Wikipedia:Reference desk/Archives/Science/2007 June 18

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[edit] June 18

[edit] Attractiveness

Are straight people capable of finding themselves beautiful, and other people of the same gender? Are gay people capable of finding people of the opposite gender beautiful? Are assexual people unable to find any human being beautiful? A.Z. 00:22, 18 June 2007 (UTC)

I'm no psychologist but I do think that beauty does not always relate to attractiveness. There exists men who think other men are handsome, and women who think other women are beautiful (hence a lot of jealousy stories!). x42bn6 Talk Mess 00:25, 18 June 2007 (UTC)
Is this right? One can be jealous of a woman because she is beautiful, even though one only thinks she is beautiful because her body has the right proportions and is symmetric, and because they know that other people find her beautiful. But I think that finding someone beautiful (I mean, looking at someone and thinking it feels good to look at that person and things like that) always relates to attractiveness! even though perhaps not always sexual attractiveness. I think this is a way of putting the question: can you feel attracted to a human body in any way that is not sexual attraction? A.Z. 00:43, 18 June 2007 (UTC)
By the way, I must be quite heteronormatively biased, since I didn't notest before that you wrote the sentence "there exist men who think other men are handsome" when you meant "there exist straight men who think other men are handsome". A.Z. 01:05, 18 June 2007 (UTC)
Of course there are. It's perfectly possible to look at someone you have absolutely no interest in and see how attractive they are. The problem is, beauty is in the eye of the beholder, so it's rather impossible to judge. Some (male) I might find cute, the majority of women might find nerdy. It might not be an inaccuracy on my part, but a matter of opinion -- Phoeba WrightOBJECTION! 01:49, 18 June 2007 (UTC)
Gay men are highly represented in the fashion industry, which pretty much revolves around appreciating and enhancing the beauty of the female form. That suggests to me that homosexual men are very capable of appreciating female beauty, just as I (a straight man) am very capable of appreciating the beauty in a very handsome man. I'm sure only the most sexually repressed man would shy from admitting that they can see that, for example, Brad Pitt is remarkably beautiful. However, appreciating and understanding what we commonly defined as beautiful humans of either sex - symmetry and robust health indictors, mixed with cultural foibles - is very different from being attracted to that beauty. As for straight people finding themselves' beautiful... ask Narcissus. Rockpocket 02:06, 18 June 2007 (UTC)
That's interesting. I had thought about gay men that claim to be able to appreciate female beauty, but it's hard to understand how that could happen. Maybe gay men who can appreciate female beauty are not totally gay, but somewhat bisexual, and maybe straight men who can see that Brad Pitt is handsome are able to do so only because they are a bit homosexual, as in not a zero on the kinsey scale.
I (a gay man) am very capable of appreciating that, say, Gisele Bündchen is not an ugly thing to look at and has good skin (is healthy) and things like that, and I realize that others find her attractive, and, as the article on beauty states, others derive from looking at her "a perceptual experience of pleasure, meaning or satisfaction to the mind", though I would never find out that she is attractive and beautiful to some if no-one had told me so.
Nonetheless, I'd be rather disturbed if I looked in the mirror and saw something about which all I can say is "that is not ugly, and other people say it's attractive". What first made me think of this subject was precisely that straight people would seem to be incapable of realizing their own attractiveness, and could only be aware of it if someone told them that they are attractive, and could only trust others on that, without being able to make their own judgement. I mean, they could see the symmetry and such traits, but they could never actually feel how attractive they are... It would be like looking at dolphins or some other animal and finding out which traits are attractive to other dolphins, and then saying "therefore, my conclusion is that that dolphin is quite attractive", though they would not be emotionally involved with the conclusion, and wouldn't ever be able to experience the attractiveness of the dolphin. A.Z. 03:23, 18 June 2007 (UTC)
Um, I was a bit surprised to learn that Brad Pitt is celebrated for his beauty. (Some males that I do consider pretty: Paul Newman, George Harrison, Orlando Bloom as a mortal, Billy Dee Williams.) —Tamfang 06:33, 18 June 2007 (UTC)
I think you're missing the larger thing about beauty here. You do not have to be sexually attracted to something to find it beautiful (for example: a rose, a sunset, the Grand Canyon).--Pharos 03:33, 18 June 2007 (UTC)
Maybe I'm missing something, but I'm not sure what it is. Is it possible to find a person physically beautiful in a way other than sexually? Which way would that be? Does Wikipedia have an article on that? How is it to recognize that someone is handsome and not feel attracted to them? A.Z. 03:40, 18 June 2007 (UTC)
In the same way that someone can find a horse physically beautiful, but not be a zoophiliac. I'm pretty sure that's how most portrait artists appreciate their subjects.--Pharos 03:48, 18 June 2007 (UTC)
Brad Pitt = 1.6180339887?
Brad Pitt = 1.6180339887?
So, Rockpocket above finds Brad Pitt beautiful the same way he would find a horse beautiful? And so do gay men who work in the fashion industry with women? I'm not mocking your response, I'm really interested in understanding it. A.Z. 03:50, 18 June 2007 (UTC)
