Wikipedia:Reference desk/Archives/Science/2009 December 27

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December 27

Male involvement in pornography

1) How do females who work in the realm of pornography maintain a non-platonic relationship with a male counterpart while being involved in pornography?

2) How do males get involved in pornography-related careers? Are there aesthetic criteria they must meet, or does any guy get in? Both points seem odd to me when I think about it. DRosenbach ^{(Talk | Contribs)} 03:09, 27 December 2009 (UTC)

By "non-platonic" does that mean the opposite of Platonic love, as this linked-to article would define it? Bus stop (talk) 03:20, 27 December 2009 (UTC)

Well, I figure that there might be a pornographic actress who is married and tries to become pregnant with her husband and work might 'get in the way.' DRosenbach ^{(Talk | Contribs)} 05:24, 27 December 2009 (UTC)

Oh, I see. I misunderstood. I was thinking the non-platonic relationship being referred to was with the male porn star. You should have referred to the male as a "significant other" or some such locution. Or I should have thought about it more. Bus stop (talk) 05:45, 27 December 2009 (UTC)

I think the solution is two-fold: 1. People in porn tend to be young, and 2. Most males or females might be willing to forgo their normal sense of jealousy for the bragging rights (and supposed sexual benefits) of dating a porn star. It's also presumably possible that the type of personality that would pursue a career in the porn industry is one that would tend toward a single lifestyle. And, for what it's worth, a fair portion of porn doesn't actually involve significant penetrative sex. ~ Amory (u • t • c) 13:28, 27 December 2009 (UTC)

I've seen two documentaries on the pornography business in general. Any woman can get in. Just like any acting, it is mostly just luck to become a star. As for men, both documentaries stated the same thing. Men begin in gay movies and, if they are star quality, they move into hetero movies. Many don't make the jump because the pay drops severely for men when they move from gay to hereto movies. The exceptions are very rare. For example, some lady wrote into her contract that she would only do anal sex with her husband. So, he got to be in her movies - but unpaid. Both documentaries also pointed out that the modern (post-VHS) pornography business is very different from the 50s through the 70s when the business was still run like a movie business. Now, it is a distribution business. The product is not important, just the quantity and availability. -- kainaw™ 03:34, 27 December 2009 (UTC)

Are you saying that all men who are in porn were in gay porn first? Dismas|^(talk) 06:12, 27 December 2009 (UTC)

yeah, that seems like an implausible reality. DRosenbach ^{(Talk | Contribs)} 13:57, 27 December 2009 (UTC)

I agree, very implausible. --Tango (talk) 14:49, 27 December 2009 (UTC)

Apparently some people need to read up on what "exceptions" means. I personally haven't tracked the filmography of every male porn actor. I am only relaying the content of two documentaries. -- kainaw™ 16:18, 27 December 2009 (UTC)

Nowadays, with internet distribution, naught but self-censorship prevents anybody from filming themselves doing whatever they want and attempting to sell it. The difference between art, blogging, and pornography is a very thinly legislated line that serves mostly for marketing purposes; there is no shortage of upscale user generated content/amateur pornography which is marketed as art of varying grades; etc. Probably the best answer to this question can be found in the humorous set of FAQs on Wikipedia's own Talk:Penis:

“ Q3: I would like to upload a picture of my penis.

A3: Unfortunately, the realities of supply and demand are not in your favor. There is a large supply of Wikipedia editors willing to photograph their penis in the name of science. However, the demand is much lower. If you feel that your penis is more deserving of placement on the article page, you are free to make your case below.

”

The same is probably true of male pornography - the reality of supply and demand does not favor males entering the industry. One way to change that equation is to act in alternative pornography, where there is (presumably) less supply. But nothing requires any member of the pornography community to ever act in anything they do not consent to (this is a well-defined legal distinction between a consented and non-consented act, e.g. exploitation or human trafficking). As such, the only barrier to males' porn success is marketability - the reality is, there is less demand for them. Nimur (talk) 17:24, 27 December 2009 (UTC)

I know what "exceptions" means - you said they were very rare. That may be true, but it sounds implausible to me. --Tango (talk) 17:46, 27 December 2009 (UTC)

The answer to both questions has changed slightly over the last few years as "home-based" porn has turned out to be rather profitable. Our articles on Heather Harmon and Wifey's World indicate that the answer to 1) is "with no trouble at all" and the answer to 2) is "have a hot wife". Your mileage may vary an enormous amount, of course. The old story about males having to go through gay porn first is probably not as entrenched as it used to be; the easiest way to become a male porno actor these days appears to be by simply buying a decent digital video camera, hiring the girl for POV work, and working out some kind of distribution deal either through an existing network or by starting up your own website/mail order. Matt Deres (talk) 19:37, 27 December 2009 (UTC)

LOL, By the way, if there's a science to pornography, I may have to go for my MSc! Do they still comp you for home study? Matt Deres (talk) 01:01, 28 December 2009 (UTC)

Yes Matt, with a big thesis you may matriculate. Cuddlyable3 (talk) 18:55, 30 December 2009 (UTC)

The association between gay (homosexual) pornographic performers and the aesthetic criteria for straight (heterosexual) male performers has a reason. The typical straight male viewer would like to identify himself with the male actor and what he is doing. This is easiest if the actor meets homoerotic desiderata such as being youthful, athletic, hairless and able to demonstrate genitalia that are physically dominating or even over-normal in erect size, activity and ejaculate volume. Preference for a particular straight male performer has nothing to do with how attractive he is to females, a lot to do with his availability, capacity for continual production and ability to act as ordered (read: not lose erection and ejaculate only when told to do so). There is no strong need to show a male's face in straight pornography but it is almost essential to show a female's face.Cuddlyable3 (talk) 01:35, 29 December 2009 (UTC)

Big bang?

