose a fly is at 30 mm/s at t=1. It has a good chance of decreasing around 10 mm/s in the next (1/15) second. Then its acceleration will be (v2 - v1) * 15 fps = -300 mm/s^2 at t=2. But according to the acceleration return map it's likely that acceleration will now go to zero in the next frame +/- 50 mm/s^2 (velocity would increase or decrease 3 mm/s max) at t=3, so we can deduce that velocity will most likely remain around 10 (+/- 3) mm/s at t=3.

But now that acceleration is close to zero, it will most likely choose acceleration values anywhere from 0 to 500 mm/s^2, so it would prefer one of the two modes (increasing or maintaining velocity) but not the decreasing velocity mode, such that velocity will be anywhere from 7 to 43 mm/s at t=4, but not below that, even though the velocity return map would allow for values between 0 to 7 mm/s otherwise. At t=5, it is likely the fly will decelerate (according to the acceleration return map, because it just accelerated) proportional to the acceleration chosen-- this locks out the increasing-velocity mode -- but because v can be anywhere from 7 to 43 mm/s (roughly) and acceleration anywhere from 0 to 500 mm/s^2 at t=5, we can't deduce much about t=6. (The acceleration return map cuts off because of how I cropped it but the lines reach +/- 500 mm/s^2.)

Of course, if v=30 mm/s at t=1, it's v could also be 30 or 60 mm/s at t=2 (with less probability), going into loops that will be broken by drift. Walkthrough: If velocity stays the same (at 30 mm/s) at t=2, acceleration is zero at t=2, so it will likely accelerate at t=3, in which case the velocity return map indicates ~60 mm/s^2, in which case acceleration will be roughly +450 mm/s^2 at t=3. But then acceleration will likely be -450 mm/s^2 at t=4 (note it does not have a good chance of accelerating or staying at the same velocity, which you would expect if the discretization was due to quantization error) so it will go back to 30 mm/s^2 at t=4. But this implies (according to the acceleration return map) that acceleration is zero at t=5, i.e. at t=5 v is 30 mm/s^2 with acceleration at t=6 being anywhere from 0 to 500 mm/s^2, but with a bias to accelerate it at +450 mm/s^2 towards 60 mm/s at t=6 for the cycle to begin again. (Stochastic drift, or chance of being an outlier, allows the fly to escape this cycle.) But, if v = 60 mm/s at t=2, then a = ~+450 mm/s^2 at t=2, which means a ~= -450 mm/s^2 and v ~= 30 mm/s at t=3, a ~= 0 mm/s^2 and v ~= ~30 mm/s at t=4 and v = 60 mm/s and a = 450 mm/s^2 at t=5 -- another short-term loop which will be broken by drift.

This is just for v = 30 mm/s at t=1 -- I haven't even gone through the deduction process for other values yet. If the discrete divergence of modes were simply due to quantization, these implied cycles wouldn't exist and you would see more than one preferred "next acceleration" for a given current acceleration at time t. (t+1 acceleration varies the most when acceleration is zero at time t.) Using the info from both plots, we can see sometimes one can "eliminate" one or two other modes from consideration in deciding behavior at the next step. I don't think I would be able to deduce this much information if the discrete modes were due simply to quantization error. Again, I think I would get clusters rather than continuous lines. Nothing gold can stay (talk) 01:48, 2 August 2012 (UTC)

I find it intriguing that no other contributor (at the science desk!) except Nimur points out that this data doesn't make sense (biologically) and looks like a clear example of measurement and/or processing artifacts. What do you suggest as interpretation of your data? Drosophila has somehow only three modes of acceleration? And nobody noticed before? Do you have some kind of control experiment? That tests that your equipment and your analysis pipeline is really able to measure what you want? I would bet that a control experiment with some light point in random motion (or some other insect/small animal, which could be easier to arrange) captured the same way would give the exact same "split" of data points. And I think this is the way to proceed, if you ever want to publish this data in some form. Is there something comparable already published in your field? Or did you set up the method yourself? It would perhaps be helpful to look how others have setup their measurement and analysis. Sorry for my harsh tone, but I really think the RefDesk Science could do better in such a central question as measuring artifacts, so I find it important to bring my point across. --TheMaster17 (talk) 09:11, 2 August 2012 (UTC)

Another important point concerning your expectation of cycles because of quantization is that you are dealing here with quantization in every single measured variable (x,y and t). It is not trivial to extrapolate what kind of artifacts you get when quantization errors have an effect on each other and on your derived values, such as v and a here. Circles are definitive not the shapes I would expect. --TheMaster17 (talk) 09:16, 2 August 2012 (UTC)

Do you know how return maps work? It is not that hard to conjecture what happens because the effect of noise and discretization on return maps has been studied. Please not that velocity or acceleration is not confined to discrete points. You seem to make this mistake a lot. At each point t, there seems to be 3 choices (sometimes less-- possibly two or one , due to the patterns implied, which likely wouldn't happen with discretization), but each choice has a certain element of drift and randomness in it, and the output velocity or acceleration is dependent on this choice and the previous velocity or acceleration. Even if there were no stochastic noise at all, very chaotic behavior can arise from very determined behavior -- see the logistic map, in which determined equations make a function wander all over the place. People haven't also answered my question at why discretization would separate modes most at fast accelerations and speeds, rather than slow ones. Nothing gold can stay (talk) 11:30, 2 August 2012 (UTC)

But do let me conduct the control experiment. But my goal is not to study this sort of thing, it's simply to find an assay that will differentiate genotypes or drugs. But few people seem to have answered my statistical questions.... Nothing gold can stay (talk) 11:25, 2 August 2012 (UTC)

It is surprising, but we shouldn't reject data out-of hand just because it's not what we expected. For example, the observation that the expansion of the universe is accelerating seemed very odd, at the time, but has since been verified by many others. Perhaps, using a car analogy, they tend to "floor it", "maintain cruising speed", or "slam on the brakes", rarely picking any acceleration in between. While I wouldn't have expected this, it's not exactly shocking. And, if it can be verified by others, this is an interesting observation worth publishing. StuRat (talk) 09:18, 2 August 2012 (UTC)

You are totally right, and I never proposed to just discard the data. But the OP really needs to address some questions if he wants to get a firm interpretation. And coming to your example, exactly for the same reasons the expansion of the universe was only accepted as fact after it was confirmed around the world by different measurements in different groups: to quote Laplace, "The weight of evidence for an extraordinary claim must be proportioned to its strangeness." And I really cannot imagine that this simple setup with camera was never tried by others. I remember, for example, a study about movements of some social insects (ants, bees or termites probably) which plotted routes of them inside the nest, which would probably use a similar setup. Concerning your "it's not exactly shocking" statement, I must admit that I would find it rather shocking when a complex animal like drosophila would only ever have three kinds of acceleration. Even plots of bacteria and other single celled organisms moving through or over medium show a diverse range of speeds and acceleration depending on a broad range of factors, and not just three discrete modes. This is why I wouldn't believe the data just as they are now. With appropriate controls this could change, of course. --TheMaster17 (talk) 09:55, 2 August 2012 (UTC)

Maybe this behavior is limited to drosophila. If so, it would be interesting to isolate the genes which cause it. StuRat (talk) 10:22, 2 August 2012 (UTC)

Dude, possible accelerations are not discrete, they vary continuously. However style of acceleration seems to be discretely dependent on t and the previous acceleration, but the freedom in which to vary is large (for example when previous acceleration (t=1) is zero, acceleration chosen is likely to be anything positive thus ensuring that when t=3, acceleration is likely to be anything negative), plus there is the stochastic randomness in which a fly chooses to "break" the trend or slowly drift away from it. One test to see if this is an artifact of data processing is to freely vary the time lag interval (i.e. t and t+2, etc.) I bet you that at t+5 the correlation would probably disappear. (Let me check this.) From what I see, groups have applied return maps to animal behavior, but generally things like "interval time between rats pressing levers" etc rather than motion. I don't think this is an extraordinary finding. Of course, my PI doesn't think this a thing worth pursuing until it can separate the effects of different drugs or genotypes.

