Wikipedia:Reference desk/Science

Wikipedia:Reference desk/headercfg

October 8

muscular development

if a ten year old child carried a piglet half a mile (or more, how much can a ten year old handle) then would the child be able to continue carrying the pig as it grew into an adult? or would there be a point where the pigs growth outstrips the benefits of the exercise for the child? how would it be after a few years? how about if the kid was a few years older? this has been bugging me for a while, thanks 81.96.164.140 00:20, 8 October 2007 (UTC)

There's too many variables to ever give a reasonable answer here. How big is the child? How big is the piglet? How much development goes on in each? Does the pig wind up as bacon? -- Kesh 00:24, 8 October 2007 (UTC)

ok then: assuming you bought a ten year old boy a normal domestic pig that's one week old for his birthday (his tenth birthday), and then assuming that both he and the pig developed as averagely as possible (aside from the extra development he would gain as a side effect of carrying the pig) would there be a point, say when he's thirteen and the pig is three, that he would be unable to lift the pig? or would he get used to its weight because of the slow speed of its growth and become a freakinishly strong child?

Well, piglet-carrying is like any other form of exercise: it'll build muscles, but only up to a point. Competitive athletes exercise intensively just to stay at their personal limit of muscle strength, but they can't get beyond it -- which is why some of them take drugs to raise the limit. If there are child athletes who at the age of 13 have developed by conventional exercise the strength to carry a 3-year-old pig, then it ought to be possible for the hypothetical piglet-carrier. If there aren't, then probably it's impossible. --Anonymous, 05:03 UTC, October 8, 2007.

This is an old idea - but it depends on a couple of logical flaws:

1. It assumes that a child can increase muscle capacity at a rate that is greater than that a pig can gain weight. I doubt this is true. Since the weight of the pig increases as the cube of it's size yet the kid's muscles (whose power is proportional to the cross-sectional area) only increase as the square of the kid's size. If the kid and the pig were to grow at the same rate, the weight of the pig would rapidly outpace the kid's ability to put on muscle cross-section. That would be true if kids and pigs grew at comparable rates - but they don't. A pig grows to full size in just a couple of years - a kid needs nearly 20 years to do the same thing.
2. It assumes that the kid never has a 'bad day' - if the kid were to get a bad cold - then maybe it would be unable to carry the pig even at it's old weight for several days in a row - the exercise regimene would be broken and it's likely that the kid would never catch up.

SteveBaker 11:52, 8 October 2007 (UTC)

I seem to recall Herakles doing something of the sort with a calf. DuncanHill 11:55, 8 October 2007 (UTC)

That would be a Myth however. Here on the science desk we are generally looking for something more like Reality. SteveBaker 13:00, 8 October 2007 (UTC)

Good grief!! You mean they taught us things in primary school that aren't real? What about that guy who was nailed to a tree and came back to life?? lol! DuncanHill 13:08, 8 October 2007 (UTC)

Nonetheless, it provides proof that "This is an old idea", and is thus useful. Skittle 13:06, 8 October 2007 (UTC)

I seem to remember lifting these things called 'barbels' up and down to make me stronger - which worked until I stopped and all the muscle went floppy - does this have any relevance here?87.102.17.101 13:58, 8 October 2007 (UTC)

No - pigs don't have barbels you're thinking of fish. :-) You'd have gotten further by lifting Barbells.SteveBaker 17:54, 8 October 2007 (UTC)

SB point no 1 about the difference in human and pig growth rates is an important one. Also do note that the vast majority of adults would probably have great difficulty lifting let alone carrying a fully grown pig (from sources 41-120kg). Admitedly most people could perhaps with a large amount of weight training (but why you'd want to I'm not particularly sure). Also if you make your child carry a piglet every day, you may find your local child welfare organisation and/or the police wanting to interview you and perhaps even your local animal welfare organisation Nil Einne 12:57, 9 October 2007 (UTC)

• I have actually performed this experiment with a baby human. In the first few years of its life I could lift it with no problems at all, and did so many times per day. However, I kept feeding it to the point that it became uncomfortable to lift. Now I avoid doing so altogether, to avoid embarrassment to all concerned. --Sean 16:46, 9 October 2007 (UTC)

Just goes to show how anonymity will cause people to admit to the strangest things.87.102.18.10 18:38, 9 October 2007 (UTC)

silicon life forms

Have any silicon based life forms ever been discovered or is it know whether such life forms are possible by comparison of the properties of silicon versus the properties of carbon? Clem 00:21, 8 October 2007 (UTC)

None have been discovered as of yet. Finding one would be a monumental breakthrough in biological science. As to whether they are possible, that's still being debated. -- Kesh 00:28, 8 October 2007 (UTC)

The origins of life (1964) by George Wald had a discussion of issues such as why carbon is used in living organisms, not silicon. --JWSchmidt 01:56, 8 October 2007 (UTC)

The abilities of carbon to form complex molecules exceeds that of silicon, but as biology here on earth sometimes uses materials not suitable for the purpose (from the knowledge of humans), it might possible to create a full new-biochemistry based on silicon (with carbon as minor partner). Silicon in earth biology has only limited use and it is not used to create larger molecules, with the exeption of silicium dioxid shells of diatomeres.--Stone 09:22, 8 October 2007 (UTC)

The major problem with silicon based life forms is that they would breath out SiO2(as we do CO2), SiO2 is sand, and would not be a nice thing to have in ones lungs :DShniken1 13:49, 9 October 2007 (UTC)

This one made me fall off my chair. --Ouro (blah blah) 14:44, 9 October 2007 (UTC)

Afterthought: ain't so sure, I mean, I don't think simple substitution of C with Si cuts it. A silicon-based life form would surely have different biochemistry all over, and this'd include breathing probably. I think. --Ouro (blah blah) 14:47, 9 October 2007 (UTC)

Friction in Trains

Hello all. I'm having some trouble finding information for my school poster. The topic is "Friction in Trains." I tried looking for information here and on google but I couldn't find it. If anyone could help me here it would be greatly appreciated. P.S I'm looking for information relevant to a year 11 level (Upper High School level). Lots of thanks in advance. Cuban Cigar 05:11, 8 October 2007 (UTC)

A web search is unlikely to reveal much unless your project is more clearly defined. Assuming you mean kinetic friction as it applies to railway transport (see friction), take a look at our articles on rolling resistance and drag.--Shantavira|^{feed me} 09:42, 8 October 2007 (UTC)

With specific application to trains and railways, we have articles on rail adhesion, sandbox (railways) and slippery rail. Gandalf61 10:39, 8 October 2007 (UTC)

I know this might sound old fashioned, but you might better be served by visiting your local library, and speaking with your librarian about the subject. You should learn to research a subject using multiple sources, not just the internet. It might give you some places to start, but Wikipedia, like other encyclopedias, should not be cited as a source of a reference. -- JSBillings 10:41, 8 October 2007 (UTC)

As a way to approach this problem, you might do well to consider all of the things that move in trains and try to find some analyses of those moving things. For example, the wheels move on the rails but the wheel axles also turn in bearings of some kind. The air moves against the train but also flows through any internal combustion engine in the train. And so on...

Atlant 12:42, 8 October 2007 (UTC)

I think you should think about: Friction of the wheels against the track (you need some friction or the wheels will just spin and the train would stay still) - friction in the wheel bearings (which is bad because it slows the train down and requires more energy - fuel - to overcome it) - friction inside the engine(s) (also bad - same reason). Friction is also desirable in other places - the couplings between the train carriages for example. If they were super-slippery, they might come undone. The brakes need to use friction to slow the train down. Friction inside the train also matters - you don't want really slippery floors or table-tops if passengers are to be comfortable. There are lots of things to think about in this topic. SteveBaker 17:50, 8 October 2007 (UTC)

• There's also a pretty good article at Howstuffworks called "How Diesel Locomotives Work". Some non-obvious sources of friction to ponder: friction among the engine parts (very much like in an automobile, with substances very much like an auto's motor oil to reduce it) and friction in braking (where the friction is how the brakes work). --M@rēino 03:37, 9 October 2007 (UTC)

This is all very good thanks for the help.Cuban Cigar 08:02, 9 October 2007 (UTC)

materials&metallurgy

which steel is used for railway tracks?203.94.231.74 11:19, 8 October 2007 (UTC)

Pearlitic steel see pearlite See http://www.chiark.greenend.org.uk/~cneal/rails.html but also http://www.msm.cam.ac.uk/phase-trans/parliament.html — Preceding unsigned comment added by 87.102.17.101 (talk) 12:08, 8 October 2007 (UTC)

Switch rails may be special steels. — Preceding unsigned comment added by 87.102.17.101 (talk) 12:09, 8 October 2007 (UTC)

here's some info on american steels http://findarticles.com/p/articles/mi_m1215/is_n3_v198/ai_19239923

You could search the web for 'rail steel' — Preceding unsigned comment added by 87.102.17.101 (talk) 12:51, 8 October 2007 (UTC)

• Bonus points -- in addition to steel, thermite is used for repairs. --M@rēino 03:39, 9 October 2007 (UTC)

Human Horns

Do you have any information on abnormal bone structure among humans that presents like two mini horns on the top of a human head? — Preceding unsigned comment added by 87.232.1.88 (talk) 11:32, 8 October 2007 (UTC)

Never heard of such a thing, but if this about the old, old myth that Jews have horns, see this section of our article on Moses --Dweller 12:43, 8 October 2007 (UTC)

I've heard of it. Here are a couple of sites that may be of interest - [1] and [2]. -- JackofOz 14:07, 8 October 2007 (UTC)

Interesting stuff! Thanks for a better answer than just sending the poster to watch "Spanish Fry". DMacks 18:38, 8 October 2007 (UTC)

I recall that some adherents of the body modification subculture have metal balls or lumps of coral inserted underneath the skin on their head so that they resemble horns. Exxolon —Preceding signed but undated comment was added at 21:00, 8 October 2007 (UTC)

I remember reading something about human horns related to Shope papilloma virus 71.226.56.79 05:33, 9 October 2007 (UTC)

Oxidant, oxidising agent, oxidation...

Is "oxidant" the same as "oxidising agent"? And does an "oxidant" oxidise or reduce? Thanks. Oidia (talk) 12:23, 8 October 2007 (UTC)

An oxidant is the same as an oxidising agent. The linked article will explain what they do much better than I can! DuncanHill 12:48, 8 October 2007 (UTC)

How was precession of the Earth's axis explained in Geocentric models of the solar system?

So precession of the axis was discovered way back during the heyday of Greek astronomy, and apparently even heavyweights like Ptolemy studied the topic, so it must've been addressed in some way - but the article on geocentrism doesn't mention how it explained the apparent movement of the stars (obviously they wouldn't have thought of it as a movement of the Earth but of the stars), and some more searching turns up Trepidation which seems to be close but not the same thing. So how did they account for this phenomenon? --Gwern (contribs) 15:26 8 October 2007 (GMT)

They couldn't explain it in scientific terms, but then they probably didn't feel any need to do so. They didn't have the sort of mechanical understanding of the universe that we have today. They assumed the Earth was fixed, so precession must therefore just be another motion of the heavens. If it hadn't been for questions such as this (and retrograde and direct motion) it might have been many more centuries before we finally figured out what was going on.--Shantavira|^{feed me} 17:20, 8 October 2007 (UTC)

They certainly could explain it in scientific terms. To assume that pre-Copernican astronomers were devoid of mathematical understanding is simply incorrect. Retrograde motion was not too hard for them to explain either, given enough epicycles. Bigger threats were things like comets which totally screwed up the model of perfect spheres of the heavens, much less something like the phases of Venus which was totally incompatible with a Ptolemaic system. (James Lattis' Between Copernicus and Galileo is an excellent study of the work of Christoph Clavius, probably the last major geocentric astronomer in Europe of any real mettle.) --24.147.86.187 19:29, 8 October 2007 (UTC)

What they were doing was to consider each object in the sky as being attached to a wheel - or a wheel mounted on another wheel - possibly on another wheel. Wheels could be different diameters and rotate at different rates. In effect, they were turning all motion into cycloids. Or to put it another way, they were summing a bunch of sine waves of varying amplitude, frequency and phase. This technique is something we use all the time in Fourier analysis/synthesis - and we know that ANY mathematical function can be broken down into the sum of some number of sine waves. So it was inevitable - that with enough wheels of the correct size ("amplitude") and frequency - they could reproduce exactly the motion of all of the heavenly bodies. Of course Fourier analysis hadn't been invented back then - so they thought it miraculous that their idea of how the universe worked fitted so well with reality - but that was because they'd inadvertently stumbled on something that could be used to describe ANY motion. Of course they rarely used enough wheels to get the motion down with 100% accuracy - but whenever they noticed a discrepancy and analysed it carefully enough - they'd discover that just adding one more teeny-tiny wheel would 'fix' the problem. It's all kinda elegant in a way. SteveBaker 17:36, 8 October 2007 (UTC)

Well, they were specifically spheres, not wheel or disks. This is important — the spheres didn't have to rotate exactly on a single axis, which could explain a lot of things. Additionally, in Ptolemy's system the spheres did not necessarily rotate around their center — they could "wobble" (see equant). Kuhn's The Copernican Revolution is an excellent and readable overview of the pre-Copernican approaches to astronomy. --24.147.86.187 19:29, 8 October 2007 (UTC)

Yeah - there were all sorts of elaborations on the basic idea - especially as more exacting measurements caused ridiculous amounts of additional complexity in the system and efforts had to be made to prop it up. But in the end, it's a sum of sine-waves (possibly in two or three dimensions) - which explains why such a wildly "wrong" system could produce results that actually worked out pretty well in practice. It's quite impressive that they cobbled this together from raw measurements - with no theory of WHY all this worked the way it seemed - and a total lack of understanding about what they were doing mathematically (Fourier series weren't known until the early 1800's - by which time Copernicus's ideas were totally accepted). The fact that it enabled astrologers to do a reasonable job of predicting where planets would be at some time in the future is pretty amazing given that they'd missed the critical simplifying idea of putting the sun in the middle. SteveBaker 19:47, 8 October 2007 (UTC)

Well, my understanding was that their physics and observations didn't really let them accept a heliocentric model and that it wasn't until sometime after Galileo that it actually made better predictions (drawing on some fuzzy memories of Feyerabend's writings). But is this the answer? That they had no problem introducing another epicycle for the celestial sphere itself? --Gwern (contribs) 20:27 8 October 2007 (GMT)

I'm reasonably sure the celestrial sphere did not have its own epicycles, if that is what you are asking in the end there; if I recall correctly from Kuhn, it was simply given the ability to have its orbit "wobble" a bit (imagine a sphere which rotated in more than one direction and at somewhat different speeds). And the Copernican system as put forward by Copernicus was still filled with epicycles (and also lacked the more nuanced understanding of ellipical orbits that would be Kepler's major contribution). In any case the Ptolemaic model pretty much died with Galileo's work, though Galileo's work did not exclude other geocentric models (like the Tychonic system), which is observationally identical for all intents and purposes to the Copenican model within a certain range of observation. --24.147.86.187 21:37, 8 October 2007 (UTC)

For 'ANY mathematical function' read 'any function that is even slightly pleasant, including all arising in nature'</pure mathematician's pedantry> Algebraist 19:11, 8 October 2007 (UTC)

Yes - absolutely. I was trying to minimise the amount of clutter around an already-too-complicated explanation! You need a repeating function without nasty discontinuities and such - but the motion of all of the planets and moons and orbital 'stuff' fulfills those requirements (so long as nothing collides with anything else!) - so in this context, we're OK. Thanks for the correction. SteveBaker 19:33, 8 October 2007 (UTC)

Sorry about that; no real place in this discussion, I'm just too much of a pure mathematician to ignore a false statement, however justified. Algebraist 23:19, 8 October 2007 (UTC)

Geology of the Balearics (Mallorca)

Im writing a report on the geology of Masllorca. But I have some problems finding litterature on the subject. Im studying to become at teacher in the Dansih school. Im not a geologist or anything. I know that the islands in the mediterrian sea, where formed due to the collision of the african and the eurasian plate, but after what I have read so far it seem to me, that its a bit more complicated than that. I hope someone can help me!!!

The ameteur geologist Martin —Preceding unsigned comment added by Martinchristiansen (talk • contribs) 18:10, 8 October 2007 (UTC)

I recently had to teach myself Geology 101, so to speak, and I found this to be a good overview of the science of physical geography. It helped me understand the other more specific material I found. --Milkbreath 20:36, 8 October 2007 (UTC)

There is probably an in-country journal for this sort of local detail. Also there may be geological maps available, with accompanying notes - but they could all be in Spanish. Are you going to write the wikipedia article for this too? Graeme Bartlett 03:21, 10 October 2007 (UTC)

No...I don´t really feel that i´m a qaulifyed writer for that kind info. I just resently visited Mallorca with fellow students and we had to write a paper on the subject of Mallorcan geology. I was just looking for some info on the subject.

I have a French article that mentions Balearics a little, but chances may be better if we look elsewhere. The geology is in the same style as the north coast of Africa and the south east coast of Spain. Also if you are interested I could give you a list of names of Spanish Geological journals. Your question has triggered me producing a Geology of Spain article. THough its not uploaded yet. Graeme Bartlett 02:50, 12 October 2007 (UTC)

Atomic Composition of Animals

Could someone direct me to a site that would have the atomic percent composition (by mass) of animals (specifically mosquitos). Would the composition be very close to the same among say, mosquitos and humans or any other animal. 64.230.97.20 18:15, 8 October 2007 (UTC)

Pretty much, yes. Being that we are all carbon-based life, we are largely carbon, oxygen, hydrogen, and nitrogen. I imagine that a big difference is that something with an exoskeleton is not going to have the calcium that goes into an internal skeleton made of bone. --24.147.86.187 19:23, 8 October 2007 (UTC)

Mushrooms

Are mushrooms considered more animal than plant? --WonderFran 18:57, 8 October 2007 (UTC)

Mushrooms are a type of fungus. Fungi were once considered plants, but now are generally considered to be a separate kingdom of their own. Algebraist 19:04, 8 October 2007 (UTC)

They aren't more animal than plant - but they aren't "plant" either. These days, we consider fungi to be a completely different thing from either plants or animals. SteveBaker 19:29, 8 October 2007 (UTC)

Then again, animals and fungi are both in the group of opisthokonts, while plants are not, so some biologists must think they're more closely related. —Keenan Pepper 19:36, 8 October 2007 (UTC)

I was just reading in Richard Dawkin's The Ancestor's Tale about how animals and fungi are more closely related to each other than either is to plants. It made me wonder though -- How come both plants and animals are thoroughly abundant on land and in the sea while fungi are limited to the land? Is there something about fungi that makes them utterly unable to colonize the sea? And.. wouldn't the common ancestor split between fungi and animals have been way back when all life was in the sea? Was there once sea fungi? Is there still? Pfly 04:56, 9 October 2007 (UTC)

The Fungi article says "Most fungi grow in terrestrial environments, but several species occur only in aquatic habitats." So your premise isn't entirely correct. It could be that there may be few aquatic species, but that those few proliferate and thus still have a considerable biomass. Does the book say anything on that? DirkvdM 08:41, 9 October 2007 (UTC)

It could be that the Mycorrhizal symbiosis with plants that got fungus a big start on land -- without it, plants probably wouldn't have been that effective on land. -- JSBillings 10:29, 9 October 2007 (UTC)

This hypothesis is supported by some sources, e.g. see [3], [4],[5] & [6]. [7] is about animal colonisation but briefly mentions the current state of knowledge at the time vis-a-vis fungi colonisation and is full text. Nil Einne 12:45, 9 October 2007 (UTC)

Locations of virtual image charges versus optical images

The electric field produced by a point charge and a conducting plane is the same as would be produced by the point charge and a second, opposite point charge on the other side of the plane, called an image charge. This image charge is at the same place an optical image would be if the plane were a mirror. It seems to me this must be the case, because if the charge were vibrating at optical frequencies, it would radiate light, and the reflected light had better appear to come from the same position behind the reflecting plane as the image charge.

However, for a spherical conductor, the image charge is at a different location from the optical image in a spherical mirror. If the radius of the conductor is r and the distance from the center of the conductor to the charge is x, then the distance from the center to the image charge is $r^{2}/x$. If the conductor were a mirror, on the other hand, the distance from the center to the image would be $xr/(2x-r)$. These do not agree except in the limit $x\rightarrow r$. It's as if the "focal length" for the electrostatic case is equal to the radius r, whereas we all know the optical focal length of a sphere is r/2.

How can this be? Why is the image in one location for electrostatics, and a different location for electrodynamics (optics)? —Keenan Pepper 19:32, 8 October 2007 (UTC)

The flat mirror is only a special case and there's no a-priori reason to suspect that optics and electrostatics should be linked like you suggest. You may imagine a large conducting flat mirror where a slab of it is replaced with plastics or removed. In optics, this wouldn't affect the reflections in other parts of the mirror, while I believe the "image charge" would get distorted by this.

In electrostatics, there's no "reflection" of the field lines, only the requirement that they intersect the conducting plane at a 90 degree angle, so as not to have a current running. In optics, there's no case of a part of the mirror affecting the light at anoter, while in the electrostatic problem this is how an equilibrium with no current running is set up. EverGreg 09:08, 9 October 2007 (UTC)

Actually, it's not true to say that removal of a part of a mirror does not affect the rest of the image. There is a kooky little effect that happens very close to the edge of a mirror (argh - I can't recall the name) - too close for you to ever really notice. It's explained very nicely in Feynman's book on quantum electrodynamics and it requires bizarro quantum effects to explain it. It had been noticed long before quantum effects were known and had been a mystery for some hundred or more years. Darn! I wish I could remember the name of it. SteveBaker 15:42, 9 October 2007 (UTC)

Dialysis bag permeable to sucrose?

Disclaimer: This is a homework question in some measures. In any case, I could have sworn my instructor said that dialysis tubing is not permeable to sucrose, but when doing the literature search for this lab, I wanted a reliable source to cite. surprisingly it seems like Dialysis tubing should be permeable to sucrose: this site says that sucrose has a molecular weight of about 340 Daltons, and this site says that dialysis tubing usually has cut-offs in the tens of thousands of daltons. Can anyone confirm or deny what I'm seeing? With a reliable source of course. --Ybbor^Talk 19:41, 8 October 2007 (UTC)

Sucrose is indeed 340ish Da. I don't know the specifics of the Dialysis tubing you are using, but a disaccharide such as sucrose might well pass through. Look at the google hits for sucrose "dialysis tubing" to get a sense of what is likely. DMacks 19:49, 8 October 2007 (UTC)

You could help us by giving details of the particular protocol being used, but it is not uncommon for people to use dialysis tubing and sucrose to concentrate dilute solutions. The first Google hit I found with an example (go down to day 5). In general, the sucrose can cross the tubing (although some dialysis membranes claim 0.1 kD cut-offs) that is used, but the point is, if there is a high concentration of sucrose outside, then water will quickly leave the solution that is inside the tubing. --JWSchmidt 20:24, 8 October 2007 (UTC)

Sorry, can't give you much details of the specific type of tubing being used :( Okay, so sucrose will move across the tubing, just not nearly as fast as water, and not significant enough to offset the movement in water. Is that understanding correct? Thanks for your help :) --Ybbor^Talk 20:47, 8 October 2007 (UTC)

Wormhole creation

If wormholes are permissable by General Relativity, is their creation permissable? I didn't see anything in the article on any hypothetical formation mechanisms for wormholes; I don't see how you could imagine them actually being formed while still being within the bounds of GR. And if there was no real permissable route for creating them, then they probably don't exist, theoretically valid or not. Any thoughts? No maths please if possible. ;-) --24.147.86.187 21:31, 8 October 2007 (UTC)

Check out casimir effect for stabilization theories at least. --Cody Pope 22:59, 8 October 2007 (UTC), Nasa's got stuff on wormholes too. --Cody Pope 23:17, 8 October 2007 (UTC)

The latter seems to be about artificially created wormholes, which is interesting though it doesn't sound like a feasible technical problem. I'm interested in natural wormholes in particular. And the Casimir effect page wasn't exactly in terms that I could make real sense of... --24.147.86.187 00:23, 9 October 2007 (UTC)

Quantum foam could be permeating space and could be full of tiny wormholes, ready to expand to macroscopic size. Graeme Bartlett 00:27, 9 October 2007 (UTC)

The worry about wormholes is, as you probably know, that they seem to allow for time travel, which violates causality due to the grandfather paradox. As a paradox usually hints at a flaw in the theory, the possibility of wormholes is usually interpreted as meaning one of the following three things: (i) There is some flaw in the theory of general relativity because a sound theory should not allow for paradoxes. (ii) There is some flaw in the reasoning that general relativity allows for wormholes; closer investigation will show that it actually does not. (iii) There is some flaw in the argument that a wormhole causes a paradox.