Certainly there is substantial evidence of cosmic expansion, but what is the evidence restricting this expansion to only empty space? I mean, to say something is not expanding is like saying that it's not a part of the universe. The Earth is expanding underneath us while we all and everything around us expand as well. Considering its size though, the earth expands quickly in relation to us, so gravity, right? It seems they're trying to make this expansion be relative to some fixed point, but that leads back to a big bang which mathematically has been shown not to work. --Neptunerover (talk) 03:55, 27 December 2009 (UTC)

Um..what? Sorry, it's just not clear to me what you're saying. The Earth is not expanding appreciably, and any minute changes that occur in its volume are not related to the metric expansion of space. The expansion of space can truly be thought of simply as solid objects getting farther apart. And where has the big bang been shown mathematically not to work? I think that would be news to a lot of physics enthusiasts at this desk. Someguy1221 (talk) 04:07, 27 December 2009 (UTC)

Sorry, I think I mixed two questions there, really, I hadn't meant to bring gravity into it initially when I started the question. Isn't the big bang in conflict with quantum mechanics because of how it tries to jam a whole universe into a little plank space? I thought I read something about that anyway. I'm just wondering what the proof is that things are staying the same size relative to the space between them expanding. --Neptunerover (talk) 04:29, 27 December 2009 (UTC)

(EC) Gravity is NOT caused by earth's expansion. The earth is NOT expanding. Who is that 'they' you are talking about? The Big bang expansion is not relative to a fixed point. And the Big bang has NOT been shown not to work. Dauto (talk) 04:10, 27 December 2009 (UTC)

I guess I mean the scientists who study the expansion of the universe. And by the way, how could gravity from expansion be disproved? Constant acceleration. Its the same thing whether the earth is pushing us or pulling us.--Neptunerover (talk) 04:35, 27 December 2009 (UTC)

Disproved? Occam's razor isn't a proof, but there are lots of bizarre explanations that would account for ordinary phenomena in bizarre-seeming ways. I'm not sure we disprove them, so much as go with models that make more sense to us... -GTBacchus^(talk) 04:38, 27 December 2009 (UTC)

Exactly, make as few assumptions as possible. Constant size is an assumption, though a very understandable one to make. Einstein taught us though about relative perspectives being equal. Is the Earth pushing, or is it pulling. You say tomato...--Neptunerover (talk) 04:49, 27 December 2009 (UTC)

Except that the earth expanding model doesn't work. Try explaining how come the surface of the earth does not hit the moon within your expanding earth thingamagick model. Dauto (talk) 05:57, 27 December 2009 (UTC)

That's just a reverse of the same model, though instead of using size as a fixed reference point, it switches over to space.--Neptunerover (talk) 06:07, 27 December 2009 (UTC)

I understand what you are saying. But the problem is that this alternate model DOESN'T WORK. If the earth were expanding at such a rate it would hit the moon in short order. Dauto (talk) 06:13, 27 December 2009 (UTC)

I mean the Big Bang uses size as a fixed reference point while planets bulging into each other is just a switch of reference points. The goal should be to avoid those.--Neptunerover (talk) 06:14, 27 December 2009 (UTC)

Meaning please... Dauto (talk) 06:17, 27 December 2009 (UTC)

Okay, the big bang model keeps everything the same size, with only the distance between celestial objects changing. The opposite model would keep the spaces between everything constant while the objects increase in size, filling the space between them until there is no more empty space. Neither of those models works, so the space between objects expands while the objects expand as well. With everything expanding at the same time, it's not something that can be measured except against how it was in the past. It can only be indirectly verified, with redshift and I think, gravity. --Neptunerover (talk) 06:44, 27 December 2009 (UTC)

Why does space expanding not work? The space between gravitationally bound objects doesn't expand, is that where the confusion is coming from? --Tango (talk) 00:16, 28 December 2009 (UTC)

Space expanding works, but just not by itself. If that were the case, then the distance would increase between everything, causing there to be no local groups of anything. What we call gravity is just another way of looking at the reason there are local systems of planets, stars, etc., which is because space alone does not expand. With the space between the planets doubling in the same time that the planets double in size, there would be no noticeable change in the size of these things relative to each other, but we would get gravity. --Neptunerover (talk) 02:56, 29 December 2009 (UTC)

Neptunerover, if assuming that everything is expanding affords a better explanation of the phenomena than assuming that everything is staying the same size, then I'd say you've got something. Until then.... I don't see any gain in switching to that extremely counterintuitive model. Can you come up with some experiment that would distinguish everything-growing from not-everything-growing? If not, then it's not a testable hypothesis, and it's not in the realm of science at all. -GTBacchus^(talk) 06:58, 27 December 2009 (UTC)

See, that's why I asked the question. I noticed in a few articles where the assertion is made that the expansion is not in the size of things, but only in the space between them, but there's no citation for that, so I'm just a David Hume here saying, how do they know? If expansion is limited to only certain parts of the universe, then, why? I think it makes more sense the other way, and I think it sort of solves some things too. Like how can the universe be so young with all we know about the age progression of stars.--Neptunerover (talk) 07:29, 27 December 2009 (UTC)

