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March 3

Rapidly turning on and off an LED lamp

I remember as a kid I was always told not to turn the lights on and off rapidly because it would make the bulb burn out faster. Is the same true for LED lamps or is it safe to rapidly turn them on and off without any adverse effects? ScienceApe (talk) 00:41, 3 March 2015 (UTC)

The answer is not appreciably. In fact one the very things that make LEDs so useful is their ability to turn on and off very rapidly, such as in fiber optics or optocoupler. Also, since an LED is either on or off, you can't reliably make it "half as bright" like a lightbulb by giving it less current, the way you typically controll an LEDs brightness is by using Pulse-width_modulation which also turns the led on and off typically in the KHz range, which surprisingly is not mentioned in the article, but does not appreciably reduce the life of the LED.. Vespine (talk) 04:15, 3 March 2015 (UTC)

Not true. LED brightness is almost linearly related to drive current. There's lots of discussion (some of it wrong) on the web, but this gives some graphs. Typically, LEDs are run at high current with low duty cycle to give them a high perceived brightness. However, they could also be run at 100% duty cycle and variable current to provide varying brightness.--Phil Holmes (talk) 10:46, 3 March 2015 (UTC)

Ok, I did get that one fact wrong, but it doesn't invalidate my response to the OP. It is true that typically, LED brightness is adjusted using PWM, especially in applications where the LED brightness needs to vary, i.e. is not fixed. LED drivers for displays use PWM, not varying current. Vespine (talk) 22:52, 3 March 2015 (UTC)

I just read Phil's user page :) Let me just add, I'd trust him more than me on this subject. :) Is the rest of my response "roughly right" Phil? I'm actually a big fan of LEDs and I have made a few LED projects, one I'm particularly proud of but it's a far cry from making lasers and pin diodes in a professional capacity ;) Vespine (talk) 22:58, 3 March 2015 (UTC)

It's certainly true that a key feature of LEDs is their ability to be switched on and off quickly. It's made optical communications (and therefore telecommunications/the internet) what it is today. I would say that, as a general rule, LEDs are used as being either on or off: it's not common to modulate their intensity. However, given that they are almost always pulsed in use, then using pulse width modulation would certainly be an option if you wanted to do this.--Phil Holmes (talk) 10:36, 4 March 2015 (UTC)

Reading your question again, my reply specifically refers to the diode part, however an "LED LAMP", especially one you can stick into a domestic light socket is typically far more than just "a lighe emitting diode" or two. It's usually a bunch of components, resistors, capacitors, rectifiers, if it's fancy even some sort of control IC. These components might very well be far less forgiving to fast switching and fail far sooner than the actualy LED part of the lamp. Vespine (talk) 04:21, 3 March 2015 (UTC)

I agree that you might hypothetically be right - but LED's are DC devices and we're feeding them with AC current - so there must be some circuitry to take care of that - which probably slows down switching transients to the point where they're not a problem. At any rate, if there is a problem, it is entirely negligible compared to the issues of rapidly switching incandescent lamps. SteveBaker (talk) 04:03, 4 March 2015 (UTC)

Basic science: Switching incandescent bulbs off and on stresses the glass-to-metal seal, thus, leading to an early lose of vacuum.--Aspro (talk) 00:25, 4 March 2015 (UTC)

I'm gonna call [citation needed] there (it's possible, but I can envision other possibilities too). There are lots of mechanical details that could potentially fail, and possibly due to changing thermal stresses. It seems like it would be easy to determine which one is most common. DMacks (talk) 18:18, 4 March 2015 (UTC)

Why didn't this hurt? (Not medical advice)

So here's a question I've had for a while and I don't think it qualifies as medical advice as it's something fully In the past that no longer affects me in any way (except that I do have a fantastic scar). Anyway, at the start of last summer, I managed to cut open the radial artery in my right hand whilst in Israel. For those who want to survey the damage to give a better answer/like seeing this kind of thing, here's a lovely picture of it popping up to say hi to everyone. After six hours and losing a litre of blood, the doctors (who spent most of the time bickering with each other as Israeli doctors are known to do) finally managed to get the artery cauterised and the wound stitched up. I was prescribed beer (to drink only with my left hand), and sent back to my friends' house without painkillers or any supplies.

Now an odd thing about this particular injury is that I never felt pain from it any point. Not when it was cut open (though there was a feeling of warm liquid on my hand and something draining out of me at times), not when I had it wrapped in paper towels and a hand towel, not when the doctors ran it under water for no good reason, nor when they unwrapped my bandage and had me hold my hand over a sink so they could argue with each other while I watched my life fountain out of my hand into the drain and nearly passed out from blood-loss, etc. In fact, the only time I felt anything was the searing intense pain when the doctor cauterising the artery—which really does smell like chicken—accidentally touched a bone.

I could attribute this to shock (as the whole time I was making morbid jokes and feeling loopy), but even the next day I felt no pain (remember there were no painkillers), and not any time after. There was no nerve damage, and there was still glass in my hand (as evidenced by the glass I pulled out a week later even though my hand had been x-rayed twice). Occasionally if tried working with my bandaged hand in the first week of digging (which started three days after the incident) to pick up a pickaxe or use a handpick, it would hurt from the vibrations, but otherwise nothing.