Since you mention me specifically, I thought I would answer here. With regards to your first question. To some extent, yes, I can appreciate the beauty in a man in the same way I can a horse or a dog. But I think there is more to it that that. A beautiful male face is not so different from a beautiful female face. The key is right/left symmetry, and the balance of features in certain ratios. There appears to be an inherent, perhaps genetically encoded, aesthetic pleasure in this balance. While we might not be consciously aware of symmetry being a key factor in what we find beautiful and attractive, it appears to be subconsciously persuasive. For example, we prefer the smell of people who have greater facial symmetry than those that don't, we don't know why that is, but it suggests that symmetry is a key factor in attractiveness. So, I would propose that the reason straight males appreciate beauty in other males is simply because they have the same basic biological mechanisms in place to register the visual cues females (or gay men) use to determine fitness. The only difference is that these mechanisms are decoupled from the sexual response in straight males. Rockpocket 06:50, 19 June 2007 (UTC)
I might look at someone and instinctively think "Mmm, it'd be good to spend some private time exploring that", but then immediately realise that we're not dealing with pieces of uncovered meat here but human beings. It's possible to be strongly attracted to a person because of their human qualities while being indifferent to their body and to have no sexual feelings for them; conversely, it's possible to have sexual thoughts about a person's body while the thought of associating with them in any other way - or any way at all, including sexually - might be horrendous. To answer your original question from the gay male side, it's very, very possible for gay men to appreciate beauty in women; that's because gay people are human beings and all human beings love beauty - just what constitutes "beauty" differs from person to person, but I don't think it's as simplistic as "gay people only find people of their own sex beautiful and straight people only find people of the other sex beautiful". As others have said, appreciating beauty in another person, and being attracted to that person, are different things entirely. I deliberately used the words "being attracted to [someone]", rather than "finding someone attractive", because the latter gets away from the physical instinctual feelings one may have about a person and into the area of intellectual judgement of them. Such language could find its true home in situations such as "I find you attractive, but I am not personally attracted to you". -- JackofOz 04:02, 18 June 2007 (UTC)
Yes, I think that appreciation of beauty of something of a universal, and it's only related to sexual attraction in certain contexts. Certainly it is possible to find a horse beautiful without the need of feeling sexually attracted to it, and I see no reason for this effect to disappear in interactions with humans. But if there's no context for sexual attraction (the subject is the wrong sex, or as in my example the wrong species) that just doesn't arise.--Pharos 04:14, 18 June 2007 (UTC)
To JackofOz and Pharos: I would like, then, to find out one day how would it be to find the body of a man beautiful without feeling sexually attracted to it. I can only compare it with a horse, or with a fish, which can be colorful and beautiful even though I don't want to have sex with it. But, when it comes to people, I have a hard time getting it. Perhaps the fact that there are only male and female people is preventing me from being able to understand how one could find another person beautiful without the sexual attraction, since I'm apparently not one of those gay men to which the body of women is an example of beauty. Then again, I can't think of any non-sexually attractive human body that I find beautiful, even a body of a male. Perhaps I'm someone who just doesn't find anyone beautiful, and all that I have been calling beauty so far is in fact sexual attraction. A.Z. 04:21, 18 June 2007 (UTC)
OK, what about Brad Pitt, the supposedly archetypically paragon of human beauty, to whom people of both sexes are attracted in legendary numbers. Imagine if Brad had a horrible motor accident and his torso was mangled and scarred and distorted, but his face was untouched. Would he still be attractive to people? Is it his whole body that people find attractive, or his face? Is it something that comes from his eyes and mouth, or from his chest and frame, that attract people? Is it both? And can one work without the other? -- JackofOz 04:54, 18 June 2007 (UTC)
Beautiful to everyone, I think. (Aficionados of the abstract excepted)
Beautiful to everyone, I think. (Aficionados of the abstract excepted)
My best answer to this would be: Ask an artist. And preferably take art classes too, particularly a figure drawing exercise. Because I think you are confusing beauty and sexual attractiveness – and an artistic perspective will help set that right. And I don't know what your point of reference is for this discussion is – whether revealing pictures of celebrities, people you know personally, or whatever. But as I said, I think if you're looking for beauty you should look toward the artistic, and even if you don't want to take any classes you should at least try to appreciate the beauty of the sex you're not attracted to, in your case, women in art.--Pharos 07:52, 18 June 2007 (UTC)
You might be interested in reading Asexuality, particularly the 'variations' section. I consider myself asexual (i have never felt any desire to have sex or even 'fool around' with somebody), but i am perfectly capable of deeming a person physically attractive. How that's 'possible' i guess i can't say; it just is! ~ lav-chan @ 04:44, 19 June 2007 (UTC)