Is there a constant for the gravitational force that could be compared to the rate of the accelerating universal expansion? That could be sort of like a test, I think.--Neptunerover (talk) 08:28, 27 December 2009 (UTC)

With that though, something may need to be accounted for with the Doppler effect, since with this idea of a uniform expansion, the distance between objects will not increase as much as it would if they were to stay small while just separating in space.--Neptunerover (talk) 08:54, 27 December 2009 (UTC)

With another way of looking at gravity (not a better way, but just another way(assuming it fits all the evidence)), maybe that could help people in figuring out a way of repelling it. Hey, and if nobody could copyright that, wouldn't it be great? --Neptunerover (talk) 10:06, 27 December 2009 (UTC)

Ok, wait a second. Neptune, just so I'm completely clear on what you're saying... Based on this section of your talk page, you are suggesting that the sensation of gravity may be interpreted not as us being pulled toward the Earth, but rather as the Earth pushing up against us as it expands? Is that right? Someguy1221 (talk) 10:20, 27 December 2009 (UTC)

I think so. When we consider we're dealing with spacetime, then maybe thinking of cosmic expansion as being an expansion through time as opposed to an expansion through space (which would be like an explosion) could help overcome this counterintuitive concept of an incessant bulging of everything. But what would expansion through time be? Another tricky hurdle of thought is required for that. --Neptunerover (talk) 11:24, 27 December 2009 (UTC)

Looking around us, even though everything is bulging, we don't see things bulging, because of what everything is bulging in relation to, which is nothing. Looking at it this way, the Earth stays the same size because there is nothing for it to be getting bigger than (Like the big bang has everything start from nothing, but if everything is getting bigger than nothing, does that require any actual change in size? With nothing to compare size to, I'm not sure there would be a noticeable size difference in things that are expanding in relation to nothing.) So the Earth gets bigger in relation to nothing, meaning its size stays the same. But if the earth is now staying the same size, what about gravity? It's the interchangeability of space and time that lets us keep the earth the same size in space while it remains expanding forward in time, and gravity is then the response to that expansion. That's what I'm thinking anyway.--Neptunerover (talk) 11:55, 27 December 2009 (UTC)

How does something "expand in time"? And why are space and time interchangeable? I'm no scientist, but I've hung around this refdesk for a while and I've never heard of either of these concepts. Vimescarrot (talk) 13:25, 27 December 2009 (UTC)

I just meant moving forward in time while considering what could possibly be a cause of that. --Neptunerover (talk) 20:06, 27 December 2009 (UTC)

I was thinking of spacetime as needing to remain steady, meaning if one thing occurs in space, then it needs to be accounted for in time as well, and vice versa. --Neptunerover (talk) 22:13, 27 December 2009 (UTC)

There is just one problem with this model: IT DOESN'T WORK! To create a sensation of gravity through expansion the earth's surface would have to be expanding at a rate of 9.8 m/s². Other planets with different surface gravity would have to be expanding at different rates to match their surface gravities. That does not fit your uniformly expanding universe. Your model is also unable to explain gravity's inverse square law. This model is no-good. Dauto (talk) 14:13, 27 December 2009 (UTC)

Okay. I thought it seemed too easy. --Neptunerover (talk) 14:55, 27 December 2009 (UTC)

I think you are confused about how the equivalence principle applies. It does not at all imply that the Earth is expanding—it implies that our sensation of gravity is completely physically equivalent to constant acceleration. Those are not the same thing, at all. --Mr.98 (talk) 15:36, 27 December 2009 (UTC)

So it doesn't imply the Earth is expanding, but rather accelerating in all directions at once. I get it. --Neptunerover (talk) 20:42, 27 December 2009 (UTC)

And that fits right along with the universe accelerating in all directions, so I think you're right. --Neptunerover (talk) 21:05, 27 December 2009 (UTC)

Maybe they should call it cosmic acceleration in all directions instead of expansion or inflation, which gives the impression of an explosion outward.--Neptunerover (talk) 22:19, 27 December 2009 (UTC)

OK, I'm now convinced that you are just playing around. --Mr.98 (talk) 00:07, 28 December 2009 (UTC)

I am sincerely not trying to play with or fool around with anyone. I'm just playing with an idea, and if it's right, then there is no proof for this non-uniform cosmic expansion model they're trying to push. I'm not saying it therefore must be wrong. How would I know? I certainly don't know all the details. It just seems to me they're assuming something without there being a valid basis for doing so, and so I came here wondering if there is any actual proof. I don't think they can prove that some things are expanding in relation to nothing while other things are staying the same size in relation to nothing. The word 'nothing' by itself does not indicate a size. You cannot say (the)nothing is small or that it is big, since these terms only apply to actual things that can be measured. (the)Nothing is absent of anything measurable, and so measuring anything in comparison to it is folly. Even trying to explain it could be folly because sentences don't only mean one thing. I just think for the big bang to suggest that universal expansion is an expansion in the size of the universe in comparison to nothing is absurd.--Neptunerover (talk) 04:12, 28 December 2009 (UTC)

The expansion of space is not "in comparison to nothing". The benchmark is the speed of light. See Metric expansion of space. Gandalf61 (talk) 07:21, 28 December 2009 (UTC)

Hey yeah, it mentions right there in [1.1] about expansion into time, which I was asked about before. So I thereby cannot be accused of making things up.--Neptunerover (talk) 07:53, 28 December 2009 (UTC)