Also, there are very few papers on Drosophila walking-tracking (there are a lot on a fly with clipped wings being held by a force gauge to measure pseudoflight) -- I have consulted other papers doing tracking studies, but they never looked at return maps. Nothing gold can stay (talk) 11:06, 2 August 2012 (UTC)

I can read the plots, that is why I said "discrete modes", not "discrete accelerations". But what you are proposing in your interpretation is that there are only three classes of points in your a and v plots for t and t+1. Why should this be real? What could be the biological cause of this? And I cannot really follow your narrative in your previous explanation. Why should a(t=3) be negative? If the fly is continuously moving (because it accelerated between t=1 and t=3), I would expect it to be around 0 sometime after this, after the animal has picked up velocity and is moving at its preferred speed (depending on the context). What you are proposing is really that the animals are jumping, in steps of 15th of a second, between accelerating and deaccelerating (sometimes no acceleration at all) continuously? This would be really wasteful. Another thing that comes to mind: Did you check that the alignment of your camera pixels does not influence the quantization of the position? You could, for example, get preferential different results for v (and therefore a) if the animal is running along a neat line of pixels, or in diagonal, because the quantization error differs systematically between the two cases. --TheMaster17 (talk) 12:03, 2 August 2012 (UTC)

But there are surely papers of walk-tracking for other insects. Did they ever describe something similar? I would see no reason why drosophila should be different in walking pattern than say, for example, an ant or a bug. And if it is really different, you would still need extraordinary proof for this extraordinary claim (and probably have a hypothesis why it is special). Before you really dive into this, I think you have to check your data and setup. Nothing feels as bad, in my opinion, as to realize after half a year that you hunted an artifact the whole time. Happened to me, too. --TheMaster17 (talk) 12:10, 2 August 2012 (UTC)

And let's not forget the important point that Nimur already mentioned: Using your (already quantized and therefore having a measurement error) x,y differences to compute numerically the first derivative v and then the second derivative a is not the way to go, because you will invariably inflate errors. There really is no reason why the fly should only be able to chose certain classes of velocities and accelerations at t+1 depending on its speed and acceleration at t. A fly has a longer memory than 1/15th of a second, and both speed and acceleration should form a continuum and not split into three classes at high values. --TheMaster17 (talk) 13:02, 2 August 2012 (UTC)

"There really is no reason why the fly should only be able to chose certain classes of velocities and accelerations at t+1 depending on its speed and acceleration at t.". I can easily imagine a cause -- something like a central pattern generator -- different neurons are taking over movement at different points at time. I am going to sample at different points to see how the patterns change.

"This would be really wasteful." Sustained movement is often a cycle. Have you thought about how you run? You accelerate sharply, cruise for a bit, then decelerate. Is that wasteful? The same thing goes with wing flapping.

"But there are surely papers of walk-tracking for other insects." There are not very many using return maps. Drosophila is an important model organism.

I do not expect deviation from other insects. I have used my data to investigate other things like velocity-curvature relationship, and Drosophila appears to be close to the 2/3 power law described for velocity-(radius of curvature) throughout nature, from eye saccades to hand movement. Nothing gold can stay (talk) 14:37, 2 August 2012 (UTC)

Processing data

Velocity graph with circles every 10 units from origin, and data points divided into 3 colored "blobs", with the lines shown which were used to determine the "blobs".

I took the velocity data you supplied and made my first attempt at dividing it into 3 "blobs". However, as I noted before, we have a problem where the three blobs overlap. It's not a severe problem for the central blob, since presumably an approximately equal number of data points are lost (or gained) at both edges. However, a clear skewing effect is seen at the lower and upper blobs. So, we should drop the data in the region where the overlap occurs. I'll leave it to you to decide how much to drop, but it looks to me like data in the 40 unit range from the origin has this problem. Once you let me know how much data you'd like to drop, I can then provide you with CSV files for the 3 blobs, and you can then run those through your favorite curve fitting application. StuRat (talk) 08:17, 2 August 2012 (UTC)

Wow thanks! Could you provide me with the script perhaps? I have many data plots like this, so it's not the csv file I need. Also, is there a way to weight a probability mapping for points that seem to be "shared" by either blob-- perhaps a point in the middle would have a 50% weighting for one blob and 50% for the other. (Or perhaps a probability function can be used to decide which blob a point should belong to.) Can this technique be applied to the acceleration graph? Acceleration does seem more cleanly separated after all. Nothing gold can stay (talk) 11:11, 2 August 2012 (UTC)

I could assign a probability if we knew the distribution ahead of time, but we don't. For example, if I just said a point midway between two lines has a 50% chance of being in either, I'd likely be wrong. So, I really don't think we can get any useful data out of the place where all three blobs overlap. StuRat (talk) 17:48, 2 August 2012 (UTC)

You would find less statistical skewing if you used an actual classifier algorithm, like I described in my very first post. But, since you're already taking great liberties with data-processing, why not just throw out any subset portion of the data that is statistically destroyed by an intermediate processing step! But seriously, if you're actually planning to pursue this as a topic of research, you've got to identify your methodological error first. Not after you spend a week analyzing invalid results. You're flying at 60 mm/sec down the wrong road here. "Science" is about understanding your data, and its natural causes, not about running an elaborate post-processing algorithm to a point-cloud. Though, if you announce to the world that you've discovered something huge based on a statistical anomaly, only to recant six months later because all you discovered is that you don't know how to operate and interpret your own experimental equipment, you'd be in good company. I've got a recommendation: Proakis and Manilakis, because I think you're missing some fundamentals of elementary signal-processing techniques. And once you've mastered regular signal processing, here's an even more advanced book, available for free online: Statistical Signal Processing. I'd also recommend that you review how your trajectories are generated from your raw data. I'd also look at your raw data. StuRat has called my responses vitriolic, and I apologize. I am not trying to discourage your work; but from over here, what it looks like is that somebody handed you a copy of MATLAB and told you to "use it" to process fly trajectories. They may as well put you in front of a Cray. It is also a very powerful number-crunching machine, but you don't know how to use it. The computer will spit results out, and StuRat can even write a program to color-code them, but... that doesn't mean anything. Nimur (talk) 15:41, 2 August 2012 (UTC)

I agree that the preliminary data needs to be checked for systemic error, but this doesn't necessarily need to be done prior to curve-fitting. Indeed, curve fitting may help to detect some types of systemic error. It could also be used to request better equipment or a colleague's assistance (in the same lab or another), to verify the results. StuRat (talk) 19:29, 2 August 2012 (UTC)

The author of the program I'm using got back to me, and apparently my program does some sort of superlocalising. "Ctrax calculates the position and orientation of flies by fitting ellipses to connected groups of foreground pixels using the spatial moments of each connected component. The precision of this calculation is limited by the bit depth and spatial resolution of the source images, but the relationship isn't straightforward." Nothing gold can stay (talk) 22:31, 2 August 2012 (UTC)

Biological explanation ?

