Wikipedia:Reference desk/Archives/Science/2008 July 26

= July 26 =

Brain development
Which is better for improving your brain, listening to music or watching TV? —Preceding unsigned comment added by 79.76.216.89 (talk) 02:00, 26 July 2008 (UTC)


 * I'd say it depends on the shows. Listening to Howard Stern has got to be worse for your brain than watching Charlie Rose, while listening to NPR has got to be better for your brain than watching Jerry Springer. StuRat (talk) 04:24, 26 July 2008 (UTC)


 * Reading, playing games, problem solving, doing puzzles, exercising and eating well are better than music or tv. That said, music is better than tv because it takes more imagination to experience it. -LambaJan (talk) 04:45, 26 July 2008 (UTC)


 * "I like radio better than TV...because the pictures are better." StuRat (talk) 04:50, 26 July 2008 (UTC)


 * Actually, music is said to give patience to mind. It increases mental concentration according to Sigmund Fraud because of its rhythemic sequences of audible frequences. Brain is linked to ears through auditory nerves. The music produces periodic vibrations in our eardrum and drags our concentrations more towards it. But if you say frankly, no such effect is produced by TV. TV combines both sound and video (and many a times the sound is not in a singsong manner,i.e periodic).Electromagnetic Transverse light waves from TV entering our eyes and longitudinal sound waves dilate each other's effects.Hence, no net development is caused. In my words, frequent adds in the TV often carry away our minds by making us impatient.So, music is better than TV. Thanks for asking such a realistic question. Best Regards.117.201.96.242 (talk) 19:42, 26 July 2008 (UTC)
 * Was that a Freudian slip when you misspelled Sigmund Freud? ;-) AlmostReadytoFly (talk) 20:48, 26 July 2008 (UTC)


 * Yes, it was indeed. I'm sorry. I'm not a good typist.117.201.96.242 (talk) 21:22, 26 July 2008 (UTC)

Treated or untreated lumber?
Is it possible to tell, based on visual inspection, whether an existing wood structure was built with treated or untreated lumber? If so, how do you do it? —Preceding unsigned comment added by 71.162.242.76 (talk) 02:23, 26 July 2008 (UTC)
 * Treated wood often has a stamp indicating what kind of treatment it's had. Also, older treatment methods tended to turn the wood green.  Also, if the structure's been there for a while, and it's touching the ground, and there's no rot where it's touching the ground, and it's not cedar or one of the other naturally resistant species, it's a good bet that it's treated.  --Sean 69.134.125.191 (talk) 04:23, 26 July 2008 (UTC)

Anti-Light
Is it possible for there to be anti-light which when shined on a surface gives the opposite colors to what light would have given? —Preceding unsigned comment added by Jamesernator (talk • contribs) 02:27, 26 July 2008 (UTC)


 * Mmm, I'm thinking no. Think about how "light" works—"white light" is a broad spectrum of frequencies, most of which are absorbed by the surface you are shining them on except for a few that scatter off and produce what we consider to be the "color" of something. (This is a very rough approximation, I know.) So what you're asking for is a way to shine frequencies of light at something in a way that will instead reflect back different frequencies than they normally would. If something appears red, it's because it absorbs all frequencies except red. So how are you going to make that possible reflect back green? It's not going to happen. It doesn't have to do with the light. (If you shined light at it that didn't contain any red, you'd get something that looked blackish and washed out, like what happens when you drive through tunnels with very narrow frequency lighting and all the cars look greyish.) --98.217.8.46 (talk) 03:23, 26 July 2008 (UTC)
 * What is the opposite of red? Colors don't have opposites.  Plasticup  T / C  03:41, 26 July 2008 (UTC)
 * Yes they do (after a fashion). Cyan (a combination of blue and green) is the opposite of red.  Since people percieve color using three kinds of color receptors in their eyes that roughly correspond to red, blue, and green, then every color can be approximately represented as a combination of red, blue, and green where each component has an intensity between 0 (absent) and 1 (fully saturated).  This RGB color scale thus gives rise to natural opposites, where if a color has RGB components (r,g,b) then it's complement is the color represented by (1-r,1-g,1-b).  Dragons flight (talk) 05:01, 26 July 2008 (UTC)