Okay, let me look up this speed of light thing. --Neptunerover (talk) 07:53, 28 December 2009 (UTC)

Sorry, but I'm lost on what you mean by the benchmark of lightspeed. That sounds like another frame of reference, but doesn't the speed of light always recede as you approach it, like a rainbow? --Neptunerover (talk) 08:21, 28 December 2009 (UTC)

Not like a rainbow (which is a fixed angle, though perception of distance varies with terrain), but asymptotically (i.e. we can get as close as we like to it, but never reach it in finite time). Dbfirs 09:04, 28 December 2009 (UTC)

thanks for the term. --Neptunerover (talk) 11:03, 28 December 2009 (UTC)

Maybe the problem is that there are two ways of approaching the speed of light. One is through time, and the other is through space. Through space would be measured by size and mass, while through time would be what, energy? --Neptunerover (talk) 08:45, 28 December 2009 (UTC)

Don't you need both space and time to measure any speed?
Like you, I have never been happy with red-shift explained by receding galaxies or by expansion of inter-galaxial space. I have always felt (intuitively) that we are missing a wider viewpoint that would explain observations, but I don't think expansion (or contraction) of the local metric provides any alternative explanation. Meanwhile, metric expansion of 3-D space (excluding gravity-bound clusters such as galaxies) into the dimension of time seems to fit the observations, so it seems to be the best model at present. Dbfirs 09:13, 28 December 2009 (UTC)

I'm not sure time is well enough understood to say something like that. There's that problem with not being able to get a reading on both a particle's location in space and velocity. Maybe that is because the particle's velocity is through time, whatever that might mean...?Neptunerover (talk) 11:03, 28 December 2009 (UTC)

IT rather surprises me that anybody ready to embrace an expanding earth would be worried about an expanding universe being absurd. Rest assured though. There is no reason to worry. The universe expansion is a fairly simple thing. It's nothing more than the idea that the galaxies are moving away from each other. That movement has been clearly observed through the doppler effect. Most galaxies' light is observed to have a redshift which means they are moving away from us. Dauto (talk) 13:43, 28 December 2009 (UTC)

... or that the doppler effect is caused by some other aspect of space-time that we don't understand?
Does metric expansion of inter-galactic space imply that far-distant galaxies are actually travelling away in the sense of a real velocity? Dbfirs 14:48, 28 December 2009 (UTC)

Yes. By definition if their distance from us is increasing over time than they are travelling away. But extra care must be taken whenever talking about the speed of a distant object such as a distant galaxy. Unlike local movement It is NOT impossible for a distant galaxy to move away from us faster than the speed of light. Dauto (talk) 16:06, 28 December 2009 (UTC)

Point taken. I have this intuitive distinction between "relative velocity" meaning increasing distance with time, and "travelling" meaning "covering distance over time". I agree that, since there is no preferred inertial reference frame, the distinction is only in my imagination. Dbfirs 23:31, 28 December 2009 (UTC)

Small text is by Ref. Desk convention used for frivolous interjections. It should not be used for interpolative debating on the subject, neither by the OP, nor by someone who doesn't sign their post, and especially not by someone who lives in the error that IT'S is a posessive pronoun, as in the nonsensical construction "it's velocity is". Cuddlyable3 (talk) 00:52, 29 December 2009 (UTC)

I apologize, I've never experienced small text, and I was unsure how to respond to the small text that was in front of a paragraph of regular sized text, while making it clear the response was to the small text, so I thought responding with small text might work. I should've signed both sections I added with the one edit, and that was my mistake. (I'll copy the signature now to show when it was added.) --Neptunerover (talk) 01:21, 29 December 2009 (UTC)

... and I apologise for starting the small text with a comment that wasn't really frivolous. Dbfirs 07:38, 29 December 2009 (UTC)

Using successive indents (do by starting a post with colon(s) ) is the best way to show whether one is posting to an existing discussion thread like this one, or one may start a new thread without indent. Dbfirs in this manner I added to your indent and hope you don't mind. Cuddlyable3 (talk) 22:58, 29 December 2009 (UTC)

Not at all. (I hesitated on the indent because I was replying to both of the previous edits.) Dbfirs 12:31, 31 December 2009 (UTC)

diamond vs ceramics

Is diamond a ceramic? give reasons. —Preceding unsigned comment added by Kumar 3069 (talk • contribs) 07:06, 27 December 2009 (UTC)

That certainly sounds like a homework question, apologies if that assessment is wrong. There's plenty of information in both the ceramic and diamond articles that should allow you to reach a conclusion. If there's something you don't understand, then come back and ask a specific question. Mikenorton (talk) 12:12, 27 December 2009 (UTC)

Interesting question. Unfortunately, I don't know the answer. The Wikipedia page on ceramic has this description:

“ A ceramic is an inorganic, non-metallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous (e.g., a glass). Because most common ceramics are crystalline, the definition of ceramic is often restricted to inorganic crystalline materials, as opposed to the non-crystalline glasses. ”

It seems that the answer to the question hinges on the definition of ceramic. Diamond meets the criteria of being inorganic, non-metallic, solid, and crystalline. The part that's not so clear is whether it is "prepared by the action of heat and subsequent cooling." Heat is involved in at least some methods of synthesizing diamond, but whether that counts as "prepared by the action of heat and subsequent cooling" I don't know.