Presumably max acceleration and braking takes more energy than more gradual velocity changes. If this turns out to be real, one possible explanation for having 3 discrete acceleration modes might be preemptive predator evasion. Other flies randomly change direction when flying, whether they detect a predator or not. Perhaps these guys also randomly change acceleration, which certainly would make it difficult to catch them in flight. StuRat (talk) 19:35, 2 August 2012 (UTC)

Flies often do path-finding saccades, because they are constantly trying to explore new territory as well as revisit old ones to make sure they haven't missed anything. The velocity-curvature relationship roughly follows the 2/3 power law. I found that the pattern continues (but gets more noisy) comparing f(t+2) against f(t), f(t+5), and at f(t+10) you can still see the separate arms but they are very fat and short. (Going to upload pictures.) So apparently velocity and acceleration in one frame have a longer-term memory of a dozen or more frames back, which makes sense, because I am sampling at an arbitrary frrequency. Also a reason why I argue against noise is that angular velocity's return map does not break up into discrete lines -- it's a semi-random map with a weak/moderate f(t+1) = -f(t) signal. Nothing gold can stay (talk) 21:45, 2 August 2012 (UTC)

I see that Nimur posted once in the meantime, trying to point you to relevant sources to understand your sampling problem. I just want to give you a simple thought experiment to help you grasp the basic problem of quantization and numerical derivatives: Imagine a point-like fly that is moving in x-direction (skipping y for simplicity) with a velocity of 3 mm/s. Your temporal resolution is 1 s, and your camera+software has "bins" of 5 mm into which it sorts the position of the fly. The point-fly starts at t=0 s at x=0 mm. At t=1 s, it is at x=3 mm, fitting into the first bin. t=2 s, real position is x=6 mm, second bin. t=3 s, real position x=9 mm, still second bin. t=4 s, real position x=12 mm, third bin. If you now look only at the bins, as this is the output you get from the software, you would think the fly stopped between t=2 s and t=3 s, giving you a classical quantization error. Although, in reality, the fly had constant speed and an acceleration of zero, you would, with your method, calculate non-zero acceleration and changing speeds just because of the way your detection algorithm works. Granted, this example is very simplified, but I just wanted to give you a start for thinking. In your real dataset, you have quantization of every measurement (x,y,t), plus unknown interactions with the software that computes the detected position from the pixel-positions (as I mentioned: does it make a difference if a fly runs diagonal to the pixel grid? Did I understand correctly that the sampling rate of your software is different than the sampling rate of your camera?), followed by the calculation of numerical derivatives from the already error-prone measurements. All those error sources could amplify each other, and without systematic testing for that it is impossible to give a proper interpretation of what is real and what is noise. --TheMaster17 (talk) 07:41, 3 August 2012 (UTC)

Could your tracking software pick up a small steel ball? I have seen videos of Drosophila tracking experiments in which a small steel ball was added to the arena, and a motorized magnet located beneath the arena moved the ball along a defined trajectory. You could run your analysis software on recordings of such a ball as a control. This could be something as simple as strapping the magnet to a motor that makes it spin in a circle. Someguy1221 (talk) 07:52, 3 August 2012 (UTC)

August 2

No electricity for you!

According to a news article discussing the recent massive blackouts in India, [21], 1/3 of India's 1,200,000,000 never have access to a supply of grid electricity at all, under the best of circumstances, even for part of each day. It's hard to imagine viewing a house for sale in the US or the UK and hearing that there is no electric line close enough to supply it with electricity. How long ago were electric lines extended to more than 2/3 of the population of the US, the UK, France, and Germany ? Was it 100 years ago, 50 years ago, or what? Do the nonelectric 400 million Indians use Kerosene lamps, candles, or what, once the sun goes down? Edison (talk) 01:13, 2 August 2012 (UTC)

This is one of my favorite graphs. The US hit the 2/3 mark a little over 80 years ago, and we hit the 100% mark about 50 years ago. This graph is by households, and I can't rule out that that the average number of household members might be different for wired and unwired homes. Someguy1221 (talk) 01:27, 2 August 2012 (UTC)

A substantial number of that 1/3 don't even have houses. They live in camps, train stations, or wherever they can find a bit of shelter. Looie496 (talk) 01:41, 2 August 2012 (UTC)

But aren't the train stations electrified? 203.27.72.5 (talk) 02:51, 2 August 2012 (UTC)

I suspect in the more rural areas they may not be, and even if they are the lights etc are likely turned off when no train is expected. Nil Einne (talk) 05:22, 2 August 2012 (UTC)

How many homeless in India? Literally no shelter, not even a public shelter, a derelict automobile, or an improvised shack? Sleeping on the ground, in the open? In some countries many people live in hovels, but tap into electric lines and steal current. The key thing would be having mains run somewhere near the house/shack. Edison (talk) 03:03, 2 August 2012 (UTC)

Theft of electricity is a common problem in India (our article appears to be solely on the situation in India), but I think much more among those who already have or could have electricity [22] [23] [24] [25] [26]. For those in situations you mention, they are unlikely to be able to convince corrupt officials to turn a blind eye, plus if someone's shack in the middle of no where has electricity it's a bit of a dead giveaway. Not to mention they may not have the skills or tools to do it, or the equipement to do anything useful with the eletricity. (And if they did have the tools and skill, they'd probably be better of just stealing the wire to sell provided they can avoid vigilantes [27] [28].) Nil Einne (talk) 06:08, 2 August 2012 (UTC)

Agree with Someguy. In the US, the 2/3 mark was reached by about 1927, and electrification was essentially universal by 1952. Can't say about India, but the house I grew up in in Pennsylvania was not electrified until 1972 because of a combination of remoteness and local political bickering (whereas my grandparents' home in the nearby city was electrified from when it was built in 1920). Lighting and refrigeration were powered by propane gas, supplemented with kerosene lamps, with candles for dinner. The level of comfort, though, far exceeded that that you will find in rural India, even in those areas that are electrified. Clotheswashing was probably the only chore that was significantly more time consuming than in a contemporary electrified household. So comparing when the US and India reached the 2/3 mark is like comparing apples and oranges. It does not mean the levels of comfort and convenience were comparable at that point. Dominus Vobisdu (talk) 02:00, 2 August 2012 (UTC)

Another factor you need to take into account is home generation. In Australia, large amounts of the population outside of metropolitan areas of the large cities were not covered by grid electricity until the 1960's. But what people had was gasoline or kerosene - powered home and/or farm generators. So they had all modern electric lihting and appliances, it's just that they were powered from their own generators and not from a power station. In many small rural communities in those days, often a local business such as a gas-station would provide electricity to nearby houses and other buildings in the village centre. I imagine a similar thing happened in rural USA and many other countries with a significant dispersed largely farming based population. And some people had gasoline powered washing machines. Wickwack120.145.176.119 (talk) 03:08, 2 August 2012 (UTC)

I think kerosene lamps are the most popular source of lighting besides electricity in Indai by far [29] [30] [31] [32] [33] [34] [35] for households. (Despite what [36] may lead one to think, propane doesn't seem to be a significantly lighting source.) From the last two results, the percentage of households without lighting is fairly small although given the population of India, still around 1.1-1.2 million households depending on which source you use (not sure what percentage of the population this is). BTW, with reference to some of the answers above, according to the census data at least, the number of houseless households (according to the definition they use) is relatively small, although given the population of India still affecting close to 2 million people as of the 2001 census [37]. I expect the number is an underestimate (the PDF mentions it may be an overestimate but also mentions how they only visited certain areas and how they may have difficulties getting cooperation). Perhaps more importantly, just because you have access to kerosene lighting doesn't mean you use it regularly. In fact some of the other sources also note that just because you are nominally connected to the electric grid doesn't mean you have a reliable or even particularly usable supply, even discounting things like the recent blackouts. Nil Einne (talk) 05:58, 2 August 2012 (UTC)