Can't help but add a comment -- if human beauty is equivalent to sexual desire, one has a very narrow definition of "beauty". That is all. Pfly 09:01, 18 June 2007 (UTC)

Precise definition of terms and word-use would make this entire issue a moot point. Nimur 10:41, 18 June 2007 (UTC)
This question has aspects of belonging at the Humanities desk ("What is Beauty?") and aspects of belonging at the Science Desk as a Psychology question (Can male homosexuals find a woman "beautiful" or "attractive"? Can male heterosexuals find a man "handsome," "beautiful," or "attractive"). And Mutatis mutandis, similar questions with respect to a woman's fancy. "Girl crushes" are well known now [1] and they were well known in the 19th century, in which a (self-described heterosexual) woman sees another woman and becomes breathless, stammers, flushes, thinks she is "supercool" and wants to be around her, without the desire or liklihood of having a lesbian relationship.Of course denial is more than a river in Egypt, and there is evidence that college girl crushes sometimes blossomed into much more [2] Heterosexual young adult women also have close friendships with solidly homosexual men, with no hint that it might blossom into a sexual relationship because of some bisexuality. Demographics of sexual orientation includes Kinsey's finding that on a 7 point scale with 0 for completely heterosexual and 6 for completely homosexual, all but a small percentage of the population were to one degree or another bisexual (falling on the scale from 1 to 5). Thus on the male side, there is a continuum from fishing buddy relationships among males or guys wanting to hang out with a star athlete because they can pick up the girls he doesn't, to Brokeback Mountain relationships, but there does not seem to be as much writing about it. Edison 15:47, 18 June 2007 (UTC)
The two have some positive correlation it seems. I'm male, and I don't see why I would have to have sexual interests to judge a persons beauty. For men, I compare how they look to me. If I think they look better then I do, then I would say they are "good-looking". Because I percieve myself to be "good looking" (due to that thing about humans where we almost always think ourself better then average). Of course, it seems frowned upon for other men to comment on another man's appearance, yet there is no such thing for women observing other women.--GTPoompt(talk) 15:15, 18 June 2007 (UTC)

So, wait a minute, if I'm understanding all of this correctly, and I know I'm not, then Narcissus was gay?! ;) 38.112.225.84 14:50, 19 June 2007 (UTC)

Not necessarily. When you look in the mirror, you see a face that can be anywhere on the spectrum of "extreme like" to "extreme dislike". It changes from day to day, subtly or grossly, depending on various factors, such as self-esteem. It has nothing to do with the sexuality of the person looking in the mirror. -- JackofOz 02:54, 20 June 2007 (UTC)

[edit] Atomic mass of 5

I am not a chemist or physicist. What would be the most likely explanation for a GC-MS graph with a peak at 5 amu?

— Omegatron 02:25, 18 June 2007 (UTC)

Nucleii with mass of 5 are extremely unstable, Helium 3 is quite rare, and some of your compounds are probably not stable at all eg pentahydrogen. Your hydrohelium sounds like the only possibility from your list for a real ion. Another exotic possibility is Helium 4 with one electron substituted with one antiproton. However given the description on the picture you have supplied the preferred alternative would have to be Hoax. Another way to get a peak at 5 would be to have a doubly ionised with weight of 10 molecule. GB 03:24, 18 June 2007 (UTC)

Aha! Misunderstanding of what the machine is measuring could also explain things. How likely is the doubly ionized molecule as a gas byproduct of water electrolysis? (I don't know what electrolytes were added to the water.) Would the ionization come from the electrolysis or from the spectrometer itself? — Omegatron 03:32, 18 June 2007 (UTC)
Looking closely at the picture, the peak is not precisely on the 5 but about 10% below, so spurious response could be possible. In fact there are few molecules with atomic weight of 10. You could have one sotope of boron, but what happened to the other boron-11 atoms? A triply ionised N-14 atom it pretty unlikely too. Do we know that water electrolysis was invlolved? Is this your own experiment Omegatron? GB 05:46, 18 June 2007 (UTC)
Aren't the actual masses of particles slightly different from their individual components due to mass-energy conversion? It looks like there are three other much smaller peaks at 3, 6, and 7 that aren't even close to the amu markings.
Certainly not my experiment.  :-)
This guy claims to have created a new form of matter from water electrolysis in a special machine, and somehow got it into the International Journal of Hydrogen Energy. The gas and the company that makes it were covered in the news alongside even more bogus claims, like water-powered cars, and the videos are now making the rounds on YouTube. See Talk:HHO_gas#References for videos and articles.
Another claim is that burning this gas in a torch can "sublimate" tungsten, and is therefore burning at tungsten's boiling point of 10,000 °F. But when they do the demonstration, it's in air! The tungsten is just oxidizing at a much lower temperature, like a light bulb filament.
I've been working hard to cover and debunk these claims in Wikipedia, but the articles keep getting shot down for stupid reasons. The latest version was put up for deletion, a roughly 19:15 majority voted to keep it, and it was deleted anyway. Now it's going through a messy DRV. It's very frustrating. — Omegatron 00:19, 19 June 2007 (UTC)
Having now had an opportunity to read the paper from which the linked figure is drawn, I can safely and comfortably conclude that it is complete bollocks. It's possible that the author of the paper in question isn't deliberately perpetrating a hoax in order to buttress his 'discovery' of an "apparently new mixture of hydrogen and oxygen gas hereon referred to as the HHO gas (international patent pending)", but is genuinely deluded. Readers with online access to the International Journal of Hydrogen Energy are strongly encouraged to read this paper (R.M. Santilli, "A new gaseous and combustible form of water" Int. J. Hydrogen Res. 31:1113-1128) if they ever need a good laugh. TenOfAllTrades(talk) 17:02, 18 June 2007 (UTC)
 :-) Yep. What I don't get is how this was peer-reviewed. He runs a vanity press journal to publish his theories on "hadronic mechanics", but this article is supposedly in a legitimate journal...
— Omegatron 00:19, 19 June 2007 (UTC)
I know next to nothing of chemistry, but before publishing something wherein a mass spec shows the product of electrolysis to have the amazing atomic weight of 5, would'nt you run reference samples throught the instrument to show that elements with atomic weights near 5 (below and above and near 5 ) register as expected? Is it possible for such an instrument to get out of whack, or for calibration to drift? That was the minimum requirements in any lab of any sort where I ever worked. Edison 23:08, 18 June 2007 (UTC)
There are copies of the paper on proponents' websites for those without journal access. See the above reference for a .doc file. I don't know enough chemistry to judge whether it's a deliberate hoax, unintentional misinterpretation of the graphs, or something else. Would contacting the laboratory provide any information on a test done 4 years ago? — Omegatron 00:19, 19 June 2007 (UTC)
I'm not familiar with the equipment in question, but would a deuterium-tritium molecule be a reasonable explanation? --Carnildo 00:07, 19 June 2007 (UTC)
That would be a stable compound, wouldn't it? Probably not found in the same concentration as regular 2 amu H2, though, especially if the electrolysis involves normal water, and you'd also see peaks for DH, DT, HT, and so on, right? — Omegatron 00:19, 19 June 2007 (UTC)
Wait a second... What would happen if you electrolyzed heavy/tritiated water with significant amounts of deuterium and tritium? Heavy hydrogen gas would form near one electrode, and form into diatomic molecules, right? Would the weights of the nuclei affect the stability of the bonds so that certain compounds were preferred over others? Are H2 and DT significantly more stable than D2 or DH? — Omegatron 00:31, 19 June 2007 (UTC)