So, anyway, my question after all of this is this: why the heck didn't I feel any pain from this thing? Again, I don't want any advice on what to do as it's a nice healthy scar that doesn't unthreatening me in any way, shape, or form, and I don't plan on opening up any more arteries as I hate not being able to do heavy work on digs for two week. I just want to know why it never caused me pain even though it was a potentially fatal injury. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 12 Adar 5775 01:51, 3 March 2015 (UTC)

Some parts of the body are less sensitive than others. Consider getting a flu shot or whatever. It's a needle poking into your arm, but it's not particularly painful. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:04, 3 March 2015 (UTC)

When I was 5, I managed to put my arm through a window and slice it open. I had stitches and still have a scar, but, like you, there was no pain. I do recall the stitches itching, though. So my theory was that there was nerve damage. I have full nerve function there now, so, perhaps due to my young age, I was able to regenerate those nerves. StuRat (talk) 04:25, 3 March 2015 (UTC)

This one basically cut through the artery and somehow avoided the radial nerve. I only felt some loss of sensation between the knuckles of my index and middle fingers (which came back after four months–I'm 25, so don't know if that helped). They tested for nerve damage (which felt weird because I had to watch and it felt like something would pop out of the hole in my hand) and found nothing wrong. My stitches also itched a bit (especially as they got covered in sweat). Sounds like a badass scar though, Stu. Maybe it's a sort of prolonged shut-down response (after shock has subsided) so your body doesn't process what should be agonising pain? We're not talking minor pin-pricks in either case, but rather massive damage. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 12 Adar 5775 04:49, 3 March 2015 (UTC)

Oh, come on Sir William Matthew - you may feel like you're only 25, but by my reckoning you're almost 162 years old! Richerman (talk) 10:50, 3 March 2015 (UTC)

Ha, that's what I get for naming my account after Petrie.... Sir William Matthew Flinders Petrie | ^{Say Shalom!} 14 Adar 5775 23:08, 5 March 2015 (UTC)

Have you read Acute stress reaction? How about Nociception#Regulation, or Pain#Theory? Also check out pain tolerance and the distinct pain threshold. I doubt you can get conclusive answers, but food for thought at least. Also I thought at least one person should provide some references, and wanted to congratulate you on your injury :) SemanticMantis (talk) 15:15, 3 March 2015 (UTC)

I'm also wondering now about how 'clean' the wound was. WP:OR: getting sliced by a razor hurts way less then being mauled by a saw, no matter where on the body it occurs... cuts from very sharp objects are generally preferable to those incurred by dull blades, in terms of healing time, scarring, stitches, pain, etc. SemanticMantis (talk) 01:04, 4 March 2015 (UTC)

Oooh, these are useful. Thanks, Semantic! And thank you for the grats. It was a very good object lesson for the noobs about always paying careful attention. One that I shall use for years to come.

I would say not clean at all. It was basically a freshly broken otherwise sturdy section of plate glass that I guess fell against my hand and then on the ground. It also left a nice little piece in my neck that avoided anything carotid-like (also shredded some lovely cotton-linen trousers of mine and cut the sides of my driving loafers, though the latter were at least salvageable after I got the blood out using my trusty saddle soap). It seemed to be fully healed after a week and then the stitches were left in for another week. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 14 Adar 5775 23:08, 5 March 2015 (UTC)

Reference 4 in 'Malnutrition in South Africa'

Hi there,

I am looking for the actual reference for reference 4 in 'Malnutrition in South Africa', as the link is unfortunately invalid. ( http://en.wikipedia.org/wiki/Malnutrition_in_South_Africa#cite_ref-Malnutrition_in_South_Africa_4-1 ) The reference is ""Malnutrition in South Africa". Retrieved10 December 2012." The invalid link is http://myfundi.co.za/e/Malnutrition_in_South_Africa

Thank you very much for your time. I am currently looking into volunteering for Wikipedia myself and really appreciate your help.

OliviaOlivia Beth G (talk) 11:46, 3 March 2015 (UTC)

Hi Olivia, a few things: First, welcome to Wikipedia! Feel free to be WP:BOLD, and if you see a problem, WP:SOFIXIT - WP only exists because people like you want to make it better. If you need help learning how to edit the article, include the citation, etc, you can ask at WP:HELPDESK. You can also try this tutorial/game thing called Wikipedia:The_Wikipedia_Adventure.

Now, for this issue - the best place to post this problem (which is link rot) is on the talk page for that article [1]. But it is also fine to post it here.

As for the broken link - we could probably use the wayback machine to find the version of the page that as originally cited, even though the link no longer works. Another alternative is to find other references that say similar things. For instance, here [2] is a journal article that found 27.3% incidence of anemia among 2-year-olds in South Africa. Probably better references can be found (this one is a little old), but that's the first one I got. If you need help accessing the full article (or other similar), you can ask at WP:REX. Good luck, and thank you for helping to make WP better :) SemanticMantis (talk) 16:02, 3 March 2015 (UTC)

I've checked the wayback machine, and unfortuanatly, the page isn't archived by it. I've added a { {deadlink} } to it. This records that the link is broken, and puts it on a list of pages to be fixed, but there is a sizable back log. LongHairedFop (talk) 16:06, 3 March 2015 (UTC)

You can try asking the folks at WT:WikiProject South Africa, we're friendly and some of us have a talent for finding good sources. Roger (Dodger67) (talk) 17:41, 4 March 2015 (UTC)

Why does hyperglycemia not cause necrosis?

The whole question is: why when administrating glucose in the vain and it's going outside the vain (para) it causes to necrosis while hyperglycemia (more than 500 mg/dl) doesn't causes necrosis? (It's about the explanation of this phenomenon. not medical advice). Thanks 11:52, 3 March 2015 (UTC) — Preceding unsigned comment added by 149.78.32.22 (talk)

Intravenous sugar solution is 5% = 5 g/ 100 ml = 5000 mg/dl = 50g/l. Hyperglycemia is dangerous over 300 mg/dl. I think the effect of missing the vein is simple osmotic shock from that very high concentration of solute in the sugar solution, which is required in order that a reasonable volume have an effect on the entire blood supply. Wnt (talk) 14:04, 3 March 2015 (UTC)

When the glucose outside of the cell, which one pumps the other?

