Wikipedia:Reference desk/Archives/Science/2015 March 4

= March 4 =

risk of cancer from oral sex
According to Wikipedia on oral sex there is a 250 percent increased risk of cancer if one has one to five oral sex partners. What is the average lifetime risk for developing head and neck cancer in percentage? — Preceding unsigned comment added by 199.119.235.240 (talk) 01:17, 4 March 2015 (UTC)
 * What article did you get that 250% info from? ←Baseball Bugs What's up, Doc? carrots→ 01:21, 4 March 2015 (UTC)


 * With two cites no less! Sir William Matthew Flinders Petrie &#124; Say Shalom! 13 Adar 5775 01:27, 4 March 2015 (UTC)


 * We can't give medical advice, see your doctor, and mention that according to our archives you have a compulsion to ask this question every few months  in public fora, because he can probably also help you with that issue as well. c (talk) 03:07, 4 March 2015 (UTC)

What are you talking about I have a compulsion? — Preceding unsigned comment added by 199.119.235.240 (talk) 03:39, 4 March 2015 (UTC) This is the first time I've posted her. — Preceding unsigned comment added by 199.119.235.240 (talk) 03:41, 4 March 2015 (UTC)

Instead you could be more polite and simply say we don't give medical advice instead of implying a personal attack that I'm mentally ill.
 * Your style is similar to that other user that you claim not to be, so it's not difficult to jump to a conclusion. As to mental illness, nobody said that except you. It's time to see your doctor. ←Baseball Bugs What's up, Doc? carrots→ 08:20, 4 March 2015 (UTC)

Apologies for the would-be Internet cops who clearly don't realize that this is a common fear, getting more popularity since various celebrities have been reported to possibly have throat cancer (e.g. Val Kilmer), and people nowadays recognize the link with human papillomavirus - to which a vaccine, trade name Gardasil and Cervarix, is available (though many right-wingers indignantly refuse to vaccinate their kids; I think their thinking is wrong but I have to agree with their point that schoolkids shouldn't be forced to take vaccines that don't affect disease transmission at school). There's an interesting anomaly that Gardasil is apparently not promoted to protect against throat cancer, but HPV 16 causes much throat cancer and is a target of the vaccine - I assume that this is because of the relative rarity of the condition but I don't actually know. Wnt (talk) 13:18, 4 March 2015 (UTC)


 * on the implication that those who come from right-wing backgrounds are less likely to vaccinate their children against this (or any) disease? Let's avoid making generalizations along ideological lines unless it's a sourceable statement that might be of use to our OP. Last I heard about the statistics on this issue, people were much more divided primarily by nationality on this issue, first and foremost; the biggest uptake in participation in HPV vaccination has been Australia, which has a strong conservative movement and has seen increasing ubiquity of vaccination amongst women.  And within a given nationality, it's often along different lines than the "right vs. left" divide.  You seem to be speaking to the American context, but you know what? You'd probably be wrong even there, because, while the tendency is the U.S. may be to see conservatives as more apt to deny consensus science, it's actually been observed broadly in journalism on the specific issue of the anti-vaccine movement in the U.S. that it's strongest base is composed largely of those who identify as being on the left... Mind you, I warrant the issue is somewhere in the middle, but as to your assertion, I'd recommend striking it if you don't have a source.  Otherwise it's just subjective WP:OR judgement/guesswork.  S n o w  I take all complaints in the form of epic rap battles 14:36, 4 March 2015 (UTC)

Well, sorry for overreacting to that person. — Preceding unsigned comment added by 199.119.235.240 (talk) 13:27, 4 March 2015 (UTC)

When he said that i should see a doctor about my compulsion I thought he was accusing me of ocd. — Preceding unsigned comment added by 199.119.235.240 (talk) 13:45, 4 March 2015 (UTC)