In the UK, nearly all houses were connected to the "National Grid" by the 1960s. The nearest mains electricity to where I live was five miles away until 1961. A few houses had their own generators, but most of us used paraffin or bottled gas for lighting. One house near where I live was not connected until about ten years ago, and there are still just a few isolated properties in the UK without a connection to the "grid", but they are rare. Dbfirs 07:10, 2 August 2012 (UTC)

It's a technical quibble, mostly, but the national grid and mains electricity aren't the same thing. "Mains" just means you get electricity from a shared community power supply; "national grid" means there's a high-voltage connection between that community power and the UK's overall generating capacity. In the islands of Scotland, plenty of people have mains electricity but aren't on the grid - e.g. people on Orkney are on both, but on Shetland the power grid is isolated from the national grid. Eigg only recently got mains electricity (meaning householders didn't have to generate their own) but still isn't on the grid. -- Finlay McWalterჷTalk 00:26, 3 August 2012 (UTC)

Thanks for the correction. I'd forgotten about some of the Scottish islands. I think all the English and Welsh islands are connected to the National Grid, or at least the ones with significant population. Dbfirs 07:59, 3 August 2012 (UTC)

Why Does the Annual Mortality Rate Rapidly Increase Between Ages 113 and 114?

A 113-year old person has about a 50% chance of surviving to age 114 on his/her 113th birthday, but a 114-year old person has about a 30% chance of surviving to age 115 on his/her 114th birthday. How come? Futurist110 (talk) 02:46, 2 August 2012 (UTC)

I want to point out that the annual mortality rate stays roughly constant at ages 110-113, yet rapidly increases for ages 114 and 115. Look at the Gerontology Research Group's supercentenarian tables and you'll see what I mean. Futurist110 (talk) 02:49, 2 August 2012 (UTC)

From [38]:

Human mortality after age 110 is at at a constant level of λ = 0.7. This implies an annual probability of death of q_x = 0.5. This result confirms the previous analysis by Robine et al. (2005). Correspondingly, life expectancy after age 110 is about 1.4 years. Beyond the age of 114, data become too sparse to allow us to make reliable statements. (emphasis added)

There just aren't enough people who live to 114 in order to get good statistics on their mortality rate. Dragons flight (talk) 03:23, 2 August 2012 (UTC)

We had a similar question a couple months ago. You may be interested in some of the answers to it. Evanh2008 ^{(talk|contribs)} 03:26, 2 August 2012 (UTC)

When researching my answer for that question, I came across a wide variety of sources that gave wildly different estimates for the death-rate-vs-age curve. I recall once finding, although I can't remember where, a review that compared different methods of calculating that curve. Based on which source you went by, you could make the curve come out as a positive, negative, flat, or some exotic non-monotonic function, and the values themselves varied significantly, but all probably in the vicinity of 70% at those ages. The numbers of data points to go on at those ages is really just too small for good statistics, if you want to incorporate years worth of mortality data, you have to keep in mind that the lifespan average is a moving target, complicating things significantly. You can only trust a lifespan histogram for a cohort that is 100% dead. Someguy1221 (talk) 04:58, 2 August 2012 (UTC)

Mortality rates (or at least the ones that I'm using) are all for dead people only. And for the record, it's interesting that as the 115+ year old people ever sample got larger over the last 10 years, the mortality rate at age 114 and 115 actually increased a lot, from about 50-55% in 2000 to about 70% right now. Futurist110 (talk) 05:58, 2 August 2012 (UTC)

There are enourmous numbers of different mortality tables created by different people for different purposes based on different populations and datasets. To talk about the mortality rate is meaningless. Please link to the mortality table you are talking about. Normally, mortality tables are pretty much just guesses after around age 90. They use real data until there isn't enough to draw meaningful conclusions (which, depending on your dataset and methodology will be somewhere between about 90 and 110 - definitely well before 113), and then you just pick an arbitrary age as the maximum possible lifespan and pick some smooth curve to get you up to 100% by then. You shouldn't take any mortality figures too seriously after about age 90. They are based on too little data. --Tango (talk) 17:41, 2 August 2012 (UTC)

http://www.grg.org/Adams/B2.HTM - Here is the table that I was talking about. The mortality rates are very easy to calculate from it. Futurist110 (talk) 19:48, 2 August 2012 (UTC)

That's not a useful data set for this kind of work. It is collated from various sources with no way of knowing it if is complete or unbiased. It spans more than 20 years, during which time mortality rates have changed enormously. It spans multiple countries, which have widely varying mortality rates. It is also far too small. Your 30% figure is, with 95% confidence, assuming a simple binomial model, anywhere between 21% and 37%. Your 50% is actually anywhere between 33% and 61%. So, you see, they could actually be exactly the same and it would still be consistent with your data. Your dataset is too small to give enough make the confidence intervals small enough that they don't overlap. That means you can't draw any conclusions. --Tango (talk) 01:14, 3 August 2012 (UTC)

Ah, the miracle of the confidence interval. --TheMaster17 (talk) 08:54, 3 August 2012 (UTC)

Earthing

What is the simple way to check whether the earth wire of a house electrical circuit is properly grounded? Thank you.175.157.5.252 (talk) 03:17, 2 August 2012 (UTC)

Call a competent electrician and ask them to check it out. Nil Einne (talk) 05:20, 2 August 2012 (UTC)

I tried looking this up online, only to deduce that doing it properly is not simple at all. Someguy1221 (talk) 05:26, 2 August 2012 (UTC)

The OP geolocates to Sri Lanka. I'm not at all certain, but Sri Lanka should be a country that uses the Multiple Earth Neutral System (MEN), or a close variant. In this system, the house earthing system has two main parts: An earth stake buried in the soil, and a connection to the street distribution nuetral wire. The house earth stake is of prescribed length, and it is generally sufficent to make a visual inspection. If the stake has no significant corrosion, and the wire connected to it is sound and the method of connection is sound (ie a pip clamp in good condition), then assuming the original installer did the right thing, that's all that's realy needed. The earth stake at each house does not ON ITS OWN do much - the system relies on all earth stakes at each premises fed from the street distribution having all their earth stakes connected in parallel by the power company's nuetral wire. All the earth stakes in parallel provide a low impedance to sink fualt currents even though an indiviual eartb stake caould not do so. If the neutral connection from the power company's strett wires to the house nuetral is deffective, then the house will have no power. If you know how to use a multimeter, check between your nuetral bar (in meter box) or the nuetral or earth pin of any wall outlet and the earth stake, on the earth stake below where the wire connectes to it. Check first for voltage - there should be well under a volt. If there is no voltage, then check resistance - it should be less than one ohm. These checks do not 100% guarantee everything is fine - beyond that you need a trained electrician. However they cover alll common deficiencies in an MEN system in a reasonably built up area. If you live in a new, undeveloped area or are isolated in a remote location, there's a bit more to it. Kiet121.215.2.150 (talk) 05:55, 2 August 2012 (UTC)

