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December 7

Electric Tooth Brush

I have a couple of questions regarding these tooth brushes: does their effectiveness correlate with their frequency?

I don't know about effectiveness - but you couldn't design something like that. No two teeth are the same size or shape - so the resonant frequency of each tooth would be different. SteveBaker (talk) 02:11, 7 December 2008 (UTC)[reply]
Some frequency searching feedback could fix that - talk about having a tune on your mind! -hydnjo talk 03:06, 7 December 2008 (UTC)[reply]

Probably a small hammer that would hit the tooth and measure the resonating frequency would do that right? Assuming it is practical, would it make sense to design it?77.243.73.133 (talk) 11:30, 7 December 2008 (UTC)[reply]

Putting aside the fact that hitting your teeth with a small automated hammer may not be all that healthy, I don't think there's any particular benefits to a resonating toothbrush. Their purpose is to remove unwanted substances from the surface of the tooth, so causing the tooth itself to vibrate doesn't sound very necessary. There will definitely be a correlation between frequency and effectiveness, but it's more to do with finding a balance between swiftly removing plaque in the limited period the user is touching a particular tooth, but not having the toothbrush blasting away so fast it wears down the teeth or damages the gums. ~ mazca t|c 12:33, 7 December 2008 (UTC)[reply]

Rare meat

Why does rare meat taste so much better than well-done? Or rather, as de gustibus non est disputandem, what chemical changes account for the difference in taste between rare and well done meat? DuncanHill (talk) 00:18, 7 December 2008 (UTC)[reply]