Here's a better analysis. --Tbeatty 02:20, 19 June 2007 (UTC)

Hmm? I don't see anything about the 5 amu claim on there. — Omegatron 06:30, 19 June 2007 (UTC)

[edit] Idle question about Blood pressure

Hello. Why is it that one's blood pressure increases with one's heart rate? After all there is a fixed amount of blood in one's body. Is it to do with the speed of the blood moving through one's arteries? In other words is it static pressure or dynamic pressure? Best regards 195.137.96.79 03:51, 18 June 2007 (UTC)

I would like to understand that as well. If the heart is to pump more blood, the pressure will increase on one side, but decrease on the other, because blood has been taken from there. A.Z. 04:00, 18 June 2007 (UTC)
Indeed. Maybe I made a false assumtion - maybe blood pressure does not go up with heart rate... 195.137.96.79 04:16, 18 June 2007 (UTC)
I don't actually know the answer to the question itself, but maybe I can provide some more information. If the only change is that blood is pumping faster, blood pressure would actually be lower due to bernoulli's principle. But then there are the complicating factors of vasoconstriction and vasodilation, so this principle often doesn't apply to blood flow. Autoregulation can regulate blood flow to a particular organ, so you can also have changing volumes of blood flowing to different areas. So, blood pressure is complicated, but anyway, according to tachycardia, the heart beats faster in response to lowering blood pressure in attempt to raise it. Unfortunately it doesn't say specifically how this works. I'm sure someone else can provide a more complete answer. Someguy1221 05:07, 18 June 2007 (UTC)
Consider how Mean arterial pressure is calculated. Next consider if both systemic vascular resistance and central venous pressure remain constant. Only cardiac output may change. This is affected by stroke volume and heart rate. If heart increases and stroke volume remains constant, cardiac output will increase and so will mean arterial pressure. You would expect ventricular diastole to decrease so you might expect cardiac output to remain constant. But I would presume the heart compensates by increasing the duration of contraction and/or strength of contraction. Therefore the stroke volume does not drop enough that it completely negates the increased heart rate. As the blood pressure increases, you should achieve the same end-diastolic volume over a shorter duration. In conclusion then, strictly speaking it probably isn't just the increased heart rate that increases blood pressure. Nil Einne 10:56, 18 June 2007 (UTC)

Don't forget the volume of blood inside the heart, which is partially pumped out during a heart beat, temporarily increasing the volume in the veins, arteries, and capillaries. StuRat 13:20, 18 June 2007 (UTC)

I'm not sure if this helps at all, but when my pulse rate increases my body is getting more oxygen, so my heart doesn't have to beat as hard, and the blood doesn't have to be forced around as hard, so my blood pressure drops slightly. But this only works if I am doing something slightly active like walking.

Thanks a lot for your help with this folks - and thanks particularly for the links provided by Nil Einne. I have to say I'm still largely in the dark about the actual physical explanation for this, but your comments are very informative about the way these terms are used in the medical world. Thanks a lot, and sorry for not responding sooner. Best regards to all 195.137.96.79 22:31, 18 June 2007 (UTC)

[edit] re:heat and sound

please can any one help me that

if i pass sound waves on a metal(or thermometer) piece what can i expect about the temperature \of the metal piece .please give appropiate reasons.(relating rarefraction ..potential energy of medium etc) Reveal.mystery

You don't have to get that complicated. I would expect any obstruction in the path of the sound waves to absorb some of the energy from the sound - which would make it get a teeny-tiny bit hotter. In detail, as a sound wave passes by, the pressure change will push against the object making it bend and flex - which will transfer some energy from the sound wave and transfer it into the object as heat. SteveBaker 04:40, 18 June 2007 (UTC)


thanks for reply but i want to effect the transmission of heat through gases by using sound waves.

Similar to a question asked a few weeks ago. I thing the answer was: Acoustic refrigeration or sommat--88.110.201.197 01:02, 19 June 2007 (UTC)

You might be interested in high intensity focused ultrasound, which uses a focused sound wave to heat up tissue at a point.