What you are heading at is the possibility (ii): Maybe it will turn out that physics does not allow the creation of wormholes and so avoids the paradox. This is actually the principal reason why physicists like Kip Thorne and Paul Davies investigate whether the creation of a wormhole is feasible in principle. Their ideas are so wild that it seems ridiculous to assume that one could actually build them. But whether this impossibility is just a technical infeasibility or an impossibility in principle is an important question to judge whether our fundamental theories harbour a flaw or not. And if one identifies a way to build a wormhole in principle, this may help to pinpoint the flaw. 85.127.183.143 00:28, 9 October 2007 (UTC)

You are forgetting (iv) that paradoxes are not impossible. In a many-worlds view of the universe, going back in time and killing your grandfather is not a problem since the version of the universe you came from will simply not be the version of the universe in which your grandfather is dead. Time travel devices come in two distinct varieties: The kind which allow you to travel back in time only back to the point where the device was created (as is the case with wormhole-based time machines) - or the "H.G.Wells" devices where you can travel back to before the time the machine was created. The latter type can be responsible for all kinds of wierdnesses - but the former type are less problematic. For example, we can answer the question "If time machines exist, how come we havn't seen any time travellers yet?" - because we don't have a wormhole yet. SteveBaker 15:35, 9 October 2007 (UTC)

just applying logic to the question (as I am not a physicist) I would say that if something exists, then its creation must have been possible. —Preceding unsigned comment added by 88.109.198.32 (talk) 00:42, 9 October 2007 (UTC)

I know that. They don't know if they exist—they have never observed one (or evidence of one). My point is that if the creation is not possible, then they won't exist. --24.147.86.187 14:30, 9 October 2007 (UTC)

Well, yes - but remember that we didn't know for sure that black holes existed until we found one just four years ago. Between the time someone first though up the idea (John Michell in 1783) until the first one was actually discovered (Maillard, Paumard, Stolovy and Rigaut in August 2003) was 220 years! Discovery of these weird things often lags the theory that they could possibly exist by decades...or even centuries. So wormholes might exist - but it could easily take hundreds of years of searching with exotic instruments like orbiting telescopes for us to find one. SteveBaker 14:48, 10 October 2007 (UTC)

General relativity relates the local geometry of spacetime to the local distribution of energy and momentum. Wormholes are inherently global, so general relativity doesn't say anything about them. It's consistent with them, but that's not saying much, because it's consistent with anything. The field equations don't constrain the geometry, they just tell you the energy-momentum distribution of any given geometry. So the first question is whether there's any traversable-wormhole geometry whose energy-momentum distribution resembles any known form of matter, and the answer to that is no. (I think there's a theorem to that effect.) Even if it were yes, it doesn't follow that you can construct a wormhole by deploying matter in the required configuration, because GR doesn't tell you whether the two ends connect up, and I have trouble even imagining a post-GR dynamics that would allow for such a thing. -- BenRG 11:45, 9 October 2007 (UTC)

Tetrachromatic, ultraviolet, etc

I've been reading up on colorblindeness and tetrachromatic vision. In a book I have on psychology, there is a diagram of four pictures, three with different types of color removed, and if any of them look the same then it means you are colorblind (I apparently passed the test and am not colorblind). However, a while back I was talking to a physics major and a biology major, who say that there are similar diagrams for people who may be tetrachromatic, or even tests for ultraviolet vision, where a "normal color" picture is lined up with a tetrachromatic or ultraviolet one. Do any of these diagrams exist of the internet? I can't find any, but perhaps an optometrist could be of help. 130.126.67.144 22:26, 8 October 2007 (UTC)

Given that monitors work on a trichromatic RGB system, I'm not sure anything you pull off of the internet would work. GeeJo ^(t)⁄_(c) • 22:33, 8 October 2007 (UTC)

Is there a cheap and easy way to test a person IRL for trichromaticism? 130.126.67.144 22:48, 8 October 2007 (UTC)

Indeed due to colour calibration, reproduction accuracy and other issues, many sites testing for colour blindness warn that you really should see a professional or at least use a book designed for the purpose Nil Einne 12:14, 9 October 2007 (UTC)

If you mean "an easy test to determine if someone can see ultraviolet" you could use window glass. It dosn't let through UV, which is why you can't get a tan indoors on a sunny day. So the outdoors should look quite different through glass. There are also certain flowers that have patterns that's only visible in ultraviolet light. EverGreg 09:15, 9 October 2007 (UTC)

the Tetrachromacy has some links and a google search on "test for Tetrachromacy" bring up papers that might point to test for the condition of extra sensitivity somewhere between green and red. EverGreg 11:25, 9 October 2007 (UTC)

Bear in mind if you aren't female the chances of you being a tetrachromat are probably very very slim (although this is still AFAIK still not a very well researched area from our current knowledge this is the case) Nil Einne 12:10, 9 October 2007 (UTC)

I thought that if you were female, your chances are very slim (like one in 20 million) - if you are a male, it's utterly impossible to be a tetrachromat. SteveBaker 14:00, 9 October 2007 (UTC)

People who have lost the lenses from their eyes (due to cataract surgery perhaps) can see a little further into the UV than the rest of us. Computer displays only produce 'pure' red, green and blue light - nothing else. So it's impossible to generate a UV test on a computer.

Tetrachromats see two hues of green (yellowish green and 'pure' green) as 'different' colours. Tetrachromats find synthetic pictures of all kinds (books, computers, TV, movies) unrealistic because they don't reproduce both kinds of green correctly and they can tell (we can't). So all you need to test for tetrachromacy is to show a 'spectrum' of colour on the monitor - and have the person compare that to a spectrum spread from sunlight using a prism - if the two look pretty similar, you're a 'normal' person - if the spectrum on the computer is missing a bunch of colours around green - then you're a tetrachromat. But this is kinda like testing for colourblindness by showing a monochrome photo and asking whether it looks real...not a really conclusive test since it requires a judgement call from the viewer. The standard tests require you to see a number or shape in a bunch of coloured dots - and it's really an all-or-nothing, definite answer kind of thing.

However, tetrachromats are used to the very unrealistic colouration of computers, TV's movies, books, etc and they may find this 'normal' for them because they know that these devices are horribly unrealistic. You can't print a tetrachromacy test with normal cyan/magenta/yellow/black (CMYK) printing techniques - although a specialised test for tetrachromats could be printed on a printing press that can use more colours. I suppose you could also do a test for UV vision using specialised UV inks...but again, this isn't something that is routinely easy to do.

SteveBaker 14:00, 9 October 2007 (UTC)

This helps me—but are you saying that tetrachromats only see green differently, and not other colors? I read of supposed tetrachromats picking out differences between reds and dark purples that are supposed to be black. —Preceding unsigned comment added by 130.126.67.144 (talk) 20:37, 9 October 2007 (UTC)

I don't know where you read that - or why we keep talking about human tetrachromats in the plural. So far, only ONE human is known to be a tetrachromat. It takes a really rare combinations of circumstances that make this happen - it requires a woman with a particular set of colour-blindness symptoms in all four grandparents - and a lot of luck as the genetic dice are rolled.

The lady in the UK who has been shown to have this quirky genetic makeup has two sets of green sensors that are sensitive to different frequencies near green. That's the only form of tetrachromacy that's possible.

HOWEVER, you make the rash assumption that her brain lets her see two very similar colours for the two greens. That's not the case. Those two greens are as different to her as red and blue are to you and me. We really only see the three primaries (red, green and blue), plus mixtures of two of those (yellow, cyan, magenta), plus all three together (white) - at different saturations and intensities. She sees four primaries (red, green, splot, and blue - I'm calling her 'other' green sensor by the nonsense word "splot" because we don't have a name for it and I want to emphasise how different it is) - plus six secondary colours that are mixtures of two colours (yellow, green/splot, splot/blue, magenta, red/splot, and cyan) - plus four tertiary colours that are mixtures of three of her primaries (red/green/splot, red/green/blue (not white because it has no splot in it), red/splot/blue, green/splot/blue) plus all four primaries at once (which I presume she'd call 'white').

We have seven basic combinations that look like different colours, she has fifteen colours that are likely to be as different to her as red, yellow, green, cyan, blue, magenta and white are to us! It's WAY more than just a little more subtle ability...it's and ENTIRELY different perceptual system. We simply cannot comprehend what the world looks like to her...there is no way to comprehend that. She has a good idea what the world looks like to us - because that's how TV, movies, books and computer screens look to her (these things don't produce splot - so they can't produce eight of the fifteen colours she can see).

SteveBaker 03:02, 10 October 2007 (UTC)

Do normal humans lack the mental ability to comprehend such colors, or is it just a matter of physical eye characteristics? I mean, I remember reading an article in Vanity Fair about a blind man with a primitive vision device resembling sunglasses wired to his brain who was able to see very basic light/dark differences--if the passage of time allowed such a device to be built which had a tetrachromatic spectrum, would our minds be able to deal with that? Would they be able to deal with something even wider in range, such as infrared or ultraviolet information?

And by the way, I would like to thank you for all of the time and patience you have taken here too.

We do lack the ability to comprehend things we havn't learned to see - but the brain is amazingly adaptable - so I think we would be able to learn to see with extra colours. People who are cured of blindness - or deafness do eventually learn to use their new senses. The lady who was born a tetrachromat has evidently learned to use her extra colours. I read someplace that she had worked for a while in a knitting yarn shop and had realised that her sense of colour matching was vastly better than that of her customers.

There is an interesting perceptual problem that perhaps 5% of people suffer from. Lots of babies are born with cross-eyed eyes. Usually, this problem corrects itself within just a few days of birth - but for some babies it takes months. Sadly, that period is when the brain learns to use the different images from your two eyes to estimate 3D depth - so kids with this problem NEVER learn to see in true 3D over much of the range of vision. As I said, as many as 5% of adults have this problem! I was reading about a lady who had this problem who managed to teach herself to see in 3D and 'educated her brain' to start seeing in 3D correctly. It's interesting to note that quite a few of the people reading this posting are suffering from this problem and don't even know it!

People who have cataracts removed and can see a little into the ultraviolet are a different case though. They don't see any 'new' colours - it's just that things that formerly had a UV component to their colour now look to have more blue in them. Things like flowers (which are often patterned with UV spots and stripes) would have new patterns on them that 'normal' people can't see - but those spots and stripes would appear as a perfectly normal blue tint.

SteveBaker 13:51, 10 October 2007 (UTC)

Those don't go together! =(

Would Nuclear devices dropped and detonated in volcanoes would cause an unbelievable amount of destruction? In cartoons and sci-fi stories the results vary but still, is there any evidence to support this? The most logical things I could think of would be something like this:

Option 1: The Nuclear device detonates, causing both the volcano and nuclear bomb to explode. (Worst case scenario)

Option 2: The Nuclear device detonates, causing the volcano to explode and send tons of ash, dust, rocks, sulfur and, now radioactive, debris into the air causing widespread radiation poisoning and (ergo) death. (Worse-than-Worse Case Scenario)

Option 3: The Nuclear device detonates, causing the volcano to collapse on itself. (O.K. Scenario)

Option 4: The Nuclear device detonates, does NOT cause an eruption and due to the extreme heat, melts the inside surface on the volcano and "glasses" it. (Best Case Scenario)

Option 5: The Nuclear bomb detonates, and the volcano is destroyed in a manner that would ensure that it could not erupt again (like, if the volcano shattered, and due to the extreme heat, melted over again) (Best-than-Best Case scenario)

Which would be the most likely outcome of an event like this? The yield and size of the bomb and volcano may vary but in general....

Thanks for your time on my bizarre question!

♥ECH3LON♥ 23:50, 8 October 2007 (UTC)

My bet would be a combination of options 2 and 3. You'd probably get a lot of ash and fallout from the bomb, but it would probably cause the volcano's top to destabilize and fall in on itself. Now of course you've left out the option where the heat of the volcano just melts the bomb into an un-usable state... -24.147.86.187 00:28, 9 October 2007 (UTC)

To start, a couple of questions for you. What kind of (Active, dormant) and type (stratovolcano, caldera, etc.) volcano are you picturing? Anynobody 00:46, 9 October 2007 (UTC)

In general, I don't see much reason to put it at anything significantly beyond the otherwise-imminent eruption and/or nuke, as appropriate. A nuke won't make an inactive volcano erupt. While a nuke might trigger an eruption prematurely, it's unlikely to change the scale of the eruption -- even nukes aren't that powerful. And while yes, there will be radioactive dust, a single nuke isn't world-shattering -- particularly if people know that it's a nuclear explosion, precautions can be taken. Dust is relatively easy to filter, and by the time you're talking about the high-altitude world-circling dust from the eruption, the radioactivity should be diffuse enough to be a relatively minor concern. In short, there's not much synergy. — Lomn 01:47, 9 October 2007 (UTC)

I think you're very misunderstood about the fallout risks that would be in place from a ground-level nuke in a rocky environment. It would produce a lot of nasty heavy bits that, with a bad gust of wind, would contaminate a large area, making it quite difficult to live in, much less raise crops in, etc. It wouldn't be good. That being said, it's not terribly different from setting off a nuke next to a mountain in any situation; it being a volcano doesn't change much in that respect. --24.147.86.187 05:14, 9 October 2007 (UTC)

Would that be worse than a volcanic eruption? DirkvdM 08:49, 9 October 2007 (UTC)

I dont know how to qualify "worse" in this case, but it would be different. If we are assuming a worst-case volcano eruption (immediate, massive, followed by massive lava floes and mud slides) then maybe not. If we are assuming an eruption where you could get warning out and evacuate, then definitely. The fallout would make the land far more uninhabitable as a health risk in the long term than the eruption (which is to say, it's not that people would immediately die if they went on the last—of course not—but if they stayed on it and ate from it and etc. they would develop much higher risks of cancer, birth defects, etc.). --24.147.86.187 14:03, 9 October 2007 (UTC)

Does this somehow pertain to scientology doctrine about H-bombs and volcanoes? 130.126.67.144 04:39, 9 October 2007 (UTC)

Would anyone care (irrespective of what it is)? DirkvdM 08:49, 9 October 2007 (UTC)

Just a little too much of a coincidence. See Operating_Thetan#OT_III:_The_Wall_of_Fire and Xenu#Summary. Snicker. No word yet on why you'd need wings in space. --froth^t 04:01, 10 October 2007 (UTC)

A grown-up Bart Simpson would love this question. I'm picturing a Doomsday H-bomb of 100 megatons lowered into the pipe as far as it will go and then set off. I don't suppose it would alter the appearance of the average volcano very much; volcanoes are pretty big. But it might sort of blow the top off if it were set off shallow in a steep cone like Fuji. I'd expect to see a jet of nightmare isotopes shoot out the top and plume out downwind as fallout, ruining the lives of anything living there. What the volcano would do would depend upon what state it had been in at the time. If you had done that to Mount St. Helens one day before it blew, I suppose the nuke would have made it go then. You see estimates of around 35 megatons equivalent explosive yield for the eruption itself, so 100 megatons of bomb is not insignificant and would have actually punched it up a notch or two.

If you look at pictures from the underground A-tests in the US West, you see a spherical cavern of fused rock that has collapsed on itself somewhat. In a volcano, the blast would have someplace to go, up, and the chief effect would probably be melting. If the volcano was dormant at the time was because of a plug, the nuke just might dislodge or damage it enough to cause an eruption, I guess. (This is what you want, right? Idle surmise? I'm no vulcanologist nor nukeologist neither.)

So, option one: Sure, under the right conditions. Two: Same thing. Three: Most likely, I think. Four: Not much different from three. Five: Can't see that happening, because the forces at work have time on their side, and add up to more power than our little firecrackers have. --Milkbreath 11:36, 9 October 2007 (UTC)

Our articles notes Mt. St. Helens eruption as 350 Mt equivlent (not 35 Mt) while the largest bomb ever built was only 50 Mt. (Tsar Bomb) Rmhermen 18:17, 9 October 2007 (UTC)

I was under the impression that the Tsar Bomb was the largest bomb ever [i]detonated[/i], not necessarily the largest ever built. Though I may be wrong --Teacosythesecond 21:07, 25 September 2008 (GMT)

A megaton here, a megaton there, pretty soon you're talking real destruction. I just had 100 in my head for that Ruskie bomb at Novaya Zemlaya that time. It was only a piddling 50? What the hell were we boomers so worried about? And a quick google on "saint helens eruption megatons" gives figures much lower than 350. OK, but still, 50/350 is a chunk. --Milkbreath 19:07, 9 October 2007 (UTC)

The Tsar Bomba was originally designed as 100Mt, but they decided it would be a good idea to scale it back a bit. Algebraist 19:40, 10 October 2007 (UTC)

October 9

Banned airlines

I was just looking at our list of air carriers banned in the EU. Is there an equivalent list for the US? I couldn't find one.--Shantavira|^{feed me} 10:03, 9 October 2007 (UTC)

I can't find a US airline blacklist either; apparently there isn't one[8]. FAA does have a country-level assessment, International Aviation Safety Assessment Program. Weregerbil 11:30, 9 October 2007 (UTC)

The winter plumage of large gulls...

This is a Herring Gull, but the effect is the same for the closely-related LBBG.

My local black-backed gulls have now fully moulted into their winter plumage (basically, their heads and necks become streaked with diffuse greys and browns and look 'dirty' from a distance). I was watching them feed today and I found myself wondering if this plumage feature is related in any way to the solid black/brown 'hoods' that some species of gull (e.g. Black-headed Gull, Mediterranean Gull) display in the summer months. A genetic vestige of something from a common 'proto-gull' ancestor, altered by evolution over millions of years, perhaps? Some LBB/Herring Gulls have many more darker feathers on their heads than others - in certain birds, it almost looks as though they have the 'hood' anyway. Anyone know for sure/have any ideas? Cheers. --Kurt Shaped Box 10:10, 9 October 2007 (UTC)

Hi, Kurt. That's an interesting idea. I have no idea if there is a connection. However, it might be relevant that black-headed gull species lose much of their dark cap in their winter plumage, the opposite of white-headed gull species. Also, the related terns have the same pattern as black-headed gulls: black cap in summer that is greatly reduced in winter. What does that mean? I don't know. I'll have to look up some information on gull evolution. I'm not at home right now, so I don't have any of my bird books handy.--Eriastrum 15:40, 9 October 2007 (UTC)

So, did you manage to find out anything interesting? --Kurt Shaped Box 19:52, 13 October 2007 (UTC)

Oop! Sorry Kurt. I didn't find anything that seemed relevant. Tons of stuff on plumages, but nothing on whether the black cap is a derived or ancestral character. I'll dig some more.--Eriastrum 15:39, 14 October 2007 (UTC)

Okay man, no worries... :) --Kurt Shaped Box 07:41, 15 October 2007 (UTC)

Degradation of Ubiquitin

Though vast information is available about the role played by ubiquitin in the degradation of proteins, very little literature is available on the degradation of the ubiquitin molecule itself. Generally, after degradation of a protein, the ubiquitin molecules are recycled for another round of protein degradation. But, how is ubiquitin ultimately degraded?

Swellbeing24

link for ubiquitin mediated degradation of proteins: http://en.wikipedia.org/wiki/Ubiquitin —Preceding unsigned comment added by Swellbeing24 (talk • contribs) 12:48, 9 October 2007 (UTC)

Here is a starting point in the literature that you can download: Ubiquitin Depletion as a Key Mediator of Toxicity by Translational Inhibitors. My guess is that cells normally produce an excess of ubiquitin and when there is "excesss", more of it gets destroyed by proteasomes because less effort is put into removing ubiquitin from proteins that are degraded. If ubiquitin becomes depleted, then changes are made to the proteasomes that increase the efficiency of releasing ubiquitin which can then be re-used. See A ubiquitin stress response induces altered proteasome composition. --JWSchmidt 15:58, 9 October 2007 (UTC)

That was extremely helpful. The NCBI article provided just the hint I was looking for- 'The proteasome-associated deubiquitinating enzyme Ubp6, which spares ubiquitin from proteasomal degradation, is induced by ubiquitin deficiency'. Thanks! Swellbeing24

mass of phosphorus

What is the molecular mass of phosphorus? I don't want molar mass. --MKnight9989 13:16, 9 October 2007 (UTC)

There are several allotropes of phosphorus, but white phosphorus=P₄ appears to be the only one that comes in molecules. ³¹P seems to be the only isotope found in nature, so unless your molecule comes from a nuclear reactor or something, it will have a relative molecular mass of (very very slightly less than) 124. Algebraist 13:37, 9 October 2007 (UTC)

And red phosphorus is P4 chains giving a molecular mass of 124 x N, ... the others are macromolecules87.102.18.10 14:41, 9 October 2007 (UTC)

Peroxide blocking

In the TUNEL assay, hydrogen peroxide is added for the purpose of "peroxide blocking". Why (or how do I find out why) is this blocking necessary? --137.120.90.152 13:41, 9 October 2007 (UTC)

TUNEL assay says, "dUTPs that are secondarily labeled"; in particular, the nucleotides used in the assay can be biotinylated and then once the biotinylated nucleotides are enzymatically incorporated into cells they can be detected with Streptavidin coupled to horseradish peroxidase (HRP). However, some cells/tissues contain endogenous peroxidase activity. So before adding the Streptavidin-HRP, it is often useful to "block" the endogenous peroxidase activity. See this article. --JWSchmidt 14:30, 9 October 2007 (UTC)

Comet ETA

When can we expect the next comet to pass by Earth? Halley isn't due until 2061, and the Great Daylight Comet won't be back until 4144877 AD. Beekone 16:50, 9 October 2007 (UTC)

What so you mean by 'pass by Earth'? If you mean be bright and impressive when seen with the naked eye, then Great Comet explains that it is hard to predict when they will occur, but they do so about once a decade, the most recent being Comet McNaught this year. If you're happy with comets visible with binoculars, then that happens all the time: c/2006 vz13 right now for example. Algebraist 17:15, 9 October 2007 (UTC)

No it isn't, that's out of date. Algebraist 17:18, 9 October 2007 (UTC)

That's exactly what I mean. Visible by binocular is cool too, but i prefer a reason to drive to the country and lie in a pasture. Is there a solid date on that kind of action? Beekone 17:34, 9 October 2007 (UTC)

Quoting Algebraist above:

Great Comet explains that it is hard to predict when they will occur, but they do so about once a decade, the most recent being Comet McNaught this year.