Blood. You are experiencing a pleasure in the taste of fresh blood. I do not know if this is any good an answer for you but certainly you will find more blood in your raw flesh than in your burnt one. ~ R.T.G 01:24, 7 December 2008 (UTC)[reply]
I like cooked blood too. DuncanHill (talk) 01:25, 7 December 2008 (UTC)[reply]
My understanding is that the red stuff that comes out of a rare steak is not actually blood (the animal is bled before butchering), but a thin fluid of proteins leaching from the muscle tissue. I don't have a specific cite handy, but I heard it on Good Eats, which is unusually fact-based for a food show. Matt Deres (talk) 02:13, 7 December 2008 (UTC)[reply]
The red stuff is Myoglobin, here's a book source about the flavor part. -hydnjo talk 02:36, 7 December 2008 (UTC)[reply]
Yeah, the red stuff is definately not blood. Blood isn't found spread evenly among all of your tissues; its pretty well confined to things called veins and arteries. There is no blood inside of your muscle tissues. Blood is also pretty terrible for the flavor of meat; if it is not quickly drained, and it does enter the meat, it pretty much ruins it. The red stuff is just the stuff that makes muscles red in general; as noted above, its myoglobin. --Jayron32.talk.contribs 03:14, 7 December 2008 (UTC)[reply]
The red color of meat is certainly caused by the myoglobin (and that also explains why chicken isn't bright red) - but "There is no blood inside your muscle tissues"??? Er...are you sure about that? Our article on muscle says that they are "densely" suffused with capillaries - and the article on capillaries says that they carry blood. So there ought to be a fair bit of blood in muscle - and hence in meat from an un-bled animal...but I'm no biologist - I could be wrong. SteveBaker (talk) 05:34, 7 December 2008 (UTC)[reply]
Capillaries will have blood in them. Whether you consider them part of the muscle tissue or seperate may vary Nil Einne (talk) 09:02, 7 December 2008 (UTC)[reply]
OK, nice semantics - but they are definitely a part of the steak - some of them are so fine that red blood cells have to fold up to get through them...there is absolutely no way you could dissect them out during butchering! I doubt very much that 'bleeding' the animal after slaughter would drain those teeny tiny tubes - so we may safely deduce that there IS blood in steak. SteveBaker (talk) 02:49, 8 December 2008 (UTC)[reply]
Would that work with meat that is frozen almost as soon as it's killed or eaten fresh without being drained? We never drain anything and it never tastes odd. CambridgeBayWeather Have a gorilla 04:57, 7 December 2008 (UTC)[reply]
You hunt meat, kill it, and then don't drain the blood? Really? --Jayron32.talk.contribs 05:31, 7 December 2008 (UTC)[reply]
While today you might be able to get back to town and find a heated area to drain it before the meat freezes, in older times that would not have been possible, it's unlikely that you would get back quick enough. CambridgeBayWeather Have a gorilla 06:59, 7 December 2008 (UTC)[reply]
Why do you need to find a heated area? You can drain blood rather fast if you adopt the Muslim/halal method of killing an animal. (If you kill the animal while hunting that won't be possible but I'm pretty sure traditionally people would have been far more likely to wound rather then immedietly kill an animal. Arrows, spears and the like aren't going to guarantee and immediate kill.) Unless you are living in liquid nitrogen, the animal is not going to die that fast Nil Einne (talk) 08:56, 7 December 2008 (UTC)[reply]
Did you mean dhabihah rather than halal? To do that would you not need to be able to catch the animal first? It would seem to me that wrestling with a wounded muskox or even a caribo and trying to cut it's throat is going to be a problem. Still the animals were never (and still aren't) drained prior to eating. CambridgeBayWeather Have a gorilla 12:13, 7 December 2008 (UTC)[reply]
No I did mean halal. Dhabiha methos of slaughter is generally compulsory for halal meat for many Muslims. Anyway ignoring the semantics for now, I disagree it's going to be a big problem. Ultimately you have to kill the animal. Whether you slit it's throat (note it could be a spear or whatver, it doesn't have to be a knife) or try to stab its heart, both obviously require some skill but aren't not going to be that hard if you're used to that sort of thing. Otherwise humans would never have succeeded at hunting Nil Einne (talk) 15:54, 14 December 2008 (UTC)[reply]
I should note that not everyone prefers rare meat Nil Einne (talk) 08:57, 7 December 2008 (UTC)[reply]
A few notes from a cooking point of view. Many people like a rare steak. In this case the outside of the meat is cooked very quickly and the sugars undergo caramelisation. The taste mixes salt and sweet, which is generally pleasant. I expect there is umami involved as well. There is also an agreeable contrast between the crispy outside and soft middle of the steak. Let's also consider the counterfactual: long-cooked meat. If you cook a steak for a long time it may become tough and rubbery. However, some cuts of meat respond very well to slow cooking. Often we sear the meat first, to achieve the caramelisation, then add liquid (water, stock, wine, beer etc.) and cook slowly for hours. The meat becomes fibrous but not dry. The taste of the meat is transferred to the liquid and any vegetables that are included. Itsmejudith (talk) 12:55, 7 December 2008 (UTC)[reply]
Many thanks to you all - some fascinating stuff. DuncanHill (talk) 12:59, 7 December 2008 (UTC)[reply]
And given CambridgeBayWeather's very high latitude, where the average low is below -10ºC all year long, I'd guess that the meat and its blood would freeze rather rapidly if you didn't find a heated area. Nyttend (talk) 14:49, 7 December 2008 (UTC)[reply]
Whoops, I probably should have indicated that I live in Cambridge Bay, Nunavut and the mean daily average is −14 °C (7 °F). Sorry for any confusion. CambridgeBayWeather Have a gorilla 22:50, 7 December 2008 (UTC)[reply]
In the old days of farming, a farmer would kill hogs when the temperature dropped cold enough to preserve the meat but perhaps not way below freezing [1]. The animals throat would be cut and he would be hoisted by his hind feet to drain the blood within a couple of minutes. I don't see why that wouldn't be desirable for a deer as well. Field dressing [2] should get rid of the blood as well as speeding the cooling of the meat. Edison (talk) 03:51, 8 December 2008 (UTC)[reply]
All of that seems to involve the hanging of the animal but without trees that's not practical. Anyway, the thing is that we don't drain the blood and the animals taste fine, which seems to contradict with the earlier comment. CambridgeBayWeather Have a gorilla 06:44, 8 December 2008 (UTC)[reply]
"Globin" such as "myoglobin" and "haemoglobin", is a word used to describe blood cells, one is red, one is white. They contain stuff like salt, sugar, iron, etc. The red colour is partly caused by the iron, which in its natural form is pure rust or red rock, is the building block (a magnet) upon which oxygen is carried throughout the body therefore being well spread in a length of veins long enough to reach around the planet several times (that much veins must go into muscles or something) and being several six inch nails worth in a human body and as may be known has a strong taste. Salt, its very important, you are stuffed with it, what it does I do not recall, it has a strong taste. Sugar, again you are packed out with the stuff. It is the coal for you fire. It is the acid by which your blood and stomach burn. It burns the food and lets off the gas and steam and again it has a quite strong taste. Unfortunately what is sad but true after this point is that other stuff with a strong taste in its basic element sort of goes as far as calcium, clorophyll (or whatever gives that green taste), and narcotic tasting stuff like caffine and aspirin which tastes more alike the more pure it is. It's all sugar, salt and steel. Even natural flammable gas has no smell or taste. The smell is added so that if you are about to suffocate or set it on fire you have some sort of warning. Even when making soya milk it tastes pretty much like carboard unless they add calcium, salt and sugar (or apple juice which is common in the tastier stuff). Tastes pretty much like milk but is basically that same old stuff you are tasting. Ask any chef what is most important in a good meal... colour and presentation. What do they make fake meat out of? Corn. Can they make it taste like real flesh? Little fatty bits and all. Yik. ~ R.T.G 19:23, 8 December 2008 (UTC)[reply]
Um quite a bit of what you're saying is wrong. For example, I never, ever heard someone call Myoglobin a 'blood cell' in my 4 years at university doing biology which isn't surprising given that it isn't found in the blood. Nor have I ever heard some call myoglobin a white blood cell which isn't surprising since besides the aforementioned reason myoglobin when oxygenated is generally red (or brown) as with haemoglobin. BTW, the vast majority of Meat analogue is made with soyabean and sometimes a variety of legumes like chickpeas not corn. Nil Einne (talk) 16:01, 14 December 2008 (UTC)[reply]

