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September 27[edit]

Can a hearing child speak properly if he is raised by deaf parents?[edit]

How do hearing children learn to speak when they may never have heard a word other than grunts from their parents? Do they have a hearing caretaker that provides speech training or something? And how do the parents know that their children can actually hear? 71.79.234.132 (talk) 00:01, 27 September 2014 (UTC)

We have an article on it: Child of deaf adult. Mingmingla (talk) 00:09, 27 September 2014 (UTC)
OR of course, but yes my cousin's husband is one such. He is much in demand as an interpreter by the police and ambulance service.
Very few children are restricted to hearing only their parents, so a child with normal hearing and deaf parents will hear plenty of talking from other people. They learn speech pretty normally that way. These days, of course, the ubiquitous television plays a role too. HiLo48 (talk) 22:10, 27 September 2014 (UTC)
I've heard that children's dialect/accent owes more to their peers than to their parents. (If so, in Lost it made no sense that Walt spoke American rather than Australian.) —Tamfang (talk) 08:46, 1 October 2014 (UTC)

What happens to the energy produced in respiration?[edit]

What happens to the energy produced in respiration? I'm especially interested in the brain. How does the brain use energy? Where does the energy go? 49.183.204.196 (talk) 10:40, 27 September 2014 (UTC)

Do you mean the physical process of respiration? If so, the heat produced by the muscles involved in respiration is dispersed round the body and, if it is not needed, flows to the atmosphere via perspiration etc. Our article on the brain includes a section on metabolism though it gives only an outline. The energy consumed by the brain is also largely dispersed as heat. Dbfirs 11:43, 27 September 2014 (UTC)
Can the energy be converted into light for use in photosynthesis? Or otherwise converting the carbon dioxide and water back into oxygen and glucose? 49.183.204.196 (talk) 12:21, 27 September 2014 (UTC)
I can't think of any process within the body that could turn heat into light. The liver and kidneys do synthesise glucose, but I think they need more than just carbon dioxide and water. Dbfirs 12:32, 27 September 2014 (UTC)
Of course, other plants and animals are bioluminescent, meaning they convert energy into light. For example, a firefly. However, the amount of light produced is very little, and you couldn't do photosynthesis with that tiny amount. (You can tell how much brighter sunlight is because you can't even see bioluminescence in full sunlight.) StuRat (talk) 19:41, 27 September 2014 (UTC)
Why is the amount of light produced very little? Energy is conserved. Why can't you use the energy generated by respiration to power photosynthesis or otherwise turn the carbon dioxide and water back into glucose and oxygen? 49.183.204.196 (talk) 21:38, 27 September 2014 (UTC)
Let me clarify the Conservation of Energy law. While the total amount of energy is the same (except for some theoretical cases where it's converted into mass), when any conversion of energy forms takes place, some of the energy is converted into heat, and heat can not be converted back into other forms of energy (although large differences in temperature can create other forms of energy, as in a Carnot engine). Most energy conversion processes are quite inefficient in this respect, so converting energy back and forth eventually gives you nothing but widely distributed waste heat. StuRat (talk) 06:09, 28 September 2014 (UTC)
The second law of thermodynamics says that entropy can never decrease in an isolated system, but is it not possible to create a system where entropy stays the same? 49.183.204.196 (talk) 11:14, 28 September 2014 (UTC)
Theoretically, yes, but practically, no, at least not where there's friction, resistance, etc.. An exception might be possible with superfluidity, superconductivity, etc. StuRat (talk) 23:12, 28 September 2014 (UTC)
BTW, I believe there is some micro-organism that basically behaves as a plant during the daylight, using photosynthesis to produce energy, then turns into an animal at night, burning that stored energy. Does anyone remember the name ? StuRat (talk) 06:12, 28 September 2014 (UTC)
It depends what you mean by respiration. Are you asking about Respiration (physiology) or Cellular respiration? The only fuel the brain uses is glucose see [1]. The energy it gets from this is used to produce electrical energy which powers the brain's processes and the excess is lost as heat. Richerman (talk) 14:33, 27 September 2014 (UTC)
As far as where the energy goes, much of it eventually turns into heat, which then dissipates into the person's environment. This is why we tend to be warmer than our surroundings. StuRat (talk) 19:37, 27 September 2014 (UTC)
Er, not really. Our bodies are designed to run at around 37°C which may be warmer or cooler than the surrounding environment. If that doesn't happen we're soon in in deep trouble. Richerman (talk) 21:13, 27 September 2014 (UTC)
Let me explain further. Most people are uncomfortably hot in places that are at our body temperature (with an exception for when in water, which can dissipate body heat more quickly). The reason for this is that our normal metabolic processes create heat, and if we start out in an environment already at our target body temp, that extra heat would make us overheat, or at least sweat profusely to cool down by evaporative cooling. This is why we prefer cooler temps than our body temp, or, looking at it the other way around, "This is why we tend to be warmer than our surroundings". StuRat (talk) 00:24, 28 September 2014 (UTC)
Temperatures significantly above body temperature will cause the body to absorb heat from its surroundings, and cause hyperthermia. The laws of physics are a mean bitch, and since heat cannot flow spontaneously from cooler temperatures towards warmer temperatures, people cannot maintain physiologic body temperature in an environment where the ambient temperature is above physiologic body temperature. --Jayron32 00:41, 29 September 2014 (UTC)
That's true at 100% relative humidity, but evaporative cooling can allow people to survive at temps significantly above body temp, provided they have a water supply, low humidity, and perhaps some wind to help the evaporation process along. StuRat (talk) 01:05, 29 September 2014 (UTC)

Mushrooms with holes[edit]

Drilled mushrooms.jpg

What's going on with these mushrooms? They look like someone has been drilling into the tops. They are right outside my workshop, but I don't think I am that careless! SpinningSpark 11:21, 27 September 2014 (UTC)

Slugs? Thincat (talk) 11:28, 27 September 2014 (UTC)
Have you observed other mushrooms like them, except without holes, in the vicinity of your workshop? Nyttend (talk) 13:27, 27 September 2014 (UTC)
Yep, definitely slugs. I saw one just like that the other day with a large slug sitting on it eating away. Richerman (talk) 14:03, 27 September 2014 (UTC)

Climate Change[edit]

One quick one...why hasn't this article addressed the recently published findings by the National Academy of Science, through the Federal study by the National Oceanic and Atmospheric Administration, in conjunction with the University of Washington?

Many people say that "Wikipedia" is left-biased, and although I defend you, it is becoming more difficult when differing scientific opinions are dismissed completely.

Thank you 50.158.98.69 (talk) 14:00, 27 September 2014 (UTC)

Which findings? And WP:SOFIXIT. DuncanHill (talk) 14:02, 27 September 2014 (UTC)
The fact that recent findings haven't been added yet doesn't mean they've been dismissed - it just means they haven't been added yet. Now's your chance to add something useful to the encyclopedia anyone can edit. And I don't think people on the left wing of politics are any more likely to disbelieve that climate change is happening than those who lean towards the centre or the right are they? Richerman (talk) 14:09, 27 September 2014 (UTC)
A better place to discuss this would be on the Talk page for the article at Talk:Climate change. But it would be nice if you could give us a link to this publication so that we have at least a rough idea of what you're talking about.
As you might expect, there have been a lot of contentious debates about the Climate change article - and it's currently under discretionary sanctions from the ArbCom folks (meaning that people had better behave themselves there - or retribution will be swift!). As far as I can see, nobody has yet added a reference like that to the article - so it's not like there is some kind of active suppression of this information. You'd (perhaps) have grounds for complaint if it had been inserted, and then deleted again without good cause.
Right now, I think you should carefully ensure that the article you're planning on 'addressing' meets Wikipedia's guidelines for "reliable sources", and if you're sure that it does, go ahead and change the article. If you're not 100% sure (especially given that ArbCom are watching) - then you should perhaps discuss it first on the Talk page...and, I'd strongly advise you to follow the "assume good faith" rule and not start off by accusing the people who work on that article of being biassed! That's a fairly insulting thing to say here - and the Wikipedia rule that you assume people are behaving in a nice way (until proven otherwise) is essential in this kind of matter. So it would be better to assume that the paper you're talking about simply didn't get noticed by them - or was rejected for solid reasons - rather than charging in and proclaiming bias, as you've already done here.
Ordinarily, a little slip in your assumption-of-good-faith would go unnoticed - but because that article is on a hair-trigger (and for good reason), I advise you to tread gently and to be as polite and assuming-of-good-faith as you can manage!
SteveBaker (talk) 14:39, 27 September 2014 (UTC)
It may have something to do with this, although I can't see at first glance how this would would impact on the climate change article. Mikenorton (talk) 16:07, 27 September 2014 (UTC)
That workshop looks quite technical to me, and at first and second glance does not contain much that would affect our current articles. I certainly found nothing that seems to conflict with my high-level understanding. --Stephan Schulz (talk) 17:25, 27 September 2014 (UTC)
More to the point perhaps, the title and content suggest that if anything, info from there is more likely to lead what the OP would call a left wing bias and not demonstrate it by excluding it. I think the OP is more likely referring to [2]. My uninfotmed thoughts are 1) It was published in PNAS but as with all such articles it's simply the peer reviewed work of the authors not the findings on the NAS. (I suspected this.) 2) It's simply a single recent article, peer reviewed sure, but as with all such things on both sides, needs to be used with care compared to more established stuff from reviews or at least studys which have become well accepted etc. 3) It hasn't even been published now (although accepted) it's even more silly to get worked up about it not being currently used. Nil Einne (talk) 16:45, 30 September 2014 (UTC)
Climate change is a significant political issue along the left/right divide only in the United States so this may be a good opportunity to point out that this website is not the Yankopedia. Roger (Dodger67) (talk) 16:14, 28 September 2014 (UTC)

scale of climate belts[edit]