Determining that you have a ground is relatively simple, but determining that it's a proper ground is not. For example, you might currently only have a ground because a puddle of water is making the connection, which obviously isn't a proper ground, as you will no longer be grounded once that puddle disappears. StuRat (talk) 08:27, 2 August 2012 (UTC)

With the MEN system, that isn't generally a factor. A visual inspection, and grasping the stake and attempting to wriggle it is sufficient, assuming the installation was done in accordance with standards, as the electrical resistance to the "great body of earth" of an individual earth stake is unimportant. If an earth stake is so badly corroded that a puddle makes any significant difference, you'll almost always notice it on inspection. The most common defect is the wire is broken or the wire is no longer connected to the earth stake due to accidental damage or a defective clamp - all of which is easily spotted on visual inpection. In unusual situations such as remote area single-wire-earth-return feeds, there's more to it, but I did include a disclaimer. Keit120.145.189.101 (talk) 10:28, 2 August 2012 (UTC)

The suggestion to "wiggle the stake" is utter nonsense except to note that the wire is not connected to the ground rod. Such a practice could result in you holding a wire broken off by the action from the ground rod, with lethal high voltage on it, flowing through your body to ground. A utility I worked for would drive ground rods at transformer sites in 5 foot or so incremental lengths, with each stake screwed into the previously driven one. I would use a "ground megger" to measure the resistance of the new ground to several remote grounds. Sometimes it required 30 feet of ground rod to get to a required low impedance in soil underlaid by sand. A puddle at the surface would have scant effect on the portion 10 or more feet down, Several rods might be driven several meters apart and connected in parallel by large cables. One approach was to drive multiple grounds and use solution of a system of equations to determine ground impedance. Another approach was to use a remote ground. as a reference.Requirements might be less severe at a residence. Local codes will specify how low the impedance must be.and how many amperes of fault current the ground rod or system must sink without melting, possible thousands of amps for some time until fuses or breakers operate. In some US locations, codes might allow a clamped connection to a cold water pipe connected to a municipal water system by sturdy metal pipe, with a suitable jumper bypassing the water meter. It is not a job for the uninformed novice. Electrical shock hazard or structural fire might be the punishment for a mistake. The local ground has as one job the prevention of dangerous high voltage on all the conductors in a building if the transformer has a fault and primary voltage arcs to the low voltage secondary. Edison (talk) 05:14, 3 August 2012 (UTC)

If you are testing grounds relative to other grounds, how is it determined that the first ground is working? Someguy1221 (talk) 07:54, 3 August 2012 (UTC)

Special instruments are available, for which the internal operation is a bit complex to explain here, at least without diagrams and assuming a sound knowlege of mesh circuits. Essentially, what they do is force a current through earth stakes chosen as potential reference access points, and force a current rhough the earth stake under test, monitored by a sensing coild clamp around the electrode or its connecting wire. The instruments do an internal calculation to find the resistance to "great body of earth" of the electrode under test. As long as the resistance of the reference electrodes is less than a certain amount, the resistance of reference electrodes does not affect the result. Earth electrodes near each other and near to other structures (eg metal pipes) share current paths through the soil to the great body of earth - this is manifested in what electrical engineers call "common resistance" - a resistance common to nearby stakes/electodes and added to the "component" resistance each electrode. In other words, 2 nearby electrodes form what is equivalent to "Y"-shaped circuit to great body of earth. I hope this is clear, as the subject is actually of some complexity, and the accurate measurement of earth systems is actually something that requires specialist knowlege of engineers.

I point out that the words "ground" and "grounded" is USA terminology, but has spread around do to the wide availability of US textbooks and magazines. This is unfortunate, as the meaning of these words depends on context, and can be a source of confusion. The correct terminology for most of the English-speaking world is earth, meaning the great body of earth, earthed, meaning effectively connected to the great body of earth, earth stake or earth electrode, meaning the means of connecting to the great body of earth. Keit120.145.181.139 (talk) 11:15, 3 August 2012 (UTC)

spina bifida case

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This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

203.27.72.5 (talk) 08:16, 2 August 2012 (UTC)

Big Bang of nothing

Was the initial condition of the Universe an infinitely tiny bit of totally empty space? Since the initial mass of the Universe would be zero, dividing zero mass by zero volume does not give a singularity.

Then cosmic inflation hits and this empty space is blown up at vast speeds. This is all fine and dandy until a virtual meson pops up. This virtual meson is then torn apart before it can pop out. In order to avoid two bare quarks, each of the quarks gets paired up with another quark, giving a universe of two mesons. Each of these two mesons is then torn up, giving four mesons. Then eight, then sixteen, etc.

Exponential meson production continues until the Universe has enough mass/energy to reach a flat state and this stops inflation. The mesons then decay through the weak force, which applies its bias towards matter over antimatter. Would the result fit the observed Universe? Hcobb (talk) 13:14, 2 August 2012 (UTC)

I'm not an expert cosmologist, but as far as I understand the current theory, the standard models of the big bang start at infinite (or at least very high) densities, not at density zero. Energy already existed during cosmic inflation and was "stretched flat" by it - this explains the largely flat, isotropic and homogeneous appearance of the cosmos. If matter/energy was created during inflation, there is no good reason for this flatness. --Stephan Schulz (talk) 13:25, 2 August 2012 (UTC)

For most of the inflationary epoch, the universe is almost empty except for the scalar field (the inflaton), which is similar to the modern-day dark energy and the Higgs field—it has mass/energy but it's not matter in the conventional sense. Eventually the inflaton field decays, and that's the origin of all of the matter in the present-day universe. Any ordinary matter from before inflation is diluted to the point of irrelevancy. There is interest in looking for magnetic monopoles as relics of the pre-inflationary universe, but there's no theoretical reason to suppose there's even one of them in the present-day observable universe. -- BenRG (talk) 19:45, 2 August 2012 (UTC)

One outstanding question in cosmology is whether the early universe was isotropic and homogeneous. For example, consider reading this section, anisotropy in the observed cosmic microwave background. To the best of my understanding, the universe we see today appears very isotropic and inhomogeneous: it is still unknown if today's universe evolved from a similar isotropic, inhomogeneous initial condition. Nimur (talk) 15:10, 2 August 2012 (UTC)

If you mean the universe of 13.7 billion years ago, there's no question that it was extremely isotropic and homogeneous. The present-day universe is still very much so at large scales (~1 billion light years), but it's neither homogeneous nor isotropic at smaller scales. This is a result of magnification of slight inhomogeneities in the early universe by ordinary gravitational attraction. This process is well understood (though not by me). If you mean the universe before inflation, nobody has any idea. According to the inflationary model, the observed fluctuations in the CMB come from quantum fluctuations during inflation. They have nothing to do with the pre-inflationary universe. -- BenRG (talk) 19:45, 2 August 2012 (UTC)

Stephen Hawking insists that there was nothing prior to the big bang.