When glucose found in high concentration outside the cell, which one pumps the other? Is the cell pumps the glucose (and in this way the cell is going to die) or the high concentration of the glucose pumps the cell's content (and in this way the cell is going out of life). Thanks — Preceding unsigned comment added by 149.78.32.22 (talk) 12:01, 3 March 2015 (UTC)

Read the article titled Glucose transporter. --Jayron32 12:04, 3 March 2015 (UTC)

Your question "which one pumps the other" is unclear. According to the article Jayron32 linked to, the process is facilitated diffusion, not pumping (which would require energy). Glucose enters cells if the concentration is higher on the outside than the inside, which is usually the case for an energy-consuming cell. Glucose doesn't kill cells, as you seem to imply. Cells use glucose as fuel, and some cells additionaly build large glucose polymers (glycogen) for use as energy storage. In diabetes the problem is dysregulation of the facilitated diffusion, resulting in a surplus of glucose on the outside of cells that are starving. The "pumping" or rather "facilitated diffusion" is catalyzed by proteins that sit in the cell membrane. Some cells can synthesize glucose (gluconeogenesis), and release it to the environment for the benefit of other cells. Some cells, especially liver cells, assemble glucose into glycogen when supply is high (after a meal), and break down the glucose and release it between meals, thus keeping the glucose concentration in the blood fairly constant. In the kidneys, glucose is actively reabsorbed from the pre-urine against a concentration gradient (i.e. "pumped", to avoid loss of an important nutrient) in a process that requires energy (see Glucose uptake for the details). --NorwegianBlue ^talk 18:01, 3 March 2015 (UTC)

Can humans live with other apes?

Considering that there’ve been anthropologists who’ve lived with foreign people, has anybody ever attempted to live with non‐human apes in the wild? And while I’m at it, is it possible for chimpanzees and humans to co‐exist pacifically? Sorry if these questions sound weird but considering how similar hominids are, I thought that it might still be at least possible. --66.190.99.112 (talk) 20:43, 3 March 2015 (UTC)

Jane Goodall is a good starting point. Sir William Matthew Flinders Petrie | ^{Say Shalom!} 12 Adar 5775 21:12, 3 March 2015 (UTC)

Yeah, I was going to suggest Goodall and Dian Fossey, but neither actually lived with them, per se. Besides Tarzan I'm not aware of anyone who has. ―Mandruss ☎ 21:18, 3 March 2015 (UTC)

Generally, in the real world, humans are bad for non-human primates and their survival outlook. Habitat loss, poaching, etc. The International_Gorilla_Conservation_Programme will have a lot more info on the anthropogenic threats to gorillas.

A few human people do spend a lot of time with apes, the most famous are probably Jane_Goodall and Dian Fossey. To those that say they didn't "live with" the apes, I'm pretty sure they would have been camping right near by, and all the local troop members would have known them by sight and smell. A colleague of mine spent a whole summer in Africa camping next to Geladas, and I would describe that as basically living with them... Anyway, you can still easily get Fossey and Goodall's books and read their research papers to see how close they got, and Gorillas in the mist was also adapted into a movie. Chimpanzee#Interactions_with_humans has some relevant info, as does Gorilla#Interactions_with_humans.

It's also good to think about what can happen when chimps live with humans. Travis_(chimpanzee) ripped someone's face off, and Oliver_(chimpanzee) made many sexual advances on human females [3]. SemanticMantis (talk) 21:23, 3 March 2015 (UTC)

• The question might better be, "Can humans live with other humans?" The history of animal rights activists in Sub-Saharan Africa is frightful, see the death sections in the Dian Fossey and Joy Adamson articles, as well as that of Adamson's husband. See also Ernest Gibbins and Category:Murdered scientists as well. μηδείς (talk) 03:16, 4 March 2015 (UTC)

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 | ^{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 [4] [5] 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. Snow ^{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 [6] or [7]. 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 [8] which will link to larynx [9]. 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, March 4, 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% [10]. 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, March 5, 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, March 5, 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. --Jayron32 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.

Noopolo, please see chromophore, optics, pigment and (of course) color and let us know if you have any more specific inquiries. Snow ^{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. --Jayron32 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. Snow ^{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?. ―Mandruss ☎ 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)

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#New_editions_and_the_used_book_market, [11]. SemanticMantis (talk) 20:03, 4 March 2015 (UTC)

March 5

Jet stream clouds?

Can a long, straight cloud like this be associated with the jet stream (upper left to lower right)? It went for as far as I could see in both directions. This was the widest I could get with the lens I had on. This is today's jet stream and the blue area in the southeast US is where I took the photo. (Sorry, it won't let me put in a shortened URL.) Bubba73 ^{You talkin' to me?} 00:39, 5 March 2015 (UTC)

That's a jet contrail, not a cloud. Clouds are never that long, straight, and narrow. ―Mandruss ☎ 00:45, 5 March 2015 (UTC)

But jet contrails can cause clouds to form in their wake. Those clouds are initially long, straight, and narrow, but then tend to diverge in shape. StuRat (talk) 00:57, 5 March 2015 (UTC)

Resolved

Thank you. Bubba73 ^{You talkin' to me?} 00:47, 5 March 2015 (UTC)

When I see such a long URL, I like to try deleting each field to see which of them are redundant. —Tamfang (talk) 08:59, 5 March 2015 (UTC)