Natural orbitational phenomenon

As in the orbitational phenomenon. What are the odds? Lets say you could remove the moon to outside the system and send it toward the Earth repeatedly on random courses until you got a stable orbit. What are the odds? Would the time scale of orbitational phenomenon occuring naturally fit in with the time scale of the orbital decay (or opposite) of the celestial bodies we have in the system now? i.e. the moon and other orbiting stuff will eventually crash or fly away... will this happen so slowly as new similar sized bodies will find such orbits before they do? Is there any known records of anything like a comet or a meteor that flew into a new orbit in our solar system? Any comets or meteors been recorded which are not beleived to have some sort of orbit in our system? ~ R.T.G 01:20, 7 December 2008 (UTC)[reply]

When looking for the likelihood that something the size of the moon would get "caught" in the orbit of earth you'd have to acknowledge that the moon didn't likely come towards the earth and then get caught in orbit (Giant impact hypothesis). Now if someone can try to do some math to give you a real answer, that'd be impressive. Chris M. (talk) 02:04, 7 December 2008 (UTC)[reply]

It's not a matter of statistics...it's not possible. SteveBaker (talk) 02:09, 7 December 2008 (UTC)[reply]
"orbitational" isn't a word. I guess you're asking how the earth could have 'captured' the moon? The answer is that it couldn't. There is no course that the moon could arrive along that wouldn't result in it shooting off back out into space - or crashing into the earth. But you should read our article on the Moon#Formation - it explains that the 'capture hypothesis' doesn't work. The generally accepted theory is that another planet collided with the earth and the moon was formed from material ejected from the collision. The moon's current orbit isn't 100% stable - it will gradually move further from the earth. This applies to other objects heading towards the earth - they'd have to find some means to lose exactly the right amount of energy as they arrived in order to make a stable orbit. Notice how our spacecraft heading into orbit around other planets have to use an 'orbital injection burn' of their engines - or use the drag of the atmosphere of the planet - to lose some energy and make a stable orbit. Meteors and comets don't have energy - so atmospheric drag is the only way to get into orbit...and an incoming moon would need to shed far too much energy for that to work. SteveBaker (talk) 02:09, 7 December 2008 (UTC)[reply]
But the need to slow down is because the spacecraft is going so fast. If an object approached the Earth at a lower speed, essentially tangent to the Earth's orbit about the Sun, it might be possible for it to fall into a stable orbit. Certainly not a likely scenario with an object the size of the Moon, but still possible, I suppose. StuRat (talk) 04:35, 7 December 2008 (UTC)[reply]
Nope - no matter how close to the correct orbital velocity you were going (Remember: velocity means speed and direction), you couldn't be at the exact correct velocity without already being in orbit. Hence you either have to gain or lose energy from somewhere...which means that you need either some engines, sufficient drag through the atmosphere or some third body to shed the excess energy into. SteveBaker (talk) 05:19, 7 December 2008 (UTC)[reply]
You talk as if there is only one possible orbit. Aren't there an infinite number of orbits at different distances (and subsequently speeds) from the Earth ? And, therefore, won't a body moving in a certain range of speeds naturally move into a stable orbit by either getting closer to, or farther from, the Earth ? StuRat (talk) 23:03, 7 December 2008 (UTC)[reply]
No. Conservation of energy means an object has the same amount of total energy (potential+kinetic) at all points in its orbit, either that is enough energy for it to escape or it isn't. You can't move from one type of orbit to another without a change in total energy. One way to look at it is to realise that the laws of gravity are completely time symmetric, so if it is possible to go from a hyperbolic orbit to an elliptical one, it is possible to do the reverse - that means you can break orbit without needing to fire your rockets, which is clearly not true. --Tango (talk) 23:29, 7 December 2008 (UTC)[reply]
Ah! Thanks Tango! That's an elegant way of saying what I was trying to get across. Time symmetry...yeah. SteveBaker (talk) 02:34, 8 December 2008 (UTC)[reply]
Ok, so let's say the Moon's orbital velocity (at one point in it's orbit) is now X. You're saying that, if the Earth didn't have a Moon, and an object identical to the Moon approached the Earth at tangent to the Moon's orbit, but at a velocity of 0.999999999999 X or 1.000000000001 X, that instead of settling into a slightly higher or lower orbit, the Moon would fly off into space or crash into the Earth ? I find that impossible to believe. Orbits aren't that unstable. If so, then when some ancient meteor hit the Moon and increased or decreased it's velocity that much, it would have been knocked out of orbit, too. StuRat (talk) 14:51, 8 December 2008 (UTC)[reply]
If an object were at that speed in that position then it would already be in orbit. You can't get from a long way from Earth to a lunar distance from Earth without the Earth's gravity accelerating you (we call moving towards a massive object due to gravity "falling") so you would be at a too great a speed to be captured. --Tango (talk) 15:19, 8 December 2008 (UTC)[reply]
Escape speed at a given distance is √2 times the speed of a circular orbit at that distance, by the way. (In a Newtonian universe; near a black hole that's likely off.) —Tamfang (talk) 08:44, 14 December 2008 (UTC)[reply]
Quibble: velocity means speed and direction, yes, but direction isn't important here: if the kinetic energy is less than (the absolute value of) the gravitational potential energy, the body is in orbit, no matter which way it's going. —Tamfang (talk) 08:44, 14 December 2008 (UTC)[reply]
To expand a little of SteveBaker's excellent answer; orbital capture COULD theoretically work for a small chunk of rock that happened to hit the atmosphere at just the right angle and slowed down to exactly the right speed. The main problem with the moon is that its, and this is a scientific term, pretty friggin huge. With the exception of the now-demoted "Pluto" system, the Earth-Moon system represents the closest in size between a satelite and a planet in the solar system, by far. The moon is about 2% the size of earth; no other satelite is even CLOSE to being that large relative to its planet. Orbital capture works; but not for something that size... --Jayron32.talk.contribs 02:50, 7 December 2008 (UTC)[reply]
Actually, it might be possible to capture a moon-sized object by gravitationally scattering it off of our existing moon-sized object. An incoming planetoid with just a little more energy than escape velocity might be captured if it transfered enough energy to our existing moon. Of course, that would leave both objects in eccentric and probably unstable orbits, but why be picky. Dragons flight (talk) 03:32, 7 December 2008 (UTC)[reply]