If our big bang article is correct, the concensous among scientists currently is to asume that the universe started of as a singularity with very very very high tempretures and pressure. The whole thing is very very complicated (I haven't been able to digest it completely yet) and coupled with the fact that the article provides a lot of info on this I feel that I don't need to repeat all of it here.Aliafroz1901 (talk) 16:10, 2 August 2012 (UTC)

Singularities are maths way of telling you you've made a mistake. I'm not sure any scientists actually think the universe had infinite density at time t=0 - what would that even mean? The singularity just tells us that it doesn't make sense to extrapolate all the way back to t=0 like that. Our understanding of physics starts a tiny fraction of a second after the "Big Bang", at which point the density was extremely high, but finite - we don't know what actually happened before that. It may well be that nothing interesting happened at t=0, it's just the time you happen to get to if you incorrectly extrapolate back. --Tango (talk) 17:51, 2 August 2012 (UTC)

Given the evidence,[39] it's safe to say that it all happened in the Big Inning. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:21, 3 August 2012 (UTC)

The inflaton field does not need to decay. Just mix with virtual particles and Quantum chromodynamics will suck the energy out of the inflation field into a uniform meson soup. It's Hawking radiation on steroids because as soon as any mesons are created they'll exponentially multiply like rabbits. No new physics is needed, just an empty tiny bit of space suffering from a Negative Space Wedgie. Hcobb (talk) 00:37, 3 August 2012 (UTC)

Tango I never said that the universe had infinit pressure, what I said was that it may have had extremely great pressure. And you are correct We don't know what was there at T=0, I know that and I was not presenting unchalengeable facts, only presenting the sciontific concensous on the matter.Aliafroz1901 (talk) 10:46, 3 August 2012 (UTC)

How do antibodies kill antigens/pathogens?

How do antibodies kill antigens and pathogens? Does the antibody kill the pathogen/antigen directly, or does immune cells kill the marked pathogen/antigen, or both, and if the antibodies kill the pathogen/antigen directly, how does that work? — Preceding unsigned comment added by 187.126.186.208 (talk) 14:10, 2 August 2012 (UTC)

See the Wikipedia article titled Antibody which explains all of that, and a lot more. --Jayron32 16:17, 2 August 2012 (UTC)

I found the following in the above article

"An antibody (Ab), also known as an immunoglobulin (Ig), is a large Y-shaped protein produced by B-cells that is used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, called an antigen. Each tip of the "Y" of an antibody contains a paratope (a structure analogous to a lock) that is specific for one particular epitope (similarly analogous to a key) on an antigen, allowing these two structures to bind together with precision. Using this binding mechanism, an antibody can tag a microbe or an infected cell for attack by other parts of the immune system, or can neutralize its target directly (for example, by blocking a part of a microbe that is essential for its invasion and survival). The production of antibodies is the main function of the humoral immune system.

Antibodies are produced by a type of white blood cell called a plasma cell. Antibodies can occur in two physical forms, a soluble form that is secreted from the cell, and a membrane-bound form that is attached to the surface of a B cell and is referred to as the B cell receptor (BCR). The BCR is only found on the surface of B cells and facilitates the activation of these cells and their subsequent differentiation into either antibody factories called plasma cells, or memory B cells that will survive in the body and remember that same antigen so the B cells can respond faster upon future exposure. In most cases, interaction of the B cell with a T helper cell is necessary to produce full activation of the B cell and, therefore, antibody generation following antigen binding. Soluble antibodies are released into the blood and tissue fluids, as well as many secretions to continue to survey for invading microorganisms."

So the answer to your first questionn seemes to be that both antibodies and immune cells kill antigens. and for the second it semes to be that antibodies kill pathogens via several methods with one of them being blocking an issential part of a microbe.Aliafroz1901 (talk) 16:49, 2 August 2012 (UTC)

Weight increments on a digital scale

I have always been curious and puzzled by this. Can someone please explain this to me? I have consistently noticed that digital weight machines (for weighing the human body) always seem to present the person's weight in increments of 0.2 pounds. So, the person weighing himself might get results of, say, 170.0 or 170.2 or 170.4 pounds, and so forth. But, the scale will never list weights such as 170.1 or 170.3 or 170.5 pounds. Why is this? I assume it has something to do with accuracy, precision, and rounding, etc. But, still, can't the machine (scale) "round" to the 0.1 pound increment, just as easily as its programmers selecting to round it to the 0.2 pound increment? This befuddles me. Any input? Again, I am referring to digital scales that measure the human body (e.g., a person trying to lose weight). I am not referring to the smaller types of scales that might measure fruit or food (in ounces or grams) or such. Thank you! Joseph A. Spadaro (talk) 16:51, 2 August 2012 (UTC)

A digital scale typically has an electronic sensor that converts weight to a voltage. This analog voltage is then converted in an analog to digital convertor (ADC) to a digital number. The ADC outputs a number with a fixed step size, each step representing a voltage difference of, in this case, 0.2 pounds. The ADC has a fixed and limited number of output values, so the scale cannot detect changes smaller than the step size of the ADC. To display these changes, the scale would need a more sensitive, more expensive ADC. It is also possible that manufacturers prefer to use the same ADC in scales that use pounds as they use in metric scales, which have often a step size of 0.1 kg, which is roughly 0.2 pounds. - Lindert (talk) 17:13, 2 August 2012 (UTC)

I've noticed that digital scales also have programming to make it look like you weigh exactly the same thing unless there's some large difference. This keeps it from giving a slightly different weight if you step off and right back on, and thus makes it seem more precise than it really is. I'm surprised they don't randomly sometimes add 0.1 to the weight (and then remember that), to make them look more accurate as well. (Heck, they could evenly randomly add several digits, to really make it look accurate, but that would cost more in display digits.) StuRat (talk) 17:43, 2 August 2012 (UTC)

Never confuse resolution with accuracy. Most digital scales for body weight are designed to weigh to a maximum weight of 130 kg or 300 Lb, with a display resolution of of 0.2 kg or 0.2 Lb. That's a resolution of 0.2/130 => 0.15% (in metric mode) or 0.2/300 => 0.07% (USA mode). The accuracy won't be anywhere near as good as that - 2% accuracy would be a good achievement with standard electronic circuitry. So while the display can resolve to within 0.1 kg or 0.1 Lb in terms of available digits, when weighing a 100 kg (220 Lb) man, you can only trust it to within 2 kg (4.4 Lb).

So why do they display to within 0.2 and not 0.1? ADC's (as mentioned by Lindert above) are made in standard resolutions: 8-bit, 10-bit, 12-bit, 16-bit, and 24-bit. The more bits, the greater the cost. If a scales manufactuer chooses to buy 8-bit ADC's, and decides to set the maximum weight at 300 Lb, the resolution will be 300/2⁸ = 1.17 Lb. That's good enough weighing a 300 Lb man (it exceeds the system accuracy) , but what if Mother wants to weigh her 20 Lb child? The resolution is then 1/20 ~ 5% - not too good. So, most manufacturers wil choose a 10-bit ADC. Then the resolution will be 300 /2¹⁰ = 0.3 Lb. Most electronic engineers, though, know a simple circuit trick to get another bit of resolution without the expense of a 12-bit ADC. So the system resolution is 11 bits i.e., 0.15Lb. Since to display this will require the cost of an extra digit, a quick bit of programming of the internal micro-computer will round it to 0.2. This can also save a few cents on the cost of a transistor etc to drive the display to resolve to 0.1.

The reason for the disply stability mentioned by StuRat is an issue with digital readouts well known to electronic engineers known as "Least significant bit uncertainty". In digital systems fed by an analog (ie continously variable) inputs such as force measuring strain gauges, small random variation in the input value and noise in electronic circuitry can, if the measured vaule is close to toggling the last digit, cause the last digit to rapidly flip between two adjacent values. Electronic engineers are used to this, but it can make non-technical people think the device is faulty or not trustworthy. So what we do is add hysteresis - the weight must increase at least twice the display resolution before the display is updated. Most bathroom scales wait until the weight is stable for a few seconds before settling on a value though.