Can someone versed in material science provide a technical definition of what ceramic is? --71.185.178.230 (talk) 17:53, 27 December 2009 (UTC)

It may also depend on your definition of "organic". One sometimes sees chemists who will expand the title of "organic" to all carbon-based compounds even when they aren't associated with living things. Dragons flight (talk) 16:15, 28 December 2009 (UTC)

That was close to the generally accepted definition of 'Organic compound' when I studied chemistry decade or four back. Although the term 'organic' in this context originated in the belief that only life could create some compounds, which all happened to contain carbon, it was realised in the early 19th century that this was not so (see Organic chemistry) and the term was extended. Our article Organic compound currently says "There is no "official" definition of an organic compound. Some text books define an organic compound as one containing a C-H bond. Others state that if a molecule contains carbon it is organic."

With regard to the OP's question, does not the term 'ceramic' implicitly refer to manufactured materials? This would exclude natural diamond and similar substances; synthesized versions might be open to argument. 87.81.230.195 (talk) 02:15, 29 December 2009 (UTC)

Our article on solids says that ceramics are polycrystals (i.e. contain "grains"), which diamonds would not. Our articles seem not to concur as to whether this is part of the definition or just something that's typical. If someone does indeed know the answer to this question, the articles I've linked to (and ceramic) need to be harmonized. Matt Deres (talk) 04:47, 28 December 2009 (UTC)

It would seem that an agreed definition of ceramic does not exist [1][2][3][4][5]. Most authors, but by no means all, seem to be excluding diamond either explicitly or implicitly. SpinningSpark 03:12, 29 December 2009 (UTC)

Most diamonds aren't true perfect crystals (e.g. a lot of interstitial impurities) but AFAIK the amount of vacancy "holes" is very low relative to most metals and ceramic materials. Though I wonder about the interfacial impurities of diamond...I get the feeling that poorly connected "interfaces" simply fall apart (into separate diamonds). Compared to metal-metal bonds, C-C covalent bonds are very strong. Ceramic materials (homogeneous or heterogeneous) made of organic compounds, e.g. organic polymers are held together by hydrogen bonding, polar/ionic interactions and Van der Waals. Ionic bonds, while fairly strong, are fairly labile and easy to displace with other ionic bonds. This is prolly responsible for why diamond doesn't behave like many ceramic materials. AFAIK this makes diamond have very low molar entropy values -- because C-C bonds aren't very labile -- so there isn't a lot of room for "disorder" in diamond, (kinda why graphite is thermodynamically favoured over diamond at lower pressures).John Riemann Soong (talk) 08:36, 29 December 2009 (UTC)

nanocrystalline materials

What are the applications of nanocrystalline materials in automobiles? —Preceding unsigned comment added by 117.204.22.16 (talk) 07:12, 27 December 2009 (UTC)

Modern electronics rely heavily on semiconductors, which can be described as nano-crystalline materials. Nearly every modern automobile will contain at least a few semiconductor parts for control, power regulation, sensors, and any onboard computers. Nimur (talk) 17:39, 27 December 2009 (UTC)

Semiconductor devices usually are monocrystalline, not nanocrystalline. -Yyy (talk) 09:48, 28 December 2009 (UTC)

I don't think "nanocrystalline" is a well-defined term. Our article, nanocrystal, provides a definition, but I'm not certain it's in wide use. Nimur (talk) 00:53, 30 December 2009 (UTC)

Naked Singularities, Hawking Radiation, and Quantum Gravitation

Well, today I for no reason suddenly started to think about Black hole electrons. Well, but as the mass of a blackhole decreases, its Hawking Radiation should rise and electrons therefore are not stable. But then I knew if the electron was a blackhole, it would have to be a Naked Singularity. I then looked on the article for Hawking Radiation. Well, the sentence "Hawking radiation is required by the Unruh effect and the equivalence principle applied to black hole horizons" under "Emission Process" immediately caught my eye. So is it that Naked Singularities do not radiate Hawing radiation? Or (assuming electrons are black holes) they don't emit radiation just for some other reason like because the energy is more than the total energy of an electron(obviously including the mass energy from $E=mc^{2}$)?The Successor of Physics 14:31, 27 December 2009 (UTC)

That analysis relies on semiclassical theory, and only makes sense for black holes with masses much larger than the Planck mass. Otherwise the notion of Hawking radiation is not applicable - you need quantum gravity. 69.140.13.88 (talk) 16:33, 28 December 2009 (UTC)Nightvid

Tomato

Are tomatoes vegetables, or fruits? Or both? cheers--79.38.22.37 (talk) 15:37, 27 December 2009 (UTC)

See tomato and let us know if you have further questions. -- kainaw™ 16:20, 27 December 2009 (UTC)

Indeed. The article has an entire section that answers this. Ultimately, this is a question better suited for the language desk, because it deals with contextual word usage and the ambiguity of vernacular English. Both fruit and vegetable (...and tomato!) are terms that mean different things in different contexts. Typically, only "fruit" has a well-defined scientific meaning; in such a context, the tomato is clearly defined as a fruit. Nimur (talk) 17:33, 27 December 2009 (UTC)

According to Wiktionary, a Vegetable is:

1. Any plant.
2. A plant raised for some edible part of it, such as the leaves, roots, fruit or flowers, but excluding any plant considered to be a fruit, grain, or spice in the culinary sense.
3. The edible part of such a plant.

So a Tomato is a vegetable under (2) - but in a culinary sense, it's not considered to be a vegetable if it's also a fruit/grain/spice.