Hi,
I wonder why the climate belts' scale is constant, and why it is what it is.
I mean, why one year can't the northern belt reach the equator? what prevents it?
Exx8 (talk) 16:59, 27 September 2014 (UTC)

1) Sunlight hits the tropics more or less straight on, while near the poles it hits at a shallow angle. This means much less light hits there, and as a result, there's much less solar heating. See insolation.
2) Ice at the poles exaggerates the above effect, by reflecting most of the little sunlight they get.
3) Heat can move around a bit, in the atmosphere and oceans. But most of the heat in the atmosphere moves around parallel to the equator. If you look at Jupiter's cloud bands, it's more visible there. The rotation of the planet causes this.
4) So, the atmosphere doesn't move much heat away from the equator, but the oceans do. See the Gulf Stream for one example. (I believe, in the absence of land, water currents would continue to move parallel to the equator, just as air currents do.)
5) The atmosphere can also be redirected, at times, by the jet stream. So, when it gets a kink in it, heat may be directed away from the equator, or cold air away from the poles. StuRat (talk) 17:09, 27 September 2014 (UTC)
Even in the absence of land the currents wouldn't go parallel to the equator but form cells because of the Coriolis effect. The great red spot on Jupiter is probably one of these. Dmcq (talk)
Well, the primary direction is still East-West on Jupiter, and I'm sure it would be in our oceans, too, if the path wasn't blocked. StuRat (talk) 19:21, 27 September 2014 (UTC)

Is it possible for a camera to take photos in low light conditions without image noise[edit]

Even the most expensive and advanced digital camera still produces Image noise in low light conditions. My friend bought a $2,000 digital camera and it still has image noise in low light conditions. My question is this a physical inevitability or is it a technological limitation and with sufficiently advanced technology, cameras in the future will not have this problem? ScienceApe (talk) 18:53, 27 September 2014 (UTC)

It's a technology/price limitation. I believe astronomers have cameras that can detect a single photon, and record them over time to build up a complete image. Noise on those would make them useless. Apparently either $2000 isn't enough, or he got ripped off. StuRat (talk) 19:25, 27 September 2014 (UTC)
See (Digital camera ISO speed and exposure index) and F-number. As far as "future technology" is concerned, in theory it is a matter of recording photons hits and sorting out the signal from the noise. 71.20.250.51 (talk) 19:59, 27 September 2014 (UTC)
Concerning the practical example, (using current technology) presumably the expensive camera has a decent max ISO; buying a lens specifically for low light photos might be a solution (i.e.: f/1.2 lens). 71.20.250.51 (talk) 20:06, 27 September 2014 (UTC)
As an old film photographer who has made many interesting photos with l-o-n-g exposures in low light conditions:, I wonder if a time exposure similarly allow integration of light over a period of seconds or minutes in a digital camera? Edison (talk) 20:48, 27 September 2014 (UTC)
Yes. Of course that requires a tripod and a subject that doesn't move (unless a blurry subject is desired, which often makes for an interesting photo). 71.20.250.51 (talk) 21:06, 27 September 2014 (UTC)
Detecting one photon at a time when there are not many photons will still give you a noisy image. There is a limit to how much information there is in the light, and you cannot get that information if it is not there. Graeme Bartlett (talk) 21:35, 27 September 2014 (UTC)
I don't follow. A telescope on Earth can be expected to get stray photons from reflections/refractions in the atmosphere, if that's what you mean. But a telescope in space shouldn't do that much, especially when looking at a very narrow speck of space. Is this the "noise" you meant ? As for the signal, if you only get one photon at a time from a distant spiral galaxy, you should eventually be able to see the spiral shape emerge, if you collect enough photons and are able to place them in the correct location. StuRat (talk) 00:29, 28 September 2014 (UTC)
Extremely low noise cameras already exist. The problem that has to be overcome is to reduce the amplifier noise; this requires cooling the camera to extremely low temperatures. You can then take extremely long exposures at extremely high ISO settings without much noise.
In practice, it's quite easy to eliminate the noise you get using ordinary cameras when taking long exposure pictures. What you do is you take multiple exposures with shorter exposure time instead of a single, long exposure. You then combine all the individual images, but instead of simply adding up the grey values for each pixel, you take the median. This automatically removes outliers. Count Iblis (talk) 22:58, 27 September 2014 (UTC)

Back to our question, expensive hardware can help, but as with other photography, or other just about anything, there's a lot more to it. Astrophotography hints at the great mental effort require to do it well. As with just about anything. Jim.henderson (talk) 00:45, 28 September 2014 (UTC)

The lowest possible noise for any sensor is the Poisson noise, caused by the discrete nature of light. If a certain pixel receives 100 photons, for example, the Poisson noise will be 10 photons (square root of 100), which is 10% of the signal. This limitation is imposed by the laws of mathematics, and no amount of clever engineering can defeat it. The only solution is to collect more photons, for example by having a bigger lens or bigger pixels. --Bowlhover (talk) 00:56, 28 September 2014 (UTC)

As 71.20.250.51 has already pointed out, you're trying to solve the wrong problem. With DSLR's there's two separate things to consider when working at a fixed shutter speed: 1) the ISO or light sensitivity, which is a function of the sensor (or of the film, in the case of older SLR's) and 2) how "fast" the lens is, ie. f-stop, or in other words how wide you can make the aperture. Obviously a wider opening (lower f-stop) lets you shoot in lower light without having to increase the ISO. At high > 3000-ish ISO no matter how good the sensor, it's still going to look noisy, although some sensors are of course better than others, it's likely in the $2000 range that your friend has purchased a camera with a full-frame sensor, so that's probably not the issue. It's not lack of light that generates the noise, it's the fact that you're increasing the sensitivity of the sensor that's the problem, since you're picking up more stray light. Basically it's a signal-to-noise problem. If you're trying to shoot in near darkness, and don't want a noisy image, either get a fast lens (f < 1.8) which can be pricey, or increase the exposure time, the later option being the more cost effective since it only requires purchasing a small tripod (and probably a remote trigger) to keep the camera stationary until the exposure is complete, that way you can shoot at a low ISO and just keep collecting light until you have an adequate exposure. Never crank the ISO higher than it needs to be, or your image will be noisy. I would suggest that the OP's friend, having just invested in a $2000 camera body should probably also read up on the fundamentals of photography. (+)H3N-Protein\Chemist-CO2(-) 13:28, 28 September 2014 (UTC)

OP's friend here. The image he is referring to is one I took of a firework on the 4th of July, with an ISO of 6400 (as it was well into night time at the time the photo was taken), a zoom lens whose F-Stop was (unfortunately) F/3.5, and a 1/640th second shutter. The noise was already controlled in the unaltered photograph (being mostly limited to the areas I didn't want the viewer to focus on), and the camera itself (A Nikon D600) had won good scores for its low noise performance even at ISOs up to that level. While the unaltered image has noise, some very basic sharpening and a touch of smoothing eradicates it, turning it into a more pleasing fine grain and produces a fine photo. Simply put, he believes "any noise is a failed photograph," even if it's grain-like noise, and despite my attempts to tell him some noise (hopefully grain as opposed to color) is inevitable in pretty much any photo you take, nothing seems to be able to sway him in the slightest. Any adjusted photo (be it even basic things like color correction) is also a "fake" photo, as it does not represent exactly what the eye sees, which is his golden standard for a good photo, and hence why any noise makes for a bad photo. That's not to say I'm not learning (still am - I think I would've tried ISO 3200 or perhaps a quicker shutter speed now), but I think that he is making the picture sound far worse than it actually is. 74.77.153.216 (talk) 16:35, 28 September 2014 (UTC)
I occasionally see that purist sort of view, though more often in discussion of audio recording. The problem is that every image recordation technology since daugerrotypes has been subject to inbuilt bias or limitation based on the system, the camera, and its reproduction process. All digital images are subject to some form of processing before we even get a chance to make our own manipulations, depending on what the engineers at Nikon, Canon or Sony have built into the imaging system to make it functional, particularly at high ISOs. For instance, Canon sensors are known to produce vivid reds, which can be an opportunity or a problem depending on one's goals. Anyone who's spent time in a darkroom will know that photography is highly subjective and malleable, which is where its potential for artistic effect is realized. Acroterion (talk) 17:37, 28 September 2014 (UTC)
Yes, that's why we need the International Commission on Illumination to try to standardize things as best as possible. Count Iblis (talk) 19:01, 28 September 2014 (UTC)