Keit121.215.24.203 (talk) 23:58, 2 August 2012 (UTC)

I think they go beyond that, though. They don't want anyone to weigh themself twice in a row and get a different reading the second time, so require quite a large change from last time before they will register a change. Ironically, this improves the apparent precision while actually reducing the accuracy. You can trick it into giving you a real 2nd reading by adding a known weight, like 10 lbs, and then subtracting that. StuRat (talk) 04:16, 3 August 2012 (UTC)

That could add more error than you think it's eliminating unless you've ensured that your 10lb weight is exactly 10lbs. I highly doubt it is common practice for digital scale designers to include hysteresis, as consumer goods' sales are unaffected by small differences in post-purchase observed quality, perceived or otherwise. It is possible to see instrumentation report an identical voltage several measurements in a row, and there may even be some hysteresis effected by the circuitry, but to suggest it is intentional is unsubstantiated. BigNate37_(T) 05:27, 3 August 2012 (UTC)

It's definitely the case on my scale. I can eat a big meal, without using the bathroom, and it still reports the same weight as before. They don't want people returning the scales when they see how imprecise they are. With this system, they likely fool the people until after the return period ends. StuRat (talk) 05:32, 3 August 2012 (UTC)

Have you tried weighing yourself, and then reweighing yourself holding some weight that's say something like 5 pounds just to see if the scales still report the same thing? You could also weigh yourself repeatedly and each time increase the weight you're holding until you should be reading quite a substantial amount more. I, for one, doubt that any scales are designed in that way. 101.172.127.247 (talk) 08:13, 3 August 2012 (UTC)

Can a singularity spin?

I was watching a video by creationist Kent Hovind and he was bashing the Big Bang Theory, and one of his claims that the BBT is false is his assertion that the singularity was spinning before it "exploded" (I know it didn't explode, but rapidly expanded). He contends that due to the conservation of angular momentum, all of the galaxies must be spinning in the same direction, but he points out that some of them are spinning in opposite directions. Two questions, can a singularity spin, and if so, was the singularity that spawned the universe, spinning before it expanded during the Big Bang? 148.168.40.4 (talk) 17:55, 2 August 2012 (UTC)

The cosmos has no net angular momentum (to within experimental precision). The spins of individual galaxies come from random local perturbations in the highly uniform initial state. They point randomly in all directions.

Singularities don't really have any properties. They exist in theories and are a sign that there's something wrong with the theory (for example, the ultraviolet catastrophe is a singularity in classical physics which was solved by quantum mechanics). The big bang singularity should disappear in a better cosmological theory, perhaps based on cosmic inflation. However, a cosmos with an overall spin is possible in general relativity, so the lack of overall angular momentum does need to be explained. It is a prediction of inflationary cosmology. -- BenRG (talk) 18:35, 2 August 2012 (UTC)

I suspect that Mr. Hovind is confusing the origin of the solar system (which did start with a spinning mass of dust) and the universe. I don't think cosmologists say the early universe was spinning. thx1138 (talk) 19:11, 2 August 2012 (UTC)

It's not even clear to me what "spinning" in respect to the universe would mean. Spinning compared to what? The Universe, which emerged out of the mathematical singularity, is all that is. What would be the frame of reference to say "it was spinning"? --TheMaster17 (talk) 08:51, 3 August 2012 (UTC)

Unexplored Areas

Are there unexplored land areas left on earth? Reticuli88 (talk) 18:47, 2 August 2012 (UTC)

I'd imagine that the majority of Antarctica's surface area has never known a human footprint. Though humans may have looked out of the window of a plane at it. --Kurt Shaped Box (talk) 18:54, 2 August 2012 (UTC)

Of course, most of the surface is hidden under ice, and likely won't be explored until we manage to melt off the ice cap. StuRat (talk) 04:18, 3 August 2012 (UTC)

There are almost certainly caves that have never had a person in them either. New land may appear when ice melts off it, or when molten rock solidifies. There are also likely to be some small; islands that humans have never visited. A related question that was here before was: what is the last land to be discovered? Graeme Bartlett (talk) 23:43, 2 August 2012 (UTC)

Thinking back to the last time I remember a somewhat similar question to the OPs being asked here, there was talk of unclimbed mountains - e.g. Gangkhar Puensum. --Kurt Shaped Box (talk) 00:16, 3 August 2012 (UTC)

While the ocean depths are not lands per se, http://xkcd.com/1040/ is relevant here. Bear in mind as a webcomic it takes gratuities with the truth; for instance, David Bowie never walked the Abyssal Plain (though I believe Freddy Mercury has).

It depends what you mean by unexplored. There are 67 uncontacted tribes in Brazil, and even within 100 miles of Sydney, new discoveries are being made in the dense rainforest.--Shantavira|^{feed me} 07:28, 3 August 2012 (UTC)

Unconscious mind

Regarding the unconscious mind:

• What evidence is there to prove that it exists?
• Does the evidence point to either nonconscious processes or actual hidden thoughts?
• Is there anyway to access the unconscious mind?

--Melab±1 ☎ 19:10, 2 August 2012 (UTC)

Unfortunately this comes down to definitions. Neither "unconscious" nor "mind" have a specific universally accepted meaning, so the answer to the first question comes down to which definition you prefer. Some people, for example, don't think that the word "mind" should be applied to anything that is not consciously experienced, so to them, "unconscious mind" is an oxymoron. The best thing would be for you to read our article on the unconscious mind and come back with any questions it leaves unanswered. Looie496 (talk) 19:27, 2 August 2012 (UTC)

(edit conflict) It depends on what you mean by these terms, which are not defined the same way by different people. If you mean "are there processes in our nervous system which we are unaware and over which we don't have any conscious control", the answer is absolutely: the Autonomic nervous system governs a range of bodily functions. If you mean the "Freudian" concept of the Unconscious mind or of subconscious, the answer is that it is a lot less likely that such models accurately represent how the mind works. Concepts like "repressed memories" and the like are very controversial and poorly accepted among actual neuroscientists. People that study the "human mind" as a "soft science" (i.e. psyschology/psychiatry etc.) are more likely to work with such models of the human mind, but those that study the actual functions of the nervous system (neurologists/neuroscientists/neurobiologists) don't find them very useful. --Jayron32 19:29, 2 August 2012 (UTC)

I don't know all about that id and ego stuff but it is quite clear to me that thinking goes on without my being aware of it. I've done things like for instance stopping the car and only figuring out why it was the right thing to do a couple of seconds afterwards. Dmcq (talk) 21:50, 2 August 2012 (UTC)

There are things like reflex, training, and instinct which affect behavior, but I'm not sure what is sturcturally different than conscious behavior. Awareness is not the same thing as consciousness. --Jayron32 03:10, 3 August 2012 (UTC)

Race and obesity

Why are white and black women more likely to be obese, while obesity is much rarer among women of other races? --108.206.7.65 (talk) 20:35, 2 August 2012 (UTC)

White and black women where? Such a broad statement is unlikely to be true, so your premise is highly flawed. Certain socio-economic groups in certain countries have a gretaer propensity for obesity, so if you define which groups in which countries you seek information on, it would be very helpful. The data is very different if one is looking at Zimbabwe or the U.S. or Australia, for example. --Jayron32 20:45, 2 August 2012 (UTC)

In America. I've noticed that white and black women seem to have much higher rates of obesity than Asians, Indians, etc. --108.206.7.65 (talk) 21:27, 2 August 2012 (UTC)

Obesity is also very high e.g. among Palestinian women (31.5%, [40]), who are neither white nor black, but Arab. I would say obesity is much more correlated with culture (including subculture) and with unemployment than with race. - Lindert (talk) 21:30, 2 August 2012 (UTC)