Yep - but the idea that our moon could simply be free-falling through space, pass close to the earth and be "captured" is a mathematical impossibility. That's why this theory for the formation of the moon has been dismissed these days. SteveBaker (talk) 05:19, 7 December 2008 (UTC)[reply]
So how do the theories that certain moons of other planets were captured work? Do they rely on the other moons or nearby planets? I can see why in the 2-body problem you can't go from an escape orbit to a periodic one without a change in energy, but it must happen somehow. --Tango (talk) 13:55, 7 December 2008 (UTC)[reply]
It's only a mathematical impossibility in the 2-body point mass (or rigid ball) model. While it's unlikely, the gravitational influence of the Sun could change the velocities by the right amount, see Interplanetary Transport Network. I think at least theoretically there could be a situation where tidal forces slow down a moon while it is passing close to the planet and make the orbit more stable (but the evolution of such a orbit wouldn't fit to the current orbit of Earth's Moon). Icek (talk) 15:00, 7 December 2008 (UTC)[reply]
Great answers! The collision idea is easier to visualise. It also gave me an idea to support it I think... all of the Suns orbiting bodies are more or less in a disc formation. Perhaps this is the angle at which large stuff is more likely to bounce off and find an orbit. I must agree that thinking about how an object would hit an atmosphere sounds more likely to make it curve. Also given the fact about the moons size and its relationship to life here (it provides the tide and hence the beat) its a pity we can't compare similar systems. I have seen a few pics on TV of a comet which hit Jupiter or Saturn but that is the only mention of something large hitting the gravity of a planet I can recall and funny enough as it left a large mark (i cant rememer which planet but it was a gas giant, Jupiter I would beleive) the comet bounced like a skimming stone not just leaving one mark but a row of marks where it bounced, another collision supporting evidence too. ~ R.T.G 01:58, 8 December 2008 (UTC)[reply]
BUT... if the Moon hit the Earth causing the orbit... isnt the Earth on a stable orbit? Wouldn't the collision of the Moon cause the two bodies to orbit each other rather than one orbiting the other? I guess the Earth could have been stabilised by the Moon colliding but is that any more likely than them just happening on their orbits without colliding? ~ R.T.G 02:04, 8 December 2008 (UTC)[reply]
The earth and moon DO orbit each other. The point about which they both rotate is somewhere beneath the surface of the earth - about a third of the way down to the center. Technically - the moon didn't hit the earth. Some other small planet (called 'Theia - perhaps the size of Mars) hit the earth - the resulting energy would have forced a blob of molten matter to spirt out of the opposite side - and billions of tons of debris to be shot into orbit - rapidly forming a disk (like the rings of Saturn). Gradually, the material in the rings would clump together making a larger and larger body - which eventually consumed all of the ring material. THAT is the moon. Our article Giant impact hypothesis explains the currently prevailing theory. SteveBaker (talk) 02:34, 8 December 2008 (UTC)[reply]
The Comet that hit Jupiter was Shoemaker-Levy. It didn't bounce. The reason we saw a series of collision points was that the comet broke up (prior to collision), due to tidal forces.Bunthorne (talk) 07:49, 8 December 2008 (UTC)[reply]
That theory of Giant impact hypothesis sounds good for most part but I don't understand the pictures where the theia object moves backwards and forwards or in a sort of a squiggle shape...? Don't cellestial bodies travel in straight lines or perfect curves? And, if the moon was definitely a ring but definitely only for a hundred years... what is going on with Saturns rings? ~ R.T.G 18:45, 8 December 2008 (UTC)[reply]
The picture was probably centred on Earth rather than the Sun, so the weird path is combination of the (roughly) perfect curves of the Earth and Theia. As for Saturn's rings, nobody is entirely sure, but it may be to do with its moons preventing coalescence. --Tango (talk) 01:00, 9 December 2008 (UTC)[reply]
No, they are all pictures of the Earths orbit around the Sun and at least 3 of them show Theia moving on a random path, including making about ten percent orbit on Earths orbital line then doubling back and repeating that a few times before smashing in to the Earth instead. Maybe its just some vandalism for a laugh but some effort has been made. ~ R.T.G 02:30, 9 December 2008 (UTC)[reply]
Actually, I think the theory of how Saturns rings stay put is becoming pretty well developed - there are multiple causes of their stability - and it seems they all conspire to create the unusual density, structure and longevity of Saturns' ring system. The moons that stop the rings from coalescing - yet give them such defined structure are called 'Shepherd moons'. There has even been a recent discovery of rings around one of Saturn's moons (See: Rings of Rhea)...this is amazingly cool! SteveBaker (talk) 02:40, 9 December 2008 (UTC)[reply]
I seem to remember reading something not too long ago about an attempt to model Saturn's rings and it didn't work, they couldn't get them stable over long periods (it's possible they simply aren't stable over long periods and we're just lucky to be born at a time when they are there). --Tango (talk) 13:40, 9 December 2008 (UTC)[reply]
If you look at the animated image you'll see the Earth is staying still, whereas we know it's actually orbiting the sun, the the image is being rotated as you watch it to compensate for the Earth's movement. The movement of Theia combined with that rotation of the image is what gives the weird shape. --Tango (talk) 13:40, 9 December 2008 (UTC)[reply]
Tango, if you can't see something unusual about the Theia trajectory... also regarding the lucky timing of the rings, Jupiter, Saturn, Neptune and one of Saturns moons all have rings although only Neptune and Saturns are easy to see. Planetary rings ~ R.T.G 00:17, 10 December 2008 (UTC)[reply]
Well, its trajectory isn't a standard elliptical orbit because of the influence of Earth's gravity, but it's not far off. It just goes a little faster or slower than you would otherwise expect at certain points, which causes it to either catch up with the Earth or fall behind it. --Tango (talk) 00:38, 10 December 2008 (UTC)[reply]
Comet Shoemaker-Levy 9 illustrates something said earlier, that tidal forces may cause capture. During the two years before impact, the comet fragments orbited Jupiter (in a very eccentric ellipse). I'd guess that some other fragments escaped. —Tamfang (talk) 08:44, 14 December 2008 (UTC)[reply]