I converted it to a tiny URL, but Wikipedia rejected it, saying that it was a blocked site. Bubba73 ^{You talkin' to me?} 00:26, 6 March 2015 (UTC)

A different type of "jet stream", apparently. On youtube I saw a clip that some alert person had uploaded, from a Daniel Boone episode, where someone says goodbye to Fess Parker and heads off into the distance - with a jet contrail clearly visible in the bright blue sky. There weren't really all that many jet airplanes in Boone's day, ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:43, 5 March 2015 (UTC)

Risk of cancer from oral sex: Mark 2

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? — Preceding unsigned comment added by 199.7.159.115 (talk) 00:55, 5 March 2015 (UTC)

Lifetime risk of what ? What article ? StuRat (talk) 00:58, 5 March 2015 (UTC)

Apparent continuation of #risk of cancer from oral sex. There is no need to start a new section, just add to the existing one. ―Mandruss ☎ 01:01, 5 March 2015 (UTC)

No, 250% increase means 2.5x more. So if 1.1% of the population has a condition, and some behavior shows a 250% increase, then you would expect 2.5x1.1% = 2.75% of the people who exhibit the behavior to develop the condition. For this example, lets say that of 1,000,000 people, 1.1% develop cancer. That would be 11,000 people. If all 1,000,000 people performed the risk behavior, that would result in 27,500 people now developing the condition. That doesn't, of course, mean that all 1,000,000 engaged in the risk behavior. Let's say that only 1 in 10 exhibited the risk behavior, that would now result in an extra 2,750 people developing the cancer, on average, of our initial 1,000,000 people. The numbers scale accordingly for your population. --Jayron32 12:54, 5 March 2015 (UTC)

I'm not sure why the OP feels the need to duplicate their questions. But anyway, just to re-iterate a point I made above, I think it's safe to assume the average 1.1% risk includes people who have more than 5 partners/show the risk behaviour. So even if we ignore the problems combining different results (of uncertain reliability), simply multiplying the risk isn't going to I think produce an entirely reliable answer since the 1.1% would be lower if we take out those who have more than 5 partners.

Taking random numbers as examples here, it may be that if no one showed the risk behaviour/had more than 5 partners, the actual average risk would be 1%. So for 1 million people, 10,000 would developed cancer. Under this made up example, those who do show the risk behaviour would have a 2.5% average risk. The reason edit: the average risk is it's 1.1% or 11,000 people out of a million would be because some people are in the higher risk category and some people in the lower risk. (Remember of course we are only talking about one risk factor and averages, in reality, some people would be higher and lower regardless of how many sex partners due to other reasons.) If you do the sums for this random made up example, you end up with roughly 66,670 / 1,000,000 being in the higher risk category for us to end up with the earlier 1.1%. (Meaning ~933,330 people in the lower risk category of which ~9,333 develop cancer, and a further ~1,667 from the 66,670 developing cancer in the higher risk category.)

The numbers who are in the higher risk category are probably small enough that it doesn't make that much of a difference but you'd need to at least look in to this. If most people do have more than 5 partners already, then the number for the average risk for people with more than 5 partners won't be that much higher than 1.1%. Of course just to repeat one more time, combining results from different things like this is not likely to produce a good answer even if you take care.

Nil Einne (talk) 16:21, 5 March 2015 (UTC)

You're at exponentially much greater risk for STD's. ←Baseball Bugs ^{What's up, Doc?} carrots→ 14:36, 5 March 2015 (UTC)

Sounds like someone needs to learn joint probability. The way to find out if you get hit by A or B (e.g. cancer from him, cancer from her) is to take 100% - (neither A nor B). That's (not A) and (not B) and you can figure out those probabilities by just multiplying (bearing in mind of course that "percent" means "per 100", i.e. 100% == 1. So if something has a 1% chance of killing you, and something else 1%, and something else... for 100 times, that doesn't add up to a 100% of being dead. Rather it is 1-( (1-0.01)**100 ) = 63.3%. (To calculate things like this on your own I recommend downloading R programming language. You ought to do many wondrous programming tasks with it, meanwhile it makes a heck of a desktop calculator) Wnt (talk) 22:59, 5 March 2015 (UTC)

Venus and Uranus conjunction

There was a conjunction of Venus and Uranus today, when they were only about 0.1 degree apart (see List_of_conjunctions_(astronomy)#2015). I tried to photograph (just my camera - no telescope) it about 5-1/2 hours after closest approach, but I don't know if I got Uranus or something else. I got something other than Venus. I measured the distance in the photo, considering my camera and lens, and came up with 0.29 degree separation. Since it was about 5-1/2 hours after the closest point, could they be 0.29 degrees apart, or was the next-brightest object something other than Uranus? Bubba73 ^{You talkin' to me?} 04:24, 5 March 2015 (UTC)

How long was your exposure? There is a very easy way to resolve this if you install a program like stellarium. I have it at home but won't be home for a few hours. In this program you simply put in your location and the time and it shows you exactly what the sky looked like. From there you shold be able to compare your photo and fairly confidently say if what you captured was in fact uranus or not. Vespine (talk) 05:56, 5 March 2015 (UTC)

The exposure times ranged from a fraction of a second to about 1 minute. I'll check out that program. Bubba73 ^{You talkin' to me?} 06:03, 5 March 2015 (UTC)

Ok, that is a nice program. That program shows that they had moved a little farther apart. Uranus looked like the right direction from Venus, but the distance seemed wrong. But there was nothing else it could be. Then I realized that when I did my calculations based on my lens' field-of-view, I forgot to take into account the extra factor because the camera uses an AP-C sensor. So it is Uranus. Bubba73 ^{You talkin' to me?} 06:33, 5 March 2015 (UTC)