Re: remote trigger: another work around, if time is not an issue, is to set the camera for a delayed shot (2 or 10s). If you're shooting on a tripod, it will allow the shakes of pressing the button to die down before the photograph is taken, and thus reduce / eliminate blur. I did that with my Canon EOS 60D for a candlelight only shot, and it worked perfectly. The text of the book I was photographing remained perfectly legible.13:53, 28 September 2014 (UTC)

People used to hold a black page or similar very close to the lens, press the shutter, wait some seconds, and then take it away very very quickly. Sagittarian Milky Way (talk) 12:02, 29 September 2014 (UTC)
Two things. I used to shoot on ISO800 film because I actually used to LIKE the slight grain to the resulting images, (the Fujifilm 800 in particular was pretty well known for its subtle but pleasant grain). Secondly, I was interested in night time astro photography and can say that, some, perhaps not all, but a decent portion of "noise" is NOT stray light, but in fact, caused by essentially brownian motion in the CCD. You can prove this by taking long exposures with HIGH ISO in the middle of the night, with the window shades drawn, with the lens cap on, with the camera in a heavy black garbage bag, under a heavy bed sheet. etc:) You will still get a photo with noise. Vespine (talk) 06:47, 29 September 2014 (UTC)
Interesting point. You're right, I've done that with my Canon 60D. Even with the lens cap on in a shaded unlit room, there is still visible noise, so I'd have to agree that it can't be just stray light. However, CCD's are solid state, and brownian motion requires that *something* be moving diffusively in response to thermal fluctuations, so what is the "something" in this case? The only thing I can think of would be that it's light being scattered by dust, but then where does the light come from? (+)H3N-Protein\Chemist-CO2(-) 14:32, 29 September 2014 (UTC)
Or, were you thinking that thermal fluctuations were directly triggering excitation of the CCD? In which case the relevant process would be thermal noise. (+)H3N-Protein\Chemist-CO2(-) 14:34, 29 September 2014 (UTC)
Yes, it is thermal noise, which is why in professional applications where they need extremely long exposures at extremely high amplifications, they cool the sensors with liquid nitrogen or liquid helium. Count Iblis (talk) 15:22, 29 September 2014 (UTC)
Imaging the cosmic background radiation sky to WMAP precision with a CCD must be a pain in the neck... Sagittarian Milky Way (talk) 22:51, 29 September 2014 (UTC)

A low focal length (to reduce magnification) telescope is another solution. They make field flatteners too for photography with telescopes, they minify it somewhat. Sagittarian Milky Way (talk) 12:02, 29 September 2014 (UTC)

Sorry yes I accept the correction. I think I heard it once described like Brownian motion, but having just a brief look at the article it's clearly NOT Brownian motion, but thermal noise. Vespine (talk) 02:28, 1 October 2014 (UTC)

Color changing material[edit]

I've recently learnt about chemical clock phenomenon and it made me wondering whether there are any solid materials that change colour overtime.85.141.229.250 (talk) 20:06, 27 September 2014 (UTC)

Loads of them. Copper turns green over time, silver turns darker, iron turns rust-colored, bright colored paper and plastics tend to fade (although one pigment may fade faster, changing the color, too). On artificial plants, the greens tend to turn blue over time. And tattoos also lose their bright colors over time, leaving only greens and blues. White paper and bones/ivory tend to yellow over time, too. StuRat (talk) 20:44, 27 September 2014 (UTC)
Chromatophores on cuttlefish is a more interesting example. 71.20.250.51 (talk) 20:52, 27 September 2014 (UTC)
Timber fades or darkens over time, depending on the type of timber and conditions. HiLo48 (talk) 22:02, 27 September 2014 (UTC)
Metals turning colors would be due to oxidation, which would technically mean the material itself is changing, wouldn't it? ←Baseball Bugs What's up, Doc? carrots→ 22:04, 27 September 2014 (UTC)
It's a chemical change, yes, but not always oxidation. I'd bet that most color changes relate to some chemical change within the material itself. StuRat (talk) 00:16, 28 September 2014 (UTC)
Oxidation is a "chemical change within the material itself." - EronTalk 20:56, 28 September 2014 (UTC)
I think he meant that oxidation is one possible chemical change that could occur, but there might be others. ←Baseball Bugs What's up, Doc? carrots→ 22:04, 28 September 2014 (UTC)
Cobalt chloride in solid form changes colour quite dramatically in response to hydration from the environment. —Quondum 17:57, 28 September 2014 (UTC)
Yes, and our cement basement floor turns from light gray to dark grey, depending on the humidity. However, this is a reversible change, so probably not what the OP meant. StuRat (talk) 19:53, 28 September 2014 (UTC)


  • I think everyone above is missing the point of the question. The OP did say "solid materials that change colour overtime" -- but of course chemical clock doesn't just refer to any change over time, it refers to periodic change over time. The whole point is that it reverses itself over time, and with regularity. That is why it's called a 'clock.' (Didn't anyone look at the article before responding?!) The classic example is the BZ reaction, detailed in the article. To my knowledge, none of the examples above display periodic changes over time. The key to the periodic behavior in the BZ reaction is that it is a nonlinear dynamical system and constitutes a reaction diffusion system that is an example of an excitable medium. Theoretically, you could perhaps pour out the BZ reactants into some aerogel or agar or some other solid/porous object, and it may well continue to periodically change color. I don't think you'll be able to make a true 'solid' chemical clock. SemanticMantis (talk) 15:23, 29 September 2014 (UTC)

Can someone identify this green animal?[edit]

On this Life in green BBC page all the green animals are identified except the one at the very top, the first one you see when you get to that page. At least I can't find anything. Can you tell what it is? Thanks. Contact Basemetal here 22:27, 27 September 2014 (UTC)

Oxybelis fulgidus (aka the green vine snake or the flatbread snake). ---Sluzzelin talk 22:33, 27 September 2014 (UTC)
Wow. That was fast. Did you get it by Googling the image? I got nothing with that at first, then once (after you'd answered here) Googling the image did give me Oxybelis fulgidus, and now again it gives me nothing. Odd. Or do you just happen to know what that snake looks like? In any case, thanks. Contact Basemetal here 23:07, 27 September 2014 (UTC)
Google keeps doing it: from time to time when I Google for the image of the BBC site it finds this match and I am thus able to find out it's Oxybelis fulgidus and at other times it only returns the very BBC image I was searching for as a match and so I get nothing. And it's doing this apparently at random. I didn't know Google was so unreliable. Contact Basemetal here 23:53, 27 September 2014 (UTC)
TinEye led me to Getty Images [3]. Thanks for the question about this elegant creature! ---Sluzzelin talk 23:58, 27 September 2014 (UTC)

Allergy rates across countries[edit]

Is there any significant difference between developed countries in the level of diagnosed allergies? I remember reading somewhere that the UK has much higher rates than other rich countries, but I can't find the reference and now suspect it was just a made-up factoid. 213.205.251.92 (talk) 23:45, 27 September 2014 (UTC)

One published study said that only a few countries have credible data on allergy rates in children. Edison (talk) 00:04, 28 September 2014 (UTC)
It seems like whether a condition is a "sensitivity" or an "allergy" is subjective. That being the case, how can you come up with a meaningful comparison when different people may use different criteria to decide ? StuRat (talk) 01:10, 28 September 2014 (UTC)
It is known that indigenous people in Africa like the Hadza people have far lower allergy rates than people who live in Western countries, see e.g.. here: "One hunter-gatherer community was found to not only have a higher diversity of bacteria, but only one in 1,500 suffered from an allergy - compared with one in three in the UK.". Count Iblis (talk) 01:56, 28 September 2014 (UTC)
Right, that would be the hygiene hypothesis, but the Q was specifically about developed countries only. StuRat (talk) 05:59, 28 September 2014 (UTC)

September 28[edit]

Trees shedding leaves[edit]

When deciduous trees shed their leaves in the autumn, are the outermost leaves the last leaves to fall from most species of trees?
Wavelength (talk) 02:30, 28 September 2014 (UTC)