 * I don't defend the way Medeis handled this, but on the other hand, they and BB weren't the only one who came to that conclusion. I wouldn't have said anything because I didn't think it mattered (I wasn't aware at the time the editor in question had been blocked for sockpuppetry), but I also didn't bother to properly read the question and so wouldn't have said anything. My point is that without defending the way tis was handled, there is a potential net benefit here since me, and perhaps others may be willing to WP:AGF when you say you aren't the same editor yet I and perhaps others may have just ignored your question otherwise.
 * Anyway a simple search for 'life time throat cancer risk' will probably find either or . The former says "Lifetime Risk of Developing Cancer: Approximately 1.1 percent of men and women will be diagnosed with oral cavity and pharynx cancer at some point during their lifetime, based on 2009-2011 data". The later has 1.55% for men for "Oral cavity and pharynx", and 0.67% for women. The risk of dying from it is also present. These are only some of the cancer types covered under Head and neck cancer. The later link seems to have larynx. It doesn't seem to have trachea, it's possible this is too rare, or alternatively it's included in the other stats. The former ref doesn't have larynx directly, but if you browse around the site view the other "more cancer types", you should end up at  which will link to larynx . It doesn't have trachea either, not particularly surprising since these are different subdomains of the same site so I expect their data may be the sme. Also this is for the US, not other countries.
 * If you're asking specifically about the lifetime risk of head and neck cancers for people who have had "one to five oral sex partners", I have strong doubts that level of detail has even been studied sufficiently to provide a reliable answer, but I could be wrong.
 * Nil Einne (talk) 14:06, 4 March 2015 (UTC)
 * There's evidence enough the two are the same person, but the issue here is, if the OP is worried enough about the topic he should see a doctor who can examine him, vaccinate him, and assure him much better than we can. μηδείς (talk) 16:57, 4 March 2015 (UTC)
 * If the OP isn't the same person, then we have no clear evidence the OP is "worried enough about the topic". That said, I do agree with their latest responses, they are showing strong signs they are the blocked editor. Nil Einne (talk) 15:43, 5 March 2015 (UTC)


 * Note that a 250% increase on 1.1% is 3.85%. Even if you believe the numbers from the study apply to the real world (they never do), you can have all the oral sex you want and still have a 96.15% shot at not getting throat cancer. Or greater, considering a good chunk of that 1.1% were already having oral sex. InedibleHulk (talk) 20:14, 4 March 2015 (UTC)
 * This is a very good conceptual point to make. We can multiply very tiny percentages of incidence by huge numbers, and still get tiny incidence rates. E.g. I wouldn't mind increasing my risk of lightning strike sometime in my life by 1000% . SemanticMantis (talk) 20:28, 4 March

Will I be able to find the lifetime risk for people with more than 5 partners (I misread the article) by simply adding 250 percent to 1.1 percent?
 * No. For starters you shouldn't be adding but multiplying. Second, the average lifetime risk would likely include people with more than 5 partners, and people with less. Finally, combining results like that is never likely to produce anything close to a reliable answer. Nil Einne (talk) 15:39, 5 March 2015 (UTC)


 * Also, both numbers are almost absolutely meaningless. If you repeated the 250% study the exact same way, with a different group of 300 people (under a millionth of the US population, way smaller than the world), you'll get a different number. You can replace the variable "had oral sex" with "watched TV", "drank wine", "wore purple" or anything you want, and always find a result that either suggests the variable causes or prevents cancer. And you will always find someone to publish that suggestion as a fact in the headline.
 * It doesn't have to be cancer, either, but it usually is, because there's an enormous surplus of cancer research donations, and every day, that pile gets bigger. InedibleHulk (talk) 19:14, 5 March 2015 (UTC)


 * The 1.1% is a bit more legit, but that depends on what's already happened, and constantly changes according to what happens later. You can't use it to predict things. InedibleHulk (talk) 19:15, 5 March 2015 (UTC)

Why does stuff have color?
OK, the short answer is that different materials absorb different wavelengths of light, but why do different materials absorb different wavelengths of light? And how materials that are totally different have the same color, and things that all most the same have different color?--Noopolo (talk) 01:34, 4 March 2015 (UTC)
 * Read color (and quantum mechanics if you want). Basically, the color you perceive depends on lighting, how the material absorbs and reflects wavelengths differently, and how your brain interprets that in the context of surrounding visible materials. μηδείς (talk) 03:11, 4 March 2015 (UTC)


 * Color has much more to do with human biology than it does with physics. I always recommend this video, made by an alien, for a funny (and very accurate!) explanation of color.  --Bowlhover (talk) 08:56, 4 March 2015 (UTC)