On a tangent, superfluid liquid helium transmits heat in waves called "second sound". — Omegatron 01:45, 19 June 2007 (UTC)

[edit] Global Warming and Precipitation

Since the world is a closed system, logically the melting of the polar ice caps would result in more free water, which would mean more rain. So why do scientists tell us that there could be severe droughts in parts of the world? --75.85.7.149 05:19, 18 June 2007 (UTC)

A lot of information can be found here. In short,

A range of potential effects of global climate change on water resources and agricultural management has been suggested. These include increased surface temperatures and evaporation rates, increased global precipitation (but with greater geographic variability), increased proportions of precipitation received as rain, not snow, earlier and shorter runoff seasons, increased water temperatures, and decreased water quality. Variability in precipitation patterns is also expected to increase, resulting in more frequent droughts in the U.S. and elsewhere (see Adams et al. 1999, for a review of the effects of climate change on agriculture and agricultural resources).


Someguy1221 05:55, 18 June 2007 (UTC)

One of the big unknowns is the change in cloud cover due to global warming. cloud cover can reflect heat energy from the sun and moderate the effects of global warming. The second piece is that warmer air can hold more water. No one knows which process will win although our rather stable temperature suggests a very strong feedback cycle that keeps temperatures constant. --Tbeatty 06:53, 18 June 2007 (UTC)

Actually, the world isn't really a closed precipitation system. There is loss when 2H2O(v) --> H2(g) + O2(g) is split (likely by some form of incoming radiation). Some of the lighter diatomic hydrogen gas will escape out of the atmosphere into space, but the loss is, not surprisingly, quite small. On the other hand, this is some flux in to the hydrologic system with juvenile water, which according the National Weather Service glossary is "water formed chemically within the earth and brought to the surface in intrusive rock" (I'm sort of shocked we don't have an article on juvenile water!).
Melting the ice caps may introduce some untapped water into the hydrologic cycle, and if memory serves me right, about 1% of Earth's water is liquid fresh water, and 2% is ice water. Not all of that ice is going to be melted, and a lot of that liquid water will drain into saltwater sinks. I'm sure this infiltration will decrease salinity somewhat, akin to trying to put out a major building fire with a personal fire extinguisher.
The major issue is that the changes in temperature may cause climatic shifts whereby some regions get less rainfall and others get more. Sure the saturation mixing ratio will be higher due to warmer temperatures, but given the kinds projected increases in temperature, I wouldn't anticipate a huge increase in the saturation mixing ratio that would indicate a vastly greater water capacity (the numbers can be computed based on average temperatures and expected increases, but I'm too lazy to do it). In addition, cloud cover in and of itself is not an inherent moderator of temperature increase, especially if temperature increases are occurring through warmer minimum/low temperatures (greater cloud cover will limit the heat flux from the warmer surface to the cooler air). And even disregarding these issues, the point needs to be made that these are more complex issues than are resolvable by examining a few specific processes; the equations governing standard dynamics are complex enough.
One further issue to consider that is completely aside from issues of climate change. As world population size increases, the availability of fresh water as a resource will become scarser as demand increases but supply remains relatively level or is limited due to issues of imbalanced distribution, water quality, and purification issues. Even if climate change has a limited impact, there will be only increased needs for water (see water resources among other discussions). –Pakman044 13:19, 18 June 2007 (UTC)
In short it's due to local variations. For example, globally, there may be warming, but locally there can be cooling, such as at the South Pole (and the North Pole is actually heating up more than the rest of the world). With precipitation, not so much change is expected in the global average (although there is a lot of uncertainty), but regionally, changing winds and air moisture may make certain regions wetter and others drier. Also, why would more seawater mean more precipitation? The surface area of the water will change little (although those small coastal areas that may get flooded may also have large populations since most people live near water). DirkvdM 07:28, 19 June 2007 (UTC)

[edit] why can I aim a gun?

Last week I took my dad to a target range, where he shot my .22 pistol and I shot my .40. Afterward we discussed the physics of recoil. He estimated that my pistol's axis moves about 3 degrees while the bullet is in the barrel – and presumably this varies a lot depending on my grip (the strength of my arms, whether I brace the gun with my other hand...). So how is it that I can hit anything? I can see where his crude estimate of the angle must be high, but how far off? —Tamfang 06:50, 18 June 2007 (UTC)