— Lomn 17:47, 9 October 2007 (UTC)

So there's absolutely no way to predict when another comet will be coming? I get that it's "hard" but that should mean "speed bump" when it comes to science. Should the aforementioned quote read "...it is impossible to predict..."? Thanks for treating me like an idiot though, Lomn, that was pretty cool. Does anyone else know when another comet will be coming? Beekone 18:13, 9 October 2007 (UTC)

I'm sorry I offended you, but it's likewise "cool" to ignore the answer (and reference) you've been given just because it's not the one you wanted -- twice now. In case any doubt remains, no, there is no way to predict a Great Comet. Orbital mechanics are fine for determining when a comet is observable in astronomical terms, but determining that a comet will be daylight-visible like McNaught is guesswork. — Lomn 19:16, 9 October 2007 (UTC)

"Orbital mechanics are fine for determining when a comet is observable in astronomical terms" This is actually a great start, this is exactly the info I'm looking for! You can tell because I previously said "When can we expect the next comet to pass by Earth?" So, using orbital mechanics, when can we expect another Great Comet to pass by Earth? Beekone 19:33, 9 October 2007 (UTC)

(de-indent) We don't know. We can't know, because predicting a comet is not at all the same thing as predicting a Great Comet. In the last 200 years, only two Great Comets (Comet Hale-Bopp and Comet Halley in 1910) were even known to exist more than 6 months prior to perihelion, and only Halley anticipated prior to that. Many were discovered less than 3 months before perihelion, and even HB had less than two years' foreknowledge. Additionally, the history of comets is rife with expected Great Comets that fizzled (for example, Comet Halley in 1986) as well as Great Comets that no one expected until they suddenly brightened. Obviously, orbital mechanics are no good at predicting something when we don't know what its orbit is. As for "when will the next comet pass by Earth?" (do you see the distinction?) -- comets are observed in astronomical contexts on a near-constant basis. — Lomn 20:13, 9 October 2007 (UTC)

Yes, flawless execution. Thank you for the explanation Beekone 20:23, 9 October 2007 (UTC)

This won't answer your question, but to give you an idea of the complexity of the problem, take a look at this site [9]. For example, it says that so far in 2007, 77 comets alone were newly discovered! The author of the site includes his email address, so you could contact him and see if he can give you some kind of idea of when the next "wow" comet might be visible. He also includes a number of links you could explore to see if you can find anything.--Eriastrum 23:05, 9 October 2007 (UTC)

Influenza vs Common Cold

hi, can anyone explain to me the difference between influenza and the common cold? thanks a lot. —Preceding unsigned comment added by 193.195.187.186 (talk) 16:53, 9 October 2007 (UTC)

From influenza: 'Sometimes confused with the common cold, influenza is a much more severe disease and is caused by a different type of virus.' Try the two linked articles for more details. Come back here if you still have questions. Algebraist 17:10, 9 October 2007 (UTC)

As noted, they are caused by different viruses. And although the symptoms are similar, fever is rare in colds, common in flu, generalized aches and pains are rare in colds, common in flu, weakness is far more severe in flu, and the potential complications of influenza are more severe. Other differences: you can be vaccinated against the flu, but not against colds. - Nunh-huh 06:26, 10 October 2007 (UTC)

Difference between seagulls with white and dark heads

Is it just a coincidence that gulls with white heads are bigger and more predatory than the ones with dark heads? --84.69.19.94 23:27, 9 October 2007 (UTC)
Remember to WP:AGF D: --froth^t

There are lots of species of Gull. If you look at the gallery at the bottom of the article, it looks like there are a number of species with black/grey heads. I can't think of any reason why having a dark head would be related to size or aggressiveness, but then I know absolutely nothing about birds. By the way, the Black-headed Gull - which is a particular species, and the most common one with a black head where I live - only has a black head in winter summer (oops, that was stupid), so maybe there is some kind of seasonal change in its behaviour? Bistromathic 20:28, 10 October 2007 (UTC)

In the northern hemisphere, there are 16 very closely-related species of 'large white-headed gull'. Have a look at the gull article for the species names - but the familiar Herring Gull (the archetypical 'seagull') is one of them. IIRC, they're that genetically close that most of them are capable of interbreeding and producing fertile hybrids. They're all very big, bulky, aggressive, cocky (around humans), somewhat (or outright, depending on the species) predatory birds. Most other gulls are smaller and daintier-looking in comparison to this lot - and it happens that some of those have the 'hoods' in summer. --Kurt Shaped Box 21:53, 10 October 2007 (UTC)

EDIT: There is one hooded species (that I know of), the Great Black-headed Gull, which in terms of size and behaviour could easily go to-to-toe with the Great Black-backed Gull. --Kurt Shaped Box 21:57, 10 October 2007 (UTC)

Hydrogen fuel

I've heard some people talk about Hydrogen based fuel (with no pollution and all that stuff). How would we get the hydrogen? I've read somewhere that extracting hydrogen from water takes more energy than what is released by the combustion of hydrogen. Is that true?

I've got some other questions:

• How can neutrinos have antiparticles even though they have zero electric charge?
• I know that bosons are force carriers but how can certain isotopes of elements be bosons? What force do they carry?

Thanks in advance. --wj32 ^{talk | contribs} 23:59, 9 October 2007 (UTC)

To begin with, you're referring to a fuel cell. The hydrogen could be extracted from water through electrolysis, or alternatively from hydrocarbons. And yes, extracting from water would consume more energy than recombination of hydrogen and oxygen would release. If it didn't, you'd have a perpetual motion device on your hands (although the inventor of the water fuel cell would like you to believe that this is possible). Antineutrinos are opposite their respectiveneutrinos in terms of helicity, not charge. As for bosons, there are elementary bosons and composite bosons (both explained in boson). The composite bosons are not force carriers, but they posses physical properties unique to bosons, such as independence from Pauli's exclusion principle. This leads to bosonic matter displaying some very wierd characteristics (superfluidity and supersolidity). Someguy1221 00:12, 10 October 2007 (UTC)

That answers all of my questions! Thanks a lot. --wj32 ^{talk | contribs} 00:29, 10 October 2007 (UTC)

To continue the fuel cell bit, it's worth noting the theoretical appeal of fuel cells if it's a net energy loss. As it stands now, the electricity needed to "crack" water tends to come from "dirty" sources -- coal-fired power plants and the like. Burning coal to make clean hydrogen isn't really an improvement over burning oil directly in a car engine.

Suppose, however, that you've got a clean power source: perhaps solar in the small scale now or cold fusion someday (or fission now, but I'd prefer to avoid the debate as to whether or not that constitutes "clean"). Once you've got a ready eco-friendly power source to crack water, it's not a problem to accept the energy inefficiencies that come with generating hydrogen for portable fuel cells. — Lomn 02:21, 10 October 2007 (UTC)

I think it's reasonably true to say that most renewable energy sources (hydro, wind, waves, solar, geothermal) produce electricity. So does nuclear and (eventually) fusion power. So it would be sensible to build electric cars. The problem is that battery technology isn't up to the job for lots of reasons - and when you run out of charge, you might need HOURS to recharge the darned things.

So one alternative is to use electricity to crack water to make hydrogen in some big factory someplace - then put the hydrogen into a tank in the car and use a fuel cell to turn the hydrogen back into water + electricity - you can store quite a lot of hydrogen in your car, and refuelling might also be quick and easy - just like a gas station. Now, to be sure, the process of converting electricity to hydrogen and hydrogen back into electricity again is wasteful (both processes are about 80% efficient) - so you'll waste maybe 36% of the energy in the process. However, that's still a lot better than gasoline powered cars - and all that comes out of the tail-pipe is warm water. So if this can be perfected, it's a net win. It would be much nicer if we could come up with a better battery technology though.

SteveBaker 02:35, 10 October 2007 (UTC)

Did you even read battery-electric vehicle? Battery electric cars are far more efficient than Hydrogen Cars. The latest models are capable of incredible performance as well. 0-60mph in 4 seconds, top speeds of over 200 mph, and ranges of 100-200 miles. Sometimes better. Of course those models are probably expensive. 64.236.121.129 13:25, 11 October 2007 (UTC)

And if you ran some refrigeration coils around and a big tank, you could have a drinking fountain in your car! Now that's novel. :) -Wooty [Woot?] [Spam! Spam! Wonderful spam!] 03:29, 10 October 2007 (UTC)

It would actually be kinda useful too - one of the challenges with fuel-cell hydrogen cars is how to warm up the hydrogen as the pressure is released. Keeping a fridge full of non-alcoholic beer frosty-cold would help! :-) SteveBaker 13:38, 10 October 2007 (UTC)

Actually, alcohol would do a better job because it takes much more energy to freeze it. DirkvdM 09:01, 11 October 2007 (UTC)

Steve, hydro- and windenergy don't strictly speaking produce electricity. It's just that that's a form of energy we have an extensive infrastructure for, so we convert the energy to that. Wind and rivers are both flows. We translate that into rotation and then use turbines to translate that into electricity. And then (in this case) into hydrogen again. Maybe efficiency would be served if we could translate the flow more directly into hydrogen. What about using the triboelectric effect? Alas, water and air aren't mentioned in the article, but what if we'd have a material that would build up a charge that can then be used for electrolysis to produce hydrogen? DirkvdM 09:01, 11 October 2007 (UTC)

October 10

9th cartilage of the larynx

I am trying to complete my notes on the larynx. I was double checking between my notes from a lecture to that of the article here on wikipedia. I seemed to have never completed my notes on the cartilages. I've got down for the cartilages the cricoid, thyroid, cuneiforms, corniculates, and arytenoids. The cricoid and thyroid are single (unpaired) cartilages while the cuneiforms, corniculates and arytenoids are paired. I counted 8 cartilages all together. What is the 9th cartilage of the larynx? Thanks --Agester 01:01, 10 October 2007 (UTC)

Epiglottis (single). --Milkbreath 01:50, 10 October 2007 (UTC)

Here is the relevant page from Henry Gray's Anatomy http://www.bartleby.com/107/236.htm Richard Avery 08:50, 10 October 2007 (UTC)

Are we Monkeys?

We have evolved from apes and a ape is a tailess monkey, so therefore what kind of animals are we monkeys?

We are our own species. You could always take a crack at Human evolution. This article includes a nice chart diagraming our split from what became chimps. Someguy1221 03:05, 10 October 2007 (UTC)

We are apes, not monkeys, and apes are not simply "tailless monkeys," as you suggest. Apes are, like, smarter and better.--The Fat Man Who Never Came Back 03:24, 10 October 2007 (UTC)

No - we aren't monkeys. Neither are chimps, gorillas, bonobos, orangutans, etc. There are three kinds of Simians/Primates. The three types are: Old World monkeys, New World monkeys and Apes. Humans are apes - so we are not monkeys - but (like the monkeys) we are all primates. SteveBaker 04:04, 10 October 2007 (UTC)

what about lemurs? they're not monkeys or apes, are they? --The Fat Man Who Never Came Back 04:07, 10 October 2007 (UTC)

Lemurs are prosimians. From Primate: The Primates order is divided informally into three main groupings: prosimians, monkeys of the New World, and monkeys and apes of the Old World. — Scientizzle 04:23, 10 October 2007 (UTC)

We also didn't evolve from any current species. Rather every species have evolved through different paths and we have a common ancestor. --DHeyward 06:16, 10 October 2007 (UTC)

That's true - but we are still evolved from creatures who we'd call "apes" - just not any specific present day ape. SteveBaker 13:35, 10 October 2007 (UTC)

Jared Diamond's book The Third Chimpanzee takes its title from the statement that, if you look at it impartially, you'll find that the genus Homo is not really sufficiently distinct to be considered as separate from the genus Pan. The latter genus includes the common chimpanzee and the bonobo or pygmy chimpanzee, so the idea is that Homo sapiens should really be Pan sapiens, a third type of chimpanzee. --Anonymous ___ sapiens, 22:14 UTC, October 10, 2007.

Indeed, while I've never read Mr. Diamond's book, cladistically a Homo/Pan distinction is completely arbitrary and anthropocentric. --Cody Pope 05:00, 11 October 2007 (UTC)

There might be more sympathy for this view if they proposed 'Homo troglodytes' and 'Homo paniscus' for the chimpanzees rather than using 'Pan sapiens' for humans.

Wasn't the common chimp formerly called Homo silvaticus? —Tamfang 19:25, 14 October 2007 (UTC)

I don't know, but above I was misremembering what Diamond said about the name for the single genus. He actually said that since the name Homo was older as a genus name than Pan, nomenclature conventions would require Homo to be extended to chimps rather than Pan to humans, if they were officially merged. Sorry about the error. --Anon, 06:08 UTC, October 15, 2007.

I'm very fond of the fact that there is more genetic difference between a male human and a female human than there is between a male human and a male chimpanzee or between a female human and a female chimpanzee. It turns out that (biologically speaking) this is really no surprise - but it explains a lot about 'the human condition'. SteveBaker 05:10, 12 October 2007 (UTC)

Source of fruit flies

I looked at the article on fruit flies, but it did not answer my main question. Where do all those fruit flies come from when you open a banana and leave it uneaten over night. The flies only appear once the banana is opened, so are the eggs inside the peel? What triggers the hatching? How do the bananas become impregnated? I have difficulty imagining a little fruit fly with an ovipositor longer than its body length inserting eggs beneath the peel. How long can the eggs survive before hatching? Any answers will be appreciated.

See Spontaneous generation.--The Fat Man Who Never Came Back 03:41, 10 October 2007 (UTC)

Yep! That's what my momma told me too. - hydnjo talk 03:54, 10 October 2007 (UTC)

Why don't you do a science experiment? Buy a banana. "open a banana". Place banana inside a glass jar. Seal the glass jar completely. Leave the banana overnight. 202.168.50.40 03:50, 10 October 2007 (UTC)

Maybe you just have fruit flies wherever you're opening them. I can attest I've never found a fruit fly on fruit in my house. Someguy1221 03:55, 10 October 2007 (UTC)

Well, you have a mommy fruitfly and a daddy fruitfly who love each other very much...er...sorry, wrong answer. I don't think the egg has to be laid all the way in the core of the banana - if the larvae are mobile, they can work their way into the middle of the banana from just under the skin. The eggs develop in between 7 and 50 days depending on the temperature. SteveBaker 03:57, 10 October 2007 (UTC)

A fruit fly researcher I know has just informed me that the little guys are unlikely to lay eggs on fruit that's not even ripe yet. Someguy1221 05:01, 10 October 2007 (UTC)

That makes it very unlikely that these flies were inside the banana all that time then. If the fruit has to be ripe when the eggs are laid - and they take a minimum of 7 days to mature into flies. So the banana would have to be (at a minimum) 7 days past being ripe. They must have been in the house all along and were simply attracted to a handy opened banana. SteveBaker 13:33, 10 October 2007 (UTC)

It's not just bananas, we have resident fruit flies in our house that seem to replace themselves over several months, but never exceeding 2 or 3 that fly around entering and leaving one's field of vision in a cursedly annoying way. They definitely prefer grapes and apples, sometimes we don't have bananas. I assumed they had flown in from the garden where we have zillions in our compost bin. Richard Avery 08:45, 10 October 2007 (UTC)

If you are in a climate where fruit flies thrive, you need to keep fruit shut away in a refrigerator (low temperatures dramatically increase the time it takes their eggs to hatch) and to dispose of leftovers in a garbage disposal unit - or at least remove your kitchen trashbags regularly. Any piece of fruit left lying around for more than (maybe) 7 days at room temperature is going to be a source of new fruit flies. SteveBaker 14:31, 10 October 2007 (UTC)

Drosophila melanogaster love bananas (specifically the yeast) and some variety of it is likely what you are talking about. This is one of the reasons they became model organisms for genetics—they are super easy to breed, you just leave out a bunch of bananas for awhile and they show up in spades. Eventually the Morgan group found a cheaper form of food than bananas for them (some sort of yeast agar or something like that). I didn't even realize that those little gnat like guys were the fruit flies of fame and fortune for a long time. (A great book on the subject of the flies and genetics: Lords of the Fly by Robert E. Kohler) --24.147.86.187 22:26, 10 October 2007 (UTC)

need info on milk

Sir

what does butter fat mean?

How it is useful for growing kids?

How a pack of milk is special due to butter fat content?

Why do pepole prefer milk, is it because of taste,practise or anything else.

Regards

Sathish

Dear Mr. Sathish, You can go through the article Butterfat. I am not sure if I can go into any details on the topic myself but my obvious suggestion would be for you to check Milk, Fat (importance for living organisms), and the above link Butterfat. Hopefully, as you read the above articles, someone will come and give definite answers to your questions. Regards, Kushal --Kushal^{Click me!} write to me 05:16, 10 October 2007 (UTC)

Identify this spider

Hello, I'm no spider expert. Could somebody identify this one? Image:Spider-2007-10-09.png. Thanks! Sancho 07:20, 10 October 2007 (UTC)

Tegenaria domestica better picture in the German article (marks on the back)--Stone 08:31, 10 October 2007 (UTC)

Tegenaria gigantea, Tegenaria agrestis have different size, but look similar, so you have to decide how big the spider is. Tegenaria agrestis (Hobo spider) is dangerous according to the article.--Stone 08:37, 10 October 2007 (UTC)

Its body was about 1cm, with a leg span of about 3 cm. Sancho 15:40, 10 October 2007 (UTC)

Are electrons gaining weight?

I remember being told in science classes, when I was a kid, that electrons didn't have any mass. I've just skimmed over the electron article and found that they do have mass. Did something change in the last 15-20 years in our understanding of electrons or am I remembering incorrectly? Dismas|^(talk) 09:15, 10 October 2007 (UTC)

I don't think this is a recent development, but you may not be remembering wrong either. Quite often at school level, simplifications are made, or approximations are made for the sake of doing calculations. The electron weighs about 2000 times less than the proton, so it is often appropriate to simply ignore the electron mass as it is so much less. You may also be interested in neutrinos, long thought to be massless, but recently their tiny masses have been detected. Cyta 11:31, 10 October 2007 (UTC)

It's mass is around 1/1823. You were likely told in high school that it had no mass because its mass is so small as to be neglible and can usually be ignored. Backsigns 12:41, 10 October 2007 (UTC)

I was taught that electrons had 1/1823rd of the mass of a proton. That was in high school ~40 years ago. So either they were teaching you an untruth or an approximation that's only relevent when calculating atomic masses and such...or perhaps your memory has failed you. Maybe you are remembering photons or neutrinos? Photons are often described as having zero mass (technically, they have zero 'rest mass') - and neutrino's were probably still thought to have no mass back 15-20 years ago although now we know they do have a very tiny mass. In 1963, John Updike wrote:

Neutrinos - they are very small.

They have no charge and have no mass

And do not interact at all.

...which is now known to be untrue. (There is more to the poem here). —Preceding unsigned comment added by SteveBaker (talk • contribs) 13:28, 10 October 2007 (UTC)

Lest there be any uncertainty, this is not a recent development: on discovering the electron, J. J. Thomson immediately measured its mass/charge ratio and found it to be small but nonzero. Algebraist 19:31, 10 October 2007 (UTC)

You may be remembering the first half of the full name of the most common neutrino, which is the "electron neutrino." This particle was thought to have no mass and is now thought to have a really, really small mass -- much less than the mass of the electron. -Arch dude 20:45, 10 October 2007 (UTC)

So while "they have no mass" could be viewed as a reflection of the slightly wrong understanding of the time, the "do not interact at all" part had to be understood to be not quite correct even then. If they didn't interact at all, then they also could not have been created by any interaction (by the CPT theorem or something). But both assertions are well within poetic license even today. --Trovatore 20:56, 10 October 2007 (UTC)

It could also be that, since the electrons are ~1/1800 the mass of the neutron or proton, they have zero mass number, while neutrons and protons have a mass that's a bit more than one atomic mass unit, are considered to have a mass number of 1. Confusing Manifestation 01:23, 11 October 2007 (UTC)

solanine poison

Amit3405 09:54, 10 October 2007 (UTC)amit3405 what is the postmortem findings in solanine poison in human.

Check out Glycoalkaloid. Alas, the link that would probably answer your question is currently broken. --Mdwyer 18:47, 10 October 2007 (UTC)

I don't understand any of it but Solanine has a section called Solanine poisoning. Could you see if there is any material (or external references and links) there that you could use? --Kushal^{Click me!} write to me 20:44, 10 October 2007 (UTC)

bovine serum albumin blocking

I don't understand the use of bovine serum albumin in immunostaining. --Seans Potato Business 10:26, 10 October 2007 (UTC)

It is the same idea as discussed at Western blot#Blocking. Cells and tissues will often "non-specifically" bind proteins. BSA is one of several relatively inexpensive proteins that is commonly used to block non-specific protein binding sites in samples. --JWSchmidt 14:01, 10 October 2007 (UTC)

I see. I was looking at it backwards. Do you know any examples of components that bind non-specifically? It's not important, I'm just wondering... --Seans Potato Business 16:45, 10 October 2007 (UTC)

One possibility that comes to mind is that "heat shock proteins" or chaperonins might bind some partially denatured antibodies during immunostaining. I doubt if anyone has ever tried to study this; "non-specific protein binding" sorta implies that it would be hard to figure out what is going on because the molecular interactions would be a complex jumble. --JWSchmidt 17:54, 10 October 2007 (UTC)

Neutrons and protons in the nucleus

I just read Neutronium and whilst it makes sense (no force to hold the neutrons together?) it made me wonder what exactly holds the protons and neutrons together in the nucleus of an atom. Are the neutrons simply trapped by the protons? Backsigns 12:38, 10 October 2007 (UTC)

It's something called the nuclear force, that only operates on very small ranges. Normally it holds them pretty tight but if you can make the nucleus super big then its constituent parts will fall outside of its range and the electromagnetic force will kick in (forcing the two positive nuclei to repel rapidly from one another) as is seen in nuclear fission. In nuclear fusion the whole trick is getting positive nuclei close enough together so that the nuclear force will kick in over the electromagnetic force. --24.147.86.187 12:47, 10 October 2007 (UTC)

Heh, this should have been obvious to me. Thanks a lot, that article is very helpful :) Backsigns 12:49, 10 October 2007 (UTC)

And for the real-life neutronium that may exist in neutron stars (see the article), the answer is that gravity holds it together. --Anon, 22:19 UTC, October 10, 2007.

British fetus embryo standards

According to a science story released today at ScienceDaily [10] from UPI, and cited to the Daily Mail, the British health minister, Dawn Primarolo, has given permission for British scientists to create human-animal hybrid fetuses embryos (pony boy? goose girl?) but the "chimaeras" will be "destroyed within 14 days of creation and will not be allowed to develop into living beings." My question is, on what day of fetus embryo development does a hybrid fetus embryo, or even a purely human fetus embryo "develop into a living being" (edit) per British laws and standards, and what basis was used for deciding whether the fetus embryo was "living?" Or is it considered "living" from day one but not yet a "being?" How many days could such a hybrid fetus embryo survive with today's technology in vitro, or could it conceivably be implanted into a human or animal uterus and develop to term? Did the press release as published in ScienceDaily misstate the government pronouncement? Edison 13:46, 10 October 2007 (UTC)

It makes little sense to use the term "fetus" in this context. A human embryo less than 14 days old is basically a collection of cells. These experiments are designed to use chimeric embryos as a way to isolate human stem cells, not a chimeric fetus. --JWSchmidt 14:08, 10 October 2007 (UTC)

Technically, this would be an embryo - not a fetus (the arbitarily chosen time when the terminology switches is 8 weeks after fertilisation). Our article on Prenatal development has a week-by-week account of what forms and when - but basically, 2 weeks after fertilisation, there is no heart or digestive systems, no arms or legs, no brain or spinal cord - the embryo is still a blob of cells just a couple of millimeters across with no obvious 'head' or 'tail'. There is no definite time when you can say the embryo is a "living being" - it's been "living" since day one (actually, before day one - in some senses) - and the definition of a "being" is a judgement call - so pick whatever time suits your personal biasses. The embryo implants into the uterus at day five after fertilisation - whilst I'm certainly no expert, I presume that two weeks is far too late to implant it into a live animal/human. SteveBaker 14:17, 10 October 2007 (UTC)

What would a nuke do to a Tornado?

If a nuke were detonated in a tornado, what would it do to it? Ignore the effects of the nuke on the surrounding enviroment, structures. What would it do to the tornado itself? 64.236.121.129 15:31, 10 October 2007 (UTC)

I don't know what would happen, but I just wanted to say that this question is hilarious in a really awesome way. I hope someone knows the answer. Beekone 15:51, 10 October 2007 (UTC)

I would expect the heat from the detonation to immediately evaporate any of the water droplets that had made the tornado visible. Next, the blast pressure caused by the explosion would dominate the pressures that cause the tornado to form. The rotation that was present before the detonation would be masked as only a very small component of the expanding blast wave and blast winds that reach speeds of several hundreds of miles per hour. Sancho 16:10, 10 October 2007 (UTC)

I get this mental image of Bush saving us from the threat of the tornado using this miracle cure-all. Very entertaining post. Beekone 16:31, 10 October 2007 (UTC)

With a big enough nuke, the shock wave should be able to disperse the cumulonimbus cloud that was powering the tornado (just look at some of the film of old nuke tests - the bomb literally rips a hole in the cloud cover). Of course, if by some magic, the bomb failed to stop the tornado, then you'd have a swirling column of radioactive dust cutting through the countryside - not nice! Laïka 19:30, 10 October 2007 (UTC)

Would an airplane pilot dare to fly into a tornado to do this? – b_jonas 06:40, 11 October 2007 (UTC)

Hurricane researchers do that 'all the time'. A hurricane is pretty destructive to something standing on land because it is standing still. An airplane can 'go with the flow'. Still not without risk, though. And of course, a tornado is not a hurricane. It's much smaller in size, so you can get closer to its centre. Then again, you could also use a rocket. Problem solved, yes? DirkvdM 09:18, 11 October 2007 (UTC)

Would the blast wave not disrupt the cloud cover, thus stopping the tornado? Also, what's preventing us from lobbing a couple of high explosive bombs set for airburst into a hurricane to disrupt the cloud cover? We could get a plane, drop a few at very high altitude, mess with the clouds and presto, no hurricane. Of course, we have to take into account that accuracy will be poor since these bombs are flying through 100mph winds and such.