The Wiktionary definition of a fruit is:

1. (botany) The seed-bearing part of a plant, often edible, colourful/colorful and fragrant, produced from a floral ovary after fertilization.
2. Any sweet, edible part of a plant that resembles seed-bearing fruit, even if it does not develop from a floral ovary; also used in a technically imprecise sense for some sweet or sweetish vegetables, such as rhubarb, that resemble a true fruit or are used in cookery as if they were a fruit.

The Tomato is the seed-bearing part of the plant - it's edible, colorful and fragrant and it comes from the floral ovary - so there is utterly no doubt that it's a fruit under any sense of the term.

But under the definition (2) of "vegetable", it's ALSO a vegetable...unless you are talking in a culinary sense - in which case it's only a fruit.

However, people misuse the words "fruit" and "vegetable" all the time. Scientifically - they are definitely fruit AND also vegetables. In culinary usage - they are technically only fruit - but they are rarely called that because they aren't sweet like most other fruit. In common parlance they are almost always called vegetables. In government regulations, they are all over the map. It's a mess. But from a scientific perspective - they are most certainly fruit. SteveBaker (talk) 17:39, 27 December 2009 (UTC)

Actually, you have one bit backwards. A tomato is only a culinary vegetable, and not a culinary fruit, because it is used in savory applications. From a culinary (cooking) perspective, a fruit is something used in sweet applications, while a vegetable is used in savory applications. This is different from the botanical definition of fruits, a tomato is a botanical fruit because it is the seed bearing part of the plant. All culinary fruits are also botanical fruits, but there are MANY botanical fruits that are culinary vegetables. See also cucumber, squash, eggplant, chili pepper, etc. etc. which are, like tomatos, also botanical fruits, but not culinary fruits. In the botanical world, the word vegetable has no meaning, since vegetable is used only in the culinary world. A plant scientist would use words like "stem" or "leaves" or "fruit" to describe plant parts... --Jayron32 21:16, 27 December 2009 (UTC)

Not if you trust Wiktionary. It's saying that while scientifically, all fruits are also vegetables - in culinary terms, something is either a fruit or a vegetable...never both. But the dictionary definition of a fruit is unambiguous for things that are scientifically fruits - and only difficult in culinary terms when things like Rhubarb is considered to be a fruit. I don't see any way (with the Wiktionary definitions) for anyone to legitimately claim that a Tomato is NOT a fruit...although only non-culinary applications of the term 'vegetable' apply to the Tomato. I can't find another way to interpret that...unless of course Wiktionary is wrong. SteveBaker (talk) 03:11, 28 December 2009 (UTC)

What??? Steve, I can't really follow your logic here. Using the definitions you report (I won't check Wiktionary now because it might have changed in the mean time), a tomato is not a fruit under definition (2), because it's not sweet. So that means it does satisfy definition (2) of vegetable, because the exclusion "unless considered to be a fruit...in the culinary sense" does not apply (again, because it's not sweet).

Am I missing something in your argument? As far as I can see it's pretty simple: "Not sweet" implies "not a culinary fruit". (Except, I guess, for fruits that are so sour that it's difficult to taste their sweetness, but that are usually used with added sugar — I'm thinking of e.g. lemons here.) --Trovatore (talk) 07:36, 28 December 2009 (UTC)

"From a culinary perspective, a fruit is something used in sweet applications" ... "All culinary fruits are also botanical fruits" is arguable, I'd say. Rhubarb would likely be considered a fruit by most cooks (as "something used in sweet applications") but it's definitely not a botanical fruit. Carrots, however, quite firmly classed by cooks as a vegetable, are delicious in a "sweet application" such as carrot cake or Christmas pudding. The distinction isn't important (unless you're a government official trying to create red tape). Tonywalton ^Talk 01:36, 28 December 2009 (UTC)

Well, there aren't bright lines here; there are some foods that will stradle some of these distinctions; however those are very few. --Jayron32 01:52, 28 December 2009 (UTC)

Nonlinearity of the sRGB and Adobe RGB color spaces

The Wikipedia articles on sRGB and Adobe RGB articles state that both color spaces are nonlinear (with the latter having a gamma of 2.2 and the former approximately 2.2). So does it mean that if you use an image editor to create composite of a 50%-opaque image superimposed on another, 100%-opaque image, you are not getting the same resulting image as you would if you project the two source images onto the same reflective screen at half intensity? It seems to me that such non-linearity would create all sorts of unexpected weirdness when one is using an image editor, but I never noticed any. What gives? Do image editors internally use representations that are linear w.r.t. intensity when applying transformations and remap the pixels to the nonlinear color spaces on saving? Or is it true that the working representations are actually nonlinear, just that any "unexpected weirdness" is not noticed by most people? --71.185.178.230 (talk) 18:29, 27 December 2009 (UTC)

Bear in mind that the gamma in the image file is intended to counteract the 'typical' non-linearity present in the display device - such that when you double the brightness going into the image - you get twice the amount of light coming out again. Hence, you certainly wouldn't expect the results of adding two non-linear things together. Since gamma(a)+gamma(b) is not equal to gamma(a+b) - you would not expect your experiment to work unless the image editor is handling it right. In an ideal world, the loader for the sRGB image would convert it into a linear image for editing and convert back into non-linear as it displays it and when it writes it out to disk again...however, that's not always done properly - and a lot depends on which image editor you're using. But slightly more concerning is that you're talking about compositing by transparency...and that gets complicated since it depends on whether the alpha channel is also gamma-corrected. The whole thing is a bit of a mess...complicated by the fact that it's rare for any real-world display to have a gamma of 2.2 and not something wildly different. SteveBaker (talk) 02:59, 28 December 2009 (UTC)

Sound pressure, sound intensity, sound loudness, and decay with distance

This webpage http://www.sengpielaudio.com/calculator-ak-ohm.htm says that: "The sound pressure level (SPL) decreases with doubling of distance by (−)6 dB..... The sound pressure decreases with the ratio 1/r to the distance.