Assuming the bullet has muzzle velocity of 300m/s (pessimistic estimate) that accelerates linearly, it takes less than 1/300 s for it to leave the barrel of 50cm. If in that time your hands moved 3 degrees from rest, and assuming your arm's length is also 50cm, it moved 2.6cm in less than 1/300 s, which means a mean speed of 7.85m/s and assuming a linear acceleration, the final velocity would be double that, or 15.7m/s. That's more than 55km/h, and your hands had gone through acceleration of nearly 2g. Now does that look anything like when you shot your gun? (This is just very rough estimation, and I don't guarantee the correctness of my math.) The bullet most likely left the barrel before you move the axis a full 3 degrees, and will follow roughly the original axis that you pointed at. --antilivedT | C | G 07:09, 18 June 2007 (UTC)
The recoil comes (primarily) from exchanged momentum with the bullet. In other words, the gun can't jerk backward until the bullet has simultaneously gone forward. The bullet has left the barrel before there is a significant change of direction. Some amount of recoil is part of the inaccuracy of the gun; different types of weapons have different responses (thus various accuracies). Nimur 10:50, 18 June 2007 (UTC)
Agreed. Also, if the recoil is consistent, you might compensate for it, by aiming a bit low if the gun tends to pull up, for example. StuRat 13:09, 18 June 2007 (UTC)
Also there is a super neat trick you can use for target pistol stability when standing. Photographers use this when conventional tripods can not be used. You need 20 feet of parachute cord. Make a loop in one end four or five inches in diameter and tie this with a Bowline. This will be a foot styrrup. Tie a Clove hitch around the front of the barrel so the line of sight to the front sight and target is centered on the middle of the target. Not easy I know but other highly secret tricks can be used to do this reasonably fast and accurate. Loop the remaining cord under the vacant foot and clasp the end between the palm of your hand and the gun handle. Now make cord length adjustments so that the cord is pulled very tight when the sight is perfectly aligned with the center of the target. Yell "4"! No that's golf. Yell "everhbody watch out, I'm going to pull the trigger." Wait 10 seconds and then pull the trigger. 71.100.3.132 15:25, 18 June 2007 (UTC)
I've read various explanations of how much a given gun does or does not move before the bullet exits. I don't understand the math well enough to have any opinion on the facts of the case. But, regardless, your sites are set to be accurate at a certain range. The point of impact versus aim may change somewhat with different loads- anyone can observe this. What I'm getting at it that however much the barrel moves or doesn't move, this is already factored in to your point of aim. So, leaving aside the question of how much the gun moves, the reason you're able to hit anything is that you're using sights, and your gun is sighted in adequately for your purposes. Friday (talk) 15:28, 18 June 2007 (UTC)
Yes, but that assumes that the recoil is consistent in direction, magnitude, and speed. You can't precompensate for an unpredictable recoil. StuRat 22:22, 18 June 2007 (UTC)
Well, guns have recoil, and they can be aimed. This suggests that any variance in recoil is not a large factor. Different loads would make a bit of difference, but outside of that, why would there be variation? Friday (talk) 22:33, 18 June 2007 (UTC)
Since a person is holding the gun, the mass of their hand and arm must be figured into the calcs, as they must also be accelerated (unless the gun flies right out of the person's hand). The way in which the person is holding the gun would also affect whether it pulls straight up, to the right, to the left, etc. StuRat 05:28, 19 June 2007 (UTC)
Well, the gun moves way more after the bullet leaves than before. In real life, I haven't seen this change point of impact much, if at all. A strong grip may result in less muzzle flip than a lighter grip, but here we're talking about things that happen long after the bullet has exited. As for left or right, in my experience it's the twist of the rifling that determines this (and it only gets significant with heavier bullets). Friday (talk) 14:25, 19 June 2007 (UTC)

[edit] Do clones have introns

Do clones have introns (Junk DNA) as their DNA sequence is made from RNA which has none? Think outside the box 10:55, 18 June 2007 (UTC)

I think you may be getting confused here. The article you linked to refers to the method of molecular cloning which as the article says is used for "isolating a defined DNA sequence and obtaining multiple copies of it in vivo". The DNA sequence in this case would usually contain no introns. However artificial reproducive cloning used to produce cloned organisms like Dolly etc is something completely different and usually involves somatic cell nuclear transfer for animals and a variety of methods for plants and bacteria (many of which can reproduce asexually anyway) Nil Einne 11:07, 18 June 2007 (UTC)
I'm not quite sure what the question is, but here's an answer... Molecular cloning can be used on any DNA sequence, and it looks like you're describing a subset of it that uses cDNA ("complementary DNA" produced from reverse transcription of RNA). You're right, this type of DNA won't have introns in it, they have already been spliced out. Cloning cDNA fragments, rather than directly from genomic sequence, is useful technique for people who want to "express" the gene in bacteria (make the bacteria produce the protein contained in the gene). Bacteria don't use these types of introns in genes and don't have the spliceosomes necessary for removing them. The product of these genes are effectively pre-spliced and go on to make the correct protein product. Madeleine 15:37, 19 June 2007 (UTC)

[edit] disease polices

When a patient with an infections disease (eg HBV) undergoes surgery do they require to inform staff that they have an infections disease?Brown886 11:36, 18 June 2007 (UTC)

You should ask a doctor or lawyer. I recommend full disclosure, for your safety and theirs. Nimur 12:12, 18 June 2007 (UTC)

The hospital will certainly ask that on forms you need to fill out before surgery. However, whether lying on those forms is punishable by law will vary by jurisdiction (and possibly by the disease). StuRat 12:15, 18 June 2007 (UTC)

There is no US law compelling any patient to tell any doctor anything and no penalty for lying. Doctors and nurses are aware that many people fail to tell the truth about many aspects of their health history. The purpose of universal precautions policies in hospital was to mitigate the twin risks of deception and discrimination. As has been pointed out, while it is possible that your health care provider may think differently about you if you admit certain information, I can promise you that if you are found to have deliberately concealed information like that, they will continue to be professionally polite, but will consider you a contemptible fool who is dangerous to himself and his healthcare providers. alteripse 13:42, 18 June 2007 (UTC)

This question is asking for both medical AND legal advice. I think we need a bigger sign at the top of this page. Nimur 13:49, 18 June 2007 (UTC)
They are neither asking us to diagnose a medical condition nor to recommend a legal course of action, so neither policy applies. Not all "medical" and "legal" questions are banned. For example, "what is that weird winged staff with the snakes around it you see in medical settings" (caduceus) and "what is it called when you want a second opinion from another judge after you lose a court case" (legal appeal) are medical and legal questions which are perfectly legit, as is this question. StuRat 22:31, 18 June 2007 (UTC)

[edit] geography

WHICH PLANET EXCEPT EARTH HAS ATMOSPHERE?