Note, of course, that a nuclear bomb would be of no effect on something as large and diffuse as a hurricane. --24.147.86.187 13:32, 11 October 2007 (UTC)

That's what I would have thought too, but Hurricane#mechanics says that the energy released by a Hurricane is equivalent to "exploding a 10-megaton nuclear bomb every 20 minutes". So it's sort of in the same order of magnitude. At least for 20 minutes. :) DirkvdM 18:15, 11 October 2007 (UTC)

I wouldn't want to fly an airplane into a tornado. Hurricanes are pretty safe -- they're large, predictable structures, without much in the way of sudden wind shifts. Tornadoes are much more compact -- a small plane might find itself with one wing in the strong updraft of the center, the fuselage in a 200 mile-per-hour headwind, and the other wing in the relatively still air outside the tornado. --Carnildo 21:53, 11 October 2007 (UTC)

So, There is a difference between flying in a hurricane and above a hurricane isn't there?
Mrdeath5493 06:03, 12 October 2007 (UTC)

What does blood color mean

If a non-human primate has brighter-red (rather than darker red) blood than normal, what might be inferred? --Seans Potato Business 16:57, 10 October 2007 (UTC)

Nobility if your blood is blue, right? Beekone 17:07, 10 October 2007 (UTC)

It could be a result of a couple of things, one is that it could indicate a higher level of blood oxygenation (specifically the ratio of deoxyhemoglobin to oxyhemoglobin). Oxygenated blood is a bright red in color, deoxygenated blood is a darker shade of red, which is why venous blood is darker than arterial blood. Of course, there could be other explanations, as some animals have higher levels of beta-carotene in their plasma which may result in changes in the colour of their blood. Rockpocket 17:35, 10 October 2007 (UTC)

Perhaps the blood has been infused with carbon monoxide which will make the colour more bright red. Graeme Bartlett 20:57, 10 October 2007 (UTC)

I believe blood is sort of a maroon color when de-oxygenated , only turning bright red when exposed to oxygen. —Preceding unsigned comment added by 88.110.114.11 (talk) 23:59, 10 October 2007 (UTC)

what is water phase?

The water phase was adjusted to 300 mM NaCl and diluted with 2.5 volumes of ice-cold 100% ethanol. - this is a line from a methods section in an article; when they're talk about the 'water phase' do they mean the component that was water, among their mixture that included phenol: chloroform:isoamyl alcohol (16:16:1)? Is this immiscible with water or something? --Seans Potato Business 16:53, 10 October 2007 (UTC)

Indeed. When you add phenol: chloroform : isoamyl alcohol to a solution containing water, you will get two phases: an aqueous phase (usually on top) and an organic phase. From the protocol you quote it sounds like someone wants to separate DNA, which will be in solution in the aqueous phase, from protein. You can precipitate the DNA by adding cold ethanol to to aqueous phase to form a floccule (which is one of my favorite words!). See Phenol-chloroform extraction, followed by ethanol precipitation, for more details. Rockpocket 17:23, 10 October 2007 (UTC)

White Tailed Eagle

Can someone tell me what predators the White tailed Eagle has? —Preceding unsigned comment added by 64.193.145.145 (talk) 17:17, 10 October 2007 (UTC)

White-tailed Eagle#Near-extinction and recovery in Europe "White-tailed Eagles are alpha predators"

The eggs might be subject to 'predation'87.102.79.56 17:54, 10 October 2007 (UTC)

We humans - probably. There are people out there with guns who get unduly excited about this kind of thing. SteveBaker 16:13, 11 October 2007 (UTC)

Image of Sun going around the earth

I don't know if it makes any sense but I wonder (roughly) what shape would the motion of the sun make if we considered the motion of the earth and the sun keeping the earth at the center of the paper and the sun moving round it.

Please delete this post if you know what I mean AND/OR think I am talking nonsense. Thank you. --Kushal^{Click me!} write to me 20:41, 10 October 2007 (UTC)

Is this what you are on about? --80.229.152.246 21:03, 10 October 2007 (UTC)

If your coordinate system is tied to the centre of the earth and fixed stars it will be an ellipse for the shape of the sun's orbit. If the earth has coordinates fixed in the surface the sun will appear to move in a circle. Graeme Bartlett 21:02, 10 October 2007 (UTC)

For an animation of the geocentric model, there's a movie here. - Nunh-huh 21:18, 10 October 2007 (UTC)

See Tychonian system for a geocentric model that is mostly compatible with Copernican observations and is pretty much just changing the frame of reference from the sun to the earth (though the motion of the stars is not correctly accounted for in that case, but with the instruments at the time you couldn't detect that). --24.147.86.187 22:20, 10 October 2007 (UTC)

We even have an article on analemma. 85.127.20.138 22:39, 10 October 2007 (UTC)

The path of the sun around the earth would be exactly the same as the path of the earth around the sun - which to a first approximation is an ellipse (if you look very carefully, the ellipse has wobbles in it due to the mass of the moon orbiting the earth and other still smaller influences from the other planets - but the sun would appear to have those exact same wobbles if you put the earth at the center - but since the sun isn't influenced much by the feeble gravity of the moon, this is one clue that treating the earth as the center of the solar system makes very little sense). SteveBaker 16:12, 11 October 2007 (UTC)

A very sincere thanks to all of you. The Quicktime Movie closely matches what I wanted. So the path that the sun would have around the earth would be just like the path the earth has around the sun? I am still unable to picture this in my head.

Any more suggestions, links, wikilinks, etc would be very appreciated. --Kushal^{Click me!} write to me 03:17, 12 October 2007 (UTC)

The Sun's position-vector relative to Earth is the opposite of the Earth's position-vector relative to the Sun, so the curve is the same curve rotated a half-turn. Does that help? —Tamfang 19:34, 14 October 2007 (UTC)

2N in 2N HCl

What does the "2N" mean in "2N HCl"? --Seans Potato Business 21:46, 10 October 2007 (UTC)

Probably "2 normal". "Normal" HCl contains one equivalent (which in this case equals one mol) of HCl per liter (of water, presumably). 2N HCl is twice as concentrated as that. --Trovatore 21:48, 10 October 2007 (UTC)

Yes it does mean normality, which is related to concentration and molarity. But the conversion of normality to molarity varies from compound to compound. For HCl, which dissociates 1 mole of hydrogens (protons) per mole HCl, a 1 normal solution would be 1 molar. For sulfuric acid, which dissociates 2 moles of hydrogen per mole of acid, a 1 normal solution would be 0.5 molar. I think. See Molality#Normality, although it's not exactly too clear. I remember our analytical chemistry professor saying this is on his list of the most confusing and possibly pointless things chemists have ever done. --Bennybp 21:57, 10 October 2007 (UTC)

Bennybp is correct. And I agree it's somewhat pointless. I imagine it was intended to be less confusing; instead it is more. -- Flyguy649 ^talk _contribs 22:23, 10 October 2007 (UTC)

Only use I've seen for normality is with standardized solutions when you really care about the concentratation. "I know it's 2M HCl because I did an acid/base titration"—no, you know it has 2 moles of H⁺, so you can only really talk about that ion and then explain that in terms of how much HCl would make it. So yeah, confusing and pretty damn useless in most contexts. DMacks 02:18, 11 October 2007 (UTC)

As long as you understand the definition of normality, it is about as useful as any other way to measure concentration.Mrdeath5493 05:59, 12 October 2007 (UTC)

No, it isn't.

See, for example, the explicit prohibition of its use in NIST Special Publication 811, Guide for the Use of the International System of Units, section 8.6.5:[11]

2. The term normality and the symbol N should no longer be used because they are obsolete. One should avoid writing, for example, "a 0.5 N solution of H₂SO₄" and write instead "a solution having an amount-of-substance concentration of c[(1/2)H₂SO₄] = 0.5 mol/dm³" (or 0.5 kmol/m³ or 0.5 mol/L since 1 mol/dm³ = 1 kmol/m³ = 1 mol/L).

Gene Nygaard 13:42, 12 October 2007 (UTC)

But 0.5N H₂SO₄ is actually 0.25 mol/L, right? --Seans Potato Business 22:00, 13 October 2007 (UTC)

Yes. The "normality" of an acid like sulfuric acid can be thought of as the concentration (in mol/L) of the protons in the solution. Since sulfuric acid gives 2 protons per molecule, the concentration of H₂SO₄ (although it doesn't exist that way in solution) would be 1/2 the normality. It's hard for me to wrap my head around that like from the NIST, too. Somtimes, I think they try too hard (molarity is obsolete?????). --Bennybp 23:33, 13 October 2007 (UTC)

October 11

Do you think that this is real?

I've been doing some reading about hybrid macaws today. In the course of which, I encountered this image:

http://img.photobucket.com/albums/v195/nix_alba/hybg.jpg

Supposedly, it's a Hyacinth Macaw x Blue-and-yellow Macaw hybrid. I know that some of the hybrids do look a little strange and their appearances can very a lot depending on which species was the father/mother (and luck!) but this one just looks *wrong* (looks way too much like a photoshop cut+paste job to me). Would I be right in calling BS on this image?

OTOH, this image supposedly depicts the actual hybrid, which apparently really does exist. Cool huh? --Kurt Shaped Box 02:11, 11 October 2007 (UTC)

The lighting in the image is rather screwed up (probably due to using flash photography close up), but other than that, I can't see any obvious reasons for it to be fake - the image fits the shadow perfectly and there are no obvious discontinuities in the colouring or pattern. Laïka 11:55, 11 October 2007 (UTC)

The pic is too heavily artifacted for me to say for sure, but something about it just doesn't sit right with me. The head seems too large for the body, the colour shifts on the throat and breast seem too abrupt, and the shadow doesn't look right. Just below the shadows of the head, there's a shadow 'bump' that is of somewhat different quality (sharper, a little darker) and looks to me like it might have been added in. Any of those things could be accounted for by a simply poorly taken picture, but together they make it unconvincing. Again, overall poor quality makes it difficult to be sure. Matt Deres 00:07, 12 October 2007 (UTC)

Schoolgulls

At my school there are gulls that presumably feed on abandoned food after lunch. Normally there's few, if any, flying over the quad (where most of us eat), but every once in a while they all come out at once. Does anyone know why? Does any box shaped like someone (named Kurt) know why? — Daniel 03:17, 11 October 2007 (UTC)

My name is not Kurt and I'm not shaped like a box but I'd like to give a possible explaination. I heard some years ago that gulls (and vultures in Africa) operate a sort of territorial watching patrol system where they fly around in a certain area looking for food and keeping an eye on their neighbours. When they find food they drop out of the sky to scavenge it, meanwhile the neighbours of this gull, which have been watching him, see that he has dropped down to eat so they head for that spot. The neighbour's neighbours also see that their neighbours have zoomed down to sample something so they too head for the action. Very soon you've got more gulls than you were able to see beforehand. Forgive me for treading on what is cleary viewed as your territory KSB Richard Avery 07:36, 11 October 2007 (UTC)

Yup, you're pretty much spot on there, Richard. Gulls have very sharp eyesight and can presumably observe the behaviour of other gulls over fairly large distances. It's not always the case that they're all airborne at the same time either. Gulls like to sit on high rooftops and watch the other gulls - a lot.

I also wouldn't put it past the gulls to know roughly what time of the day that the kids eat their lunches too. When I was at school, I remember seeing gulls starting to congregate in large numbers on the rooftops of the school buildings overlooking the playground from about 11am onwards.

Speaking from my observations of Herring and Lesser/Great Black-backed Gulls, it's often the case that a single bird will spot food and immediately sound the famous 'MWAAK! MWAAK! MWAAKMWAAKMWAAKMWAAKMWAAK!' cry. Whether this is a joyous announcement of the presence of food to the flock or a warning to the other gulls to stay away from that individual's find is largely irrelevant (I suspect the latter) - the net result is the same, in that the other gulls hear it and scoot over to take a look. --Kurt Shaped Box 08:54, 11 October 2007 (UTC)

Dear god, we're imitating animals now? Ok, let me do a fruitfly then: bzzzzzzzzzz. :) DirkvdM 09:32, 11 October 2007 (UTC)

Hey - leave Kurt alone - we only have one gull expert and he's it! (Which is weird because we have about 1e6 relativity/quantum-theory experts!) If he says it goes "MWAAK!" - then as far as I'm concerned, that's the end of the debate! SteveBaker 16:06, 11 October 2007 (UTC)

That is spot on, and I think it's very ironic that we claim to know more about invisible particles than about macroscopic animals. I may wax philosophical, and charge our educational establishment with focusing on the wrong things; but of course, this could lead to a long and heated debate about the merits and demerits of theoretical sciences. Nimur 04:36, 12 October 2007 (UTC)

I wouldn't dare dispute Kurt's expertise on gulls. But living in a student house, I think I can consider myself an expert on fruitflies (aka beerflies in Dutch). :) DirkvdM 18:20, 11 October 2007 (UTC)

How are you on barflies? --Kurt Shaped Box 22:08, 12 October 2007 (UTC)

Beer bad. DirkvdM 09:47, 13 October 2007 (UTC)

Connecting two tanks automatic siphon?

I am wondering if this is physically possible: Imagine two water tanks. The tanks are connected together by a hose which connects to the bottom of both tanks. Assuming both tanks are at equal height, and the hose is below the water level of the tanks, it is obvious that water will flow from the tank with more water to the tank with lesser water until both have equal water height.

Now if the hose is primed with water, then the hose can actually run above the height of both tanks and the siphon action will cause water to flow from tank with higher water level, to tank with lower water level.

My question is when the water levels are equal and the siphon action stops, what difference in height between the two tank water levels will be required for the siphon to restart on its own. I know this would depend on the height of the hose above the water level of the higher tank at least...--Dacium 04:10, 11 October 2007 (UTC)

Assuming the hose didn't empty out and is still primed, the difference needed is either negligible or zero, I'm not sure which. — Daniel 04:16, 11 October 2007 (UTC)

I think you will find when the water levels are equal a vacuum will form in the higher part of the hose - it does not stay primed. The question is does the water level need to reach past the height were this vacuum is, or does it only need to reach a lower height to arrest the vacuum (as you said only a little difference)? Might have to try this practically!--Dacium 04:25, 11 October 2007 (UTC)

Why would you expect a vacuum to form? Air pressure will keep that from happening. (Well, unless the hose extends more than about 33 feet [10 meters] above the water, but in that case it wouldn't work as a siphon to begin with.)

In effect, the two tanks linked by a siphon form a single system. Any change in water level on one side will cause a flow through the hose between them to level it out.

--Anon, 04:33 UCT, October 11, 2007.

A museum, perhaps the Boston Museum of Science had an interesting demo once. There were two pairs of small plexiglass tanks and the two tanks in each pair were linked by a lever to a control knob. By turning the knob, you could raise one tank and lower the other. One pair of tanks contained water and was linked by a siphon. The other pair of tanks contained a Slinky looping over the tanks from one to the other. The cool part, of course, was that the two mechanisms behaved essentially identically. When you shifted the relative levels of the watery tanks, the water in the two tanks obviously flowed through the siphon until both tanks contained water at the same absolute level. And the Slinky tanks did the same thing, shifting Slinky coils until the "solid" portions of the Slinky stood at the same absolute level.

Atlant 12:31, 11 October 2007 (UTC)

charged particle and electromagnetic radiation .

when charged particles(electron and photon) are accelerated ; they emits electromagnetic wave(photon) . where the photon comes from ? is there any store-house of photon inside a charged particle ? what happen if a charged particle emits all of its stored photon ? what is the direction of emitted photon by a charged particle when it is accelerated ? —Preceding unsigned comment added by Shamiul (talk • contribs) 04:13, 11 October 2007 (UTC)

A charged particle does not emit photon when accelerated in general. It only emits photons when accelerated by receiving electro-magnetic energy (ie another photon).--Dacium 04:31, 11 October 2007 (UTC)

What about cyclotron radiation? --JWSchmidt 04:56, 11 October 2007 (UTC)

Actually all charged particles emit when accelerated. For all practical purposes this acceleration happens through EM interactions. In a cyclotron it is accelerated by magnetic force, for example. There is not really a photon in the electron, the photon is the form energy takes when it is released. It is the same when electrons move between energy levels in an atom. Photons are constantly destroyed and created (emitted and absorbed) there is no more a store when an electron is accelerated than there is in a lightbulb before it is turned on. See Bremsstrahlung. The direction of emitted radiation depends on the acceleration. In synchrotron radiation (circular acceleration) it is emitted in a cone in the direction of the particles travel, perpendicular to the acceleration. In general the two directions of the particle, before and after emission act like an antenna. Cyta 10:19, 11 October 2007 (UTC)

There is no 'storehouse' of photons - photons (like all matter) are just made from energy (E=Mc², etc). When a photon is emitted, it's just a manifestation of energy being lost by the emitter. When you use electricity to power a lightbulb, the energy from the electricity gets pushed out as a bunch of photons (little bundles of energy) - which rush off at the speed of light until they hit something and are absorbed by it - transferring their energy into whatever they hit, and being 'destroyed' in the process (typically, the energy they give up just makes the thing they hit a tiny bit hotter). Photons are being created and destroyed all the time in vast numbers as they transfer energy in the form of light/radio/x-rays/etc. SteveBaker 15:57, 11 October 2007 (UTC)

Source of water to create homeopathic remedies

Where do homeopaths obtain water to use in the dilution and succussion process by which they create homeopathic remedies?

The rest of this is background as to why I ask this question. It arose from discussion about the homeopathy article.

The prior history of the water used in dilution seems to be relevant. "since water will has been in contact with millions of different substances through its history, critics (of homeopathy) point out that any glass of water is therefore an extreme dilution of almost any conceivable substance, and so by drinking water one would, according to homeopathic principles, receive treatment for every imaginable condition."

Thank you, Wanderer57 05:39, 11 October 2007 (UTC)

You've discovered one of the many reasons why homeopathy is considered a pseudoscience; its basic theory is irredeemably faulty.

Atlant 12:33, 11 October 2007 (UTC)

Don't they use distilled water? 200.255.9.38 14:39, 11 October 2007 (UTC)

Related Wikipedia article: Water memory (does not answer the question). There is some discussion in this article of possible sources of water used by Samuel Hahnemann and contaminants found in water used by some manufacturers of homeopathic remedies. --JWSchmidt 14:59, 11 October 2007 (UTC)

Since the medicinal effect (such as it is) can only possibly work by the placebo effect - it only matters that both patient and the doctor believe it will work. It may be that either the doctor or the patient would only believe it to work if distilled water were used (or water from the slopes of Mount Kilimanjaro or water blessed by the Pope during a month with an 'R' in it). Hence it may well be that distilled water is required...but not for any scientific reason. All of this careful dilution nonsense is just there to convince people along the chain that the stuff will work such that when they give it to the patient, they don't give off "this is complete bullshit" vibes that would throw off the placebo effect. There is absolutely no science behind it though...please don't ever think there might be! SteveBaker 15:49, 11 October 2007 (UTC)

I think the original question is about the "logic" from the homeopathic point of view for the previous "memory" of the water they use.

That's why I cited distilled water. They could say that the distillation process "destroys" the water memory. Maybe they really say that, I don't know.

So, this "amnesic" water will have only the memory of the substances it eventually had contact in the homeopathic process.

And will be more higienic, too. 200.255.9.38 15:58, 11 October 2007 (UTC)

How do “selfish gene” principles account for biased demographic effects?

A science writer declared that there are more boys than girls born (about 55/45 ratio) because Mother Nature compensates for all the boys who will die prematurely through violence and foolhardiness. This got me thinking as to how this would square with the principle of the “selfish gene”. If the process of evolution is driven purely by the fitness of an individual organism, then how do community-wide concerns about demographics end up influencing the biological processes of reproduction in individual females? Myles325a 06:03, 11 October 2007 (UTC)

Read over sex ratio first. 55/45? Nah. --Cody Pope 06:14, 11 October 2007 (UTC)

Keep in mind, even where there might be a skewed ratio, the selfish gene principals would only only be working on genes in the X and Y chromosomes. If it were the case that there was selection for more males than females in a population, it might be because sex-linked genes that led to a higher male population were advantageous, either linked to some other selective pressure, or merely because they were linked with the sex-determining chromosome and therefore expressed more frequently. -- JSBillings 10:33, 11 October 2007 (UTC)

For the mother to have a chance of passing on her genes, she needs to give birth to a child that maximises it's its chance of reproducing by not being one of an excessively large number of females or one of an excessively large number of males. So a species will tend to produce a male/female ratio that comes closest to the ideal radio in adulthood (taking into account whatever environmental effects may kill of males in early age for example). If there were a gene that caused production of 100 males for every female, then that gene would survive just fine for a few generations - but it wouldn't be able to spread across the whole of the community without self-destructing. So the only genes that can survive are the ones that produced a 50/50 split (or whatever ratio is best suited to the environment) - so there is evolutionary pressure to produce children in the right probabilities. SteveBaker 15:40, 11 October 2007 (UTC)

Corrected a quite painful spelling mistake. --Taraborn 14:07, 14 October 2007 (UTC)

Silver nitrate staining

Co²⁺ was precipitated with ammonium sulfide and visually enhanced with silver nitrate - I understand that cobalt sulfide is black; what reaction takes place with silver nitrate? What compound is formed? --Seans Potato Business 07:07, 11 October 2007 (UTC)

You mean, "why does silver nitrate turn black if left exposed"? I know it has to do with exposure to light, or more specifically sunlight if I recall correctly. Since silver nitrate breaks down in liquid form to form silver and nitrate ions, it would have to be a reaction between either of those, and compounds on your skin, or on surfaces. It would then logically have to be a reaction between the silver and something else, since I doubt the nitrate ions can readily find other positive ions so quickly. Luckily, everything has electrons, so those can reduce the Ag⁺ ions to become stable silver atoms, therefore the stain is pure silver.--十八 07:40, 11 October 2007 (UTC)

The methode would be imilar to black and white photography, but on cobalt sulfide the layer of silver, which would form with silver nitrate and sun light, would turn into the black silver sulfide fast, because silver has a high afinety to form the sulfide. The result would be black colour like the silver itself so you get a black surface.--Stone 08:35, 11 October 2007 (UTC)

See also Silver stain. --JWSchmidt 14:47, 11 October 2007 (UTC)

Controlling earthquakes by setting them off

Inspired by the above question about nuking a volcano: Along fault lines, tension builds up and then when it is released, an earthquake takes place. Now if you know that there will be an earthquake, but not when, then wouldn't it be nice if you could release the energy and thus have more but smaller earthquakes at moments you yourself set, so people can prepare them selves for it? For example by setting off a big bomb at a crucial position (like in A View to a Kill). How much energy would that require? Would a nuclear bomb be needed or would it even be enough? And if the energy is released in many small doses, then might it be possible to build humongous shock-breakers that absorb the energy and store it in some fashion that it can be retrieved gradually and made to good use? For example compressed air or even (considering the huge amount of energy) compressed water? How much energy is released in an earthquake? The article doesn't seem to say. DirkvdM 08:35, 11 October 2007 (UTC)

There was an article along these lines in the New Scientist of 30th June 2001: [12]. I have to go to a lecture now, but I've found the article and should be able to give more information later (if you haven't got access to a library or the online NS yourself). Algebraist 10:56, 11 October 2007 (UTC)

There is a calculation of earthquake energies and a comparison against nuclear weapon energies here. Gandalf61 11:09, 11 October 2007 (UTC)

Note though that the energy released by an earthquake is much less localized than the energy released by a nuclear weapon. By analogy, the sun releases thousands of megatons worth of energy every second or so, but only a small fraction of that is focused on earth, and even of that energy it is diffused over a very wide area. The important fact about nuclear weapons—and making the megaton scale make sense on an inuitive level—is that all of the energy is released into a relatively small area and in an extremely rapid fashion. --24.147.86.187 12:57, 11 October 2007 (UTC)

The problem with controlling earthquakes is strongly related to understanding them in the first place. In order to know exactly where to place a nuclear explosive, how powerful it should be, and when to trigger it, we'd need to know a lot about the environment of the fault into which we'd be placing it. The trouble is that we mostly don't - we have very (very very) poor imaging for the subterranean environment: it's a complex 3D system of multiple faults, where each fault is a complex 3D structure made from solids with pockets of aggregates or sand, lots of (moving, sometimes) underground water, all floating on a fulminating chaotic soup of magma. If we could properly image fault systems over time we'd be able to build much better models of how earthquakes start and stop, and we'd be able to explain all their different characteristics. Right now geologist's understanding of earthquakes is akin to doctor's understanding of internal medicine in times when they weren't allowed to do dissections - they're just feeling the externalities and making (mostly statistical) guesses about what's going on in there. The missing information (what you'd need to understand, and finally predict, earthquakes) is just the same information you'd need before you could really meaningfully pursue the discipine of thermonuclear tectonic engineering. And given that all the danger, and much of the expense, of earthquakes arises from their unpredictability - if you could adequately predict them, you wouldn't need to manipulate them. -- PrettyDirtyThing 11:44, 11 October 2007 (UTC)

Concerning the tapping of the energy (for which a controlled release seems rather essential), how much energy is there in the first place? Gandalf's source says a really huge 9.5 magnitude earthquake releases about 10¹⁹ J. The world's energy consumption is about 5 x 10²⁰ J per year. So to cover that we'd need to tap all (!) the energy of 50 such earthquakes each year, but Richter magnitude scale says these occur less than once a year. A 6 magnitude earthquake releases 6 x 10¹³ J, so we'd need to tap 10 million of those. Not only are there nowhere near that many (less than a thousand), but we'd need to build way too many of such powerplants for it to be realistic. And that's assuming 100% efficiency, while we'd be lucky to get 10% efficiency. So even if this were doable in some ingenious way, the yield would be such a small fraction of the world's energy demand that it's not worth considering. So the energy source is out the window, I suppose, or did I make a mistake somewhere? Hold on, to put this in perspective: the bottom table in the Richter article says a 12 magnitude earthquake (which would split the world in half - do I read that correctly?) would release the same amount of energy the Sun shines down on Earth every day. I'm clearly barking up the wrong tree here (barking mad pseudo-scientist I am).
As a life-saver, the controlled release might still be an option, though. DirkvdM 13:25, 11 October 2007 (UTC)

On the concept of avoiding major quakes by inducing smaller ones more often: in some cases it might be possible to do this without anything as dangerous as explosives, by simply lubricating the fault. See this PDF newsletter, starting at page 6. But all the problems that Pretty describes would still apply, and I guess this method would only work if the fault wasn't badly "locked", so I doubt we will ever see this method widely used. --Anonymous, 23:07 UTC, October 11, 2007.