 * As noted above, color is a psychological/neurological effect, and not a physics one. It is influenced by physics, of course, but it isn't primarily a physical phenomenon: it is primarily a function of how your brain interprets the images coming into it, and your brain does a LOT of funny stuff to give you impressions of color.  See Qualia, particularly the quote from noted physicist Erwin Schrödinger regarding color.  -- Jayron 32 14:18, 4 March 2015 (UTC)


 * Eh, that's the third person whose supplied an answer here which is technically correct but not very helpful to the exact issues inquired about by the OP. And mind you, I'd be the first person to take the discussion in the direction of colour perception, as visual cognition with regard to this topic is very much my wheelhouse.  But the OP is clearly inquiring as to the materials science side of things--that is, the physical phenomena rather than any interaction between stimulus and visual sensorium.  No aspect of the mechanisms of the eye or the visual centers of the brain explains why two different materials have the same colour; if a photon strikes a photoreceptor, the receptor doesn't differentiate based on the material which reflected the light.  All that matters is the wavelength and so long as that is identical, and it struck the receptor in the exact same manner, the perception would be identical in both events.


 * , please see chromophore, optics, pigment and (of course) color and let us know if you have any more specific inquiries.  S n o w  I take all complaints in the form of epic rap battles 15:00, 4 March 2015 (UTC)
 * Emission spectrum describes the spectral lines that compounds emit. There's a large set of articles linked from them, but I couldn't find a good layman's overview. LongHairedFop (talk) 15:17, 4 March 2015 (UTC)
 * Yes, the issue (however) is that with the fact that something has an emission spectrum which has a specific color in it has little to do with our perception of color. Here are just a myriad of issues with thinking about spectral lines as "color"
 * 1) There's no functional difference between spectral lines which have wavelengths our visual systems can perceive and those that don't. That is, because a spectral line happens to lie in the UV range or IR range doesn't mean anything physically.  It's a total coincidence
 * 2) There are lots of other sources of light than electronic transitions (i.e. Bohr model stuff). For example, blackbody radiation, reflection, absorbtion, Iridescence, fluorescence, phosphorescence, etc.
 * 3) Even with all of that, there's very little physical connection between our perception of a color, say "yellow", and say a coherent light of 580 nm wavelength. Yes, we would perceive that light as yellow, but we would ALSO perceive as yellow lots of things, many of which may not have any light of that wavelength.  We can even perceive colors which have no spectral equivalences, things like brown and purple and the like.  Plus, there's various ways in which the environment a material is in that affects what color we see.  This page shows ways in which even the "matrerial science" answer is entirely inadequate.  Even with all of the same physical factors, simply putting an object next to different objects changes what color it is.
 * Simply put, there is no "physics of color" in any meaningful sense. Again... don't take my word for it.  Erwin Schrödinger, a physicist who has far more importance to the physics world (and the study of light and waves and all sorts of physicsy stuff) said "The sensation of color cannot be accounted for by the physicist's objective picture of light-waves. Could the physiologist account for it, if he had fuller knowledge than he has of the processes in the retina and the nervous processes set up by them in the optical nerve bundles and in the brain? I do not think so."  What seems like a simple question, like "What makes something yellow" just cannot be answered with a simple discussion of wavelengths of light.  -- Jayron 32 15:39, 4 March 2015 (UTC)
 * Eh, that's a little pedantic, in my opinion.  Don't get me wrong, I'd happily talk about colour as a perceptual/cognitive/conceptual/contextual (look through the archives and you'll see just how verbose I can be on those topics, which have consumed a not insubstantial part of my life), but again, that's just clearly not what the OP is seeking here.  Here's his direct inquiry: "Why do different materials absorb different wavelengths of light? And how materials that are totally different have the same color, and things that all most the same have different color?" He's asking specifically why certain materials reflect certain wavelengths of light.  That question is answered purely through the language of physics; psychophysiology can't inform upon the topic of colour until the light reaches the eye.