Well, i for one am impressed! can you upload the pic somewhere? I know it'll probably be just dots but i am a bit of an amateur astronomer (I own a 12" Dob telescope). Vespine (talk) 22:40, 5 March 2015 (UTC)

I don't need no stinkin' telescope! (Actually I have a 6" refractor, but I don't use it for photography.) These were taken with just my camera and what my daughter calls my "big ass lens". At first I could see Uranus only in long exposures were it made a streak. But then I could see it in others when I enhanced them. A link to dropbox. Venus was 9,100 times brighter than Uranus at the time. I think I calculated that Uranus is about 3 pixels wide. Bubba73 ^{You talkin' to me?} 00:52, 6 March 2015 (UTC)

Very nice! I especially like the star effect you're getting on venus there from your lens. Quite beautiful. Vespine (talk) 03:52, 6 March 2015 (UTC)

Yes, the star effect is from the stopped-down lens. I've seen Neptune in a telescope, but I don't think I've ever seen Uranus before. Actually I only saw it in the photos. I need to take the 'scope or binoculars while it is somewhere that I can perhaps spot it. At first I could only see it as a streak in the long photos. There were some thin clouds (as you can see in one of the photos). Enhancing the shorter exposures brought it out.Bubba73 ^{You talkin' to me?} 06:25, 6 March 2015 (UTC)

I've added another one "Venus Low ....jpg" when they are low on the horizon (uncropped but enhanced). The light from Uranus is going through a lot of atmosphere, and it is a speck just barely visible to the left of a tree branch - just barely distinguishable above the camera noise. Bubba73 ^{You talkin' to me?} 06:42, 6 March 2015 (UTC)

What is the thing that causes to contact lenses to be connected to the eyes?

Is it the surface tension?149.78.32.22 (talk) 10:57, 5 March 2015 (UTC)

Read this --Jayron32 12:55, 5 March 2015 (UTC)

If you mean very connected, read this. Usually dryness. InedibleHulk (talk) 21:16, March 5, 2015 (UTC)

See Wetting. Surface tension makes things worse, not better, because it decreases the contact area and hence the total adhesive force. -- BenRG (talk) 23:37, 5 March 2015 (UTC)

Is there an advantage to living in one location at all times?

Many animals live in the open. If they are always on the move, then there is less chance that lurking predators will prey on them and their young. So, why are humans different? Humans have two legs. They CAN move around, if they want to. But they usually stay in one location. Humans are apex predators, but even apex predators must move and follow the prey. Otherwise, they will starve. Perhaps, planting seeds forced early modern humans to settle down and guard the food supply? But what happens if the soil becomes eroded and can no longer support the same crops? What if the sky pours down heavy rain and drowns the crops? What if there is a volcano that destroys all the crops? What if a nearby population of humans spies on another population of humans and conquers the latter tribe and steal their crops? 140.254.136.149 (talk) 21:39, 5 March 2015 (UTC)

Check out Agriculture and Hunter-gatherer for possible insight on why a given culture might choose one or the other. ←Baseball Bugs ^{What's up, Doc?} carrots→ 21:58, 5 March 2015 (UTC)

And see drought, erosion, flood, famine and theft for what happens after those things happen. InedibleHulk (talk) 22:07, March 5, 2015 (UTC)

Sedentism seems appropriate. For the question, anyway. Better article within the article. InedibleHulk (talk) 22:23, March 5, 2015 (UTC)

Staying in one location allows you to build up the defenses there, for one. Castles don't make much sense if you don't stick around for a while. StuRat (talk) 06:44, 6 March 2015 (UTC)

Just ask the blue-throated Common side-blotched lizard, there are advantages and disadvantages. — PhilHibbs | talk 13:28, 6 March 2015 (UTC)

A huge number of animals give birth in a maternity den or live in burrows. Some go nocturnal for the sole reason that their predators aren't. If you can get food without exposing your tasty side, your species will outlive the ones it has delivered.

If we tear down the walls now, we wouldn't see the sort of "apex predator" you think we are. We only got that far by being cowardly. Relative to tigers, lions and sharks, anyway. Very few of us want to be persistent when we can set a trap or shoot from afar, and get back home. That's why they don't name "energy drinks" after us. Only "luxury drinks". InedibleHulk (talk) 21:38, March 6, 2015 (UTC)

Most of what's in structures built by animals applies to you, too. InedibleHulk (talk) 21:44, March 6, 2015 (UTC)

March 6

Can regular cheetoes use really stain your fingers orange?

Question as topic. Sort of along the lines of how smoking unfiltered can turn your fingers brown... Just something that I was discussing with a friend today. --Kurt Shaped Box (talk) 00:44, 6 March 2015 (UTC)

Temporarily, certainly. Surface stains on the skin don't usually last very long. ←Baseball Bugs ^{What's up, Doc?} carrots→ 01:23, 6 March 2015 (UTC)

Oh yes, I know that they can make your fingers orange until you wash it off - but I was meaning long-term, like with cigarettes. Yaknow, if you were to eat cheetoes every day, would little bits of the orange colour stay on your skin and gradually build up? --Kurt Shaped Box (talk) 01:41, 6 March 2015 (UTC)