The sound intensity level decreases with doubling of distance also by (−)6 dB...... The sound intensity decreases with the ratio 1/(r^2) to the distance.

The loudness level decreases with doubling of distance also by (−)6 dB..... The loudness decreases with the ratio 1/(2^0.6)r = 1/1.516r to the distance."

My questions: a) how is the result "loudness decreases with the ratio 1/(2^0.6)r = 1/1.516r to the distance" obtained and is it correct? b) Is "loudness level" as described on that webpage the same as how subjectively loud a sound-noise is measured in db? c) What would sound intensity be in layperson's terms if it is not subjective loudness? d) Elsewhere on the page a "cylindrical wave" is mentioned. What would that be? Thanks. 92.24.73.139 (talk) 19:21, 27 December 2009 (UTC)

See Loudness and Stevens' power law for some of the ways in which people have tried to quantify psychological responses to stimuli. The equation you have a question about above is basically Stevens' power law for hearing. Stevens based his law by taking average results across a large number of people; basically its a law based on repeated experimental trials. It works a lot like the Scoville scale does for chili pepper hotness; its based on interviewing many many many people on their perception based on quantifiable initial conditions. For hearing, what you do is you place someone in an environment with a certain dB at a certain distance from the source, and then you ask them to rank their perception of the loudness of the sound. --Jayron32 21:10, 27 December 2009 (UTC)

The page means by "cylindrical wave" a wavefront that is spreading on a cylidrical surface. A wave emanating from a point in all directions will spread on a spherical wavefront. This is not usually particularly useful for sound systems as it wastes power sending some of up into the sky and into the ground. To generate a cylindrical wavefront the generator needs to be a line rather than a point. A column loudspeaker unit with drivers facing in all (horizontal) directions will approximate to this, see line array. A cylindrical wavefront spreads out in two dimensions only rather than three. SpinningSpark 22:16, 27 December 2009 (UTC)

Your power law for loudness doesn't look right. wouldn't it be 1/r^0.6 ? Dauto (talk) 01:30, 28 December 2009 (UTC)

I don't know, that's why I'm asking. 89.242.213.201 (talk) 10:41, 28 December 2009 (UTC)

The website's formula is wrong. Dauto (talk) 14:34, 28 December 2009 (UTC)

No it's not wrong, they are just not very clear in what they are saying. The basic relationship here is that subjective loudness is roughly reckoned (at most frequencies and levels) to double with an increase of 10dB sound level. This is an inexact relationship as it involves messy human beings. For a given decibel increase the loudness increases by x 2^dB/10. For a doubling of distance the sound level change is -6dB and consequently the loudness change is 2 ^{- 0.6}. SpinningSpark 22:56, 28 December 2009 (UTC)

And 2 ^{- 0.6} is not the same thing as 1/(2^0.6)r which shows that they are wrong. Dauto (talk) 06:21, 29 December 2009 (UTC)

Yeah, they're wrong. SpinningSpark 13:20, 29 December 2009 (UTC)

PTSD and hippocampus

In the page on PTSD, it says that Vietnam soldiers with PTSD were shown to have hippocampuses 20% smaller than avg. I had part of my hippocampus taken out and have been diagnosed with PTSD and mentioned that point to my neurologist and he said that such claims were purely anecdotal. Should that part be edited? —Preceding unsigned comment added by BroncoBuff (talk • contribs) 20:00, 27 December 2009 (UTC)

Discussion of a specific page should go on the respective Talk page, in this case Talk:Post-traumatic stress disorder. If the claim regarding the hippocampus is poorly-sourced, then editing may be necessary. If it has reliable sources, then one should support alternative viewpoints supported by similarly-reliable sources (conversation with a neurologist not being one of those). -- Scray (talk) 20:22, 27 December 2009 (UTC)

An interview with a neurologist would be a reliable source if it were published in a third-party, reputable journal or news outlet. If you conducted the interview yourself (presumably in the process of dealing with your own situation), then it constitutes original research and can't be cited in the article. There should be no shortage of research into physiological manifestations of PTSD - Hypotheses and controversies related to effects of stress on the hippocampus: An argument for stress-induced damage to the hippocampus in patients with posttraumatic stress disorder. (Journal of Hippocampus, 2001, vol. 11), seems to be a a good review of the different viewpoints about this particular physiological effect. Jeez, there's a journal for everything!Nimur (talk) 20:40, 27 December 2009 (UTC)

Let me note that our hippocampus article has some information on this. The basic story is that there is extensive evidence that many types of long-term stress, including PTSD, are associated with reduced hippocampal size -- we even have a pretty decent understanding of the biological mechanism by which stress damages the hippocampus. There is, however, no evidence that I am aware of that damage to the hippocampus can cause PTSD. Looie496 (talk) 15:47, 28 December 2009 (UTC)

Finite element method - solid or shell?