 * So yes, of course a complete understanding of colour as a complete phenomena is deeply predicated upon physiological and cognitive mechanisms of the person who perceives it (I believe I stipulated as much in my first comment and it's hardly something I'm about to deny), but looking at Noopolo's question, he is clearly talking about how objects composed of matter emit or reflect the light properties they do. And it's not a trivial distinction. Other creatures have photoreceptors which are keyed to different wavelengths or neural networks (not always brains) which process them in different ways and cause a different subjective experience. Even amongst humans, there's noticeable variation in a difference in perception between individuals and context.  But the light in question still has general physical principles that remain the same, no matter the different responses it elicits in different organisms, and that is what this thread (at least in-so-far as it is defined by the OP's question) is about.  S n o w  I take all complaints in the form of epic rap battles 17:17, 4 March 2015 (UTC)

Moon floating away
What would happen if the moon were to float away from the earth? Would the effects be catastrophic? — Preceding unsigned comment added by 199.119.235.240 (talk) 05:51, 4 March 2015 (UTC)


 * Well, it would take a huge force to cause it to do that, and that force would likely effect Earth, too. But, ignoring that, the absence of the Moon would mean greatly reduced tides (the Sun would still cause minor tides).  The intertidal zones would be greatly disrupted, and many plants and animals dependent on those tides would die.  Salinity would be reduced in-shore, without tides to bring in salt-water, and that would favor some plants and animals over others.  Some animals, like moths, may also use reflected moonlight to find mates, etc.  So, it would cause a disruption, but life would adapt. StuRat (talk) 06:57, 4 March 2015 (UTC)


 * The Moon is actually currently floating away from Earth, at (I think) 4 cm per year. Earthquakes and volcanic activity is decreasing frequent. Earth will become tidally locked to the Sun - always facing the same side. A tidally locked Earth is a barely survivable scenario, scorching hot on the day side and polar winter on the night side, and chaotic weather on the twilight zone. I dare say yes, it will be catastrophic - life will be surviving instead of thriving. Plasmic Physics (talk) 12:07, 4 March 2015 (UTC)


 * Careful you don't mix up your tidal locks! It's true that the earth-moon distance is increasing, and the earth's rotation is slowing, due to the tidal locking effect between the earth and the moon. It's already the case that the same side of the moon faces the earth all the time, and that will eventually be true of the earth as well -- that is, the moon will stay over one spot on the (rotating) earth the whole time.  At the very least this will be very sad for all the other parts of the earth that won't have a moon to see at all any more, but it's got nothing to do with the earth becoming tidally locked to the sun.  That would take muuuuuuch longer.  (In fact, according to our tidal locking article, the earth won't even become tidally locked with the moon before the sun becomes a red giant and engulfs us both.) —Steve Summit (talk) 14:08, 4 March 2015 (UTC)


 * What evidence is there for a reduction in frequency of either volcanic activity or earthquakes? Mikenorton (talk) 12:32, 4 March 2015 (UTC)


 * The same tidal effect that makes the ocean move up and down a couple of times a day is also exerting a force on the rocks below our feet. Those forces contribute to the likelyhood of that kind of activity. SteveBaker (talk) 15:32, 4 March 2015 (UTC)
 * I'm aware that even minor effects such as unusually heavy rainfall have been known to trigger earthquakes (not cause them - they would have happened anyway eventually), I was just questioning Plasma Physic's assertion that earthquakes and volcanoes are less frequent, although I'm not clear over what timescale that claim is being made. Mikenorton (talk) 20:39, 4 March 2015 (UTC)


 * I meant 'trigger'. Plasmic Physics (talk) 11:14, 5 March 2015 (UTC)


 * See this BBC documentary at YouTube: Do We Really Need the Moon?. &#8213; Mandruss  &#9742;  12:12, 4 March 2015 (UTC)

Tidal effects stopping tectonic plates fusing
Inspired by the above question, does the Moon's tidal effect, which flexes the Earth's crust slightly, help stop the tectonic plates fusing together? LongHairedFop (talk) 12:27, 4 March 2015 (UTC)


 * That question is addressed here, concluding that tides do influence plate tectonics. Mikenorton (talk) 12:37, 4 March 2015 (UTC)


 * I'm not sure whether a tidal affect is required for plate tectonics, but I do know that the Earth will die without it. Plate tectonics are required to prevent the outer core from solidifying like what happened to Mars. When that happens, the planetary magnetic shield collapses, allowing the protective ozone layer to be overwhelmed and depleted by incoming ionizing solar radiation. All life, except for extremophilic microorganisms, will die from radiation. Overtime, the Earth's water will be radiolysed to hydrogen and oxygen. The resulting hydrogen in the atmosphere will be gradually depleted, blown away by space wind, to use common language. So, Earth will dry out and even those extremophiles will eventually die out, and Earth will look very much like Mars does today. Plasmic Physics (talk) 11:35, 5 March 2015 (UTC)