I'd expect the reverse, since the outermost leaves will get coldest first, which is what I think triggers them to change colors and then fall. StuRat (talk) 05:56, 28 September 2014 (UTC)
Going on simple observation (looking out of the window) it seems to be random. Alansplodge (talk) 08:05, 28 September 2014 (UTC)
It could depend on the species. I think the birch, for example, retains some of its leaves all winter. ←Baseball Bugs What's up, Doc? carrots→ 10:13, 28 September 2014 (UTC)
The shedding is a form of abscission. Our article suggests that leaf abscission is indirectly due to changes in sunlight, but it's as unreferenced as StuRat's opinions above. This suggests that ethylene plays a role. According to that site, each leaf produces ethylene and, as that builds up, it eventually triggers the abscission response. Neither of those things would be influenced much by placement on the branch - in fact, if sunlight hours are the trigger and each leaf is triggered individually, it would seem that the outer leaves would be the last to go. Of course, it could also be that the plant triggers the abscission en masse and the fall of individual leaves is mostly due to chance and/or wind. An image search of autumn tree doesn't show any particular pattern to the sequence of leaf fall, though it does seem that some branches empty ahead of others. Long story short, the facts of the matter are either poorly understood or at least are not well explained on the web. If you find something good, our article could really use an expansion. Matt Deres (talk) 12:09, 28 September 2014 (UTC)

optics[edit]

The color of an object is said to depend on the wave length. the object reflects. So if you viewed colored objects under water in which the wave length of light is different, does the color change? — Preceding unsigned comment added by Janfred keno (talkcontribs) 10:45, 28 September 2014 (UTC)

How would being under water change the wavelength? ←Baseball Bugs What's up, Doc? carrots→ 11:59, 28 September 2014 (UTC)
Going under water changes the spectral distribution of the light, because longer wavelengths are more strongly absorbed. That does indeed change the perception of coloured objects. During my Advanced Open Water Diver deep dive, the instructor (very dedicated and not afraid of sharks) pricked his finger to show us that blood looks black at a depth of 90 feet. --Stephan Schulz (talk) 13:47, 28 September 2014 (UTC)
Then the general answer to the OP's question is "Yes." ←Baseball Bugs What's up, Doc? carrots→ 14:10, 28 September 2014 (UTC)
There is probably some confusion here. The speed of light changes in water, so the wavelength for a given frequency changes correspondingly. However our eyes, if I remember correctly, don't detect the wavelength of light, they detect its frequency, which does not change. Therefore this effect does not cause a perceptual color shift. There is, as others have already said, a color shift caused by the fact that water transmits some colors better than others. Looie496 (talk) 14:58, 28 September 2014 (UTC)
It's been a long time since Physics 101, but I thought wavelength and frequency were effectively inverses of each other. ←Baseball Bugs What's up, Doc? carrots→ 15:07, 28 September 2014 (UTC)
They are related that way as long as the speed is constant. When light enters a different medium (like going from air to water) its speed changes, so the wavelength is different. But as Looie says, what really matters is the frequency and that doesn't change. It's just that, because we usually think of light moving in a vacuum (at a truly constant speed) or in air (at very nearly the same speed), each frequency has a specific wavelength associated with it when the light is in air or vacuum and we happen to use that wavelength as the way of describing colors. --65.94.51.64 (talk) 15:23, 28 September 2014 (UTC)
Speed of light in water is about 25% less than in vacuum. So for the same frequency, wavelength is reduced accordingly. --Stephan Schulz (talk) 15:29, 28 September 2014 (UTC)
Something seems wrong there, since objects don't change color when submerged in shallow water. Only deep water appears to have this effect, where enough water is present to absorb the reddish end of the spectrum. StuRat (talk) 18:50, 28 September 2014 (UTC)
What's wrong is that you're missing the point: the wavelength changes, but the color doesn't change because color depends on frequency, not wavelength. We just usually describe it in terms of wavelength. Of course it's different if the depth is sufficient for the fact that water is slightly blue to be noticeable, but that's because the color distribution of the incoming light is changed, not the color of a particular frequency of light. --65.94.51.64 (talk) 06:38, 29 September 2014 (UTC)
All of the above discussion is entirely irrelevant. Your retina is what detects the color - and that lives behind the aqueous humor and various other tissues making up your eyeballs. So the speed of light in the aqueous humor (or some other tissue of the eye) is all that matters - and that doesn't change when your eyes are in the air or in the water, so no - the color doesn't change and it has nothing to do with wavelengths or frequencies or any of that other stuff. SteveBaker (talk) 13:25, 29 September 2014 (UTC)
A photoreceptor cell detects light when a photon hits a protein in the retina and excites it to a higher state. This excitation depends on the energy of the photon, which is proportional to frequency: E=hf. That's why changing the wavelength of light doesn't change our perception of color.
By the way, color has a lot more to do with biology than it does with physics, and depends on a lot more than the wavelength of light. See this entertaining video for how human vision works. The part about color begins at 7:00. --Bowlhover (talk) 18:13, 29 September 2014 (UTC)

optics 2[edit]

how is it possible that the complete circle of a rainbow can sometimes be seen from an airplane? — Preceding unsigned comment added by Janfred keno (talkcontribs) 10:50, 28 September 2014 (UTC)

I would say it's because there is no ground to get in the way. Read Rainbow and it should answer your questions. ←Baseball Bugs What's up, Doc? carrots→ 11:57, 28 September 2014 (UTC)
You see part of a rainbow wherever the rain or mist, the sun, and your eye make a certain specific angle. So any time you are looking away from the sun, there is a cone shape with its vertex at your eye (and the line from the sun to your eye as its axis of symmetry), and if any part of that cone has rain or mist in it then you see part of a rainbow there. (If the sunlight is intense enough to make a dobule rainbow, the geometry is the same but the specific angle for the second rainbow is different.) When you're seeing a rainbow because you're seeing the sun shining on distant rain, it cuts off at ground level because that's as far as the rain falls. But if you're above ground, you can see the rain falling below you, and yes, that means it's possible to see a full-circle rainbow like this one. You can get similar effects with the rainbow is formed by the mist from a waterfall, because you can be much closer to the mist and can see down into the gorge, as in this example and also this example. It's all a matter of how much of that cone shape the mist is in. --65.94.51.64 (talk) 15:35, 28 September 2014 (UTC)

Should there be maximum speed limit for the perception of human vision?[edit]

Human eye can’t see an object if move beyond certain speed such as

1- Spinning of spooks of wheel 2- Spinning of propellers or blades of fan 3- Firing of bullet from firearm 4- Spinning of the coloured desk which turns into white

Similarly vision becomes out of sight upon moving the cursor on the recorded events (red in color) in the selected timeline faster than the normal rate (play) of any video camera e.g. surveillance

Although all above are either spinning or travel with high speed but untraceable by the human eyes. No idea if size of an object would affect that limit or not but should there be a maximum speed limit for the perception of human eye beyond which it can’t see things in motion (just like a sound for ears) if not then how light/ photon is perceptible with its high speed (299,792,458 m/s) when our eyes simply can’t notice aforementioned motion?162.157.248.16 (talk) 05:43, 28 September 2014 (UTC)EEK

Are the spinning spooks for Halloween ? StuRat (talk) 05:51, 28 September 2014 (UTC)
What do you mean by what "should" be the limit ? From an evolution POV, there would be no point in being able to spot things faster than would occur, or could be reacted to, in our evolutionary past. Much smaller animals, like insects or hummingbirds, might well benefit from faster vision, since they have the ability to move out of the way of fast predators or capture fast prey. StuRat (talk) 05:51, 28 September 2014 (UTC)
... and to answer the last part of the question ... photons are invisible as they pass by (at any speed) ... they are detected only when they enter the eye and cause a stimulus to the rods and cones of the retina. Dbfirs 06:49, 28 September 2014 (UTC)


I can see the moon, it is travelling at 2000 mph. Greglocock (talk) 07:39, 28 September 2014 (UTC)
Yes, it's not absolute speed alone that matters, but how quickly a given point in your visual field moves from not having the object in it to having the object in it, to not having it there again. The direction of movement is important, and even a bullet in motion can be visible if it's moving straight away from your eye or towards your eye (duck !). The size of the object and distance also matters, and the Moon is large enough and far enough away that it takes quite some time to move noticeably. StuRat (talk) 18:56, 28 September 2014 (UTC)
Obviously...it's the speed that the object tracks across the retina...which is the angular velocity at the eye, not the linear velocity - so it doesn't matter how fast the moon is moving in linear velocity terms - it's the rate that it moves across the retina - which is incredibly slow. The size of the object (on the retina) also matters. In the end, it's the amount of time that the focussed light from the object remains on a particular cell in the retina that matters. When you hit the cell with light, it takes time for enough light to accumulate to cause the cell to fire - and after it's fired, it takes a while for it to recover enough to fire again. However, how much time that takes depends on the brightness of the light. A very brief (but intense) flash (like a lighting strike) is enough to trigger the perception of light - but the light reflected off of a passing bullet isn't. Notice that you can easily see 'tracer rounds' fired at the same speed as a normal bullet - that's because they are so bright that the cells in your eye get enough light to cause them to 'fire' in a very short amount of time. A regular bullet at the exact same speed and distance is invisible. SteveBaker (talk) 13:42, 29 September 2014 (UTC)
Motion perception is the relevant article. Tevildo (talk) 09:28, 28 September 2014 (UTC)