Tapping the world's rotational energy

Here's the barking mad pseudo-scientist again. :) Suppose that somehow we could tap the rotational energy of the Earth, how long would that last and how dangerous would it be? Here's a calculation: Earth's mass is 6 x 10²⁴ kg. Its circumference is 40,000 km. Let's for the sake of easy calculation say that that mass is concentrated on the surface of a cylinder with a circumference of 10,000 km. So the mass travels at a speed of 10,000 km per day. There are about 100,000 seconds in a day, so that's 100 m/s. E = mv², so that would be 6 x 10²⁴ kg x (100 m/s)² = 6 x 10²⁸ J. The world energy consumption is 5 x 10²⁰ J, so at the present consumption rate that would last us 100 million years. Now I'm only a pseudo-scientist, so first question: is this a correct calculation / realistic approximation? Second question: what effects will slowing down Earth's rotation have? (And hasn't this been asked here before?) And the third and hardest question to answer: how might we do this? (Fourth bonus question: how mad am I, really?) DirkvdM 14:11, 11 October 2007 (UTC)

A stationary satellite in orbit with a (really, really) long pole dangling down to touch the earths surface with a dynamo at the end? Think outside the box 14:20, 11 October 2007 (UTC)

Essentially tidal power is exactly tapping the earth's rotational energy so the third part of the question ain't that tough. --BozMo talk 14:23, 11 October 2007 (UTC)

There's a better approximation in our article on rotational energy (one that treats the Earth as spherical rather than cylindrical); it gives a kinetic energy of 2.58×10²⁹ J. (So you're off by less than an order of magnitude. That calculation assumes a uniform density to the planet; the kinetic energy will actually be a bit lower because Earth's core is denser than its crust, giving a lower moment of inertia.) As BozMo notes, tidal effects have been gradually slowing the Earth's rotation for billions of years: [13]. Every century, a day gets a little more than two milliseconds longer. It hasn't hurt us so far, but it does cause some intriguing problems for some astronomers.

Perhaps more worrying is what might happen if we were able to tap a significant amount of that energy rapidly and make use of it on Earth. The waste heat produced by whatever processes we put the energy in to could heat the Earth's climate significantly. (For comparison, the entire Earth's surface absorbs about 10²⁴ joules of energy from the Sun over the course of a year.) TenOfAllTrades(talk) 15:17, 11 October 2007 (UTC)

• I don't have a link, but I believe some space agency tested an energy production scheme a few years ago where you lower a line into the atmosphere from a satellite, and the resulting static (?) charge provided power. If we had a magical nanotech rope we could perhaps attach one end to the South Pole, and one end to the Moon, and use the yo-yo action to generate power, but that's harnessing the moon's eccentric orbit rather than the Earth's rotation. --Sean 16:06, 11 October 2007 (UTC)

This was the Tethered Satellite System, flown on the STS-75 Shuttle mission. Essentially, a satellite on a multi-kilometer wire was extended from the shuttle into the ionosphere, generating a voltage on the wire. In fact, enough voltage was generated that it arced from the wire to the mechanism paying out the wire (which was at ground potential relative to the wire), melting the wire and resulting in the loss of the satellite. Definitely proved the technology though. Arakunem 00:36, 12 October 2007 (UTC)

Of course, you can tap the rotational power. You just need something that is held still while the earth rotates under it. The bulge of the tides, kept fixes by Earth's gravitation is quite suitable. See tidal power for more. The link Sean was referring to is http://www-istp.gsfc.nasa.gov/Education/wtether.html 85.127.182.154 17:28, 11 October 2007 (UTC)

After edit conflict:
First of all, a pat on my own back for getting so close with such a crude calculation. :) Concerning the tidal energy, 2 ms per day per century means 100,000 / 0.002 x 100 = 5 billion years until the Earth stands still (exactly when the Sun will consume the Earth - a coincidence, I assume). So that would be only 1/50 of the energy we demand now and that is assuming we can harvest all that energy. And even if we could do that, what effect would the ending of tides have on life on Earth? Doesn't sound like a good option. Concerning the heating up of Earth, I hadn't thought of that, good point. But what would the effect be compared to the energy already in the system, I mean percentage-wise, so to say? My gut feeling tells me that would be smaller than any effect the Sun could have, such as with the help of greenhouse gases. But if we would take enough energy out of the rotation to meet our present energy demand, then the speed of slowing would be more like 0.1 second per day, or about an hour per century. Still slow enough for life to adapt through evolution, I assume.
Then again, I'm a bit tired now, so any of the above may be erroneous and that is probably also the reason I don't get the three suggestions. Sean's yoyo effect sounds amusing, but assuming we could pull that off, that would mess up the Earth's axis tilt, and that sounds rather too dangerous. Think outside the box's magnet is probably meant to use the Earth's magnetic field, but I don't see how (definitely not my field). And I don't get Sean's static energy line. Is that maybe to do with the triboelectric effect? Please elaborate, if you remember any more details. DirkvdM 18:02, 11 October 2007 (UTC)

The Earth's rotation slowing won't be linear. In times near to the present, you can model it as a linear slowing, but over long periods of time, that won't be appropriate. The primary source of tides is the Moon, but the slowing of the Earth's rotation is lifting the Moon into a higher orbit - which weakens the tides and so the rate of slowing of the Earth's rotation will gradually decrease. Also, as the Earth's day length gets close to the Moon's orbital period, the raised tides will stay in a similar position on the Earth, so tidal friction will be much reduced. Eventually, the Earth and moon would be tidally locked to each other - so the rotation won't stop as you suggest. Richard B 12:23, 12 October 2007 (UTC)

Ah, followed 85's link and that indeed uses the Earth's magnetic field. But it only powers a space station, so it couldn't begin to make a dent in mankind's total energy demand. And the article points out an obvious flaw that you already hinted at - the space station isn't 'held still'. Anything that hangs in space and doesn't have a really huge mass will pick up Earth's rotation more than generate power. Or not? The article suggests something different. Really too tired now, I'll come back tomorrow. DirkvdM 18:08, 11 October 2007 (UTC)

I think the worries about waste heat from this scheme are not a pressing environmental concern. You basically can't do it -- at least, not on a scale that's going to extract any noticeable fraction of the Earth's rotational kinetic energy, prior to such time as we can build structures on the scale of the Earth.

The Earth has a certain angular momentum, which is conserved; you can't change it (you could conceivably throw some of it off into space, but then you'd be throwing a lot of the energy with it). To extract rotational KE from the system without changing the angular momentum, you have to change the moment of inertia. And we can't change it, very much, because we don't have anything big enough to change it much. If we ever do build things that big, I think current estimates of world energy consumption will no longer be terribly relevant. :-). --Trovatore 18:22, 11 October 2007 (UTC)

Angular momentum isn't a problem. By tapping the Earth's rotation via tidal power, we're transferring that momentum to the Moon: over the centuries, the Moon's orbit gets higher. --Carnildo 22:02, 11 October 2007 (UTC)

What I said was, we can't change it much. Only a minuscule fraction of the Earth's rotational KE is available for extraction in that way. (Well, I think it's minuscule; I haven't done the actual calculations. But note that the Moon's contribution to the moment of inertia goes up only as the square of its orbital radius, whereas the tidal effect diminishes with the cube of the radius.) --Trovatore 22:11, 11 October 2007 (UTC)

Ah, yes, the principle of an ice-skater extending his arms. It wouldn't have to be such a big structure, though, at least not the result - how to start construction is entirely different matter. I've once heard of a plan to make a space lift - AH, we have an article. Of course we have an article. :) Before reading it, this is what I was thinking. Once in place, the top of the cable is rotating faster and can thus 'suck up' something from Earth. This is a way to send stuff into space. But we can also tap the energy of whatever is flying off up the lift. The heavier the stuff we 'send up', the more energy we get out of it. So we'll end up doing a lot of that and eventually we'll have the material up there to build a second layer around Earth. And a third, etc. Could be useful for loads of things. But the article doesn't seem to mention this (haven't read it all). It actually assumes this will cost energy. I don't get that. The principle of what I just said is correct isn't it? I mean from a basic energy conservation pov. DirkvdM 08:00, 12 October 2007 (UTC)

Effects of concrete under high temperature

I was curious why some people blamed the collapse of the WTC for its steel construction. I checked the melting points of both iron and carbon, and they are very high. Of course they will undergo plastic deformation before melting completely, but I was wondering what are the effects of concrete under extreme temperature? What is the melting point of concrete? Will it undergo deformation before melting? At what temperature does this happen? Would the WTC have survived if it was constructed primarily out of concrete as opposed to steel? 64.236.121.129 14:07, 11 October 2007 (UTC)

I cannot provide a good source but as far as I know: generally in fierce fires concrete survives for much longer because the heat transfer/conduction into the concrete is much slower and it takes longer to heat up. After Piper Alpha some of the North Sea oilcos started coating the steel members on platforms with concrete because of this; a few centimeters gives an extra hour to the steel survival. At what temperature concrete eventually fails, and how long it takes to heat up depends on the type of concrete but also critically on how damp the concrete is. You can pour molten iron into a ceramic mould so you know survivability ie better anyway. --BozMo talk 14:21, 11 October 2007 (UTC)

The trouble is that concrete is a terrible construction material by itself - it has to be reinforced with steel rebar - as soon as the temperature gets up high enough for the rebar to give way - your concrete loses it's ability to resist twisting and tensile forces (it's really only any good under compression) - and the building collapses anyway. The extra thermal insulation the concrete would have provided might have prolonged the life of the buildings somewhat - but they'd have collapsed sooner or later anyway. But a bigger consideration is whether the impact of the aircraft itself would have caused more damage in a purely concrete construction. It's really hard to say - but it's certainly not obvious that concrete would have been better. I vaguely recall that there was a problem with the construction of the WTC anyway - wasn't it discovered that the steel beams had not been coated with the right fire-resistant stuff? SteveBaker 14:34, 11 October 2007 (UTC)

Yes, the spary-on fireproofing wasn't designed to resist the forces that resulted from airplane crashes, so it tended to blow off the structural steel. After that, it was just a question of how quickly the steel would become too plastic to carry the static loads.

Atlant 16:34, 11 October 2007 (UTC)

A bit off topic but informative: Collapse of the World Trade Center#The collapse mechanism. - hydnjo talk 15:33, 11 October 2007 (UTC)

Under very high temperatues, concrete tends to spall off. Atlant 16:36, 11 October 2007 (UTC)

A lighted torch should not be turned on concrete. Concrete always contains some moisture which may cause the concrete to explode. --Duk 15:19, 12 October 2007 (UTC)

• I see two fallacies about steel here. One, you cannot figure out the melting point of a compound or alloy just by figuring out the melting point of its elements. For example, this kind of C8H16 melts at 14.59 °C, while this kind of C8H16 melts at -101.7 °C. Two, as the WTC reports showed, steel begins plastic deformation at something like half its melting point, and it doesn't take much deformation for the top floors to come crashing down. --M@rēino 20:27, 11 October 2007 (UTC)

That wasn't very helpful. We knew all that already. The question is, at what temperature does the steel used in the WTC undergo plastic deformation, and how does reinforced concrete compare to that. Malamockq 23:12, 11 October 2007 (UTC)

Hey, it might not be helpful to you, but it is helpful to 64.236.121.129, who had not been corrected by anyone else for the error about steel's melting point in the original question. --M@rēino 23:59, 11 October 2007 (UTC)

Popular Mechanics did a huge report debunking the most popular "9/11 myths." It has details about the collapse that might be helpful to you. You can find it here.
Mrdeath5493 05:52, 12 October 2007 (UTC)

black contact lenses

In science fiction tv shows and movies, when a character goes evil or changes (like on buffy with Oz turning into a warewolf or Dark Willow) or is possesed by an alien, they often have black eyes - I mean totally black. Is this black contact lenses or ink or what? And, as Oct 31st is coming soon, where can one buy the requirements to have their own eyes turned totally black? Picture of a cloud 14:11, 11 October 2007 (UTC)

Computer generated imagery perhaps? It would be a simpler solution, but I'm sure black contacts exist. They certainly can be made. 64.236.121.129 —Preceding signed but undated comment was added at 14:20, 11 October 2007 (UTC)

They're "decorative" or "cosmetic" contact lenses. More information in the article. You can buy them by mail order from lots of places.--Shantavira|^{feed me} 14:21, 11 October 2007 (UTC)

• See scleral lens. --Sean 16:12, 11 October 2007 (UTC)

Crystallization and entropy

Quick question: does crystallization represent an increase or decrease in entropy? I think it's a decrease but not sure. Thanks! 76.247.76.242 15:11, 11 October 2007 (UTC)

Decrease, as crystals are more ordered than a random jumble of molecules. Someguy1221 15:40, 11 October 2007 (UTC)

Please see Entropy. The picture says a thousand words. --slakr^\ talk / 22:56, 11 October 2007 (UTC)

Okay, thanks! 76.247.76.242 18:18, 12 October 2007 (UTC)

Can one have echolalia with thoughts? Or is that called something else?

Just wondering, is it possible to have echolalia occur with simple thoughts, instead of language. I've heard that small children haven't yet developed the social or whatever other skill is needed to maintain thoughts that aren't out loud. (I thought that was inner voice but it doens't look like it. It might be, though.) So, would someone high on the autism spectrum possibly not repeat words so much as thoughts after a few seconds? Also, would it be considered echolalia when a person simply thinks something internally a number of times in a row after hearing it, instead of repeating it? In other words, possibly processing the information but able to do it internally? —Preceding unsigned comment added by 4.68.248.130 (talk) 15:44, 11 October 2007 (UTC)

Interesting that it has a name. I always thought that was just something children did, and the supposed 'delayed echolalia' in that article (with no sources) just sounds like "quoting", which my parents used to get annoyed at us for doing... From the sounds of the article, it can be for the pleasure of the sounds rather than buying time/processing (although it mentions that too). I'm intrigued to see what an actual knowledgable person replies... 130.88.140.43 17:16, 11 October 2007 (UTC)

Caudate nucleus left/right asymmetry

As I understand, the caudate nucleus is usually asymmetrical. Does anybody know which side is bigger in normal subjects, left or right? Lova Falk 16:48, 11 October 2007 (UTC)

According to Encyclopaedia Brittanica, "in boys without ADHD, the right caudate nucleus was normally about 3 percent larger than the left caudate nucleus; this asymmetry was absent in boys with ADHD." [14] Rockpocket 17:57, 11 October 2007 (UTC)

Thank you! Your source says boys without ADHD: right>left, boys with ADHD: right=left. I just found another source [15] that says the opposite: normal children 72% left>right, ADHD children 63% right>left, due to smaller left side. Very contradictory... Lova Falk 14:11, 12 October 2007 (UTC)

Ahh. Welcome to the world of sampling bias! Personally, I would trust your source above mine. Rockpocket 17:23, 12 October 2007 (UTC)

Photoconductive cells

What is photoconductive cells? How photoconductive cells work? (also include detailed photoconductive cells technologies circuit diagrams characteristic curves photoconductive cells component diagrams technical shets) What are their applications and explanations. —Preceding unsigned comment added by 203.81.161.142 (talk) 17:40, 11 October 2007 (UTC)

Photoresistor would be a good place to start your research, followed by typing Photoconductive cell into a Google search and reading to the top few hits. Rockpocket 17:46, 11 October 2007 (UTC)

Yes. Please dont pose your homework question like that. You must show that you are willing to do some of the work yourself by searching. We will gladly point you in the right direction but we wont hand the answer to you on a plate. —Preceding unsigned comment added by 88.109.232.130 (talk) 00:22, 12 October 2007 (UTC)

Expansion of Universe and expansion of expansion measurement device

Dodgy title, eh?

Anyway, my Physics teacher bought up a subject when studying the expansion of the Universe that if the universe is expanding then surely it cannot be measured as the tools being used to measure the expansion are also expanding. I notice the Big Bang article has a small section on why this might not be true - to assume planets and other masses as seeds on an expanding loaf of bread, but he seems not convinced - For my own understanding and the wanting to trip up an Oxford MSc does anyone have a better answer to this problem?

Thanks!

-Benbread 18:01, 11 October 2007 (UTC)

I instantly (well, almost) got your title because I have thought of something similar. When you get sucked into a black hole, you get spaghettified (love that word). But so does everything directly around you - including the atoms? So to an outside observer (as if they could observe this) you might turn into spaghetti, but from your own vantagepoint it's business as usual. One snag, though, assuming you go in feet first, the laws of physics have altered in your feet more than in your head, and that must be very confusing to the blood. Or am I now falling into the trap myself? (btw, Red Dwarf experienced a similar phenomenon in one episode). DirkvdM 18:29, 11 October 2007 (UTC)

I think the theory is that the gaps between things are expanding - not matter itself - ((note if you take all matter to be expanding you can derive a gravitational like force between objects - the 'force' depends on size not mass.. this is probably irrelevant to what you are asking..)) —Preceding unsigned comment added by 213.249.237.169 (talk) 20:17, 11 October 2007 (UTC)

NOTE if the space of the universe is expanding and the matter in the universe is expanding at the same rate - you wouldn't notice.. (except for possible 'gravitational' like effects mentioned above)

The current view is definately that things are moving apart - but the things stay the same size.. —Preceding unsigned comment added by 213.249.237.169 (talk) 20:41, 11 October 2007 (UTC)

Accelerating universe lists some of the sources of data that can be used to not only measure expansion of the universe, but also change in the rate of expansion. Data for Ia supernovae have been interpreted as indicating a change in the rate of expansion over time (billions of years). Most physicists seem to think that this observation is not confounded by expansion itself since it relies on observations of light that seem to be well understood. I'd expect a physics teacher to be able to explain these kinds of data and their conventional interpretation. --JWSchmidt 21:58, 11 October 2007 (UTC)

Things stay the same size because the laws of physics haven't changed, and the forces keeping atoms together in molecules, planets in the solar system, and stars in the galaxy are much stronger than the repulsive force that's pushing the universe apart. Only over great distances, such as those between galaxies, is this expansion easily observable (presently). Someguy1221 23:22, 11 October 2007 (UTC)

Yes essentially if there was no gravity etc, everything would be stretched (like dots drawn on a balloon being inflated) but the other forces act to hold things together. So galaxies act more like things glued onto the inflating balloon. The best evidence for measuring the expansion of the universe is red shift data. This is essentially light waves being expanded with the universe compared to our telescopes which stay the same size. From this the speed of other galaxies compared to ours can be compared. We can see from this that a galaxies speed away from us is proportional to its distance from us (Hubble's law) which can be best explained by an expanding universe. Cyta 06:52, 12 October 2007 (UTC)

ISEL vs TUNEL

Is there are difference between In Situ End Labeling (ISEL) and Terminal deoxynucleotidyl Transferase Biotin-dUTP Nick End Labeling (TUNEL)? Are there enzymes other than TdT in use for ISEL? --Seans Potato Business 18:02, 11 October 2007 (UTC)

Here are some articles that describe the differences: [16] and [17]. --JWSchmidt 20:47, 11 October 2007 (UTC)

taser

Is there any possible defence against Tasers that is safe both for me and the attacker ? —Preceding unsigned comment added by 85.52.166.104 (talk) 18:37, 11 October 2007 (UTC)

• Run away. --Sean 19:52, 11 October 2007 (UTC)
• Thor Shield. You can build it right into body armor. They might even be able to make a less-conspicuous-looking Thor Shield T-shirt; I'm not sure. --M@rēino 20:32, 11 October 2007 (UTC)

get your body completely electroplated? —Preceding unsigned comment added by 88.109.232.130 (talk) 00:19, 12 October 2007 (UTC)

Not if they were using it for self-defense. If you aren't hurt, you'll hurt them. — Daniel 01:16, 12 October 2007 (UTC)

Some have advocated loudly shouting "Don't tase me, bro!" repeatedly, but studies show this is ineffective. - Nunh-huh 02:42, 12 October 2007 (UTC)

Someone has now proposed/is now weaving metal fibers into a sweater or vest. These will conduct the majority of the Taser's electrical current rather than allowing it to flow through you.

Atlant 16:01, 12 October 2007 (UTC)

Is Kevlar effective against it? —Preceding unsigned comment added by 88.0.101.106 (talk) 18:25, 14 October 2007 (UTC)

I think thick leather would do. But I would rather see them banned - therefore I support human rights organisations... /SvNH 20:24, 14 October 2007 (UTC)

Are basic anhydrides basic according to Arrhenius's definition?