 * Right, but the RGB scale is more an artifact of our vision hardware than the physical aspects of the colors themselves, I do believe. There's no physical reason that a 700nm frequency is the "opposite" of 500nm (or thereabouts). As far as physics is concerned they are just lines on a scale, if that. --98.217.8.46 (talk) 05:42, 26 July 2008 (UTC)


 * Of course there are opposite colors: if you shine a white light on a surface that absorbes everything but colors in the red spectrum, then the surface will be red. However, if you shine a white light on a surface that does the opposite, it reflects everything except colors in the red spectrum, then you get cyan. They are opposite, complementary colors. Mix them together, and you get black, white or some sort of gray. See also Negative (photography). As for the original question, no, there is no such light. Shine a cyan light on a red surface, and the surface is going to appear black. It's never going to emit cyan because the surface absorbes those wave lengths. An even more clear example is black: a black shirt is going to stay black, no matter how much light you shine on it. It's never going to appear white under any sorts of light. ADFSGL (talk) 14:52, 26 July 2008 (UTC)
 * Again, the color wheel and all is just an artifact of our visual system. You could imagine visual systems that do not have the same "opposites". Physically there is nothing as an "opposite" of a color—that is just a physiological artifact of how our brains deal with color vision. --98.217.8.46 (talk) 23:33, 26 July 2008 (UTC)
 * I believe what ADFSGL is trying to point out is that, while complementary colors, like all colors, are indeed artifacts of the human visual apparatus, complementary electromagnetic spectra are well defined (up to a constant) by objective physical laws (specifically, the additivity of electromagnetic waves) and do, indeed, give rise to complementary colors when perceived by the human eye (assuming that both the original spectrum and its complement have intensities within the range of photopic vision, which tends to imply a lack of sharp peaks). Of course, your point that the crudity of human color perception causes some non-complementary spectra (such as your monochromatic examples) to also be perceived as complementary colors is also true.  —Ilmari Karonen (talk) 23:54, 26 July 2008 (UTC)
 * Exactly! Any perceptible color has a clearly defined opposite: its inversion in the visible spectrum. Just because we restrict the wavelengths doesn't mean that we can't have a strict definition for "oppositeness". ADFSGL (talk) 10:29, 27 July 2008 (UTC)
 * Well what do you mean, that you look at the histogram for the prevalence of every wavelength in a light source and then invert all of the values? But for every wavelength where there is zero prevalence in the initial source would have to have infinite luminosity in the anti-equivalent? If how ever you just mean invert of the RGB scale, whereas you may argue that each colour does have an opposite, it is true that this is just an artifact of our perception, and also that in this case (as in all others) the answer to the original question is no, there is no antilight, it violates conservation of energy and momentum. Philc 0780 17:52, 28 July 2008 (UTC)
 * Actually, color itself is an artifact of our visual system. There is no intrinsic quality of 700 nm light which labels it "red", it's an artifact of how our eye/brain processes the light. As the CIE 1931 color space experiments showed, you can get the exact same color perception with a mix of other wavelengths as you can with monochromatic light. So while it would be incorrect to say that a particular wavelength of electromagnetic radiation has an opposite, it's perfectly correct to say that a color has an opposite (or rather, a complement), as color is merely a human construction. An alien with tetrachromat or dodecachromat vision would laugh at our trichromatic ROYGBIV color system. Heck, even a trichromat with significantly different wavelength responses in their cones would scratch their heads. -- 128.104.112.147 (talk) 18:34, 29 July 2008 (UTC)


 * Ahem in the olden days of film photgraphy, colour negatives showed the opposites (as did b/w negs). Also remembering something about colours are one thing (such as trees really being red) but we perceive the opposite though have no ref for it. Julia Rossi (talk) 05:26, 28 July 2008 (UTC)

A question on civilization and cooling
How could a pre-electricity, pre-electronics people from the desert adapt their empire to stay cool in rain-forest climes? Could they build windmill fans, or would water mills or water-based turbines work without electricity? Would windmills work even if they didn't have a constant flow of wind going for them? Wiwaxia (talk) 08:12, 26 July 2008 (UTC)