 * How exactly does plate tectonics keep the core from solidifying? Also, I thought there was ongoing thought that Mars has a liquid core; the question was controversial, but I recall the liquid faction was ahead by a nose. Wnt (talk) 22:53, 5 March 2015 (UTC)


 * Plate tectonics act to moderate the cooling process. When there are no tectonics, subsurface heat accumulates and is released sporadically during periods of extreme volcanic activity. When this happens, there is a sudden dump of heat from the asthenosphere. The cycle of accumulation and dumping causes a planet to cool much more rapidly than if the lithosphere was non-continuous. Plasmic Physics (talk) 22:15, 7 March 2015 (UTC)


 * . It seems to me there are basically three scenarios.  1) No convention, i.e. a stable mantle that dissipates heat via conduction only, which applies to relatively small / cool objects that don't produce more radioactive heat than can be dissipated by conduction alone.  2) Stable convection / plate tectonics, i.e. a mantle that continuously moves and routinely transfers heat via both convection and conduction.  3) Unstable convection, where radioactive heat accumulates and periodically leads to overturning or other abrupt pulses of convection.  I assume the first scenario is generally the slowest at dissipating heat.  However, my guess would be that over long time periods a world with continuous convection and plate tectonics would on average be dissipating more heat than one that had only periodic outbursts, even though the periodic outbursts could be transiently very large.  Do you have a source to the contrary?  Also, for some range of mass / temperature a world in the first category might also maintain a molten core for a while without having plate tectonics.  Dragons flight (talk) 23:30, 7 March 2015 (UTC)


 * I don't remember which New Scientist article it came from, but I remember tectonics being discussed in reference to Mars, Earth, and Venus; how Mars conforms to scenario 1, Earth conforms to 2, and Venus conformed/s to 3. I also remember that it discussed how in theory these outbursts, according to scenario 3, is in the long term much more efficient at overall heat transfer than scenario 2. Compare it to these two scenarios, which stays warm longer: a cooling oven with a door which is very slightly ajar, or an oven which is regularly opened and closed? Plasmic Physics (talk) 02:21, 8 March 2015 (UTC)


 * Which cools faster, an object that loses 5% of its heat per minute, or an object that loses 50% of its heat once every 20 minutes and no heat at other times? The answer is the first one for this hypothetical.  Change the numbers and it could be that the second scenario cools faster.  It's not obvious to me what numbers apply to planets, but my guess is that overturning events ought to be pretty infrequent, which would make it more likely for first scenario to win.  Dragons flight (talk) 17:59, 8 March 2015 (UTC)


 * I can't add more to the argument without the original article. Plasmic Physics (talk) 21:41, 8 March 2015 (UTC)

Why do physics textbooks come in "with Modern Physics" and "without" versions?
I checked the latest editions of Sears, Zemansky, & Young; Serway; and Halliday & Resnick-- they all do it, where the two books are identical except about six or seven chapters on relativity, quantum mechanics, nuclear physics, and cosmology are in the "with" versions. Why? 20.137.2.50 (talk) 16:54, 4 March 2015 (UTC)
 * One version for college and the other high school? Roger (Dodger67) (talk) 17:36, 4 March 2015 (UTC)


 * Accreditation! Thanks to the arcana of academic politics, textbooks are designed to fit into either a 2- or 3-course long series on physics.  Textbook publishers segment the material along these lines: first, mechanics; next, electromagnetics; and finally (the optional third segment) on "modern physics."  Most accredited universities in the United States are able to offer a "minor in physics" by teaching only the first half or the two-semester course, and eventually granting a Bachelor of Arts in (Something) with a Minor in Physics.  The very same class can serve as the first two-thirds of an introductory physics track for major students or engineering students.
 * Nimur (talk) 17:40, 4 March 2015 (UTC)
 * The other advantage to the publishers is selling two books/editions, instead of one. Sort of doubles their market. In theory, the shorter courses could use the longer book, but not over all of it. Similar to the idea of coming out with a new edition every year that features only minor updates and some new homework problems. Some related info at Textbook, . SemanticMantis (talk) 20:03, 4 March 2015 (UTC)