Cheetos' dyes are presumably excretable; certainly this is true of their "red hot" dye, which in a scene straight out of Cujo sent kids to the emergency room because parents thought they were bleeding internally (difference being that in the real world, this generated nothing but a passing news blip, no "I'm sorry" campaign needed!). The regular version contains (at least) Red 40 Lake, Yellow 6 Lake, Yellow 6, Yellow 5. [12]; in order for it to stain fingers one or more of these would have to find some way to pass into the dermis without interacting with the outer layer of skin, and stably bind onto cells there so that it wouldn't be destroyed. Can I rule it out? Well, no... not without a whole lot of data. But it's hard to picture. To begin with, those sorts of snacks don't even really stain fingers, not like a pomegranate or something (I mean, the old-fashioned super red pipped ones that seem to grow ever rarer; nowadays they don't seem to leave me yellow-fingered at all). You wipe your fingers after Cheetos and the color leaves with the crumbs, is my impression. What the dye does internally is apparently the topic of more spirited discussion, but you didn't ask that. Wnt (talk) 01:59, 6 March 2015 (UTC)

The top layer of skin is regularly shed, so it would have to get below the growing skin to become permanent, like a tattoo. I have a splinter that managed to do that, and the wood stain on it is still there some 30 years later (although greatly faded). So, I suspect a puncture would be needed to get the orange dye that far in. StuRat (talk) 06:40, 6 March 2015 (UTC)

Right. And I would like to see some evidence that cigarette smokers have permanently stained fingers. More likely they appear "permanently" stained because they continue smoking. Like with teeth stained by tobacco use. ←Baseball Bugs ^{What's up, Doc?} carrots→ 17:47, 6 March 2015 (UTC)

It's not a *permanent* stain. It just a stain that takes a while (two or three weeks, I think it was whenever I've stopped) to disappear entirely after you stop smoking. --Kurt Shaped Box (talk) 18:48, 6 March 2015 (UTC)

Bingo. And if you were eating Cheetos constantly for some stretch of time, you might encounter that same problem (among others). Did you try soaping up with the kind you can use to wash off grease and the like? Or maybe a soap like Lava which has particles of pumice? ←Baseball Bugs ^{What's up, Doc?} carrots→ 05:31, 7 March 2015 (UTC)

Seconds of daylight gained or lost

How many seconds of daylight are gained or lost each day after solstice?Joey13952 alternate account (talk) 01:01, 6 March 2015 (UTC)

It isn't a constant number per day, and it varies depending on your exact location on earth. This website has all sorts of tools for calculating all sorts of things, I've linked directly to the page where you can search for the data you seek. Just enter your location, and it will give you tables of sunrise & sunset times, along with calculated time of daylight for any given date. --Jayron32 02:19, 6 March 2015 (UTC)

I believe it's sinusoidal, so there is very little change around the summer and winter solstices, and rapid change near the vernal and autumnal equinoxes. StuRat (talk) 06:18, 6 March 2015 (UTC)

Broadly it is, but because the Earth's orbit is not perfectly symmetrical, it means the behavior of daylight also isn't regular. See Analemma for a related discussion of the apparent position of the sun at various dates. --Jayron32 15:48, 6 March 2015 (UTC)

That's the fine detail. The broad effect is simply the inclination of the rotation axis to the plane of orbit. Dbfirs 16:01, 6 March 2015 (UTC)

Digging into Vesta

The protoplanet 4 Vesta is said to have a differentiated interior - mantle and iron core. It has a radius of roughly 260 km. With gravity just 1/40 that of Earth's (and considering that it drops to zero at the middle) that should be the rough equivalent pressure of 3-4 km depth on Earth. Which is to say, it should be physically conceivable for a tunnel boring machine to grind its way steadily to the core (with rather more difficulty than crossing the English channel, and I imagine the iron would tax the blades terribly once it reached the core). So...

• 1) Is the core cool? It was once liquefied by Aluminum-26, which should long since have decayed... since 4 Vesta is so small I'd expect it to be cooler inside, but how cold?

• 2) Would any sort of caverns be expected deep in Vesta, perhaps analogous to the cenotes of the Chicxulub crater?

• 3) Was there ever a sort of plate tectonics on Vesta during its initial cooling period?

• 4) Is there pressure, even atmosphere and water, in void spaces within the asteroid? That 3-4 km to essentially hard vacuum means that air would rapidly be lost from an open tunnel, but would the cooled exterior layers of rock be impermeable to their loss even over billions of years?

• 5) Would the complete cooling of core and mantle, if it happened, make for deposits of unusual minerals? For example, when freezing an iron core slowly, do vast layers of solid gold and platinum come out, or do they stay mixed in to the end? Would differential contraction create a fracture zone at the core/mantle boundary?

Wnt (talk) 01:45, 6 March 2015 (UTC)

(I added numbers):

1) A body that small which existed since the formation of the solar system, should be quite cool by now, unless it was actively heated by some means, such as tidal heating from a nearby planet. StuRat (talk) 06:26, 6 March 2015 (UTC)

@StuRat: That's what I'd expect, but is there an actual model or empirical rule to go by? (Conceivably there could be long-lived radioactives inside, etc., and I don't know if a lack of plate tectonics or a more solid mantle slows the rate of cooling, etc.) Wnt (talk) 14:50, 6 March 2015 (UTC)

The square-cube law explains why smaller bodies cool more quickly. However, in the case of planets, there may be an effect which counters that a bit. When still hot, convection moves heat from the center to the surface, where it then quickly escapes into space. However, once a thick crust solidifies, that stops convection from reaching the surface, slowing the rate of cooling. So, if a smaller body initially cools faster, it would also form that crust sooner and thus slow cooling more quickly. However, since all the planets, moons, asteroids, etc. have long ago formed a thick crust, that effect is likely negligible now. StuRat (talk) 20:35, 6 March 2015 (UTC)