 * I'm not sure I understand the question. Should the windmill fan create electricity or create wind? If a wind is going, you don't need a fan. Historically, there are some techniques for cooling, the most widely used ones probably evaporative cooling (humans have that build-in ;-) and manually operated fans (e.g. the slave with the palm frond). Good building construction helps (use of thermal mass and good ventilation), and so do lifestyle change. See Siesta. --Stephan Schulz (talk) 08:37, 26 July 2008 (UTC)


 * Bedouins wear white for a reason. --antilivedT 12:11, 26 July 2008 (UTC)


 * Rain forests tend to be quite humid, so evaporative cooling doesn't work well, and sweating therefore doesn't cool people down much. It tends to be cooler under the tree canopy just because no sunlight makes it near the ground, however.  People in rain forests typically wore minimal clothing, perhaps just a loin cloth, as sunburns aren't an issue and overheating can be.  As mentioned previously, resting during the hottest parts of the day can help, as can using a hand fan or taking a swim. StuRat (talk) 13:34, 26 July 2008 (UTC)


 * Yakhchal are mighty impressive to say they're two-and-a-half thousand year old technology. — Jack (talk) 20:53, 26 July 2008 (UTC)


 * Underground living. 152.16.59.190 (talk) 10:19, 27 July 2008 (UTC)


 * I don't believe that's an option in the rain forest, as any underground area is likely to flood. Indeed, many homes in the Amazon are built on stilts because of the risk of flooding. StuRat (talk) 14:30, 27 July 2008 (UTC)

Rashes from insect bites
Insect bites sometimes produce rashes that last several days. I'm talking about the kind that is red, raised, itchy, and lumpy(?). Physiologically, what's happening at the affected sites that makes them "lumpy"? —Preceding unsigned comment added by 71.162.242.76 (talk) 13:10, 26 July 2008 (UTC)
 * I think it's a histamine reaction. That article may help. --Tango (talk) 17:06, 26 July 2008 (UTC)


 * Most of it is already answered by Tango, but I want to add something. Some insects also have greater adenine concentration in their DNA. They produce a mixture of citric acid (note the formulae HOOCCH2COHCOOHCH2COOH) and histamine. The -COOH carboxyl group, being acidic, facilitates the action of histamine reaction. You can jump to the link for more information. Thank you, for asking such an interesting question.117.201.96.242 (talk) 19:08, 26 July 2008 (UTC)

Getting Punched in the Stomach And Its Effects On The Digestive System
When a person gets hit in the stomach, what are the effects of the force of the body blow to the stomach on the digestive system? Ericthebrainiac (talk) 15:19, 26 July 2008 (UTC)

The immidiete effect will be the initialization of the process of regurgitation. The blood will rush out from the mouth (due to wave of antiperistalsis) if the hurt is dangerous. It may also cause vomiting. If the hit is due to some metal piercing through then peptic infections may aslo occur. These infections can last for several days, often causing peptic ulcer. More details can be found from the thorough study of functions of stomach.117.201.96.242 (talk) 19:31, 26 July 2008 (UTC)


 * Hi. If a person gets hit in the diaphram, however, this may cause impact to the solar plexus, which knocks the wind out of the person. By the way, I have a feeling this is related to the "getting kicked in the testicles" question, which by the way is often illegal. Hope this helps. Thanks. ~ A H  1 (TCU) 16:34, 27 July 2008 (UTC)
 * FYI, I think you have diaphragm and solar plexus reversed. Illegal? It's rarely permitted in contact sports if that's what you mean, but I don't think a kick to someone's balls is any less legal than other forms of unarmed aggravated assualt. --Shaggorama (talk) 20:06, 27 July 2008 (UTC)

biology
Who coined the term tissue? ```` —Preceding unsigned comment added by 61.1.236.70 (talk) 16:31, 26 July 2008 (UTC)


 * It's an old word, apparently originating from the Middle English word "tissu", meaning "a rich kind of cloth", according to the American Heritage Dictionary. Nobody just suddenly looked at tissue and decided to call it "tissue" out of the blue. -- Captain Disdain (talk) 16:51, 26 July 2008 (UTC)

bacteria longevity
How long would (harmful) bacteria live on a dry smooth surface, such as a plate? A women's mag I like recently had a rant about bacteria collecting on dishcloths. But if I wash a plate, let it dry in the rack overnight, and use it for breakfast or lunch the next day, does anything harmful from the dishcloth still remain? I did read the bacteria article, but couldn't find the answer. Thank you.64.231.9.30 (talk) 17:21, 26 July 2008 (UTC)