If a substance releases hydroxide ion OH− according to Arrhenius it is said to be basic, OK. However, let me consider Sodium oxide. When hydrated it gives sodium hydroxide, but is it really a base? I'm asking this question because I sought over the Internet and didn't found any examples of Arrhenius bases being basic anhydrides (metal-oxygen). Thanks —Preceding unsigned comment added by 82.58.23.137 (talk) 19:14, 11 October 2007 (UTC)

According to http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/acid2.html " A substance is classified as a base if it produces hydroxide ions OH(-) in water" - so the answer is yes it is a base.213.249.237.169 20:13, 11 October 2007 (UTC)

geogaphy

what are pervious rocks? —Preceding unsigned comment added by 217.171.129.69 (talk) 20:19, 11 October 2007 (UTC)

• See Permeability (fluid). --M@rēino 20:33, 11 October 2007 (UTC)

sorry to be so boring, but did you actually type in the word 'pervious' in the search box. I just did and it gave me the right info. please try doing that next time! —Preceding unsigned comment added by 88.109.232.130 (talk) 00:29, 12 October 2007 (UTC)

But Geogaphy does nothing useful in the search box! The pervious rocks allow water or other fluids to pass through. Graeme Bartlett 06:03, 12 October 2007 (UTC)

OK it was useful enough to cause me to fix some spelling errors! Graeme Bartlett 07:08, 12 October 2007 (UTC)

• I prefer to call it earth science; I've never heard the term Geogaphy before. --M@rēino 13:51, 12 October 2007 (UTC)

October 12

Alcohol effects

Hi there! As 90% of the Portuguese students I've ingested considerable amounts of alcohol during my universitary course, specially - at least in my case - in the form of stout beer. So, the question is: What are the consequences of alcohol ingestion to the brain? I know Wikipedia has an article on "effects of alcohol consumption" and also that you cannot offer medical advice, let's skip that, ok? I want to hear your opinion. Will I be able to conclude my MsC thesis? If that matters, I'm partially drunk, despite being able to write in English. Cheers! 84.91.226.18 00:39, 12 October 2007 (UTC)

A man was horribly maimed in a farming accident, and had to have major reconstructive surgery on both his hands. He went to see his surgeon for the final time. "Doctor," says the man excitedly and dramatically holds up his heavily bandaged hands. "Will I be able to play the violin when these bandages come off?" "I don't see why not," the doctor responds. "Odd," says the man. "I never could before."

The odds are, you will be able to conclude your MsC thesis -- if, and only if, you could do so before the stout beer kicked in. - Nunh-huh 01:04, 12 October 2007 (UTC)

I would say that you will never get your MSc until you learn to spell MSc properly! —Preceding unsigned comment added by 88.109.232.130 (talk) 01:26, 12 October 2007 (UTC)

It's OK to spell it MsC when it's from a universitary. Cut him a break, it's a second language and he's drunk. Me, I have no excuse... - Nunh-huh 02:40, 12 October 2007 (UTC)

Really excessive alcohol consumption will in the long run have negative effects. But if you're still a student I assume you're too young for it to have taken enough effect. It is also a matter of what sort of skills you need for it. Memory is affected more than reasoning. The barkeep of my favourite bar in Eindhoven, where I studied, had a 'live fast die young' attitude. Didn't work. He lived pretty 'fast' (which included being drunk every day for pretty much all his life), but he's still alive, about 60 years old now, I guess. He keeps forgetting things, but his mind is still as sharp as it used to be. That is, he can still reason, but there is less in his head to reason with, so to say. DirkvdM 08:16, 12 October 2007 (UTC)

Party away! Just remember that alcohol has negative health consequences that trend quite clearly with the quantity and temporal nature of its consumption. When it comes to thesis work, don't forget that libations obviously prevent one from working or studying whilst drunk, but can seriously hinder such activities even a couple of days later, depending on hangover severity and sleep deprivation. Also, booze has a way of sapping one's wallet, which can negatively affect the ability to buy healthy, knowledge-supporting meal ingredients or paying rent on a decent apartment.

On the other end, I believe that socialization is an important part of the education process. Late-night pitchers of stout can facilitate useful discussions, collaborations, and life-long personal and professional relationships that can have positive effects on a career.

It's just a matter of moderation... — Scientizzle 20:40, 12 October 2007 (UTC)

If you drink somuch you can't pay the rent then you've really got a problem. And healthy food (nothing special, just healthy) is generally cheaper, certainly cheaper than junk food (hamburgers, crisps and the like). DirkvdM 09:52, 13 October 2007 (UTC)

I think you're missing the bigger problem. How are you supposed to finish you thesis when your too busy drinking to do the research and start the writeup? (And when you're not drinking you're too drunk to get any significant work done) Nil Einne 12:25, 13 October 2007 (UTC)

Well, no, he asked if his previous alcohol consumption will have had an effect on his abilities. Anyway, he says he can write English even when he's drunk (at least, I think that's the point he was making - then again, if he can't make that sufficiently clear, then maybe he couldn't write a decent thesis, but on the other hand, we can't know if that has anything to do with his alcohol consumption ... all very complicated. :) ). DirkvdM 07:27, 14 October 2007 (UTC)

Cutting vinyl discs

On the old vinyl discs, was there some advantage or technical limitation that made recording engineers produce discs with minimum (or inadequate) stereo separation? —Preceding unsigned comment added by 88.109.232.130 (talk) 01:02, 12 October 2007 (UTC)

My understanding was that it was a limitation of the cartridge in the replay head that limited the stereo separation quite sharply. Gramophone_record#Shortcomings seems to agree with me. SteveBaker 04:46, 12 October 2007 (UTC)

One reason is that the stereo recording format was backward-compatable with the earlier monaural format. The mono fromay moced the needle perpendicular to the surface: the groove varied in depth only. The stereo format moved the needle in two orthogonal dimensions, both 45 degrees to the perpendicular. In any actual physical system, this leads to cross-talk. -Arch dude 19:57, 12 October 2007 (UTC)

time dilations at high g

do particals in sychrotrons experience time dilations because of the high g forces involved, i.e. have longer than expected half lives? basically i have read of large gravitational bodies bending space time and was wondering if artificial gravity causes similar effects.209.204.181.5 05:52, 12 October 2007 (UTC)

The particles in synchrotrons experience a lot of time dilation due to their speed, as they are generally accelerated to nearly the speed of light. However I am not sure if acceleration due to other sources than gravity produces the same time dilation effects. Einstein used gravity-acceleration equivalence thought experiments before discovering general relativity which suggests that, yes, you'd expect the same effect, but I can't be sure. Cyta 06:56, 12 October 2007 (UTC)

The time dilation factor is the Lorentz gamma, which is also the ratio of the particle's rest energy to its speed. E.g. the Tevatron accelerates protons (~1 GeV) to energies of around 1 TeV, so the time dilation factor is about 1000 (not that it matters for protons, which don't decay as far as anyone knows). The acceleration, as such, has nothing to do with it, even in the gravitational case. Time dilation is about the geometry of the worldline. For motion in a circular accelerator, it's analogous to the fact that the wire that goes into a spring of a given length is longer than the length of the spring. For gravitational time dilation, it's analogous to the fact that circular arcs subtending a given angle have different lengths depending on their radii. -- BenRG 11:22, 12 October 2007 (UTC)

How would the [lub dub] of the human heart be represented musically?

If you had to give a drummer a piece of music to represent a healthy heartbeat, how would you do it? What's the beat, is there a taradiddle?

Thanks in advance Adambrowne666 05:59, 12 October 2007 (UTC)

Damn, a taradiddle would be one big-time arrhythmia. Nothing the heart does is that complicated. So the drummer's going to be bored. For a look at notation, see the opening measures of the Mahler Ninth Symphony. The cellos have the heart-beat. Actually, music notation doesn't really convey the info doctors listen for in auscultation very well...it's better to listen to recordings like this one (the most normal found on this site devoted to auscultation. - Nunh-huh 06:38, 12 October 2007 (UTC)

Why don't we have an article on taradiddle? Now I don't know why that would be an arrhythmia. Anyway, heartbeat is very important in music. The number of beats per minute is very determining for the mood of music because it emulates the heart rate. A normal heart rate at rest is around 80 b/m, so that should sound relaxed (not sure about the actual value - just know the principle). A faster beat should get you more excited. Maybe if the beat actually sounds like a heartbeat, the effect will be even stronger. Just listen to the beginning of Pink Floyd's Dark side of the Moon. There's a second, softer, beat after every beat. Actually, it's a 3/4 beat (or is that a triplet?), with the 'afterbeat' on the second beat. DirkvdM 08:40, 12 October 2007 (UTC)

Taradiddle would be a dictionary entry, but paradiddle we have... - Nunh-huh 18:58, 12 October 2007 (UTC)

Dirk says "The number of beats per minute is very determining for the mood of music" — which is certainly true — "because it emulates the heart rate". To this I say, to put it politely, "citation needed". Most people are not aware of their heart rate most of the time, so why would it affect the experience of listening to music? Do people with bradycardia find music more exciting, and people with tachycardia find it less exciting, than people with normal heart rates? --Anonymous, 02:02 UTC, October 13, 2007.

I wondered about that too when I heard it (sorry, can't remember where). But it is rather striking that really fast dance music has the same beat frequency as a heart of someone excited (about 120 b/m and over). DirkvdM 09:57, 13 October 2007 (UTC)

Buy the music to Heart of Rock and Roll on Huey Lewis' Sports. Delmlsfan 21:34, 12 October 2007 (UTC)

Although music is abstract, I have always assumed it's an unconscious mimicking of the music of the human voice - pathetic music mimics sobs; jolly music mimics laughter - that sort of thing. I would say too that although we generally don't hear our heartbeat, we are aware of it in other ways, especially when it's racing - so I side with Dirk on this, Anonymous, though it might be my flaky theorising; I can't provide citations. Thanks, everyone, for your interesting and useful answers. The article on the Mahler Ninth is a fantastic bonus, Nunh. Adambrowne666 03:12, 13 October 2007 (UTC)

OT: Weird. I must have seen this thread unconsciously earlier in my recent changes, because I just woke up from a nap where I dreamt that I pressed so hard on my carotid artery that my blood backed up in my chest and I could hear my heart trying to clear it. Anchoress 03:53, 13 October 2007 (UTC)

dot and cross product

why we use cos in dot product and sin in cross product? —Preceding unsigned comment added by 202.69.33.15 (talk) 06:43, 12 October 2007 (UTC)

see Dot_product#Proof_of_the_geometric_interpretation

and ask on the maths desk for a derivation of the cross product .. if you have a vector C that is at right angles to A and B vectors - you can work out for yourself what this vector will be using the dot products C.A=0 and C.B=0 - if you do the maths you should be able to see where the sin comes from - the cross product is the result of solving these two dot products..eg http://hemsidor.torget.se/users/m/mauritz/math/vect/xprodpro.htm (note in this derivation it only goes as far as getting the orthogonal vector - but doesn't show that the magnitude is ab sin(theta) - if you can get this far you should be able to do that? or ask on the maths desk87.102.87.36 12:54, 12 October 2007 (UTC)

Sorry I can't be clearer on the cross product but I can't find a link to the derivation - you best bet is to derive the cross product for yourself and then look at what the magnitude of the vector is...87.102.87.36 13:20, 12 October 2007 (UTC)

Wait for answers at Wikipedia:Reference_desk/Mathematics#dot_and_cross_product —Preceding unsigned comment added by 87.102.87.36 (talk) 13:23, 12 October 2007 (UTC)

beams that reflect from bones

thank you mr. SteveBaker and mr. Daniel for your response on the q i asked on 6th. that's true that my application matters a lot. i asked for some beams/rays/waves that reflect from bones. my application is like i'm trying to make a control system for automobiles in which i want these beams/rays to sense the living object in front of and no other object should bother the control system. for that i need some method that will sense bones only and not metal, plastic or concrete... also at these stage for me the cost and size of the method do not matter eventhough it's a non-stationary application... Neel shah556 10:46, 12 October 2007 (UTC)

Whatever beams you use will have to pass through flesh to get from your transmitter to the bone and back to a receiver. I, for one, wouldn't want that to happen to me. I'm thinking you could use echolocation to find objects in front of the vehicle and then aim a parabolic microphone at each one to listen for a heartbeat. You could electronically filter the incoming sound quite a bit, and use software to identify the repeating pattern of the heartbeat. Sounds crazy, I know, but there just might be a way to make it work. --Milkbreath 12:37, 12 October 2007 (UTC)

Also, it would be very difficult to distinguish between bone and cement/concrete, as they are pretty much made out of the same thing.Tuckerekcut 13:39, 12 October 2007 (UTC)

I very much doubt you could to this - I don't think there is any unique human 'signature' that could distinguish flesh and bone from a lot of other natural and man-made substances. SteveBaker 14:00, 12 October 2007 (UTC)

Why not measure infrared radiation (heat)? You could at least distinguish between living and non-living in that way without too much difficulty based on the shape and size of the thing in question, and I'm betting that non-living things look quite differently in an infrared spectrum. --24.147.86.187 14:34, 12 October 2007 (UTC)

The good news for your application is that if human beings can do it, at least it's theoretically possible. I'd go for a combination of systems. A simple camera image will give you some information on whether there's a living being in front of the car (based on shape, movement, etc.) An infrared image should give you a lot of information. And of course any setup with multiple cameras or other wave sensors will give you some spatial (3d) information as well. You can then combine this information into a machine learning algorithm, so that the system can learn to identify living things by itself. I think that just a simple camera could get you a pretty accurate result already. I any case, I think there are plenty of options left before you decide to start throwing x-rays around the place. :)

risk 01:34, 13 October 2007 (UTC)

So you want to avoid pedestrians, but crashing into a brick wall doesn't matter? What you need is something that will give the mass of the object and reflect back. Electromagnetic waves won't work, because they only reflect off of electrically conductive objects. I think sonar might work, but I'm not sure. You could also use some way to recognize objects. That way, you detect objects above a certain size, and see if they look like an object on a list of stuff you can safely hit (like a tumble weed). If you don't recognize it, brake. One thought that just occurred to me is to hit it with a pulse of sound and see how much it moves. The problem is that, unless have an extremely precise way to tell acceleration, it would have to be a very loud sound. — Daniel 01:44, 13 October 2007 (UTC)

?

I need instruction on how to draw the molecular structure of elements —Preceding unsigned comment added by Cali08P (talk • contribs) 13:14, 12 October 2007 (UTC)

It depends - some elements have a molecular structure, others are not molecules.. Sulphur exists as a molecule, argon doesn't - could you be more specific.

Molecular graphics has stuff about different ways to show molecules, also try Molecular model —Preceding unsigned comment added by 87.102.87.36 (talk) 13:32, 12 October 2007 (UTC)

You could also look at simple Lewis structures. Someguy1221 17:21, 12 October 2007 (UTC)

Gay twin

Is it possible for one identical twin to be gay and not the other? --124.254.77.148 13:42, 12 October 2007 (UTC)

Yes. See Biology and sexual orientation. --JWSchmidt 13:56, 12 October 2007 (UTC)

Yes. It's not generally believed to be a genetic matter. SteveBaker 13:55, 12 October 2007 (UTC)

Of course, if they're conjoined twins, there may be some logistical problems. GeeJo ^(t)⁄_(c) • 16:24, 12 October 2007 (UTC)

I understand it's not that simple - there's not a single determining factor. There are advocates for nature or nurture as causes, which, alas, has a lot to do with what people want to be true. When a Dutch researcher found indications for a biological cause, the reactions by homosexuals in the Netherlands and the US were opposite. I can't remember which way around that was, but it surprised me to hear that some homosexuals disliked this finding. I supose they interpreted it like they were 'abnormal' (which, literally, is the case of course, but that doesn't make it a bad thing - I consider myself to be quite abnormal and am proud of it :) ). But if it were nurture, then that would suggest that they're just imagining it. Like they're really heterosexual and somehow they deny their nature. Of course, none of this says anything about what the real causes of homosexuality are. DirkvdM 16:57, 12 October 2007 (UTC)

In the US it is a very complicated identity-politics issue, primarily because "biological vs. non-biological" has been interpreted to mean "inevitable and unchangeable vs. totally arbitrary and easily changeable choice." This is of course a not very scientifically-informed approach to the nature/nurture dichotomy, but it is the way this issue (and many others relating to sexuality and/or genetics) are handled in terms of US politics. --24.147.86.187 17:11, 12 October 2007 (UTC)

It is not particularly unusual. One study ([PMID 8494487]) that sampled gay individuals who were also twins found "thirty-eight pairs of monozygotic [identical] twins (34 male pairs and 4 female pairs) were found to have a concordance rate of 65.8% for homosexual orientation. Twenty-three pairs of dizygotic [non-identical] twins were found to have a concordance rate of 30.4% for homosexual orientation." That means 13 of the identical twins had one homosexual, with the other being straight. Their conclusion is that this data supports a genetic influence for homosexuality, but obviously not an absolutely determinant one. This conclusion is generally held up by similar studies. [18] Rockpocket 17:20, 12 October 2007 (UTC)

Fear suppressing drugs?

Are there any drugs that suppress or numb fear? 64.236.121.129 13:46, 12 October 2007 (UTC)

Some types of fear are described as phobia and treated medically. An example of recently published research: Glucocorticoids reduce phobic fear in humans. --JWSchmidt 14:16, 12 October 2007 (UTC)

Alcohol has traditionally been used to suppress fear. DuncanHill 14:17, 12 October 2007 (UTC)

True, but they probably want something without major effects other than suppressing fear. PCP will suppress fear too, but that effect is coupled with a number of other effects that make it unsuitable for most purposes. --24.147.86.187 15:27, 12 October 2007 (UTC)

Every drug has side-effects, or, more precisely, has multiple effects. If you desire one of the effects, then the other effects will be 'side-effects'. The suppression of fear by any drug, including alcohol and PCP, can also be quite undesirable, notably in traffic (such as when you are driving a car or others around you are). DirkvdM 17:06, 12 October 2007 (UTC)

Cocaine certainly, opiates and stimulants probably. DirkvdM 17:06, 12 October 2007 (UTC)

Beta blockers are traditionally used for stage fright. - Nunh-huh 01:47, 13 October 2007 (UTC)

It would be a useful drug to give to soldiers at the front - I bet there's been some research on it Adambrowne666 04:01, 13 October 2007 (UTC)

They used to dose them with amphetamines for this purpose, didn't they? --Kurt Shaped Box 08:50, 13 October 2007 (UTC)

Or shell the enemy with marijuana-bombs, so they'll all turn pacifist. :) I recently heard the US army experimented with something like this. DirkvdM 10:01, 13 October 2007 (UTC)

I'm not so sure that suppressing fear is a good thing in a battlefield situation. You don't want your men rushing into dangerous situations when they'd be better off staying in cover. It's noticable in video games (where people have very little fear because the consequences of death or injury is minor) - if you watch how players behave in the virtual battlefield, it's totally different to how soldiers behave in the real world - and the casualties are always very much higher. SteveBaker 11:45, 13 October 2007 (UTC)

Simple solution - dose them with PCP at the same time, so that they don't feel the bullets and also get a neat little aggression boost as part of the package... :) --Kurt Shaped Box 19:50, 13 October 2007 (UTC)

'They' (i.e. the finest minds of US military science) were trying to invent a gas shell that would instantly turn enemy soldiers gay (and presumably drop their guns and immediately start buggering each other) at one point, weren't 'they'? --Kurt Shaped Box 19:45, 13 October 2007 (UTC)

Gay bomb. Also: Homokaasu. GeeJo ^(t)⁄_(c) • 00:30, 14 October 2007 (UTC)

Sure! Antidepressants such as SSRIs work to increase the availability of serotonin in the brain which makes you feel confident/horny/manic/aggressive etc. —Preceding unsigned comment added by 88.111.61.118 (talk) 23:44, 13 October 2007 (UTC)

Graduate degree titles

If you are a nursing graduate student, when can you use the title MSN(c) for Master's in Nursing Candidate? —Preceding unsigned comment added by 71.193.119.109 (talk) 15:48, 12 October 2007 (UTC)

when you have passed the exam? —Preceding unsigned comment added by 88.109.232.130 (talk) 21:54, 12 October 2007 (UTC)

beta sheets

what is the distance between every second residue on a beta sheet? —Preceding unsigned comment added by 144.173.6.67 (talk) 15:59, 12 October 2007 (UTC)

I think what you are looking for is at Beta sheet. --JWSchmidt 16:32, 12 October 2007 (UTC)

LED flickering question.

A lot of commercial vehicles here, and some cars (continental US) now use LED based taillights and marker lights. When I look at them straight-on, they are (when lit) a steady red or amber color, depending on the light. When I'm rapidly moving my eyes or head, say from one side to the other, and an LED light is thus moving across my field of vision, it will appear to flicker, and I'll see a row of lit dots, not a continuous "smear" of light. Why is this? Do the LED units need to switch on-and-off at some rapid rate? Is it some characteristic of the vehicle electrical system? 71.112.9.77 19:10, 12 October 2007 (UTC)

I've noticed that too. Just a guess: I think that the LEDs are modulated (Pulse-width_modulation?) by flashing so there can be different brightness levels, so the brake lights can get brighter when the brake is applied. -- Diletante 20:20, 12 October 2007 (UTC)

Exactly correct, and at least some of the designers have picked too damned low a frequency for the PWM. I hope this gets regulated soon.

Atlant 22:52, 12 October 2007 (UTC)

How hard is it to hook up a few capacitors? LED's use tiny amount of current... --antilived^{T | C | G} 22:59, 12 October 2007 (UTC)

Strobing effect —Preceding unsigned comment added by 88.109.232.130 (talk) 21:53, 12 October 2007 (UTC)

No, the reason is that they are multiplexed displays. Cacycle 04:26, 13 October 2007 (UTC)

Neither of the explanations seen here makes sense to me. Taillights may operate at different brightness levels, but marker lights don't, so why wouldn't they be at full "on" all the time? And multiplexed displays are used when the elements need to be individually switchable, which doesn't apply to these kinds of lights either.

If we were talking about LED traffic lights I'd guess that they were strobing at twice the power line frequency, the way fluorescents do, but that doesn't make sense for vehicle lights that would run on DC.

Does anyone have an actual reference on this? --Anonymous, 06:57 UTC, October 13, 2007.

I know this has been asked before with a good answer given, but I can't find it in the archives. 68.231.151.161 01:36, 14 October 2007 (UTC)

Here is a description of the electronics involved in automotive LED lighting. It seems they regulate the current to the LEDs by switching a MOSFET, so they all strobe all the time. You can't power LEDs right from the battery, even with analog regulation, for several reasons, one of which is the transients you get when stuff switches on or off in the rest of the electrical system. They use a DC-DC converter driver to power the LEDs. --Milkbreath 02:00, 14 October 2007 (UTC)

Thanks! --Anon, 04:25 UTC, October 14, 2007.

LED brakelights turn on quicker than incandescent bulbs, allowing a following driver to apply his brakes quicker and avoid rear-ending the braking car. That is great. But present LED lights on cars are typically flashed on and off at high speed, above the critical flicker limit, to appear continuously on when you look right at them, but resulting in the scattered afterimages if there are eyemovements (as there normally are), which, like the questioner, I find distracting and annoying. An array of LEDs in a brakelight array could very easily be set up to operate on the 12 volts (or other voltage) supplied from the battery, without the rapid flashing on and off which results in the scattered afterimages. Of course you can power a series connection of LEDs directly from the battery! If the forward biased voltage drop for one LED is 2 volts, then connect 6 of them in series across the battery! Two or more such series arrays would allow the light to contimue operating if one series array failed. Suitable adjustments could be made for other forward biased voltage drops or supply voltages. No need to annoy everyone else on the road by flashing them 30 (or however many) times per second. (edited to add) The ref supplied by Milkbreath discusses the challenges which may have led to the strobing and afterimage problem. The designers worry about an idiot jumpstarting your car's 12 volt system with a 24 or even 36 volt battery, perhaps with reverse polarity. Crowbar circuits with a fuse could stop that sort of moronic insult to the car's electrical system. Then the designers legitimately worry about keeping constant brightness with varying battery voltage, so that your taillights and other exterior safety lights stay on even when you crank the engine for a prolonged period and the battery voltage gets down to 7 volts. You don't want someone running into your car at night. They also legitimately worry about the transient energy which might get dumped through the LEDs when the battery (a fine voltage clamp itself) is isolated from the electrical system by the ignition being shut off or a fuse blowing. This dictates DC-DC conversion incorporating protective circuitry, but note that said convertor puts out DC. The problem is they apparently found it useful to turn the DC on and off rapidly 30 or 60 times per second or sime such, I would guess. The article cited does not even mention this frequency. Looks fine in the showroom, I guess. No afterimage problem there like there is on the highway at night. If the headlights of cars also switch to ultrabright LEDs and the designers similarly use circuits which switch them on and off rapidly, the multiple afterimage problem will get even worse and more distracting. I have used solid state DC-DC convertors for decades which produce a very steady DC output, even though internally the current is switched rapidly to allow voltage multipliers etc. Edison 02:15, 14 October 2007 (UTC)

H2O2

When Hydrogen Peroxide is doing its thing (oxidising something), is ozone ever a by-product? Anchoress 20:14, 12 October 2007 (UTC)

Not usually. Ozone is a more oxidized form of oxygen than peroxide is and is less stable. DMacks 21:18, 12 October 2007 (UTC)

This explores the idea that hydrogen peroxide might be generated from ozone. This article says, "H2O2 catalyzes the decomposition of O3 via the peroxone process". --JWSchmidt 21:19, 12 October 2007 (UTC)

Ever is a pretty strong word. It is unlikely to do so as shown by the oxidation potential chart in the H2O2 article. See where ozone is more positive than hydrogen peroxide? That means that going from ozone to H2O2 is a favorable reaction and going the other way is unfavorable. But I wouldn't say never. Delmlsfan 21:21, 12 October 2007 (UTC)

Thanks all for the info and the links!! Anchoress 23:02, 12 October 2007 (UTC)

What is the name of this plant?