Is there any phenomenon in physics which can explain why 1- above mentioned spinning blades or spooks become out of sight 2- we can see through them.162.157.248.16 (talk) 22:48, 28 September 2014 (UTC)EEK

1+2) The brain averages out the spokes and the image behind them, and you see a slight graying of the image through the spinning wheel. There's a toy with a spinning wheel like that, and if half the image is blue and half is yellow, it all averages out in the brain and you see green. StuRat (talk) 23:05, 28 September 2014 (UTC)
The fact that motion does eventually blur into a smear means that there are limits. I do know that this limit varies significantly from person to person - and also across the retina. When a sequence of still images fuses into smooth motion is one indication of those limits. I used to work in flight simulation - and having flickery displays proved to be a serious impediment to people trying to learn how to do air combat in a simulator with a wide field of view display.
With the center of your eye, very few people have trouble seeing flicker in a 60Hz computer screen or TV tube - quite a lot of people see flicker in 24Hz movie theatres (they used to be called "the flicks" because they flicker). I met one guy who continued to see flicker all the way up to 90Hz. He has to use a special computer monitor that refreshes at 120Hz and he's completely unable to enjoy television or movies. I've also done experiments that show that some people still see continuous motion at 12Hz. So the limit is probably somewhere between 10 and 100Hz. However, at the edges of the retina, most people see flicker at 50Hz and quite a few at 60Hz - but very few see it above 70Hz.
SteveBaker (talk) 13:35, 29 September 2014 (UTC)
Movies haven't been 24Hz for a while, the shutter closes either 2 or 3 times a frame while the film only moves once. If someone sees 100Hz flicker, they could be pissed off if they were too poor to leave the 50Hz area (the entire Europe?) and was easily annoyed. (I'm distracted watching '14 World Cup super-slow motion, is it that hard to make 4 phase lights?) Sagittarian Milky Way (talk) 07:28, 30 September 2014 (UTC)

September 29[edit]

Alien possum ?[edit]

Sarue.jpg

Hi, white eared possums use to be Didelphis albiventris‎ species. But they live in South America. So what do you think of this guy, said to be North American but white eared and black footed unlike regular Didelphis virginiana‎ ? --Salix (talk) 09:54, 29 September 2014 (UTC)

A few thoughts: 1) the source for the image (link rotted away) is linked to a URL from the IESB, a Brazilian institution. 2) The data that says it's D. virginiana is linked to "Nordopossum" on the de.wikipedia. So, it's likely that whoever made that association was not a North American. 3)Coat pattern and color can vary quite a bit within species. With all that in mind, it seems that this is definitely a questionable ID, though I would also hesitate to say with certainty that it is a white-eared possum. SemanticMantis (talk) 15:08, 29 September 2014 (UTC)
Alien? HiLo48 (talk) 17:25, 29 September 2014 (UTC)
I'm quite certain that's a white-eared opossum, not a North American opossum. Looie496 (talk) 14:07, 30 September 2014 (UTC)
That's slightly problematic, because the picture of the white-eared opossum in our article differs in appearance from this picture, and when you check the file description, that animal is called Didelphis marsupialis. Also, a reverse search on the picture here at google gives a link to an article in Portuguese that say the animal here has a range just up to the southern border of the US, not the rang shown in our article. μηδείς (talk) 23:45, 30 September 2014 (UTC)

Are hippos the most dangerous mammal in Africa?[edit]

Hi, there are a lot of websites that state that the Hippopotamus is the most dangerous mammal in Africa, and that it kills more humans than any other - but does anyone know if there is actually any evidence to support this? All I can find is an unverified figure of 2,900 - even if this is true how does it compare to, say, the crocodile or the elephant?

I did spot a paper by the FAO (http://www.fao.org/docrep/012/i1048e/i1048e03.pdf) that suggests the crocodile has superseded the hippo, but, again, it doesn't provide any evidence.

Any help would be greatly appreciated! Many thanks.

Last Polar Bear (talk) 11:22, 29 September 2014 (UTC)

I suspect that humans are the most dangerous mammal in Africa. Wars in Africa kill hundreds of thousands humans. --Mark viking (talk) 11:31, 29 September 2014 (UTC)
Agreed. According to our hippo article, humans killed ten times that many of them alone, in the mid-70s alone, in the Congo alone. So I stopped counting. We are the undisputed champions.
A crocodile is not a mammal. InedibleHulk (talk) 11:33, September 29, 2014 (UTC)
The way I've heard it (as in a comment in National Geographic a number of years ago) is that the hippo is the most dangerous animal in Africa, not just the most dangerous mammal. Obviously, humans are biologically animals, but in this context the term is used to refer to non-humans. ←Baseball Bugs What's up, Doc? carrots→ 14:29, 29 September 2014 (UTC)

Tsetse fly has no fans? Anyway there's a lovely story of the Zulu troops of John Robert Dunn singing a song of praise with a stanza which he translated as "He is a lion. Yes, he is better than a lion—he is a hippopotamus." Scouting in South Africa Jim.henderson (talk) 15:03, 29 September 2014 (UTC)


This is not just myth, it is basically true. Here's some hard research on at least part of Africa [4]:

. Another paper here has some general numbers, but is restricted to tourist attacks [5]. I think the claim is fairly plausible, Croc, hippo and lion seems to be the top non-human killers of humans, crocs are not mammals, and lions seem to be a bit more predictable... if you check your FAO source it probably has references to the studies they were citing. Google scholar will also help you find other hard numbers. SemanticMantis (talk) 15:47, 29 September 2014 (UTC)

It's just a matter of qualifying the claim:
  • Most dangerous animal...no...humans kill more than any other animal.
  • Most dangerous non-human animal...no...the mosquito and/or tsetse fly kill far more.
  • Most dangerous non-human vertebrate...no...we think maybe the croc kills more.
  • Most dangerous non-human mammal...Yes - the hippo!!
With sufficiently careful qualification, you can get it to come out true.
SteveBaker (talk) 16:49, 29 September 2014 (UTC)
To be fair to the insects, they don't try to kill us. They just want a little blood, and happen to be infectious. Still dangerous, but not malicious or even reckless. InedibleHulk (talk) 23:05, September 30, 2014 (UTC)

Being mauled by a wolf on one's way to work was a real possibility in 13th century England, too. Civilization means clearing your neighborhood of critters whoever put there Asmrulz (talk) 17:33, 29 September 2014 (UTC)

Maybe the issue is that everyone knows crocodiles are dangerous, while the danger from hippos is not necessarily as obvious. ←Baseball Bugs What's up, Doc? carrots→ 19:30, 29 September 2014 (UTC)
Malaria would be another runner-up (most dangerous species), among other bacteria (viruses are out; they lack metabolism and therefore don't really count as lifeforms).
Among all multi-cellular lifeforms, only h.s.s. comes close. It would be interesting to see how close exactly, but data on that is hard to get...
"For only $2 a month, this african child can survive. Donate now!
p.s. Airing this commercial just killed 4,500 kids!"
However, the malaria plasmodium and the tsetse fly amount to something more deadly than the two species separately – the insect draws some blood and spreads bacteria via her saliva, and the plasmodium is the one that kills you. Not sure how that should count. The Black Plague was even doubly-symbiotic: Black rats are usually blamed, but it was their fleas that carried most of the bacteria.
BTW, bacteria don't qualify as "animals", so Steve Baker's "Most dangerous" list is accurate if the tsetse fly gets the kill (or even half the kill). - ¡Ouch! (hurt me / more pain) 09:40, 1 October 2014 (UTC)

Engineering a living conscious system where entropy does not increase[edit]