 * The answer is "it depends". Clean, dry surfaces like porcelain or glass are not friendly for bacteria. So while your plate may have some bacteria, the chance that there are enough to cause trouble is minimal. More importantly, fear of harmful bacteria is often much out of proportion (very much aided by advertising from detergent companies with disinfectants to sell). A normal household is never sterile, and probably never will be. Normal hygiene is sufficient in nearly all cases, and overly aggressive use of disinfectants is likely to be worse that the occasional microorganism. Just wash your utensils, hands, and towels occasionally (especially after handling  risky food like chicken).  --Stephan Schulz (talk) 17:58, 26 July 2008 (UTC)

Thanks!64.231.9.30 (talk) 18:24, 26 July 2008 (UTC)


 * And note that if you somehow did get rid of all of the bacteria in your life your immune system would probably suffer. The most low-level exposure you have to things like that, the better your immune responses are to larger attacks. A truly sterile household would be a recipe for disaster. --98.217.8.46 (talk) 23:28, 26 July 2008 (UTC)


 * two basic kinds of bacteria, either of which can be harmful or benign (or even good for the body). your normal bodily residents are fairly well protected against your body's constant attacks, but in the process have lost the ability to form spores and when conditions get unhealthy for them, they just die. (gram negative) overnight drying out on something nonporous like a counter or a plate would certainly do them in. they might survive in a damp sponge or some such, though. nasty varieties would include salmonella, or the toxic strains of e. coli. bear in mind that they don't come out of nowhere; they need to come from a source, like raw poultry, or an infected person, or food which has been contaminated by an infected person in the process before it got to your kitchen.
 * the other kind of bacteria, gram positive, are evolved to live out in the wild rather than in your body; since conditions are much more variable, they have the ability to sporulate whenever conditions get tough, like drying out. and the spores are damn near unkillable under normal conditions (that's kind of what they evolved to be); the standard sterilization procedure is typically 15 lbs pressure (above atmospheric) of live steam for 15 minutes, for instance, which is something typically not found in the home. concentrated bleach or various high powered acids would do it, but you probably don't want to mop your kitchen with them. in fact you're probably more at risk from routine exposure to them than any of the bacteria in question. the side effect of being able to sporulate is that their surface is more susceptible to things like your immune system, the opposite of the gram negative described above; this is why you  don't rapidly die from the uncountable  bacteria all around you all the  time. but the few who have discovered how to make an attack on the human body are, logically, pretty brutal in order to knock out your defenses. anyway they would include things  like anthrax; but nobody gets anthrax from a kitchen counter.
 * mostly, it's not a question of eliminating all bacteria, just being aware of what possible harmful bacteria are and where they are and concentrating on them; so clean up thoroughly around where raw chicken has been, for instance, or raw vegetables; but you don't have to worry that a placemat which has seen only cooked food is going to be a problem if it isn't sterilized. Gzuckier (talk) 06:42, 27 July 2008 (UTC)

Antlions and Rain
How do antlions avoid drowning in the rain? The article says that they usually build a pit where they are sheltered from direct sunlight and rain, but there are some in my yard that are out in the open lawn, and I don't know how they don't drown. Calamus Fortis  20:13, 26 July 2008 (UTC)


 * Antlions probably do drown sometimes if rain is very heavy. However, they normally build their pits in sandy soil or just plain sand that drains very well. So most rain would just seep away and not accumulate enough to drown the antlion. Also, most antlions live only in arid areas where there is very little rain in the first place.--Eriastrum (talk) 22:02, 26 July 2008 (UTC)


 * Surface tension also does an amazingly good job of keeping insects from drowning. The spiracles which lead to the insect respiratory system are very small - much smaller than your average water droplet. Add a waxy (hydrophobic) coating around the outside of the holes, and water is unlikely to cling/penetrate them, allowing easy breathing once the water drains away. It's also worth noting that cold blooded animals (like insects) have a much lower energy/oxygen demand than warm blooded humans, meaning they can survive longer without air. -- 128.104.112.147 (talk) 18:20, 29 July 2008 (UTC)