But mantle convection... on Earth, the thin layer of crust is 24% of Earth's internal heat budget. If the entire mantle cools and forms "crust" (i.e. non-convecting material) that is 100 km thick or more, 10 times that of Earth, how much heat escapes? Those sort of considerations make me want to see a better calculation. (a pre-Dawn paper here provides some info, but doesn't seem to tell me much about the expected core temperature now, and in any case ... one hopes that the models have improved now that we know what it looks like, e.g. I imagine the metamorphism is easier to understand now that the whole asteroid is known to be circled by ridges from giant impacts ;[13] is more up to date but stops at core formation. [14] is interesting but focuses fairly much on early history - alas, most of these researchers have to focus on accounting for characteristics of observed meteorites rather than catering to sci-fi fantasies - but gives a figure of roughly 100 million years for the iron core to freeze.) Wnt (talk) 23:37, 6 March 2015 (UTC)

If one assumes that Vesta is a solid sphere, then the cooling time scale is of order (thermal conductivity) / (specific heat) / (density) * (radius / pi)^2, which gets me to about 10 billion years if I plug in rock values. Suggesting it is roughly half cooled at the present day. Dragons flight (talk) 04:24, 7 March 2015 (UTC)

Check-engine lights

In general, when did American-market cars change to the present type of malfunction indicator lamp? My 2009 Hyundai has the new type of "icon" that appears at the article's top right, and it took me forever to identify what it was (reading through the manual multiple times), because I'd never noticed such a thing before, although apparently lots of newer cars have these. Conversely, my previous car had an easy-to-understand verbal warning, simply "Check Engine"; it was a 2000, and other cars of the same period appear to use verbal indicators too. Nyttend (talk) 04:36, 6 March 2015 (UTC)

This is an example of a much broader problem. Manufacturers want to be able to sell their products in all markets without modification. Since different markets speak different languages, they therefore want to remove all writing from their products, and replace it all with icons. Sounds good, except that only the simplest concepts can be shown with an icon which is universally understandable. StuRat (talk) 06:14, 6 March 2015 (UTC)

The criterion for the existence of the scientific meaning of scientific discoveries (explanations)

1) Did it true the assertion, that failed to comply with the Law of conservation of energy in scientific discoveries (explanations) is always been denied the possibility of the existence of the scientific meaning (know) of these scientific discoveries (explanations)?

2) If magnetic (electromagnetic) fields are always been moving in space at the speed of light or even at the much faster speed, so why did in these magnetic (electromagnetic) fields, the electric current did not had the same speed?--85.141.236.107 (talk) 09:36, 6 March 2015 (UTC)

3) If any magnetic (electromagnetic) fields are always been moved by speed (work) of the electric current, why did the electric current did not had the same speed (work) as had the magnetic (electromagnetic) fields?--83.237.208.214 (talk) 12:58, 6 March 2015 (UTC)

4) If the properties of all substances in nature are always been depended on the properties of the electric current which was had in these substances, so is it possible that the electric current in all environments is always been behaved in the same (identical) way? — Preceding unsigned comment added by 83.237.201.125 (talk) 14:24, 6 March 2015 (UTC) --83.237.201.125 (talk) 14:25, 6 March 2015 (UTC)

---

Note: It is always assumed, that in nature the speed (work) of the electric current is always been absolute, that is, the speed (work) of the electric current is never been depended on the properties of the environments in which the electric current is been.--83.237.201.125 (talk) 14:06, 6 March 2015 (UTC)

Please try writing your questions in English. AlexTiefling (talk) 14:20, 6 March 2015 (UTC)

I’m always assume that in nature all physical and chemical environments are always been conducted an electric current, because in these environments is always been an electric current!--85.140.143.233 (talk) 15:03, 6 March 2015 (UTC)

Yes, you find electricity just about everywhere, and it travels fast like light (see Speed of electricity), and the associated magnetic effect travels at the same speed, but, of course, the electrons themselves (if you can distinguish them) flow at a very much slower rate DC (perhaps a quarter of a millimetre per second in a copper wire) and not really at all for AC where they oscillate a couple of micrometres. Of course the electrons are also "rattling around" within each atom at a speed determined by the Fermi energy if you interpret it that way. Dbfirs 15:58, 6 March 2015 (UTC)

The case is not been in the speed of the electrons in AC or DC, but the case is been in the work of these electrons - the work of the electric current, as the form of electric energy. I’m thinking, that all substances in nature was always had existed under the laws of the electric current!--83.237.218.93 (talk) 16:41, 6 March 2015 (UTC)

Physics did not excluding the scientific fact that different kinds of energy could done its work, including the work of the AC and work of the DC!--83.237.218.93 (talk) 16:56, 6 March 2015 (UTC)

I’m suppose, that in your's countries there are be universal generators which simultaneously generate as AC and as also DC, and of course there are be such universal transformers which simultaneously transform as AC and as also DC.--85.141.232.34 (talk) 17:52, 6 March 2015 (UTC)

I like the idea of universal generators and universal transformers. I suppose Switched-mode power supplies are capable of that magic in a sense. As for all the rest, I haven't the slightest idea what you are going on about, Alex. Dbfirs 18:12, 6 March 2015 (UTC)

I’m suppose based on that, since the work of the electric current (AC and DC) is always been only the kinetic potential of energy (energy - work of dynamics), so in this kinetic potential could always been the potential of potential energy (energy - work of kinetical statics), which as also could been done the work of electric current (AC).--85.141.235.69 (talk) 23:48, 6 March 2015 (UTC)