Is it possible to engineer a living conscious system where entropy does not increase? Sustaining a consciousness indefinitely. 49.183.46.17 (talk) 12:38, 29 September 2014 (UTC)

no. --Jayron32 12:49, 29 September 2014 (UTC)
The second law of thermodynamics says that entropy never decreases; it does not say entropy must increase. 49.183.46.17 (talk) 12:57, 29 September 2014 (UTC)
There are no known systems made of real materials where entropy does not increase. --Jayron32 13:01, 29 September 2014 (UTC)
That's not true. For example, the entropy of a system does not increase if the system is already at thermodynamic equilibrium. 49.183.46.17 (talk) 13:12, 29 September 2014 (UTC)
True, but a system that was conscious (let alone living) would need to do work on the physical substrate of the system's mind (neurons or transistors), and the Second Law tells us that entropy must increase in this case. Even if we allow non-physical conscious systems (see substance dualism), any interaction of such a system with the physical world would involve work. If we allow non-physical conscious systems that don't interact with the physical world (see Afterlife), we're outside the realm of engineering. Tevildo (talk) 13:41, 29 September 2014 (UTC)
Why would a conscious system need to do work on the system's brain? 49.183.46.17 (talk) 14:27, 29 September 2014 (UTC)
Because information processing requires work. We have an article called entropy in thermodynamics and information theory that will introduce several of the concepts. Put very simply: whatever physical representation you use to store or process information must put enough work into the system to overcome the system's tendency not to store or process that same information. If you consider a single bit, it always takes energy to store a zero- or a one- because if the system were at equilibrium, the bit could flip between the two states at random. Any machine that processes information must necessarily have an energy well and then do work to put the system state into the energy well that corresponds to a particular informational state. Nimur (talk) 15:04, 29 September 2014 (UTC)
I see. So is the human brain always entering a higher and higher energy state as work is being done to it continuously? 49.183.46.17 (talk) 15:26, 29 September 2014 (UTC)
Not necessarily: let's look at the simplest possible case: let us use a single bit, zero or one. We can let it represent anything we like - perhaps it is the bit that represents the thresholded value of a thermostat, and will be used to turn on a boiler. Perhaps the bit represents The Answer to some great philosophical question that the abstract thinking-machine has to compute. For our purposes, it is a single bit: it has exactly two states.
We can build an electrical circuit to store this bit: we might have a capacitor, and if the capacitor carries charge such that its potential is greater than one volt, the bit equals "1"; if the capacitor carries charge such that the potential is less than half a volt, the bit equals "0." For this machine, that bit has more energy when it is in the "1" state.
But suppose I am a clever engineer and I do not want my machine to spend any more or any less energy, no matter what answer it computes for the result of the Great Question. So instead, I can represent one single bit using two capacitors: the same threshold values apply, but in this case, if capacitor A is high, and capacitor B is low, the state is "1." If A is low and B is high, the state is "0." I build my machine such that all other combinations are invalid.
This incarnation of my machine carries the exact same amount of potential energy for state 0 and state 1. Yet, the act of calculation - i.e. when the machine operates such that it switches state from zero to one, or from one to zero - necessarily wastes energy to heat and that energy necessarily escapes the system. This is the energy lost because the entropy decreased. By placing the device in a known configuration, energy had to be spent; work had to be done on the system.
So it is not always true that the machine must be left in a higher energy configuration after each calculation. But it is true that for each informational-processing operation, work must be done. If this were not true, state 0 and state 1 would be in thermodynamic equilibrium, and the machine could freely transit between them. There is necessarily a potential energy barrier between these states, or else they are the same state.
Nimur (talk) 15:35, 29 September 2014 (UTC)
You could impement such a system using a quantum computer that would simulate it in a virtual environment, see also this reply to a question explaining that entropy does not have a physical meaning. Count Iblis (talk) 15:32, 29 September 2014 (UTC)
Please explain: in your quantum computer, exactly which parameter would you quantize? Most computers have already quantized every value they work with: information is quantized into discrete bits; voltages are thresholded into discrete levels; time-intervals are quantized into distinct steps through the use of electronic clock pulses. Which other parameter would you quantize, and in which way would you expect the machine to behave differently because of this change?
In the example I gave above, do you believe anything would differ if you built a machine in which state was stored by the polarity of the spin of an electron, instead of the magnitude of charge on a capacitor plate? Why would you expect this different behavior? What reliable source concurs with you?
Count Iblis, it is common to have difficulty in defining entropy. You are in good company when you find it difficult to describe the physical nature of entropy. But you are frankly incorrect if you take the claim further and state that it has no such meaning. Many scientists have defined entropy and related its interpretation to physical quantities. Here is a review-article from the Plato Encyclopedia of Philosophy: Which Entropy? This article presents several historical sources, and cites other articles that provide more detailed reviews; and proceeds with a tandem description of the qualitative properties of entropy alongside a formal mathematical definition.
Nimur (talk) 15:45, 29 September 2014 (UTC)
A quantum computer is a closed system that evolves according to the Schrodinger equation, it does not decohere. This means that you can always describe the exact state it is in from the knowledge of its initial state. Thermodynamics is only really useful to give an effective description of macroscopic objects in terms only macroscopic variables. The fact that the laws of thermodynamics were discovered empirically without a sound theoretical basis, has led to entire generations being indoctrinated by wrong ideas. Most people think that concepts like heat, temperature entropy are physically fundamental quantities while in fact they are purely statistical concepts that arise when you attempt to give a closed description the dynamics of a system of say, 10^23 particles in terms of only a few macroscopic observables of that system. In general, this cannot work, but it turns out that that under suitable conditions this is possible (we call that thermal equilibrium). Count Iblis (talk) 22:58, 29 September 2014 (UTC)


A computation can be done with an indefinitely low expenditure of energy by biasing a reversible computer but the time taken goes up as you use less and less energy. Dmcq (talk) 16:31, 29 September 2014 (UTC)
I am intrigued by this idea. Can you use an arbitrarily little amount of energy to perform a computation (at the expense of computation time)? How? 49.183.46.11 (talk) 02:33, 30 September 2014 (UTC)
Taking on the second part of the question - how to run consciousness indefinitely, one idea for doing that relies on that fact that although entropy increases, the universe will never be able to attain a perfect state of uniform chaos implied by that increase. It asymptotically approaches that state - but can never, finally, reach it. There is always just a little exploitable energy somewhere. So imagine you have a consciousness embodied in a computer. As entropy increases, the energy required to power the computer gets harder and harder to find. But suppose you engineer the computer to soak up available energy until it has enough to cycle the processor through one clock tick. Initially, the clock ticks a billion times a second - but as the universe becomes increasingly uniform, collecting energy gets harder and harder - and the computer runs more and more slowly. But it never becomes utterly impossible for there ever to be another clock tick. Eventually, you might have to wait a trillion years for your computer clock to advance by a single 'tick'. So from the perspective of the consciousness inside, time would seem to gradually increase in speed - things going faster and faster. But since the universe has less and less that can change, being able to 'fast-forward' over it seems like that would be OK...perhaps even advantageous. Thinking of "time" as the accumulation of energy rather than the increase in entropy is the key here. SteveBaker (talk) 16:43, 29 September 2014 (UTC)
Heat death of the universe is the relevant article. I would argue that there _will_ come a time when there isn't a sufficiently large energy gradient anywhere in the universe to power the machine; the universe may not be at a state of perfect equilibrium, but the machine will have a minimum energy per tick that the universe will be incapable of supplying. There will eventually be a last tick. Genesis 3:19. Tevildo (talk) 17:45, 29 September 2014 (UTC)
At that point, will time cease to exist? ←Baseball Bugs What's up, Doc? carrots→ 19:26, 29 September 2014 (UTC)
No; it will just cease to be an interesting or useful way to describe events, because events will be pretty homogeneous with respect to changes in time. Nimur (talk) 19:30, 29 September 2014 (UTC)
At a certain point, that question becomes more a matter of philosophy than science. Relevant articles: Arrow of time, Entropy_(arrow of time), Philosophy of space and time, temporal finitism, and of course good old Time. It's also worth mentioning that there's lots of uncertainty regarding the Ultimate_fate_of_the_universe#Theories_about_the_end_of_the_universe, and I'm not sure if all of Nimur/Steve/Tevildo's comments above are compatible with all of the current theories. SemanticMantis (talk) 19:57, 29 September 2014 (UTC)
I should admit at this point that my contribution is shamelessly ripped-off from Barrow (as in the Strong Anthropic Principle), but I would still consider it valid at a high level of generality. Tevildo (talk) 21:36, 29 September 2014 (UTC)
  • I think perhaps some clarification is needed here. It's not possible in any meaningful sense to create an isolated complex system where entropy doesn't increase, but it is possible if the system is not isolated. In fact an animal is essentially such a system: it maintains more or less constant internal entropy, by taking in matter that has low entropy and expelling waste that has higher entropy. (This might be implicit in some of the answers above, but I can't see it stated clearly.) Looie496 (talk) 00:59, 30 September 2014 (UTC)
I think everyone here understands that - the problem here is that our OP wants a system for "Sustaining a consciousness indefinitely." - and that implies a constant entropy system. SteveBaker (talk) 01:45, 30 September 2014 (UTC)

Are chickens really cowardly?[edit]