What is this plant?
Hi folks, I was wondering if you could help me identify this plant that's been growing in my garden? I live in Nottinghamshire, England. The plant in question is a small herbaceous angiosperm with branched green leaves and blood-red stems. The flowers are small and pink. It seems to be perennial and spreads like wildfire, thriving even in very rocky soil. It was pretty at first, but is starting to create monocultures, so I assume its alien to Britain. Any takers? — Jack (talk) 20:30, 26 July 2008 (UTC)


 * I don't recognize the species, but it is obviously a plant in the Geranium Family (Geraniaceae). The unequal petals (three smaller and a different color than the other two) indicates it is not an Erodium (Cranesbill), which was my first impression. This also rules out the genus Geranium. So it must be one of the many species of Pelargonium. Take a look at this link to get an idea of how many species there are in this genus. The trifoliately compound leaves and bright red stems are a bit unusual, however. I'm sure that you are right that it is a weed. Most species are native to south Africa; certainly none are native to England. I live in California where we have a number of weeds that belong to the Geranium family, but not this one.--Eriastrum (talk) 21:43, 26 July 2008 (UTC)


 * Ah, I think I've found it! Herb Robert, I believe it's called. Thanks for pointing me in the right direction (the flower was viewed from an angle and slightly overexposed). Thanks again — Jack (talk) 00:14, 27 July 2008 (UTC)

Yes, definitely Richard Avery (talk) 07:02, 27 July 2008 (UTC)


 * Can that triffic pic go in the article or in the article Rosette? Julia Rossi (talk) 05:21, 28 July 2008 (UTC)

black hole theories
hi, i am doing a study on different aspects of black holes. i am trying to find a range of theories on how they are formed, how long they exist etc. if anybody knows any theories, that would be a great help.

p.s. couldnt find any info about it in the article.

thanks, Missy315 (talk) 23:01, 26 July 2008 (UTC)


 * Black holes are formed when a massive star dies, and collapses into itself. If it's not massive enough, it will collapse into a neutron star, or a white dwarf. But if the star is massive enough, it will become a black hole. How long they exist depends on the size of the bh, and if it's "eating" any matter. A black hole will eventually evaporate into hawkings radiation, which I believe is just photons. The rate that it evaporates also depends on its size. The more massive the bh, the slower the rate of evaporation. So not only is a small black hole going to evaporate faster because it has less mass to evaporate, but the rate is also faster. To give an idea of how long massive black holes will last, according to the heat death article, they will be the last vestiges of our universe before they evaporate, meaning everything else will be gone before they are.ScienceApe (talk) 23:09, 26 July 2008 (UTC)


 * Did you read Black hole? PrimeHunter (talk) 23:11, 26 July 2008 (UTC)

umm...i dont think so, im only thirteen by the way. i was having lots of trouble finding theories on it and somebody directed me to here. thanks, anyway. Missy315 (talk) 07:04, 27 July 2008 (UTC)


 * To understand the formation of black holes, you must know about the life-cycle of stars. The stars of central masses more than 3.2 times the Solar mass end their life cycles through a severe SUPERNOVA explosion. This explosion causes the outer parts of the star to be ejected out into space.As a result, tremendous force of gravitation collapses the centre of the star. When the centre collapses to an extent that its radius becomes less than Scwzerchild Radius, the star gets transformed to a Black Hole. A black hole always spins about itself. It is said to be "A fourth dimensonal Gateway". The black hole slowly emits Hawking radiation and in fact gets evaporated or vapourised. If you are interested in more details, should I provide you with the steps of formation of black holes?117.201.97.83 (talk) 18:56, 27 July 2008 (UTC)


 * Perhaps you want some resources to look at. Starting with the basics, are you fairly familiar with the sort of star life-cycle information here and explored here? You probably don't want to read the article where it's given in far too much information without a proper overview here. If you look here, you can get a fairly good, not too difficult to follow, overview of black holes and some theories about them. It also gives some ideas of places to look for more information. Does this help at all, and are there any particular sort of resources you need? Are these about the right level? 79.66.124.253 (talk) 21:07, 28 July 2008 (UTC)