Solanum dulcamara
Cacycle 16:26, 13 October 2007 (UTC)

It is a low shrub, found in the U.S. mid-Atlantic states. In the spring it has little purple flowers with yellow centers. In the summer the flowers are joined by green berries which ripen to orange and then bright red. Here it is in the autumn, when the flowers are gone.

-- Dominus 23:00, 12 October 2007 (UTC)

That looks to me like an ornamental pepper plant. So, I don't think they are berries. If you search for ornamental pepper plant, you'll see many plants that look similar. -- kainaw™ 02:50, 13 October 2007 (UTC)

I thought it was a pepper of some kind when I saw the picture. The shape of the fruit and the three colors are suggestive. I don't think it's a native plant where I live (southern New Jersey); I think I'd have seen it. I googled on lots of stuff like "capiscum" and "wild pepper" and came up with zilch. --Milkbreath 03:05, 13 October 2007 (UTC)

I just saw a pic of a plant that looks like it - goji. Here's the pic. Anchoress 05:07, 13 October 2007 (UTC)

After reading the goji article, I'm pretty sure that's what it is. BTW goji is a member of the nightshade family, which also contains peppers. Anchoress 05:10, 13 October 2007 (UTC)

I think Cacycle wins this one. Thank you very much! I have been wondering about this plant for years. -- Dominus 03:41, 14 October 2007 (UTC)

Is it abstract or not?

ok, someone last week tried to tell me that physics and chemistry were abstract. To me that doesnt make any sense because something that is abstract is the opposite of "concrete" and i have always been told that science is very concrete?

so could you consider physics and chemistry to be abstract? (sense this might be more of an opinion than a definite answer, input from man people would be appreciated) —Preceding unsigned comment added by 71.98.105.119 (talk) 23:19, 12 October 2007 (UTC)

It's somewhat meaningless to apply abstract/concrete to an entire field of science. Both chemistry and physics can predict and explain very detailed phenomena, which would make them "concrete." However, they can also produce broad predictions about a wide range of phenomena, which would be somewhat abstract. Someguy1221 00:02, 13 October 2007 (UTC)

It would have probably been more clear to try and press whomever told you this exactly what they meant by the description at the time. "Abstract" has many meanings. Maybe they just meant they dealt with "abstractions"—rough representations—which most thoughtful practitioners would agree with. Perhaps he meant something else. Who knows? Science deals with representations, in any case. The goal is to make these representations match as closely as possible to how things "actually are," but that has always been tough and the ultimate ability for humans to do that has often been questioned. --24.147.86.187 01:08, 13 October 2007 (UTC)

Science goes from the specific to the general and then back again. It takes many examples (through observation, preferably by experimentation) to create an abstract image of reality, which it can then apply back to specific instances to predict what will happen. So it uses abstraction to describe the specific. DirkvdM 10:05, 13 October 2007 (UTC)

I didn't read the comment but perhaps what was meant was that in many way, theoretical physics and theoretical chemistry nowadays tends to seem very abstract. Stuff like subparticles may be important, but it can be fairly hard for the average person to see the importance or relevance in real life. While this applies to all areas of science to some extent, I think it's easier for the average person to see the relevance and perhaps even important of even the more theoretical aspects of biology Nil Einne 12:15, 13 October 2007 (UTC)

Physics and chemistry can be real OR abstract - theoretical models are abstract, doing reactions is real.

In a addition the scientific models used (eg atomic theory etc) can be considered abstractions - so the answer is yes and no.83.100.254.51 14:57, 13 October 2007 (UTC)

I said that. :) DirkvdM 07:48, 14 October 2007 (UTC)

October 13

Robotic Arms

Has anyone come up with a way to make robotic tentacles? That is, long, everywhere-articluated arms like an octopus or snake? Black Carrot 01:56, 13 October 2007 (UTC)

Yes. Did you even try to Google for robotic tentacle? -- kainaw™ 02:47, 13 October 2007 (UTC)

I knew I'd forgotten something. I did check Wikipedia itself for it (and ran into some serious stubs). Thanks. 76.185.123.122 03:04, 13 October 2007 (UTC)

Make that an image-search and you get some intriguing ideas of what one could do with such tentacles. DirkvdM 10:11, 13 October 2007 (UTC)

On Saturday (in fact, on the very day this question was posed - how curious!) I was at a convention where they had a "satellite link-up" with Stan Lee, and one of the people lined up to ask him a question actually offered to make him a set of Dr Octopus arms. Confusing Manifestation 22:35, 14 October 2007 (UTC)

Runaway Global Warming

What evidence is there for and against runaway global warming? Don't talk about related, but different, stuff such as the existence of global warming and the effects of humanity on it. Please state weather the evidence is about existentially dangerous or merely catastrophic runaway global warming, or both. Site sources if possible. — Daniel 03:12, 13 October 2007 (UTC)

We shall have proof of Runaway Global Warming after the fact and never before. 211.28.129.8 09:47, 13 October 2007 (UTC)

He asked for evidence, not proof. Alas, this sort of thing was not included in the IPCC report because of the low probability (or even inability to calculate a probability). Which is stupid, of course, because risk is a function of probability and seriousness. You're asking about both (good on you). I don't know about the probability, but I can give some considerations concerning the existential risk (the chances that mankind will become extinct, I understand). Such events have taken place many times in Earth's history, and the consequences have indeed been catastrophic. Even to the point that almost all life on Earth died. But with rapid change, it's the least adaptable species that die out. It just happens that mankind's strongest point is adaptability. I think no other (land) species is as widely spread across the globe, so we've already got experience with all sorts of climates. And if we encounter a climate that we're not familiar with, we'll learn. We do that like no other species. Basically, species adapt through evolution, so they need many generations. We can do the same thing within one generation. So mankind will almost certainly not die out. Maybe some 90% will die, but even then there will be 500 million left (more than is normal for a species our size, which is the cause of the problem, but that's a different issue, which you didn't want to hear about :) ). And it won't be any fun for the survivors, but their will to survive will ensure mankind will not die out. DirkvdM 10:31, 13 October 2007 (UTC)

The effects that might cause "runaway" global warming are the ones that have an element of positive feedback to them, there are three that I can immediately think of:

1. Increasing global temperatures cause the ice caps and glaciers to melt. Shrinking polar/glacial ice reduces the area of the earth's surface that is white and increases the area that is dark. This in turn reduces the earth's albedo - which causes more absorption of sunlight - and more global warming - and more ice melting. This effect could potentially runaway until there is no more surface ice year-round.
2. In a similar vein...as the climate warms up, the oceans get warmer. As water warms up, it expands (except at temperatures very close to freezing) - and that causes a rise in sea levels. This inundates some lighter coloured land areas with darker coloured sea water - which also causes the earths albedo to drop - increasing the absorption of sunlight and adding to global temperatures - causing the sea levels to rise still further.
3. In deep parts of the ocean, there are large deposits of frozen methane. If the ocean temperatures rise too high, these will start to melt. The resulting methane gas will bubble to the surface. Unfortunately, methane is an even more virulent greenhouse gas than CO₂ - so releasing more methane traps more sunlight which raises temperatures and in turn releases more methane.

You can argue about other effects such as the disruption of certain ocean currents - but these are more about affecting the weather in certain regions than they are about global warming - they aren't any less devastating - but they aren't likely to make global temperatures change much UNLESS they cause warm water to be carried to places where more ice or methane can melt.

The nasty thing about effects with positive feedback is that even if mankind mended it's ways overnight, if we've inadvertently triggered one of these feedback loops, we may not be able to prevent ultimate catastrophy (although we ought to be able to slow it down). The tricky part is to know at what global temperature each effect will kick in. The fact that the northern polar cap and the glaciers are all melting MUCH faster than we had formerly predicted means that we've almost certainly triggered that problem in the Northern hemisphere. Fortunately, the majority of the ice is at the South pole which doesn't seem to be in a runaway situation yet.

SteveBaker 11:32, 13 October 2007 (UTC)

Follow up question: I never heard about methane clathrate back in the dark ages when I was in school. Is it technically correct to talk in terms of natural sources of "frozen methane" on Earth? Methane says the melting point is -296.5 °F. --JWSchmidt 15:27, 13 October 2007 (UTC)

The stuff was only discovered 'in the wild' fairly recently. Technically, it's not "frozen methane" it's methane dissolved in water ice. However, when the water melts and turns back into liquid water it releases the methane as bubbles - so the effect is the same. This is fairly exotic stuff and it generally only forms at great depths - which explains why we only recently discovered these deposits. Our article suggests that there is a heck of a lot of this stuff out there - and it could even (theoretically) be mined as a source of fossil fuels (except that we're trying to use LESS fossil fuels - not more!) —Preceding unsigned comment added by SteveBaker (talk • contribs) 17:26, 13 October 2007 (UTC)

Steve, the southern polar cap is also shrinking in size - that is, at the sides, where the ice is on water, so there is the same feedback effect. This is in a way compensated by the fact that the ice gets thicker in the central parts, due to heavier snowfall, so the total amount of ice remains more or less the same. But that's not what counts here. In this case, surface size matters.

Concerning the slowing down of the first two effects (both albedo related), I suggested in a previous thread that we could scatter some reflective stuff like polystyrene on the oceans to replace the ice. That would reflect the light. An alternative would be to capture it with solar panels. These would not only prevent the seas from warming up, but would also provide us with energy, for which we would then not need to burn fossil fuels, so that would give a double positive effect. For the first effect, the panels would not need to be very efficient, so we can use the technology we have now. This would give a big boost to the solar panel industry, which would then have more of the money they lack so much now to develop more efficient and cheap solar panels. A very postiive feedback indeed, I dare say. :)

The third cause, the sudden release of methane, could be truly catastrophic. Methane is a greenhouse gas that is 62 times stronger than CO₂, but it has a shorter lifetime. I don't know what the most important of these two factors would be, but it is theorised to be have been a factor in the Permian-Triassic extinction event, which killed off almost all life on Earth. If this release were to take place in our lifetime, then it would not be mainly a problem for later generations. A sudden rise in temperature by several degrees (global average!) would likely cause massive crop failures the world over. Which of course would lead to war the world over. Not WWIII, because alliances will likely break down, but smaller continuous wars all over the world (a worldwide Darfur, so to say), which would probably be a whole lot worse. DirkvdM 08:14, 14 October 2007 (UTC)

The short lifetime of methane in the upper atmosphere is only partially comforting. When it breaks down you get CO2 and water vapour. Water vapour (at those altitudes) is another gas that's a stronger greenhouse gas than CO2. The amount of these methane clathrate deposits is estimated to be equal to the total amounts of underground natural gas deposits - so even after the stuff decomposes, it would be like putting 500 years worth of CO2 from fossil fuel usage into the upper atmosphere. SteveBaker 15:35, 14 October 2007 (UTC)

There are many positive and negative feedback loops. Theoretically, you could use them to construct an accurate model, but I very much doubt we know enough to make a very complete one, and thus any we make will probably only be accurate for a short time after it is made, if at all. By studying the Earth's history, it may be possible to find evidence for catastrophic runaway global warming. Specifically, how often have circumstances similar to what we are currently in led to it. Has anyone done so? Whether we can use our own planet as evidence against existentially risky runaway global warming is closely related to the Sleeping Beauty problem. Personally, I think we can. If so, a similar study to the one I mentioned for catastrophic runaway global warming can be done for it. Again, has anyone done so? By the way, DirkvdM, solar panels absorb much of the light that hits them as heat. This could be helped by making a coating that reflects light too low of a wavelength for the panels to use. AFAIK the painting the roof of houses in warm climates white saves more energy than solar panels make, and reflects more light into the atmosphere. — Daniel 21:49, 14 October 2007 (UTC)

Human birth defects???

Any and all text related to the subject of human birth defects. 1 Abnormalities related to but not limited to the following, herniated diaphram, herniated stomach. 2 Formentioned organ and conective tissue missplaced within torso cavity resulting in underdeveloped lung or heart tissue. All other information on human birth defects welcome. —Preceding unsigned comment added by Terrynisely (talk • contribs) 04:15, 13 October 2007 (UTC)

See situs inversus, teratology, diaphragmatic hernia, hypoplasia, hypoplastic left heart syndrome, congenital disorder, dextrocardia, congenital heart disease, congenital heart defect, and articles that they link to, for a start. - Nunh-huh 07:48, 13 October 2007 (UTC)

Category:Congenital heart disease has a bunch of them. Category:Congenital disorders has a lot more, and there is also List of congenital disorders. SteveBaker 11:14, 13 October 2007 (UTC)

Other things then what's been mentioned, e.g. Polydactyly. There are so many possibilities I'm not sure if you'd really want to study them all. It depends also on your definition of a Congenital disorder. For example I noticed Huntington's disease in one of the lists. While I'm not disagreeing, as far as I'm aware it's very rare or never that symptoms are present at birth even if the disorder is. Therefore should we also include any inherited genetic disorder (which would be present at birth)? But of course even this isn't a clear cut issue since there is no boundary between 'normal' and 'disorder'. Nil Einne 11:53, 13 October 2007 (UTC)

fixed point calculation by utilisation of non stressed axial expansion joints

i would like to know how the force is calculated on the anchor points in a vertical chill water risers used in high rise buildings. all the steps in detail. these risers have expansion joints to take on the expansion and how to calculate on to where these joints can be installed on the pipe. how much should the distance be between the expansion joint and the fixed anchow point at the top and bottom fixed points. —Preceding unsigned comment added by Mohdbilal123 (talk • contribs) 13:17, 13 October 2007 (UTC)

Well, from first principles, I guess you need to consider the hottest and coldest temperatures of the water in the pipe - look up the thermal expansion coefficient of whatever the pipe is made of - and from that calculate the total amount of expansion that has to be allowed for - then (adding a safety factor) divide that by the number of pipe segments you have. However, I would assume there were standards set for such things - and if such standards exist, those are what you should follow. SteveBaker 13:26, 13 October 2007 (UTC)

I'd guess that since there are expansion joints - you would want no force on the anchor points (common sense) - therefor you want to know how much expansion the expansion joints need - to get this you need the length between anchors, the thermal expansitivity of the pipe, and the expected temperature range. For safety include extra expansion in the expansion joints for extreme conditions etc.

You can work this out in reverse as well - for a expansion joint that can expand x - calculate how much pipe it can allow to expand under given temperature ranges - so for a total pipe length you can work out how many expansion joints you need.. (Was this relevent?)83.100.254.51 13:33, 13 October 2007 (UTC)

gdfghdrg

tr RTAWT —Preceding unsigned comment added by Mohdbilal123 (talk • contribs) 13:37, 13 October 2007 (UTC)

Pardon me? —Keenan Pepper 13:58, 13 October 2007 (UTC)

You are hereby pardoned. DirkvdM 10:06, 14 October 2007 (UTC)

AYYLU. --JWSchmidt 14:50, 13 October 2007 (UTC)

¡Atención! ¡Atención!. Markovian Parallax Denigrate. Resurrect dead on Planet Jupiter. 12 Galaxies Guiltied to Omegalogical Exortations. GeeJo ^(t)⁄_(c) • 00:25, 14 October 2007 (UTC)

Google search on gdfghdrg and tr RTAWT neither of which seem promising. I suggest trying the wikipedia sandbox instead. 71.226.56.79 22:18, 14 October 2007 (UTC)

Oh great, another genius. And how many of those do we have here? *rolls eyes* But anyway, have you tried combining the two terms into one google search? NASCAR Fan24^{(radio me!)} 22:21, 14 October 2007 (UTC)

Raising metabolism

In theory, how high could the metabolic rate in humans be raised as a percentage of the average human metabolic rate?

My interest in this comes from an article I read about the powers of characters in the TV show Heroes. One character has rapid spontaneous regeneration ability and the article I read said that she would need an incrediably high metabolism to achive this. I'm aware that the ability to heal this quickly would be physically impossible (it would require constant eating and cardiovascular exercise, leading to indigestion) but I'm curious about how fast human metabolism could be raised.

-- _{Escape Artist Swyer} ^{Talk to me} _{Articles touched by my noodly appendage} 14:41, 13 October 2007 (UTC)

One problem with any significant amount of increase would be that metabolism produces heat. Increasing heat production would push up your body temperature - and taken to superhero extremes that would not be a healthy thing. This probably explains the skimpy costumes that those guys wear! :-) (Although, not in Heroes).

Oxygen is a rate limiting factor for human energy throughput. There are some numbers at VO2 max suggesting that it is rare for the best athletes to be able to sustain more than 3 times the oxygen uptake of the average person. I guess "in theory" might include genetically engineered humans. According to this dogs can do 3 times better than the best humans, so it might be possible to modify humans genetically and increase the maximum aerobic capacity. --JWSchmidt 15:14, 13 October 2007 (UTC)

And to back up my earlier point, dogs have a significantly higher body temperature than humans. There is also (across all mammals) a strong correlation between lifespan and body temperature - so increasing your metabolic rate will also (on the average) result in you dying sooner. SteveBaker 17:15, 13 October 2007 (UTC)

I've been thinking about healing and cell division and even noticed that Wikipedia has "healing factor". I've never seen Heroes, but I've had a chance to consult with my kids and they claim that on that show a character was shown regenerating a toe in a few seconds. For a relatively small amount of tissue repair/regeneration such as this, I do not think that "metabolic rate" is really the issue. There are limits on how quickly individual cells can reproduce and organize themselves. To get around these physical limitations, I think rapid regeneration would require special stores of cells and some kind of special cell migration process. After injury, pre-formed bone, muscle and other cell types would have to be quickly released from storage sites and transported (in the blood?) to the wound where they would have to efficiently assemble into tissues. There is no known mechanism for such assembly of differentiated cells into complex organs and limbs. As described at regeneration, animals that can regenerate structures form stem cell masses that must slowly differentiate and organize into new tissues using the kinds of cell-cell interactions used during normal embryogenesis. So I think you would have to say that some kind of shapeshifting is required, maybe involving some kind of nanorobotics (functional and structural components that are not conventional cells). I'm not an engineer, but it seems to me that if you can imagine some type of sophisticated self-organizing nanobots that can quickly shape themselves into a toe, then I do not see why we would have to assume that such self-assembly would require large amounts of energy....someone with the ability to design such nanobots would probably be able to make their assembly efficient. If you get into needing to rapidly produce (from conventional organic molecular building blocks?) a large mass of such nanobots in a short period of time using conventional metabolic energy sources, then in addition to energy concerns for synthesizing the nanobots, you might have a problem related to limitations on the rate at which storage molecules like glycogen and protein can be broken down and their molecular components released from cells. I end up thinking that it is unrealistic to imagine that "metabolic rate" is the only limiting factor. --JWSchmidt 18:39, 13 October 2007 (UTC)

What is the chemical composition of a typical computer?

Hey. I understand that my question might look pretty weird, but what I want to know is what elements a typical computer would be made out of- specifically, would it contain a majority of organic compounds, or inorganic ones? Any help would be appreciated. Thanks in advance! 68.54.42.126

First, make sure you know the difference between element and compound. Here is a guess at the most common elements a computer is made of: carbon, oxygen, hydrogen, chlorine, aluminum, iron, copper, silicon.

Plenty of other trace ones after these.

Because of the housing, circuit board, and wire insulation, I bet organic compounds would be most prevalent Delmlsfan 17:21, 13 October 2007 (UTC)

Iron (steel) for the case and transformer, a lesser but similar amount of copper for the wires.

There's some silicon in the chips but also in the glass fibre in the printed circuit board.

Very Small amounts of other elements in the chips eg germanium etc (tiny).

Relatively small amounts of other metals - gold/silver/tantalum etc in wires/contacts/capacitors

The remainder will be 'plastic' - almost certainly hydrocarbons eg polystyrene, ABS, polypropylene etc - a quite large perentage of the mass of the plastic will be filler - this can be chalk, gypsum, silica, feldspar, titania (any inert mineral) or even carbon fibres or other exotic materials.83.100.254.51 17:20, 13 October 2007 (UTC)

If PVC is used in plastic shielding of cables this means that chlorine will also be present, anything made of teflon (not unknown in cableing and insulation) would introduce fluorine

And the heat sinks are likely to be made of aluminium

Any paint will be carbon based - though the pigment might contain other elements

By mass I'd expect iron to be the major component - next copper, then carbon as plastics, then silicon and oxygen (not sure which is most) plus a similar amount of aluminium if you have large heat sinks (may also be present in filler), followed by hydrogen (in the plastic) and then all the trace elements (gold, boron etc)83.100.254.51 17:27, 13 October 2007 (UTC)

According to a number of computer recycling websites, there are about 5 pounds of heavy metals like cadmium, arsenic, and mercury in the computer motherboard and CRT monitor. --24.147.86.187 17:28, 13 October 2007 (UTC)

That sounds wrong - were would these elements be found?83.100.254.51 18:23, 13 October 2007 (UTC)

If you're including the CRT then you have a lot of glass (Silicon, Oxygen) and Phosphorous in the face-plate - plus a bunch more copper, etc from the circuitry and plastic in the case. I'm not qualified to guess what an LCD panel includes - certainly more plastics, copper and glass - but what is the liquid crystal made from? A plasma display presumably has some of the novel gasses in it...dunno, my knowledge just ran out! SteveBaker 17:37, 13 October 2007 (UTC)

The plasma gases are xenon or krypton according to plasma display

The phosphors are not phosphorus - they are rare earth oxides typically, or Zinc sulphide or... see the article for more details

Liquid crystals are organic compounds - C,O,H are certainties here.83.100.254.51 18:21, 13 October 2007 (UTC)

The greatest use of Indium is in thin films including flat-panel displays. Cheers Geologyguy 18:16, 13 October 2007 (UTC)

Don't forget laptop batteries - typically add lithium and cobalt to the elements83.100.254.51 18:22, 13 October 2007 (UTC)

Electronic waste might be useful.