nepeta

Catmint and catnip seem to be used interchangably. Catmint is 'nepeta mussinii' and catnipt is 'nepeta cataria'. Cat have quite different reactions to each. Can that entry be refined?


Goetzds (talk) 01:28, 7 December 2008 (UTC)[reply]

Wikipedia: The encyclopedia you can edit! SteveBaker (talk) 01:54, 7 December 2008 (UTC)[reply]
Ouch! hydnjo talk 02:26, 7 December 2008 (UTC)[reply]
WP:SOFIXIT is the link you were looking for... --Jayron32.talk.contribs 02:44, 7 December 2008 (UTC)[reply]

Why do CFL bulbs take a while to reach full brightness?

Why do Compact Fluorescent Lights take a few minutes to "warm up" to full brightness? Incandescent bulbs seems to reach full intensity instantly. --69.149.213.144 (talk) 03:34, 7 December 2008 (UTC)[reply]

I think it is literally because they need to warm up. That is, they work better once they reach optimal temperature, much like a car. Not all compact fluorescent lights have this deficiency, however, or at least not to the same extent. Regular incandescent bulbs need to warm up, too. The difference is that they warm up in a fraction of a second, because they are so much less efficient, and that wasted energy all produces heat. StuRat (talk) 04:25, 7 December 2008 (UTC)[reply]
Fluorescent lamp is a bit technical, but has more details. 76.97.245.5 (talk) 05:05, 7 December 2008 (UTC)[reply]
In that article, it isn't really so clear that there is a difference between the types of ballast. I guess that your CFLs just happen to be older and still have magnetic ballasts (a.k.a. "reactive ballasts"). (Thanks for being an early adopter!) New CFLs should have electronic ballasts and start up just as fast. This is a little bit better described at Electrical ballastSebastian 09:17, 7 December 2008 (UTC)[reply]
I don't think the OP is talking about start up time but warm up time. As in the CFL has started but is not that bright Nil Einne (talk) 11:29, 7 December 2008 (UTC)[reply]
That's correct. They all turn on instantly (no flickering or delay), but are rather dim for the first few minutes. (I think CFLs are too small for magnetic ballasts anyway, no?) --69.149.213.144 (talk) 13:47, 7 December 2008 (UTC)[reply]
My suggestion, give those old CFLs to a heavy drinker, as a light that starts out dim will be less shocking to them during hangovers. StuRat (talk) 22:40, 7 December 2008 (UTC)[reply]
Light bulbs work by making something white hot. In your older light bulbs this is a hair thickness piece of metal which even the flame of a match would burn through. It is specially sealed so that it doesnt burn itself out. In a flourescent bulb is a gas which doesnt need to be so hot to reach white hot intensity. Compare it to the movie special effects trick for making a person appear to be on fire. The stuff used doesnt burn at such a high temperature as most fire but does burn hot. So, your flourescent bulb heats up a gas and even though it requires less heat, it still is hot and to heat the whole chunk of gas to white hot in one instant would probably give you an explosion. The electricity only provides heat and the whole inside of the CFL bulb lights up not just a little strand of metal. ~ R.T.G 23:14, 8 December 2008 (UTC)[reply]
According to Wikipedia there is such a thing as flourescent lighting that starts instantly ~ R.T.G 02:58, 9 December 2008 (UTC)[reply]

What puts the fluorescence in fluorescent lights?