That depends on your definition of atmosphere and planet. Also, there are a lot of extra-solar-system planets being discovered, so that number changes as more discoveries are made. -- JSBillings 14:58, 18 June 2007 (UTC)
Yes, it depends on the two criteria above. But to answer anyway, the 8 planets in the solar system have an atmosphere of some sort (so does pluto). Mercury has one, even though unstable. On another note, Venus, mars, and a few moons have atmospheres somewhat similar to earth. Varying in density and make-up of course.--GTPoompt(talk) 15:26, 18 June 2007 (UTC)
For the extrasolar planets discovered so far, almost all of them are hot jupiters with most of their volume being an atmosphere. Of course this is because large planets orbiting close to their stars are easy to detect, not because the majority of planets are hot jupiters. --Bowlhover 01:16, 19 June 2007 (UTC)

[edit] Re-using Satellite TV Receivers

Is it possible to reuse the receiver box your cable co. makes you buy? (and won't take back after you cancel service) There has to be thousands of these sitting around.SoManyQuestions 15:52, 18 June 2007 (UTC)

Reuse suggestion at right. --TotoBaggins 22:16, 18 June 2007 (UTC)
Early electronics devices, because of the large transformers they contained and the steel cases, made pretty good boat anchors (in the absence of a concrete block). Modern electronics devices are largely empty plastic boxes, and are a bit light to serve as a door stop in the presence of any appreciable wind. In older homes, they may be useful for propping older Sash windowss open when the sash cords have broken. Edison 23:02, 18 June 2007 (UTC)
You could measure the acceleration due to gravity from the roof of your house. anonymous6494 01:30, 19 June 2007 (UTC)
Haha, those suggestions! :-) —Bromskloss 07:25, 19 June 2007 (UTC)

[edit] Deserts in Europe

Hello, Can somebody tell me an exact number and geographical names of deserts in Europe. According to the article about the deserts there are only three deserts in Europe: Hálendi – a region of Iceland and Europe's largest desert; Błędowska Desert – a desert located in Lesser Poland Voivodeship, Poland; Deliblatska Peščara - a desert located in Vojvodina, Serbia. But I also found out about the largest desert in Northern Europe which is situated on Anholt island (Denmark). And if Aleshkovskie peski (Ukraine) is the desert or semi-desert? So I would like to know an exact number and geographical names of deserts in Europe. Thanks.

A desert is an area that receives very little precipitation. As far as I can see, the amount of precipitation is not precisely defined, so the definition of a desert is flexible. Even so, I would argue that there are no deserts at all in Europe. The lack of vegetation in the places you mention is due to excessive drainage rather than any lack of rainfall. And according to Anholt (Denmark), "Strictly speaking the desert is not a real desert, but a lichen heath."--Shantavira|feed me 06:50, 19 June 2007 (UTC)

THe definition of a desert was having less than 250mm of rain each year. I think I saw a map of deserts that showed part of spain and an area around the caspian sea as deserts as well. But then I also read that there are no deserts in europe, so you can't always trust what you are told.

Don't forget that Antarctica and the Arctic are both classed as deserts because of low levels of precipitation (too cold to snow often). SGGH speak! 20:30, 20 June 2007 (UTC)

But are they in europe? The OP has already mentioned iceland.

[edit] Hang nails not at the nail

Is there a name for the condition where something very much like hang nails forms on calluses on the soles of the feet ? StuRat 19:45, 18 June 2007 (UTC)

"Gross"? — Omegatron 01:35, 19 June 2007 (UTC)

[edit] Dental hygiene

I am curious about several aspects of dental hygiene:

  1. What is the most efficient toothpaste on the market to use, in terms of health? (Not worried about whitening.)
  2. Does the type of toothbrush make a difference in keeping your teeth clean? I've read that the expensive toothbrushes, including the battery-powered ones, are completely unnecessary.
  3. How often should a person brush to keep healthy teeth? Just before/after sleeping, or after meals?
  4. Like I asked about toothpaste, what is the most efficient mouthwash on the market to use, in terms of health?
  5. How should mouthwash be used in conjunction with brushing teeth, for maximum healthiness, if at all?
  6. How often should one floss for a healthy mouth? Once a day, or more frequently?
  7. Is any kind of gum helpful in keeping a clean, healthy mouth? Or is it just marketing?
  8. Are there any foods to eat that actually help a clean mouth? I know eating celery can burn more calories than you actually take in...