When using a linear FE code such as NASTRAN or a non-linear code such as LS-DYNA, when should you use solid elements instead of shells?

I.e. If the shells thickness is 5mm could a shell element of 1mm x 1mm be used? If not why not and what happens to any theoretical assumptions used? —Preceding unsigned comment added by Cjread58 (talk • contribs) 20:32, 27 December 2009 (UTC)

Solid element FEA is much more computationally intense than shell based methods. In return, it usually better matches the real-world physics. However, depending on your actual problem and parameters, this extra accuracy may be unneeded. It may also lead to instabilities. As far as element size, you might want to read the CFL condition for numerical stability. Also note that in addition to numerical stability, your element size also determines your smallest resolvable feature (or highest resolvable spatial frequency, if you prefer to think in that domain). See sampling or resolution (we appear to be lacking an article about the generic mathematical/sampling meaning for "resolution", but most other uses (e.g. optical resolution) follows the same conceptual rules as the generic-case numerical system. Nimur (talk) 21:06, 27 December 2009 (UTC)

Lost question

I wrote question a few days ago. it seems to have got lost or erased. Why is a gyroscope stable when spinning, but not when still? —Preceding unsigned comment added by 79.75.24.71 (talk) 23:32, 27 December 2009 (UTC)

I would tell you to look at the gyroscope page, except that the explanation there, while it might be technically correct, is pretty useless. If you understand the explanation - you don't need it. If you need an explanation, the one there will not help you. I would suggest using other resources besides wikipedia. Ariel. (talk) 00:59, 28 December 2009 (UTC)

Hey, Ariel — how about giving a try to improving that article? Comet Tuttle (talk) 01:08, 28 December 2009 (UTC)

angular momentum conservation. Dauto (talk) 01:21, 28 December 2009 (UTC)

Here's my attempt at a non-mathematical explanation. You can compare a fast-spinning gyroscope to a fast moving object, such as a bullet in space (no gravity). A small amount of momentum change in the bullet perpendicular to the bullet's direction of travel is not going to alter significantly the direction of travel. It is for a similar reason that a small amount of angular momentum change (proportional to torque × duration of torque application) is not going to change significantly the orientation of the gyroscope. It is important to know that this is true only when the angular momentum change is small relative to the angular momentum the spinning rotor has. The system of gimbals in a gyroscope allows the spinning rotor to be in any orientation relative to the enclosing environment to which the gyroscope may be mounted. In other words, the gimbals prevent transfer of torque to the spinning rotor. When the rotor is not spinning, even small angular momentum change can alter its orientation significantly. This is because, compared with zero (or something very close to it), even quantities otherwise considered quite small is quite large. --71.185.178.230 (talk) 17:24, 28 December 2009 (UTC)

An even simpler response would be to compare almost any object in motion, such as a spinning top or a running human, with that same object at rest. The chief concept is that, in motion, balance can be often be found even in a position that, if maintained during rest, would not exhibit balance. Thus, a top at rest cannot be balanced on its point and a human with many of the freeze-frame positions of running would not be balanced if the runner would be at rest. DRosenbach ^{(Talk | Contribs)} 19:22, 28 December 2009 (UTC)

While that appeals to a familiar observation, I don't think that's much of an explanation. --71.185.178.230 (talk) 20:27, 28 December 2009 (UTC)

71.185.178.230 - did you learn your explanation somewhere, or did you make it up? Because it doesn't sound right to me. And DRosenbach, 71.185.178.230 is right - that's not much of an explanation. A spinning top is stable because it is a gyroscope, not because it's moving. And human running is not stable at all, the human is constantly inputting energy to keep upright. Ariel. (talk) 21:39, 28 December 2009 (UTC)

I came up with the explanation myself. Which part of the explanation do you have a problem with? --71.185.178.230 (talk) 21:47, 28 December 2009 (UTC)

The whole thing. Force causes an affect relative to mass. It makes no difference how much momentum is already in the device. In your bullet explanation: The bullet is moving left, and you are pushing it down. The motion down will only care about how much force it was given in the down direction. It does not care at all about the motion to the left. If you measure how far down it travels after a certain time, that amount will be identical, no matter how fast it's going to the left. Ariel. (talk) 21:57, 28 December 2009 (UTC)

What you missed is that, in the bullet example, although the change in vertical motion (and velocity in particular) is not affected by the horizontal velocity, the amount of deflection (measured as an angle) is. The situation with a gyroscope is wholy analogous: the spinning rotor carries a certain amount of angular momentum, which determines its axis of rotation. If the angular momentum is large, small angular impulses (from sources such as air movement, friction at the gimbal joints etc) are not going to affect the angular momentum of the spinning rotor enough to affect the axis of rotation by much. Think of it this way: the angular momentum of the spinning rotor is a (long) vector in 3D space; the small external angular impulse is another (short) vector in 3D space. The vector sum of the two (and the direction it points at) is dominated by the long vector. --71.185.178.230 (talk) 22:21, 28 December 2009 (UTC)

I don't understand gyroscopes very well, but my best explanation of them is this: Imagine an upright gyroscope. (i.e. a wheel parallel to the ground, eg a sideways bicycle). Press down on one side of the gyroscope, and it will start to move down, causing the whole thing to tilt sideways. But one moment later, the part of the gyroscope that was moving down, is now on the other side of the gyroscope. It's still moving down. But now it's causing the whole thing to tilt in exactly the opposite direction. Ariel. (talk) 21:50, 28 December 2009 (UTC)