I haven't really spent a huge amount of time around chickens, granted, but they never seemed particularly cowardly to me, or at least not moreso than any other bird that will move away from you if you walk towards it. The adult males are certainly not cowardly by any stretch of the imagination - those guys will stand their ground. Is the chicken's yellow-bellied reputation really deserved? --Kurt Shaped Box (talk) 19:45, 29 September 2014 (UTC)

I saw something on stackexchange or something like that saying that the expression originally had to do with the chicken's apparent lack of defence, though it was revived to have a slightly altered meaning.. ~Helicopter Llama~ 19:55, 29 September 2014 (UTC)
okay i found it http://english.stackexchange.com/questions/95494/etymology-of-the-phrase-chicken-out ~Helicopter Llama~ 19:56, 29 September 2014 (UTC)
No; no more than rats are traitorous, snakes are deceitful, or badgers are annoying. Nobody who's ever seen a Cockfighting rooster would ever think they are cowardly (google images at your own risk.) This stuff is all just an accident of history and culture, and little-to-none of it really holds up to biological scrutiny. I'm sure there's some culture where rats are seen as valorous, chickens are seen as clever, etc. Here's a collection of academic papers on the topic. It all comes down to the fact that metaphors aren't made by biologists: [6] [7] [8]. A few of those works cite Metaphors We Live By, which is a very interesting and influential book on the topic of metaphor. (I know this answer is more socio-linguistic than biological, but that's how I see it. Interestingly, there are some areas of biology where the folklore is basically correct, particularly the ones that have to do with phenology, e.g. "Plant your corn when the oak leaves are the size of a mouse's ear [9]") SemanticMantis (talk) 20:16, 29 September 2014 (UTC)
I bet some of those animal reputations have a grain of truth to them. Snakes are ambush predators, for example, and that could well be described as sneaky. Rats can turn on each other in the case of scarce resources, more than, perhaps, a more tightly knit eusocial species, like bees or ants. As for badgers, there I believe "badgering" was the term applied to the way dogs hunt badgers, with a pack attacking from all sides, then each retreating when the badger turns toward them. StuRat (talk) 04:40, 30 September 2014 (UTC)
With bees and ants, "each other" itself is an alien concept. One hive, one code, one mission. Somewhere between their truth and rats' is the naked mole rat. Another "sneaky" trait of some snakes is the way they weave laterally before striking straight on, without telegraphing it. More of a rapid acceleration than a snap, too. Deceptively slow. Yoel Romero does something of the same to humans. Tying it back to chickens is chicken hypnotism. There's apparently a state beyond fear and confidence. You could use it to pet them as well as behead them. InedibleHulk (talk) 05:15, September 30, 2014 (UTC)
One example that does more-or-less hold up to "biological scrutiny" is "elephants never forget" (per Scientific American) 71.20.250.51 (talk) 20:43, 29 September 2014 (UTC)
Not really. There isn't remotely enough capacity in an elephant brain to literally remember absolutely everything and never forget it. SteveBaker (talk) 20:56, 29 September 2014 (UTC)
Okay, submit that to SA for peer review. Note that "more-or-less" is not synonymous with "literally remember absolutely everything" — Preceding comment not intended to be snarky, so please don't take it personally, okay?  ;)  71.20.250.51 (talk) 21:20, 29 September 2014 (UTC)
Chinese culture has a very different view of roosters and snakes, they give them all very positive traits, just look up Chinese zodiac for examples. Vespine (talk) 23:27, 29 September 2014 (UTC)
Thinking about this further, isn't the chicken a prominent national symbol in France? Obvious political humour about French military accomplishments and foreign policies aside, I'm assuming that the chicken must have very different connotations over there too? --Kurt Shaped Box (talk) 01:09, 30 September 2014 (UTC)
The French symbol is a cock. DuncanHill (talk) 01:11, 30 September 2014 (UTC)
We have an article on it - Gallic rooster, which includes intimations of cock-worship. DuncanHill (talk) 01:14, 30 September 2014 (UTC)
  • As Mantis said, roosters are very far from cowardly. But an important factor is that roosters have spurs, which are a wicked weapon. Hens don't have spurs, and are basically defenseless, therefore timid. It's much more common to encounter hens than roosters, because you can't have more than one adult rooster in the same area without them fighting to the death. Looie496 (talk) 00:52, 30 September 2014 (UTC)
Apparently (this has come up here before), in the wild the roosters will form a pecking order within the flock and don't actually kill each other for coming too close and/or making eye contact. The subordinate males help with flock defence and finding food. --Kurt Shaped Box (talk) 01:09, 30 September 2014 (UTC)
I have six roosters, only the old, weak one gets chased (somewhat gently). If they're raised in the group, they come up knowing their place. Just the strange males that cause problems. Did that once, and eventually had to cage them both for a couple of weeks beside each other till they calmed down. It'd be the same if a strange guy moved in with our women uninvited, I think.
Compared to a cat or dog, chickens are hard to pet. But as far as birds go, their inability to fly makes them easier to befriend. I can pet three of my hens and two roosters. They all come pretty close, especially for food. Also, some hens grow spurs. Has to do with a hormone rush that comes from protecting their chicks. When they're doing that, they're definitely brave and can terrify cats, even without spurs. InedibleHulk (talk) 01:47, September 30, 2014 (UTC)
  • I think we may have been forgetting that chicken traditionally means a young bird (especially a young domestic fowl). So, we need to stop thinking about full-grown cocks and start thinking about the behaviour of young fowl. Are they cowardly? DuncanHill (talk) 01:25, 30 September 2014 (UTC)
I wouldn't identify "Chicken" with a young bird...that would be a "chick". Adults are hens and cocks - but generically, all three are "chickens". If I see a group of such birds of mixed age and gender - I'm going to call them all "chickens". I guess there are probably regional dialect differences at play here. SteveBaker (talk) 01:41, 30 September 2014 (UTC)
Chicks are the fluffy little yellow jobs. A chick grows into a chicken, which grows into a hen or a cock (of course, most male chicks don't get the chance to grow up). Collectively they are fowl. What you buy in the supermarket labeled as chicken will be a chicken, that is to say, not fully mature. Even in my lifetime I've noticed a tendency for "chicken" to absorb the other meanings. It's also noticeable, in my experience, that there is a difference in usage between people who grew up in traditional mixed agricultural areas, and those from big towns or cities - the latter calling everything chicken. DuncanHill (talk) 01:51, 30 September 2014 (UTC)
I grew up around farmers, and that's the first I hear of this. Killing a chicken for market before it's mature would just mean less meat and less money. Everything I've ever seen in stores in Canada (and on TV) was a full-grown chicken. "Fowl" is the collective term for all sorts of birds, usually chickens, ducks and geese, in a food sense. InedibleHulk (talk) 02:01, September 30, 2014 (UTC)
Chambers 20th Century Dictionary has "Chicken - the young of birds, especially of the domestic fowl: the flesh of a fowl, not always very young: a prairie chicken: a youthful person...." We used to keep hens for eggs. The ones you buy in supermarkets aren't mature - they are killed as soon as they're the right size, not when they have reached maturity. DuncanHill (talk) 02:14, 30 September 2014 (UTC)
I was thinking of a right-sized hen when I said mature, but I guess you're thinking of sexual maturity. Fair enough. Thanks for the reference, though people here would generally think it odd if you said a laying chicken isn't a chicken. InedibleHulk (talk) 02:49, September 30, 2014 (UTC)
"Laying chicken" sounds odd to me - chickens are for eating, hens for laying. DuncanHill (talk) 02:52, 30 September 2014 (UTC)
Laying hen works for me, too. And yeah, there's chicken (food). Haven't heard of hen salad or hen fingers. InedibleHulk (talk) 02:59, September 30, 2014 (UTC)
I think your notion of "chicken" is closer to the definition of "pullet" -- 'Females over a year old are known as hens and younger females as pullets[8] although in the egg-laying industry, a pullet becomes a hen when she begins to lay eggs at 16 to 20 weeks of age.' -- IMO, the fact that the prepared chicken we buy at the market may in fact be the bodies of very large-bred pullets is a bit of a red herring with respect to this question. SemanticMantis (talk) 15:51, 30 September 2014 (UTC)
Pullet is basically the Norman-French word for a chicken. In modern French poule means fowl, poulet means a young fowl. DuncanHill (talk) 16:21, 30 September 2014 (UTC)
WP:OR here but chickens do run from people unless they are brought up being held by people often. Our first batch of chickens were often being pet and held. They'd go up to strangers as well as my wife and I. Since then we've taken a more hands off approach and they do run away at the slightest provocation. Our rooster will keep with the hens but will normally take a position between us and the hens. Dismas|(talk) 01:33, 30 September 2014 (UTC)
Birds in general often run or fly away from humans. The ones that don't (such as the dodo) tend to go extinct. Penguins are supposedly unafraid of humans, but the frigid temperatures are their friend. If they lived in a warm climate, they might already have gone the way of the dodo or the passenger pigeon. And given what usually happens to chickens, running away is justified. ←Baseball Bugs What's up, Doc? carrots→ 02:12, 30 September 2014 (UTC)
Even without memories of of killer humans, I think there's an instinctual fear (in everyone) of enormous creatures. If The Friendly Giant (or a primitive chicken) came up to shake my hand and pat my back for the first time, I'd step/run away. Even after knowing him for a while, I'd stay cautious. Accidents happen. InedibleHulk (talk) 02:32, September 30, 2014 (UTC)
Chickens tend to be "cowardly" near animals that could kill them, which, for a chicken, is quite a lot. If people were surrounded by T. Rex's, then we would be rather cowardly, too. Of course, most birds are in the same boat, except perhaps those with few natural predators, like penguins or emus. Killdeers also seem irrationally brave, threatening any animal who comes near their nest. I suppose their ability to come close to the animal but veer off at the last minute and still stay out of range allows them to be that brave and survive. StuRat (talk) 04:51, 30 September 2014 (UTC)
Penguins have few natural predators? On land, perhaps, but not underwater, to judge by the article. —Quondum 05:15, 30 September 2014 (UTC)
Yes, I meant on land. Perhaps a better example is the dodo, which had no natural predators, and hence no fear, which did them in when people came around, and they neither ran nor hid from the hunters. However, this left them with the reputation of being stupid, more than brave.StuRat (talk) 05:53, 30 September 2014 (UTC)
Another brave bird for you. Found videos of this species when looking for footage of the bird that *I* know as a lapwing (which is also pretty brave in the face of a potential predator in its own right). There are loads of vids on YouTube of these Australian critters standing their ground. Note the spurs on the wings, ready to strike. --Kurt Shaped Box (talk) 08:18, 1 October 2014 (UTC)
A sandhill crane dropkicked my "playful" dog a couple of weeks ago, instead of fleeing. Apparently, even cars aren't scary enough. Here they are, chasing an alligator. But yeah, it's easy to be brave when you're tall. I haven't seen how my chickens interact with them yet. InedibleHulk (talk) 08:42, October 1, 2014 (UTC)