I would appreciate any links that help answer any of these questions. 155.91.28.231 20:25, 18 June 2007 (UTC)

I have no links to give you right now, but I do have some answers
  1. The type of toothpaste does not matter, as long as it has an appropriate amount of fluoride. If you are in the U.S., then that means any ADA approved toothpaste will do.
  2. The type of toothbrush has very little to do with any benefit to dental hygiene. Bristles that are too hard can cause damage, so generally soft or extra soft toothbrushes are recommended. Electric-toothbrushes do not provide any extra benefit (except that their timers may help people brush for sufficient time).
  3. I believe most dental organizations recommend at least twice a day for brushing and very little recommendation when to brush, except for perhaps after meals.
  4. Efficient mouthwash? I do not know if a particular brand of mouthwash is really more effective than others.
  5. Mouthwash is just not as important as brushing and flossing.
  6. I believe most dental organizations recommend flossing at least once a day.
  7. Sugarless gum will not cause tooth decay like gum with sugar and the added saliva produced when chewing gum can help increase the pH in the mouth after a meal, but gum is not really a public health solution for improving oral health.
  8. The only food that comes to my mind that is considered in the academic literature as "anti-cariogenic" (fights tooth decay) is cheese. Weird, huh?
Those are my initial responses without looking up any resources. If you had any other specific questions, just ask here or at WT:DENT. - Dozenist talk 20:51, 18 June 2007 (UTC)
Thank you for your answers. I will use them as a starting point for more detailed information. 155.91.28.231 20:59, 18 June 2007 (UTC)
Gonna add a bit more to Dozenist's very good reply.
  1. Several years ago, 20/20 did a report on toothbrushing and toothpaste, and the research's conclusion was that any amount of toothpaste greater than about the size of a pea is actually wasted. The huge chunk you see on toothpaste commercials are pretty obviously a scheme to make you use toothpaste faster.
  2. Research also found that brushing thoroughly for 30 seconds with a toothbrush pretty much gets it as clean as you can get, though I'm not sure if they meant any hardness of bristles, but they did mean non-electric ones.
  3. Brushing after meals is probably the best choice, and brushing once/twice a day should be minimum. The reason for the once/twice a day is because plaque isn't very dangerous till about 24 hours have passed, then it starts being more harmful to your teeth. So if you brush once/twice a day at the very least, plaque is no longer a big worry (I found this while researching a question on the Ref.Desk a few months back).
  4. This is personal experience, and I'm not sure how accurate it is. I have tried Scope (I normally use Listerine), and found that Scope doesn't really do as good a job (nor make my tongue unable to taste well for a few minutes). They do have a lower alcohol content though, I believe. I haven't tried any other mouthwash though.
And those are the only ones I have anything to add. --Wirbelwindヴィルヴェルヴィント (talk) 18:57, 19 June 2007 (UTC)

[edit] Open and Close stomata

Is there any place where I can get public domain or Creative Commons images showing turgid (open) and flaccid (close) stoma? deeptrivia (talk) 20:52, 18 June 2007 (UTC)

There is very little out there; Category:Stoma but these two examples to the right might work for you? David D. (Talk) 21:13, 18 June 2007 (UTC)
No, I need labelled schematic diagrams. Thanks, deeptrivia (talk) 22:55, 18 June 2007 (UTC)
Like this one. You could always create your own based on those already out there. David D. (Talk) 23:05, 18 June 2007 (UTC)
I wonder how they create these 3D looking illustrations. Is there any specific software they use? deeptrivia (talk) 16:57, 19 June 2007 (UTC)
My guess would be, with a paintbrush. You know, the old fashioned kind that you hold in your hand, dip in paint and apply to paper or canvas. Or maybe crayons — you can do amazing coloring work with crayons if you know how to really use them. —Ilmari Karonen (talk) 21:13, 19 June 2007 (UTC)
The key is the use of shading to give the impression of three dimensions [3] David D. (Talk) 22:47, 19 June 2007 (UTC)

[edit] Lepton number

What is an example of an interaction in which lepton number is not conserved? Thanks, *Max* 20:59, 18 June 2007 (UTC)

All interactions. Only neutrino oscillation, which isn't an interaction as such, can violate lepton number and has been observed. Cyta 07:31, 19 June 2007 (UTC)
How do neutrino oscillations violate lepton number conservation? Don't they just replace one neutrino with another? *Max* 13:58, 21 June 2007 (UTC)
I think Cyta confused the [lepton number]] with the three lepton family numbers. The latter's conservation is indeed broken by neutrino oscillations but they are conserved by both the electroweak interaction. The article on chiral anomaly explains how the standard model implies a possible weak breaking of lepton and baryon number, but to be honest, I do not fully understand it and cannot recall of having heard about chiral anomalies in my high-energy lectures. Now I wonder whether (a) I was sleeping or (b) the lecturer left is out or (c) the concept is not well established enough to be normally considered a proper part of the standard model. Simon A. 19:27, 21 June 2007 (UTC)
See sphaleron, too. Simon A. 20:02, 21 June 2007 (UTC)

[edit] Unknown moth

The moth close up.
The moth close up.

I found this moth near my house in Ontario, Canada and I was wondering what type of moth it is and where it is from. Does anyone know? Thanks, *Max* 21:16, 18 June 2007 (UTC)

At first glance it reminded me of an Atlas moth but there are some key differences... hmm. --24.147.86.187 00:56, 19 June 2007 (UTC)


Probably Cecropia Moth, Hyalophora cecropia, or another Hyalophora species. See pictures here (long page: scroll down or search for Hyalophora in page). Cheers, Dr_Dima.