What are the most common phosphors in commonly available fluorescent lights? Dragons flight (talk) 04:42, 7 December 2008 (UTC)[reply]

Have you actually read the fluorescent light article you linked to? There is copious information about the phosphors there. SteveBaker (talk) 05:08, 7 December 2008 (UTC)[reply]
There is some information, but most of it is not very specific (e.g. which Eu and Tb compounds?) and does a poor job of distinguishing what are the most common (as opposed to listing what is merely possible). I'd like to know which specific compounds are the most significant on the market today. Dragons flight (talk) 05:35, 7 December 2008 (UTC)[reply]
The article seemed pretty darned specific to me...the section Flourescent_light#Phosphor_composition says that the most common lamps use rare-earth doped phosphors - and provides a labelled spectrum of the light (Image:Fluorescent_lighting_spectrum_peaks_labelled.gif) - which (if you scroll down a bit from the image) lists the chemical composition of the phosphor corresponding to each peak. You won't do better than that because (as the article explains at some length) each tube manufacturer will tweak the mix of phosphors to get the exact most pleasing/natural color they feel is right. SteveBaker (talk) 06:04, 7 December 2008 (UTC)[reply]
Steve, I'm not sure if you intended to link to the spectrum image or not but incase you're not ware, if you want to link to an image without it appearing in the page you can use [[:Image:Cat.jpg]] Image:Cat.jpg (wow that actually exists) Nil Einne (talk) 08:51, 7 December 2008 (UTC)[reply]
(fixed!) Ooops! Yes, I knew - I was just being yelled at to "get away from that damned computer and do {somethingorother}" which broke my concentration. Sorry! SteveBaker (talk) 02:16, 8 December 2008 (UTC)[reply]

making Part II

Thank you for the information. However, some of it was a little too complicated for me. Let me ask another question.

Let's say I want to make Zestril (Lisinopril), a high blood pplyssure medication. Would I start with, say a plant (or some other natural being), then alter the chemical make up to create a substance. Then add several other products, chemicals, heat, transfer of the product to make a drip, then alter the drip to make another product, etc....In the end I would have Zestril.

What I want to know is what kind of initial product or plant would you start with? I'm talking all drugs, I just used Zestril as an example. I hope the question makes sense. —Preceding unsigned comment added by JelloTube (talkcontribs) 10:22, 7 December 2008 (UTC)[reply]

We don't know how to quickly select the initial product/plant to start with in drug discovery and only find out the right one via clinical tests. To compensate with the lack of data we try to obtain as much samples as possible of anything which have promising effects (for example a plant was used by native inhabitants to alleviate muscle pain while another mushroom is rumoured to have the same effect). The selection process are usually done through in toxicity and dosage tests in cell tissue, Animal testing and finally Clinical trials. Anything with adverse reactions or have nasty side effects will be removed. If we're lucky, probably out of 10,000 initial samples will yield one or two viable substances for drug use (and we have to monitor the long-term effect of that drug). This process is extremely long and expensive costing millions of dollars and years.--Lenticel (talk) 12:40, 7 December 2008 (UTC)[reply]
Lenticel is referring to the selection/discovery of the drug, but if you already know the chemical and just want to synthesize it then it would be a good idea to read the patent! Drugs are usually protected by patents, and in order to get patent protection you have to publish details of the chemical process. E. g. go to http://www.google.com/patents/ and enter "lisinopril", and one of the results is Process for the preparation of 1-(N 2-(S)-ethoxycarbonyl)--3 phenylpropyl-N6-trifluoroacetyl.... - just click on "Read this patent" and there it is. You'll probably have to do further research on cited prior art in order to find out how to make the direct precursors.
By the way, Zestril is not the same as lisinopril; the latter is one chemical, the former is a whole medical preparation containing the chemical. Icek (talk) 13:37, 7 December 2008 (UTC)[reply]
OK, a simple answer: You can buy chemicals at all levels of complexity, check Sigma Aldrich, a company that sells literally millions of different chemicals. Some are isolated from plants or other living sources, some are derived from petrol, but most are have been synthesized from these by chemical synthesis. It works like a construction kit - you assemble assemble building blocks and add molecular features. Chemist learn the rules for this game and if a chemical synthesis has been published then you can repeat the sequence. Cacycle (talk) 03:26, 8 December 2008 (UTC)[reply]
Thank you. All these were helpful. I've just always wondered how the complicated world of medications began. —Preceding unsigned comment added by JelloTube (talkcontribs) 08:44, 8 December 2008 (UTC)[reply]

Asking the gods of science for some help.