September 30[edit]

Terminology Question[edit]

Does 'immunological response to X' mean something different than 'allergic reaction to X'?

Or are they two ways of labeling the same thing?

Thanks, CBHA (talk) 00:27, 30 September 2014 (UTC)

No, not the same. See: [10]. 71.20.250.51 (talk) 00:48, 30 September 2014 (UTC)
... which explains that the former is more general. An allergic reaction is one example of an immunological response. Dbfirs 07:14, 30 September 2014 (UTC)
Would it be correct to say that an allergic reaction is a "negative" event in that the person's immune system is overreacting to a perceived threat (allergen) which would not be a problem to the person if the immune system was able to ignore it? CBHA (talk) 13:48, 30 September 2014 (UTC)
That seems to be correct, given "Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment.", from allergy. SemanticMantis (talk) 15:46, 30 September 2014 (UTC)

Puppies and running water[edit]

Puppies are, in my experience, often scared of running water. Mum and I were talking about this the other day and mum suggested that perhaps there was something in the appearance of it that could trigger an instinct to avoid snakes - the wiggly, slithery motion of a small stream perhaps looking like a snake. Has there been any research into puppies' fear of running water, and into dogs' instinctive reactions to snakes? The dog we were reminiscing about later came to love water, insisting that we threw sticks for her to fetch into any body of water we came across on our walks. DuncanHill (talk) 02:24, 30 September 2014 (UTC)

The usual cursory means of finding research sources hasn't found anything specific to puppies and running water (quite a bit about dealing with dog's fear of water, etc.). While speculation should be avoided (despite rumors to the contrary, "Wikipedia is not a forum"), I wonder if it might be related to the sound of running water. Perhaps its an instinctual reaction to rain storms and/or rushing water and the like? While an adult dog can usually deal with a small stream, generally a puppy could not.  71.20.250.51 (talk) 05:32, 30 September 2014 (UTC)
I dunno. I've both owned and seen puppies that have a lot of fun with the stream coming out of a hose. I don't think it's a species-wide thing. Justin15w (talk) 14:16, 30 September 2014 (UTC)

Volcanism of Io[edit]

Earth's volcanism is powered by radioactive decay, while Io's volcanism is powered by tidal effects from Jupiter's gravity. Since energy is drawn from the Jupiter-Io system, can it cause orbital instability? If so, when will Io fall into Jupiter? Also, can humans tap Io's volcanism as a source of energy? Jayakumar RG (talk) 17:30, 30 September 2014 (UTC)

The article on Volcanism doesn't say anything about radioactive decay. What's your source for that? ←Baseball Bugs What's up, Doc? carrots→ 22:51, 30 September 2014 (UTC)
I learnt it elsewhere, but it is mentioned in the Volcanology of Io article. The presence of magma beneath the earth's surface is because of heat generated from radioactive decay.

You might be interested in reading our article Volcanology_of_Io. SemanticMantis (talk) 19:28, 30 September 2014 (UTC)

Thank you, the article is extremely informative. But it says nothing about orbital instability. Jayakumar RG (talk) 01:18, 1 October 2014 (UTC)
It is for that reason that I directed you to Galilean_moons#Members yesterday, User:Jayakumar RG. The article has references for further reading. μηδείς (talk) 04:12, 1 October 2014 (UTC)
  • The Galilean moons also orbit in various whole number or fractional resonances. This might affect any orbital change or decay. μηδείς (talk) 23:35, 30 September 2014 (UTC)

Bumpers on motor vehicles[edit]

When and why did manufacturers of (some) motor vehicles discontinue the practice of equipping them with bumpers? I did not find answers in the article "Bumper (automobile)".
Wavelength (talk) 20:54, 30 September 2014 (UTC)

Can you give an example make/model/year? In the USA, bumpers are required for all passenger vehicles, and there is a set of safety standards that the bumpers must meet. See e.g. here from the NHTSA [11]. Certain non-passenger vehicles are exempt from those regulations, and "some vehicles do not have a solid bumper across the vehicle, but meet the standard by strategically placed bumper guards and corner guards". So perhaps you are seeing vehicles with a sort of "disguised bumper", i.e. one which meets the regulations for bumpers but doesn't have a highly visibly separate piece of metal? SemanticMantis (talk) 21:21, 30 September 2014 (UTC)
First I heard someone mention it, and later I saw some in a printed advertisement. From a Google Image Search for "2015 ford", I found this image.
Wavelength (talk) 22:07, 30 September 2014 (UTC)
That car has bumpers. They are covered by a plastic panel Greglocock (talk) 22:49, 30 September 2014 (UTC)
The Audi R8 is an example where the function of a "bumper" is integrated internally, with no conventional bumper visible.→
71.20.250.51 (talk) 23:38, 30 September 2014 (UTC)
I asked this question to myself many many many years ago. The bumper article says:
Cars were equipped with bulky, massive, heavy, protruding bumpers to comply with the bumper standards of the 1970s and early 1980s. By the late 1980s most bumpers were concealed by a painted thermoplastic fascia. The thermoplastic currently in use is a combination of polycarbonate and acrylonitrile butadiene styrene called PC/ABS. The internal aspect of the bumper usually consists of a lightweight foam or polyurethane. This foam does not contribute to the impact absorption factor of the bumper, but serves as a filler and prevents the thermoplastic fascia from cracking upon impact.
Cars always have bumpers. They are always useful. It's just they are not concealed. They do not use beautiful and big chrome plated bumpers anymore. -- Toytoy (talk) 03:19, 1 October 2014 (UTC)

October 1[edit]

Spacecraft Thermal Blankets[edit]

Voyager spacecraft diagram
Voyager spacecraft

This first illustration says: "Shown Without Thermal Blankets".

I guess the thermal blankets are the black things in the second picture.

You can see the optical equipments and the spacecraft's body panels are covered by some black fabrics.

The Voyager's 3.7 meter antenna must point to the Earth all the time to keep the connection alive.

Since it is far away from Earth, the sun must be roughly in the same direction.

Except for the antenna disc and some extended parts, almost everything else is in the antenna's shadow.

This means nearly the whole spacecraft is not lit by the sun, not to mention the spacecraft is very distant from the sun most of the time.

Then why did they put thermal blankets on it? Did they use it to dissipate the heat generated by the radioisotope thermoelectric generators and all these electric-powered equipments?-- Toytoy (talk) 03:13, 1 October 2014 (UTC)

Protects it from cold, I do believe. --jpgordon::==( o ) 04:57, 1 October 2014 (UTC)
See multi-layer insulation. DMacks (talk) 06:00, 1 October 2014 (UTC)

Photochromism[edit]

Are there any photochromic materials that can slowly change colour under the regular indoor lighting?85.141.225.141 (talk) 07:05, 1 October 2014 (UTC)