Palestinians are white, or at least defined as white by the U.S. census bureau. In regards to the original question, I saw a lot of fat Latina women here in the U.S., and I think that nowadays there is generally greater obesity among poorer people. More black and Latino people tend to be poor nowadays, so that is probably why there is a greater % of obesity among them. A lot of white people are also poor, if you go by total numbers. As for why poor people tend to be more obese, it's because they are often unable to afford healthier food or do not have the time to cook it, and thus buy and eat much more cheap fast food than higher-income people do. Futurist110 (talk) 21:42, 2 August 2012 (UTC)

A related question

Why is it that black and white women's appearances can range anywhere from very pretty to very ugly, but women from other races are almost always attractive? --108.206.7.65 (talk) 21:29, 2 August 2012 (UTC)

That is purely subjective and varies from person to person. Apperently you are of that opinion, and therefore it is only you who can answer why you feel that way. Noone can answer it for you. - Lindert (talk) 21:34, 2 August 2012 (UTC)

I agree with Lindert on this. I, for instance, have way different tastes than you do. Almost all of the women that I find sexually attractive are white and/or light-skinned. As yourself what qualities you find attractive in women and you'll probably be able to answer your own question afterwards. Futurist110 (talk) 21:39, 2 August 2012 (UTC)

The OP asked a similarly loaded question a few days ago,[41] and being from Missouri, I guess he has to be shown. ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:16, 3 August 2012 (UTC)

Baby bird identification

Can someone identify these birds? The caption is "min egen bild" with a marker identifying it as Swedish; the user has no other uploads, and the filename is not particularly helpful. Nyttend (talk) 22:11, 2 August 2012 (UTC)

Birds are not really my thing, but I get whip-poor-will vibes looking at them, or perhaps some other brand of nightjar. Looie496 (talk) 00:10, 3 August 2012 (UTC)

The WP:BIRDS guys might be the ones to ask about this. They have regular 'birds for identification' discussions on their talk page. I don't think that any of them regularly contribute to the refdesks, but I'm sure that they'd be able to come up with a concrete answer, or at least narrow it down to a genus, if it happens to be one where the young of many species look very similar... --Kurt Shaped Box (talk) 00:25, 3 August 2012 (UTC)

Copied over there. Thanks for the pointer. Nyttend (talk) 01:32, 3 August 2012 (UTC)

Look like baby European Robins. Definitely not nightjars of any sort (though I can see why you'd get those "vibes"), as those species don't build nests; they lay their eggs directly on the ground. MeegsC (talk) 03:21, 3 August 2012 (UTC)

what physically changes between the ages of 18 to 22 -- fourth years look older than first years, but is it senescence?

I look at the photos of my friends (now 22) when they were first years (at 18), and they look so young! I am sad that we have lost our juvenile features and we seem "less cute" than before. But puberty ends between 16-18 doesn't it? What biological processes are occurring specifically? I don't think its the same type of aging that occurs later -- for example, I think our collagen remains taut, we don't develop wrinkles (yet), but what is changing? Nothing gold can stay (talk) 23:33, 2 August 2012 (UTC)

The biggest, most noticeable, effects of puberty tend to finish by around age 18 in boys and 16 in girls, but it doesn't stop completely until quite a bit older, particularly in men. Chest hair, for instance, is often still developing by age 22. --Tango (talk) 01:34, 3 August 2012 (UTC)

It could just be normal mature aging, as noted at senescence above, but some people continue to grow and develop through puberty into their early 20s. One somewhat famous example: David Robinson (basketball) grew three inches between the ages of 18-22, while many people stop growing in height well before then; for example I reached my adult height at 13. There is a lot of variation. There are also significant effects of things like diet and exercise. I went through a lot of changes at that age, crappy college food and a lack of activity added significant weight which had a general effect on my facial features and body shape. --Jayron32 03:07, 3 August 2012 (UTC)edit: spelling error corrected --Jayron32 04:07, 3 August 2012 (UTC)

"Man people" ? :-) StuRat (talk) 04:05, 3 August 2012 (UTC)

I think it depends on sex as well. When I was studying human developmental psychology some 30 years ago, I was told that the male physique continued to develop and mature until the mid-20s, whereas the female body reached maturity some years earlier. There then followed a period of relatively little change until the mid-30s when the ageing process started to have undesirable effects. In the years since, these dates may well have changed (50 is the new 30?) but the general principle still holds good. --TammyMoet (talk) 08:05, 3 August 2012 (UTC)

August 3

Magnitude 10 earthquake by combination of faults

I heard on a Discovery Channel program that a magnitude 10 earthquake could occur if the Cascadia subduction zone, the San Andreas Fault, and the Aleutian Trench all simultaneously ruptured. Is this possible? If so, how likely?--Jasper Deng (talk) 04:08, 3 August 2012 (UTC)

It's mentioned in the Cascadia article you linked to. 10-14% for magnitude 9 or higher in the next 50 years. Hot Stop 04:14, 3 August 2012 (UTC)

As likely as anything else, which means not likely at all. No earthquake in recorded history has been measured or estimated to have a magnitude greater than 10. 9.5 is the highest I can find at either Lists of earthquakes or Historical earthquakes. Sadly, the Discovery Channel (and other supposedly educational channels like the History Channel and TLC) have gone down the drain over the past decade or so. When they do run a "science" show, which is rare, they tend towards the sensationalistic, like impending asteroid impacts or supervolcanos, or stuff like that. I suppose this is what happens when geologists get really drunk at parties. Could it happen? I suppose. Could it happen this week? I wouldn't hold your breath... --Jayron32 04:14, 3 August 2012 (UTC)

Such a quake could possibly be a once-in-ten-milleniums in frequency/probability; I don't hold my breath for any megathrust earthquakes anyway.

However, it seems logical. If the subduction zones could each generate 9.5 earthquakes, and the San Andreas Fault a 9.1, then this could produce something like 9.8. If it so happened that another adjacent subduction zone like the one off eastern Russia also joined in, this would easily break 10. The chances of this is extremely unlikely, but not impossible.--Jasper Deng (talk) 04:19, 3 August 2012 (UTC)

Basic answer: nobody knows. The general opinion was that the Japanese tsunami quake was extremely unlikely -- until it happened. The dynamics of large earthquakes are still quite poorly understood, and we only have about 100-150 years of good worldwide data on their frequency, so events that occur less often than that could easily be misunderestimated (as GWB might have put it.) Looie496 (talk) 04:27, 3 August 2012 (UTC)

Deicing equipment / heaters

Is there any disadvantage to running deicing heaters, whether it's the pitot tube or the other deicers, even if it's not needed? I'm talking about onboard systems too, not deicing on the ground. Shadowjams (talk) 06:06, 3 August 2012 (UTC)

1) I imagine it lowers fuel efficiency somewhat, depending on how they generate the electricity to run them.

2) Running that much electricity through wires has to increase the risk of fire, explosion, and electrocution, if the wires are damaged, but this risk should be minimal in a properly maintained airplane.

3) Running them on a hot day while sitting on the ground might actually cause overheating damage. StuRat (talk) 06:13, 3 August 2012 (UTC)

Anybody with cites or definitive knowledge have any ideas? Shadowjams (talk) 06:38, 3 August 2012 (UTC)

I'm about to board an international flight, and I'm seated in the first row. I'll see if I can quickly ask the pilot :) 101.172.127.242 (talk) 09:27, 3 August 2012 (UTC)