A member of my family is going to attent a game show of this format http://en.wikipedia.org/wiki/Deal_or_No_Deal

There are 22 boxes with progressively larger ammonts of cash in each box. I would like to ask if there are any factors which can give an advantage (something similar to monthy hall problem), something to increase the probability of winning?. —Preceding unsigned comment added by 77.243.73.133 (talk) 14:13, 7 December 2008 (UTC)[reply]

How much will I get if I tell you? Icek (talk) 14:31, 7 December 2008 (UTC)[reply]
The strategy is relatively simple: Keep track of which amounts are removed. When asked whether you quit, compute the average of the remaining amounts - that's the expectancy of what is in your box. If the amount you are offered is greater than or equal to the average, then quit, else continue. Icek (talk) 14:36, 7 December 2008 (UTC)[reply]
I think the traditional and most effective method is to sleep with the producer - but there may be ethical, moral, and sexual compatibility problems with this approach. DuncanHill (talk) 14:38, 7 December 2008 (UTC)[reply]
This has been asked on both the maths ref desk and here... interestingly the maths ref desk has produced far more constructive answers - take from that what you will! (Oh, and to the asker - please don't cross-post in future, it just ends up with effort being split.) --Tango (talk) 14:42, 7 December 2008 (UTC)[reply]
But, being on the Science Ref Desk, perhaps we should go beyond the simple mathematics of probability. For example, if offered either 100 million dollars or a 1 in 2 chance at 1 billion, just about everyone would take the sure thing, even though, on average, the gamble will pay better. StuRat (talk) 22:35, 7 December 2008 (UTC)[reply]
Calculating an average of the contents of the remaining boxes in the stress and pressure of the show may be unrealistic (at least until there are just a couple of boxes left). The likelyhood of making a slip in your mental math under the hot lights and with the adrenaline pumping is HUGE. What is needed is an algorithm that improves your odds AND which is really easy to remember and apply under pressure. I recommend sitting down with family members and picking a dollar amount that represents the amount of money that'll make a big difference to your life - an amount you would not be disappointed to walk away with. Let's say that amount is $20k. Now, instead of calculating an average - just add up the number of boxes that'll "make a difference" and the number that won't. If the offer they make you "makes a difference" and less than half of the boxes "make a difference" then take the offer - otherwise turn it down. If the offer they make doesn't "make a difference" turn it down unless none of the boxes make a difference either. This is a simple enough rule to keep in your head under pressure. This approach doesn't maximise your expected dollar return - but it does maximise the chances of you walking away with a huge smile on your face - which matters more IMHO. I very much doubt that (walking out of the studio) you'll very much care whether you won $100k or $200k. Considering the amount of money at risk here - you might want to consider getting someone to write a computer program to simulate various strategies so you can test them out. SteveBaker (talk) 02:12, 8 December 2008 (UTC)[reply]
Indeed, my answer on the Maths desk accounted for that. (It's a consequence of the diminishing marginal utility of money combined with the need for a risk premium. The additional utility of the extra 900 million is pretty small so isn't sufficient premium to be worth the risk.) --Tango (talk) 23:25, 7 December 2008 (UTC)[reply]

I'm sorry for splitting posts, I was corrupted to the dark side. I promise not to do it again unless money or women are involved :P Bastard Soap (talk) 09:06, 8 December 2008 (UTC)[reply]

Common descent

Not being very familiar with evolutionary biology, I was somewhat confused by Common descent: although it unambiguously states that the idea of a common ancestor means a single organism for all organisms living today, is this meant for specific types of organisms? Is it typically said that all animals have a common ancestor that isn't a common ancestor for plants? Or the finches: would it be normal to speak of a group of finches flying to the Galapagos Islands as together the common ancestors of today's finches? Nyttend (talk) 14:56, 7 December 2008 (UTC)[reply]