Forgot to mention all that lead and tin in the solder - quite a lot of this...83.100.254.51 18:28, 13 October 2007 (UTC)

Plus a disk drive or cd rom (as well as hard disk) will most likely have a cast metal base - these are made out of aluminium/zinc/(possibly magnesium) alloys.83.100.254.51 18:43, 13 October 2007 (UTC)

Wow, there are quite a few responses! Thanks for the help! 68.54.42.126 —Preceding signed but undated comment was added at 20:07, 13 October 2007 (UTC)

All those elements just to download porn. Delmlsfan 21:59, 13 October 2007 (UTC)

For older (pre 2005) computers, there is a fair amount of lead in the solder. Newer computers comply with ROHS and do not have lead in the solder. Quite a bit of tin either way. For CRTs, there is a fair amount of lead in the glass. -Arch dude 00:27, 14 October 2007 (UTC)

infrared

What is the reason that (absorption of?) wavelengths surrounding 3μm causes the temperature of atoms and molecules to rise? In particular, can you tell me if it is due to a correspondence between wavelength and the dimensions of an atom or molecule? Clem 16:50, 13 October 2007 (UTC)

Absorption of light of any wavelength causes the temperature to rise - it's just energy. Perhaps your question should be "Why do materials absorb more light in the 10,000nm band than elsewhere in the electromagnetic spectrum?" (I'm not sure that's true either - but it's a better question!) SteveBaker 17:03, 13 October 2007 (UTC)

Infrared spectroscopy may be of some use here, though it is of some middling quality. Essentially, molecules (not atoms!) have specific vibrational and rotational frequencies, some of which just happen to match the IR band. These "resonant frequencies" explain why the molecules absorb EM radiation of those particular wavelengths. As the energy of the molecules is increased by doing this, the average energy of the system (temperature) increases. Note though that there are many vibrational frequencies outside of the IR range (which is why UV-vis spectroscopy works). GeeJo ^(t)⁄_(c) • 17:11, 13 October 2007 (UTC)

Is there a graph of resonant frequencies showing various molecules which might reveal how they are grouped or more closely distributed around 10,000nm? And for that matter a graph showing temperature rise on a black body surface for different wavelengths of radiation at the same intensity? Clem 21:25, 13 October 2007 (UTC)

For the first question, I'm not sure anyone's really looked that deeply into absorptions around that region for the simple reason that everything in the lab is going to be emitting radiation in that band, making it impossible to get any decent resolution. For the second question, a black body absorbs all radiation by definition, so it'd be a fairly dull graph, with E=hv determining the change in energy contribution from the various wavelengths. GeeJo ^(t)⁄_(c) • 22:41, 13 October 2007 (UTC)

In general any absorbsion of any light wavelength will cause an increase in temperature - the more light - the more the temp rises - 10,000nm isn't particularily special here. —Preceding unsigned comment added by 83.100.254.51 (talk) 17:13, 13 October 2007 (UTC)

That contradicts visible light having a higher energy level than IR yet not producing the same rise in temperature as IR of the same intensity. Clem 21:28, 13 October 2007 (UTC)

You seem to be under the misapprehension that IR wavelengths are somehow "more heating" than those of visible light. If you pointed lasers with beams in the visible and IR bands at a black body, I guarantee you that the visible will heat it more quickly. GeeJo ^(t)⁄_(c) • 22:55, 13 October 2007 (UTC)

ee assay

Does anyone know what an ee assay is? It is simply any assay used to determine the mixture of enantiomers, or is it something more subtle or completely different?

Thanks,

Aaadddaaammm 22:19, 13 October 2007 (UTC)

Enantiomeric excess mentions some specific methods for assay of "ee". --JWSchmidt 16:00, 14 October 2007 (UTC)

Thank you very much! I don't know how I missed that when I searched. Cheers! Aaadddaaammm 22:22, 14 October 2007 (UTC)

becoming an alcoholic without alcohol.

How might someone become an alcoholic, if you don't include alcohol or anything that breaks down or combines etc into alcohol. Can you substitute alcohol with something else (non-alcohol) and cause someone to become alcoholic over extended, high-volume ingestion? (This is just one example, another source of alcoholism, such as a pill that affects neural structure or something jsut taken once, would also fit my request). Thank you! —Preceding unsigned comment added by 81.182.100.153 (talk) 22:21, 13 October 2007 (UTC)

Some research on alcoholism has suggested that there could be specific neurotransmitters involved in alcohol addiction. For example, endorphin activity might be enhanced by ethanol, allowing a receptor antagonist such as naltrexone to possibly inhibit addiction to alcohol (See). Hypothetically, there might be some drug that could be chronically administered which would cause a person to become addicted to that drug and would at the same time predispose the person to alcohol addiction. If you are creating a plot element for a science fiction story, it might be more trendy to invent a polynucleotide analog or a viral vector that would genetically predispose someone to alcoholism. See also: Wikipediholic. --JWSchmidt 15:40, 14 October 2007 (UTC)

Some people lack the genes to make enzymes needed to break down alcohol. This makes them predisposed to NOT be alcoholics, I suppose. This is documented in Alcohol flush reaction. Personally, I don't believe that alcoholism is a strictly phisiological condition, though. I'm not sure if what you're asking is possible. --Mdwyer 15:54, 14 October 2007 (UTC)

You'd have to convince them that whatever they're drinking is alcoholic. If they know it isn't, they'll have no way of knowing alcohol will satisfy their craving, and thus they couldn't be considered alcoholic. — Daniel 21:53, 14 October 2007 (UTC)

Resonant frequencies

Where might one find a list of resonant frequencies for various molecules? Clem 22:35, 13 October 2007 (UTC)

Any good spectroscopy textbook will carry table upon table of the things. The only one I can find on Wikipedia itself is for a few organic bonds in the near-IR range at Infrared spectroscopy correlation table. GeeJo ^(t)⁄_(c) • 23:04, 13 October 2007 (UTC)

There must also then be a graph showing the distribution of molecules across these and other wavelengths such as Different regions in the infrared. Do you know of any others aside from Summary of absorptions of bonds in organic molecules? Clem 23:14, 13 October 2007 (UTC)

There are more detailed versions of the graph you mention out there - were you thinking of organic molecules specifically or anything? - a search for "IR absorbtion bands table" or "ir functional group" turns up thousands (try image search)

For example here is one for nitrogen functional groups http://www.vidrine.com/vcorr3.htm

And here is a paper containing a spectra for silicates (scroll down) http://www.aanda.org/index.php?option=article&access=standard&Itemid=129&url=/articles/aa/full/2002/31/aah3549/aah3549.right.html

There probably are millions - if you need more help please ask.87.102.19.106 04:39, 14 October 2007 (UTC)

Yes, this seems to be what I'm looking for, one question though, are absorption frequency and resonant frequency the same or do they refer to different phenomenon, and if not, are there graphs for resonant frequency? Clem 14:01, 14 October 2007 (UTC)

Yes - in terms of IR the absorbtions cause physical vibrations of the molecules at the resonance frequency of the bond - so the absorbance frequency is the same as the natural resonance frequency of a bond. they have the same origin/meaning/frequency87.102.82.26 17:54, 14 October 2007 (UTC)

OK, then things now add up. A microwave oven works because it operates at whatever the absorbency/resonance frequency of food is so the food heats up. What I'm locking for then is an online graph that extends all the way from zero to the highest frequency known that shows the frequencies at which something (everything from atoms to kettle drum) resonates. Clem 18:30, 14 October 2007 (UTC)

Yes, that's right - though typically the microwave oven is 'tuned' to water's frequency - or OH (hydroxyl) groups - microwave ovens don't heat up fat as well as water for this reason (though they melt butter well because butter has water in)

second question - I've never seen but would like to see too such a graph.. Can't find one.87.102.82.26 20:44, 14 October 2007 (UTC)

reduction of multiple state logical equations

If “… we're overrun by really efficient algorithms. “ (SteveBaker 13:40, 8 October 2007 (UTC)) to reduce logical equations to minimum form, which of these algorithms is capable of reducing multiple state equations to minimum form? Clem 22:53, 13 October 2007 (UTC)

October 14

Maximum limit of kinetic energy?

Hey guys! So i was daydreaming today and i thought if absolute zero exists is there an upper limit to the amount of energy a particle can have? Thank you very much for your time!

24.88.103.234 02:42, 14 October 2007 (UTC)Timothy

A greatly simplified way to think of it is that absolute zero is all mass and no energy. The speed of light is all energy and no mass. So, those are your two opposites. From there, you can get into the particulars that break down the simplicity into a muddy mess of conflicting areas of science. -- kainaw™ 02:51, 14 October 2007 (UTC)

That's a level of simplification even I would never go to...In short, no. Someguy1221 04:13, 14 October 2007 (UTC)

But it is true that the speed of light sets an upper limit to kinetic energy, right? DirkvdM 10:11, 14 October 2007 (UTC)

Short answer, no. And that's exactly the reason for the odd mass increase of the accelerated particle when it approaches the speed of light. You 'add' energy to the particle, since it can't store the extra energy as speed, it stores it as extra mass. --Taraborn 14:21, 14 October 2007 (UTC)

Not really. Kinetic energy = 1/2mv, so (ignoring common sense) if you had a mass travelling at c, you could simply have another mass slightly greater than double that of the first travelling at half the speed and you'll have a higher kinetic energy. You can set a maximum theoretical kinetic energy for any specific object, but the maximum possible kinetic energy would be the entire mass of the universe travelling at the speed of light, which is a ridiculously large and pointless number. GeeJo ^(t)⁄_(c) • 10:37, 14 October 2007 (UTC)

Firstly, it's 1/2mv², secondly, that is a formula of classical mechanics, false in special relativity, and so is invalid for large speeds. In SR, the kinetic energy of a body of rest mass m and speed v is given by

$E_{k}=m\gamma c^{2}-mc^{2}={\frac {mc^{2}}{\sqrt {1-v^{2}/c^{2}}}}-mc^{2}$

And so, as the speed of a massive body approaches c, its kinetic energy approaches infinity. Thus c does not provide a very interesting upper bound. (note this does not apply for photons, which actually travel at c but have zero rest mass). Algebraist 10:54, 14 October 2007 (UTC)

<after ec, before seeing Algebraist's response>The relativistic kinetic energy of an object with rest mass m traveling at velocity v (in a given inertial frame of reference) is

$E_{k}=m\gamma c^{2}-mc^{2}={\frac {mc^{2}}{\sqrt {1-v^{2}/c^{2}}}}-mc^{2}$

This is approximately ${\frac {1}{2}}mv^{2}$ when v is small compared to c. However, as v approaches c, E_k is unbounded - it has no upper limit. What this means in practice is that no matter how much energy you pump into an object, it will never reach the speed of light. This is sometimes expressed by saying that the energy increases the object's relativistic mass or inertial mass $m\gamma$, and so makes it "harder to accelerate". Gandalf61 11:00, 14 October 2007 (UTC)

Redox reactions

I know that oxidation is loss of electrons and reduction is gain of electrons. I also know that an oxidant gains electrons whilst a reductant loses electrons.

Yet I am a bit confused about the terms (1)"oxidising strength", (2)"reducing strength", when something is (3)"oxidised", when a molecule (4)"oxidises" something else, when something is (5)"reduced" and when something (6)"reduces" something else.

I think that "oxidising strength" refers to the ability for something to act as an oxidant whilst "reducing strength" refers to the ability for something to act as a reductant. Yet I'm not completely certain.

Could somebody please define clearly the 6 above terms. (You can refer to the words oxidant, reductant, oxidation and reduction in the definition as I am confident with these terms.)

Thank you very much. —Preceding unsigned comment added by D3av (talk • contribs) 09:28, 14 October 2007 (UTC)

The oxidising strength is the tendency to oxidise - a very strong oxidant may oxidise a weaker oxidant that would usually be reduced in a reaction and not oxidised - the same goes for a concept of reducing strength - you already have the meaning of 3,4,5,687.102.82.26 17:51, 14 October 2007 (UTC)

The Redox page might be useful…besides being "yet another explanation of the ideas" (sometimes one wording just sinks in better than another), it puts them in context and explains the reactions. Memorizing terms is pretty useless without knowing what they really mean and how they work in the real world. DMacks 18:57, 14 October 2007 (UTC)

Cyanide Vs. CO

Though Cyanide and CO are both strong ligand, why is there a difference in their mechanism of toxicising the human body? —Preceding unsigned comment added by Curieous (talk • contribs) 13:51, 14 October 2007 (UTC)

See Cyanide: Mechanism of toxicity and Carbon monoxide poisoning. Xn4 18:52, 14 October 2007 (UTC)

cyanide would almost certainly poison in the same manner as CO, but there is (according to the experts) yet another way in which CN can poison.. If this pathway wasn't available to CN, then cyanide would still be poisonous in the same manner that CO is. (The two compounds CN- and CO are isoelectronic and would be expected to have very similar behaviour

A side question that arises is why doesn't CO poison in the same way in which CN- poisons87.102.82.26 20:35, 14 October 2007 (UTC)

microscopy

when the slide is moved down in what direction does the image move —Preceding unsigned comment added by 99.226.126.42 (talk) 14:43, 14 October 2007 (UTC)

Think: Which way is the lens moving relative to items on the slide? --Mdwyer 15:49, 14 October 2007 (UTC)

It depends on the type of microscope.... TenOfAllTrades(talk) 16:20, 14 October 2007 (UTC)

For the type of microscope often used in school teaching labs, the image is inverted, see this manual, page 26. --JWSchmidt 20:02, 14 October 2007 (UTC)

Effects of long term usage of asthma medication

I'm just wondering if there are any known adverse effects to long term usage of asthma medication. In particular inhalers such as Duovent. Thanks :) 84.197.59.250 15:16, 14 October 2007 (UTC)

Take a look at the page for the active ingredients: fenoterol and Ipratropium. Both of those articles are kind of short, so you may want to then feed those names into Google. --Mdwyer 15:47, 14 October 2007 (UTC)

Transport Phenomena

While browsing today in WIKIPEDIA, I came across the entry TRANSPORT PHENOMENA. I notice that our book TRANSPORT PHENOMENA, by Bird, Stewart, and Lightfoot (Wiley, 1960) has been cited. Actually there is a 2002 edition as well as a 2007 "Revised Edition." These later revisions should really be cited, since the 1960 edition is now 47 years out of date! R. B. Bird, University of Wisconsin —Preceding unsigned comment added by 128.104.178.123 (talk) 18:03, 14 October 2007 (UTC)

First of all, this is not the place to grovel about out-of-date information. Secondly, the most likely cause of the 1960 ed. being cited is that no one who contributed to the article has the 2002 or 2007 editions. NASCAR Fan24^{(radio me!)} 18:16, 14 October 2007 (UTC)

Be nice. And nobody "groveled". I copied the original message to the article's talk page. --Milkbreath 18:19, 14 October 2007 (UTC)

Guess I did bite them there. I just get mad when people don't use things for their intended functions. To Professor Bird: You may change any out-of-date information in the article. You may want to read WP:CITE to learn how to cite a book. NASCAR Fan24^{(radio me!)} 18:22, 14 October 2007 (UTC)

Some people in academia are too busy to edit, feel they have a conflict of interest or they are just unfamiliar with the wiki concept. I've had people send me email about page content problems in Wikipedia when they could have just taken a minute and fixed the problem by editing the page. "when people don't use things for their intended functions" <-- See Murphy's law. --JWSchmidt 19:45, 14 October 2007 (UTC)

There would be an air of impropriety with the author of a book citing his own work on Wikipedia (although in this case, I doubt anyone would object). It makes sense to have someone who is already an active editor of the article make the change. So the best procedure would be to post this kind of note to the talk page of the article (which Milkbreath took care of)...and if that doesn't produce a result, look at the edit history of the article and ask some of the most active editors directly via their talk pages (or email addresses if they provided them). SteveBaker 21:41, 14 October 2007 (UTC)

Spectroscopy of elements

If spectroscopy of molecules reveals the frequency at which their bonds resonate what is it the spectroscopy of the elements represents, the resonance of the subatomic particles, i.e., protons and neutrons and electrons, within the atom? Clem 18:35, 14 October 2007 (UTC)

NMR and EPR are types of spectra that analyze resonance of nuclei and electrons, respectively. Careful though…"resonance" applies to a particular kind of interaction, not a particular kind of particle. Ultraviolet-visible spectroscopy is another kind that analyzes resonance of electrons, but it's not related to EPR. DMacks —Preceding signed but undated comment was added at 18:52, 14 October 2007 (UTC)

exlcuding nmr - all these resonances are at frequencies above that of visible light - the difference between 'resonance' frequencies of electrons is electronic spectroscopy (the term resonance is possible debateable here - depending on what theory you have), the differences between energy states in nuclei is in the x-ray or gamma ray region - again it's debateable whether or not the nuclei are actaully resonating - and depends on what theory you are using..

Note that electronic spectoscopy (the electrons) also depends on the type of molecule the electrons are in - there's also (for lower down electrons) mossbauer spectroscopy and X-ray photoelectron spectroscopy amongst others,not all these spectrosopy are interpreted as being directly from resonances..87.102.82.26 20:50, 14 October 2007 (UTC)

And you can get crazy and do Raman spectroscopy, which is a measurement of electronic transitions that indicates bond vibrations. This is similar to using IR, which only examines vibrational modes, to see the effect of rotational modes on those vibrations, instead of using Microwave spectroscopy to probe rotational modes more directly. DMacks 22:10, 14 October 2007 (UTC)

CLASSIFICATION

What would a scientist have to prove to show that the organisim they had discovered was a new species?

What would you expect to see in the organisms within groups that get smaller and smaller. 88.110.21.169 18:38, 14 October 2007 (UTC) Alex McAdam

I suggest checking out the Species and Species problem articles. As for the organisms in groups that get smaller and smaller -- fortunately, there are a finite number of organisms on Earth, so if you kept dividing organisms into group, you'd at least hit the limit once you created a new group for each organism. -- JSBillings 18:59, 14 October 2007 (UTC)

Usually a lack of cross breeding with other similar species of organisms is what you need to prove that an organism is a new species. How exactly this is determined may vary between different organisms. 71.226.56.79 22:13, 14 October 2007 (UTC)

Absolute zero

I just want some input on my reasoning about this topic, or any other speculations that are floating around out there.

Absolute zero is the lack of all energy, right? So if you managed to get an atom down to absolute zero, what would happen to it? Don't electrons have potential energy based on their orbital position? In order to reach absolute zero, would they have to fall into the nucleus? What would happen then?

For curiosity's sake... justice 18:41, 14 October 2007 (UTC)

Thermodynamicists say it isn't possible to reach absolute zero. Xn4 18:48, 14 October 2007 (UTC)

Our absolute zero page has info about this topic. One important issue is that "Absolute zero is the lack of all energy" is a convenient and short explanation for the general public, but it's not the precise and correct definition. As you note, there is a non-zero minimum for various potential energy components. DMacks 18:49, 14 October 2007 (UTC)

Theoretically though, for you to reach absolute zero the electrons couldn't stay in their orbitals because of potential energy. If they hit the nucleus, what would happen? Also, I'm assuming that in real life, if we can never reach absolute zero, it's an like an exponential function- always getting closer to whatever number, but never quite reaching it? justice 19:08, 14 October 2007 (UTC)

Again, I point you to the absolute zero page, which states "It is the point at which particles have a minimum energy, determined by quantum mechanical effects, which is called the zero-point energy.". They don't stop moving and they don't have zero potential energy. DMacks 19:12, 14 October 2007 (UTC)

Yes, a necessary result of quantum mechanics is that you can never get rid of zero-point energy. Someguy1221 19:19, 14 October 2007 (UTC)

There is a certain elegant symmetry here - Einstein says we can't reach infinite kinetic energy - and the third law of thermodynamics says that we can't reach zero kinetic energy either. Nature seems to love having exponential tails to avoid having mathematical discontinuities. SteveBaker 21:31, 14 October 2007 (UTC)

It's also worth noting that ending up with zero energy could have weird implications for what it means for fundamental particles to "exist". What happens to light if it has no energy? Light is defined (in part) by its wave-like properties — would it even make sense to talk about it as existing if it had no energy, no motion? I'm no physicist but I imagine similar issues come up when you are talking about matter as well, given the deep connection between energy and matter. --24.147.86.187 22:25, 14 October 2007 (UTC)

I was going to ask about that. So nothing, as best we understand it, would exist without energy? If it had no energy, the matter would be... destroyed? justice 22:55, 14 October 2007 (UTC)

question on Sexually transmitted disease--why aren't there more of them?

Why there are apparently relatively few STDs? I think there "ought" to be hundreds of well known STDs. I mean, fluid exchange during sex is a jackpot for microcritters to evolve to take advantage of. Could it be that these missing STDs are really there but are wrongly presumed to be genetically heritable diseases, defects,(or even advantageous traits!?) since they would commonly run in families?-Rich Peterson —Preceding unsigned comment added by 130.86.14.86 (talk) 20:53, 30 September 2007 (UTC) (I put this on the STD discussion page a while back, but that isn't the right place for it, according to Wikipedia policy)130.86.14.90 20:02, 14 October 2007 (UTC)

You're running on some pretty strong assumptions there. Genetic defects are not diseases, as they are... well, not diseases. They're flaws in the DNA that cause abnormal conditions in the body's development, not body parts being attacked by a specific organism. Second, why should there be "hundreds of well known STDs." Sexual fluids are actually a less efficient method of spreading disease than blood or airborne transmission. There's nothing inherently special about sexual fluids that should be a "jackpot" for diseases. -- Kesh 20:09, 14 October 2007 (UTC)

I know what a genetic defect is.What I'm proposing is that some things thought to be genetic defects are actually diseases transmitted semen.I am interested in what you say about sexual fluids not being as efficient, perhaps you're right. Can you explain your reasoning or refer me to a source? Thanks, Rich Peterson

I don't think sex is a good way for a disease to transmit itself at all. Humans are relatively monogamous and typically have sex just a few times a week - mostly with the same partner. A common cold virus is transmitted between complete strangers via nothing more than a handshake, a cough or a sneeze - with an opportunity to transmit itself dozens and dozens of times per day. SteveBaker 21:27, 14 October 2007 (UTC)

Careful Steve, humans are not that monogamous. If you've ever had a partner who has had at least one other partner, you are part of the great sexual network. I do agree though, airborne is the best way for a pathogen to go. Returning to the original question, STDs aren't super easy to pass to your kids (it depends on the STD of course, but AIDs for example, is preventable to about a 15%-25% transmission rate in the West), and mistaking them for genetic defects seems pretty far fetched. Also, remember that diseases "should" evolve to become less noticeable and less virulent, so there are probably "STDs" that we don't even classify as diseases anymore. --Cody Pope 21:39, 14 October 2007 (UTC)

Sheesh! I said "relatively monogamous" and "typically" - just how careful do I have to be? The point is that it's pretty much impossible to have sex with someone without passing on a cold. So it's pretty much certain that a disease that can transmit itself through the air is going to have more potential contacts to spread to than an STD. The spread of AIDS is pathetically slow compared to whichever cold or flu strain is unleashed in a given year. Even in the countries where AIDS has spread the furthest, you're only looking at 10 to 20% of the population over 20 or more years. A strong flu strain can spread to a similar percentage of the population in a couple of months. SteveBaker 22:07, 14 October 2007 (UTC)

Hey, I attacked "relatively" not "typically" -- man you do need to be more careful :). But mostly I completely agree with you. --Cody Pope 22:22, 14 October 2007 (UTC)

Compare that to how often you've breathed the same air as someone. I'm not certain, but I'd be willing to bet that most people also share drinks more often then they have sex. In addition, I'm pretty certain that almost all diseases can be transmitted that way, and STDs are the ones that can only be transmitted blood to blood. — Daniel 22:00, 14 October 2007 (UTC)

Hmm, I was agreeing with Steve's observation that airborne is way more common/easy, but disagreeing with him saying that we're all monogamous -- so I'm not sure how we disagreed. Plus, I really just wanted to say "great sexual network" :). Moreover, "almost all diseases can be transmitted that way" is an odd statement (where "that way"=airborne?). Ebola is transmitted through fluid exchange (non-sexual and sexual alike) and it's certainly not classified as an STD. A lot of parasites need a vehicle that isn't air. As well as malaria, non-parasitic dysentery, TB (airborne momentarily, sure but only if someone just sneezed in your face, the bacteria isn't transmissible through sharing water glasses washed dishes though) and others. Take African sleeping sickness, it is usually passed by a fly, but can theotrically be passed via fluid exchange etc. Saying anything transmitted via fluid exchange is an STD doesn't work. --Cody Pope 22:13, 14 October 2007 (UTC) (I would add that people with Ebola almost never have sex). --Cody Pope 22:25, 14 October 2007 (UTC)

Mitochondrial genome size

Everyone seems to know that the mitochondrial DNA in humans is 16569bp long. This comes from a 1981 paper that sequenced it. My question is: there's gotta be some variation in this number - does anyone know how much give and take there is in humans? Aaadddaaammm 22:19, 14 October 2007 (UTC)

Here is a place to start: Mitochondrial diversity within modern human populations. --JWSchmidt 22:27, 14 October 2007 (UTC)

species

Does the inability of one species to impregnate another species serve as the dividing line for species or does it include the ability to impregnate but with the result of offspring so deformed they are not able to live? Clem 22:32, 14 October 2007 (UTC)

Neither. For instance, horses and donkeys can interbreed, but create infertile mules. They are still considered separate species, as their offspring cannot breed, even though said offspring are not deformed. Most modern biologists look at more than that, though, as genetics and bodily structure play into the definition of species quite a bit. It's not as simple as who they can breed with. -- Kesh 22:35, 14 October 2007 (UTC)

Generally, both genders of any offspring between the two have to be themselves fertile. Mules aren't. Of ligers and tigons, only the females are. Not sure about grolars, but then they're a lot rarer. GeeJo ^(t)⁄_(c) • 22:42, 14 October 2007 (UTC)