In any cases, in nature the electric current is always been the dynamics of electric charge, so that in nature all substances (physical environments) are always contained in self an electric current, because in nature all substances (physical environments) are always been electrified.--85.141.238.46 (talk) 06:09, 7 March 2015 (UTC)

The dynamics of electric charge was always had a electrify(-ing).--83.237.207.17 (talk) 07:22, 7 March 2015 (UTC)

Could you please let us know why you think you should be permitted to continue to use this page as a forum for your unintelligible ramblings? AndyTheGrump (talk) 07:36, 7 March 2015 (UTC)

As far as I can tell, these questions are not soapboxing, trolling, disruptive or discourteous. —Tamfang (talk) 08:19, 7 March 2015 (UTC)

As far as I can tell they are not questions. AndyTheGrump (talk) 09:06, 7 March 2015 (UTC)

I’m sorry for my mind suppose discussion, but I must said that the nature of magnetism and electromagnetism is always been the same (equal), as which was always had been the nature of electric current and electric charge. Sorry!--85.141.236.38 (talk) 10:05, 7 March 2015 (UTC)

Alcoholic pickles

Can homemade pickles contain alcohol if no alcohol was originally added to the mixture during preparation?73.160.39.193 (talk) 10:31, 6 March 2015 (UTC)

There are traces of alcohol in vinegar.

http://www.drgourmet.com/askdrgourmet/cooking/vinegar-alcohol.shtml#.VPmO8SzLyJ0

http://www.islamawareness.net/Alcohol/fatwa_vinegar001.html

"Acetic acid is produced by the fermentation of ethanol by acetic acid bacteria." If a foreign yeast contaminated your mixture it is possible that fermentation (of the pickles themselves) may produce ethanol (or even methanol which is toxic). Your pickle jar will probably explode.196.213.35.146 (talk) 11:46, 6 March 2015 (UTC)

Thanks. What would vinegar do to a breathalyzer test result?2601:C:3600:46B:34DF:F9E6:2B0F:22E5 (talk) 12:25, 6 March 2015 (UTC)

It's unlikely that the amount of alcohol in most vinegar would even register on the breathalyser, but if your pickles have fermented and you are in a country with a very low breathalyser limit, then perhaps you shouldn't eat a whole jar just before driving. Dbfirs 12:53, 6 March 2015 (UTC)

per Dbfirs, we can't give advice on what you should or shouldn't do. Be aware that many foods contain non-zero amounts of ethanol, but the amounts they DO contain is, while measurable, too small to have an effect on you as you couldn't physically consume enough of the food to have a marked effect on your blood alcohol level. Just because something contains any amount of something doesn't mean it contains a meaningful amount. For example, here's a study: [15] which measured the amount of ethanol in found in the juice of freshly picked oranges and grapefruits in California, and it found about 40 mg/100 mL concentration. For comparison, 5% ABV beer contains about 264 mg/ml concentration (see here for calculation). Thus, you'd need to consume 6.5 times as much orange juice to get the same amount of alcohol as a typical beer. Thus, a non-zero amount, but quite literally almost impossible to get drunk on; you'd need to drink nearly 1/2 of a gallon of orange juice to get the effect of one can of beer, for most people that isn't enough to go over the blood alcohol limit, and consuming that much orange juice would likely make you sick. Additionally, just about any fermented foods, including but not limited to, yogurt, bread, cheese, etc. also probably contain measurable (but insignificant) amounts of ethanol. --Jayron32 15:44, 6 March 2015 (UTC)

Two quibbles:

1. There's a factor of 100x difference between the units mg/mL and mg/100 mL, so it's 650x rather than 6.5x.
2. The figure of 264 mg/mL is not the alcohol content of the beer, it's the blood alcohol level resulting from drinking the beer.

We want to compare the alcohol content on an equal footing. 5% beer is 5% alcohol by volume. It should have alcohol content of (0.05 mL/mL) x (density of alcohol = 789 g/mL) = 39.45 g/mL. This is about 100,000x more than the orange juice. It's like in the old commercials for Total cereal: You'd have to drink a lot of orange juice! --Amble (talk) 17:08, 6 March 2015 (UTC)

Thanks for correcting my math, but now i need to correct yours. Density of alcohol is 789 g/L. 789 g/mL would be far denser than lead (11.34 g/mL). So, the alcohol content in orange juice is 1/100th that of beer, not 1/100,000th. Which makes it even MORE impossible to get drunk by eating oranges. Still, even at 1/100th, it is STILL impossible. --Jayron32 17:34, 6 March 2015 (UTC)

Turnabout is fair play :-) Thanks. --Amble (talk) 17:42, 6 March 2015 (UTC)

Non water based life

Is non water based life possible? — Preceding unsigned comment added by Joey13952 alternate account (talk • contribs) 23:02, 6 March 2015 (UTC)

See non-water based life. Possible, yes, known, no. Tevildo (talk) 00:02, 7 March 2015 (UTC)

March 7

Movie: X Men, the day of the future past

Has anyone seen this entitled movie?

There is a part where Dr. Xavier communicate with Mystic using a mechanism when she is in the airport.

Q:

1. What is the mechanism called?
2. How would you make someone else understand what Dr. Xavier was doing to Mystic? The way he is communicating with her,

a) How would you classify the part where he is using the mechanism on another person to communicate with her, e.g., when the lady was talking to her as they were picking up the boarding/passport together?

b) How would you classify when he was trying to get inside her head...using the mechanism?

Regards. -- (SuperGirlsVibrator (talk) 05:48, 7 March 2015 (UTC))

Laundry

Why is water of a higher temperature used in the washing of whites? 75.75.42.89 (talk) 14:30, 7 March 2015 (UTC)