Any given population will have a most recent common ancestor, the more restrictive that population the more recent that ancestor will be (roughly speaking). The most recent common ancestor for all life on Earth was about 3 or 4 billion years ago (I forget when exactly), the most recent common ancestor for animals will be some time later than that (somewhere around 0.5 billion years ago, I think), the most recent common ancestor for humans is somewhere in the order of 10,000 years ago (estimates vary). You may also be interested in the identical ancestors point. --Tango (talk) 15:08, 7 December 2008 (UTC)[reply]
With asexual reproduction this is a fairly strait-forward question, since each organism has one and only one parent. But, with sexual reproduction, it becomes more complicated, since we each have 2 parents. Thus, we have 4 grandparents, 8 great-grandparents, etc. (assuming no interbreeding). This means 1024 forebears at 10 generations, over a million at 20 gens, and over a billion at 30 gens (around 1000 years). Now, this doesn't actually happen, because over those time scales you get a lot of interbreeding. However, when you go back hundreds of thousands of years, a rather large percentage of the human population back then became the forebears of any given individual now. So, there may have been more than one individual who is the common ancestor of everyone alive today.
A further complexity comes in with chromosomes. You have half the chromosomes of each parent, on average a quarter of each grandparent, etc. Again, that means that you would only have 1/1024 of the chromosomes of each ancestor from 10 generations back. And, since we only have 46 chromosomes, that means we have a 46/1024 chance of having a chromosome from each ancestor. Again, this math is altered based on interbreeding, but, if you go back far enough, the chances of having any one chromosome in common with a given ancestor is small. This was assuming random distribution, however. If a chromosome contained genetic material which made survival more likely, then you're more likely to have that chromosome from your ancestor. Then there's also the possibilities of genes moving from chromosome to chromosome and there are mutations to consider. So, how much genetic material we each have in common with our common ancestor or ancestors is quite complex of a question. And can you call someone your ancestor if you don't have any genetic material in common with them ? StuRat (talk) 16:42, 7 December 2008 (UTC)[reply]
These is certainly more than one common ancestor of any population (except possibly all life), since any ancestor of a common ancestor is a common ancestor. That's why it is the *most recent* common ancestor which is relevant. --Tango (talk) 16:57, 7 December 2008 (UTC)[reply]
Note that (with the exception of the Y chromosome, which is inherited only from the father, and of which most people have at most one copy) the odds are very poor that any single chromosome will be passed on intact for multiple generations. Genetic material is swapped between pairs of chromosomes by a number of mechanisms; crossing over (chromosomal crossover) is the most common. The likelihood of a crossover event taking place is roughly 1% per million base pairs (see centimorgan) of human DNA. Even the shortest non-Y chromosome (chromosome 21) is just shy of 50 million bases long, and the longest (chromosome 1) is about five times that.
In other words, if you examined one of your copies of chromosome 1 very closely, you almost certainly wouldn't find that it's identical to the chromosome 1 of one of your grandparents. It's much more likely to be grandma's chromosome 1 at both ends, with some of grandpa's chromosome 1 swapped in in the middle. This mixing and matching within chromosomes happens with each generation. In the example above, the odds are not 46/1024 that any given ancestor would have – by himself – supplied one of your chromosomes. Instead, the odds are essentially zero; no chromosomes are likely to have survived intact for ten generations without a crossover event. However, this does mean that the odds are pretty good that you will share at least some genetic material with each of your ancestors. Due to crossing over, it's likely that you'll have gotten a piece of DNA of some length from your eight-times-great grandfather. TenOfAllTrades(talk) 19:42, 7 December 2008 (UTC)[reply]
But to go back to the original question: No, it is not meant for specific types of organism only. The science of cladistics deals with formalizing the relationships of all living being. A recent common ancestor of all Galapagos finches was probably something we would call a finch. But the most famous ancestor of all birds would be a dinosaur. Richard Dawkins' The Ancestor's Tale is an excellent book, tracking back the ancestors that humans share with increasingly larger parts of life on earth. --Stephan Schulz (talk) 22:39, 7 December 2008 (UTC)[reply]

Displaying carbon and hydrogens in Symyx/ISIS draw

I'm trying to use Symyx (formerly known as ISIS draw) to draw some molecules but I can't get it to display the carbon and hydrogen atoms. I want all atoms of the molecules to be displayed. Anyone know how I can do it? ----Seans Potato Business 16:53, 7 December 2008 (UTC)[reply]

In my ISIS Draw...select a molecule, and then Edit Molecule (double-click the seelcted structyre, use right-click popup, or use the Object menu). There, in the Atom pane, you can control how the hydrogens are displayed. It looks like this always gives condensed structures ("CHn") rather than drawing explicit bonds to H atoms. DMacks (talk) 19:18, 7 December 2008 (UTC)[reply]
This fixes the hydrogen isssue but not the carbon issue. I'm also unable to get the program to display the molecule at right angles. If I click Chemistry > Clean then bonds adopt more realistic angles which is not what I want. Trying to drag them into regimental order is labour-intensive an ineffective. ----Seans Potato Business 20:38, 7 December 2008 (UTC)[reply]
Not sure I understand what you mean (i.e., what you want it to to look like). Actually, I am sure I don't understand. Could you give us a sample diagram of what style you're trying to accomplish? DMacks (talk) 21:21, 7 December 2008 (UTC)[reply]
In this image, in the upper section, you see angled bonds (which I don't want) and in the lower section, regimental, right-angled bonds which I do want]. I also want every carbon atom to be displaced. I know it's possible somehow, because I'm looking at it in a text book. ----Seans Potato Business 21:43, 7 December 2008 (UTC)[reply]

A California earthquake causing an associated blackout and causing people to see the Milky Way

Hi. There was an earthquake in California that caused a blackout at night, causing people to run outside and see the Milky Way for the first time. Authorities and a local observatory were flooded with calls. I have also posted this at Talk:1989 Loma Prieta earthquake, which might have been responsible for this blackout, but it might also have been the 1994 Northridge earthquake, which struck in the middle of the night, and since I want this to be included in an article and I don't want to post OR, does someone know which earthquake it is, and preferably find a reliable source as well? Thanks. ~AH1(TCU) 18:37, 7 December 2008 (UTC)[reply]

Here's information on a related event during the Northeast Blackout of 2003: [3]. --Jayron32.talk.contribs 18:47, 7 December 2008 (UTC)[reply]
I'm guessing not Loma Prieta; I didn't think to look at the sky, but lights were on in patches soon after dark. —Tamfang (talk) 08:50, 14 December 2008 (UTC)[reply]

Rhizobium

Hi the article on Rhizobium says that the bacteria convert atmospheric nitrogen to ammonia. My question is can plants use this ammonia directly to form their proteins etc or does it need to be converted to other molecules - e.g. nitrates before the plants can use them? Thanks. —Preceding unsigned comment added by 139.222.240.167 (talk) 19:58, 7 December 2008 (UTC)[reply]

See Nitrogen fixation#Biological nitrogen fixation and Nitrogen cycle#Assimilation. It looks as though the ammonia is quickly converted to ammonium ions, which are what the plants use. No doubt someone who understands this far better than I will soon be along with additional information. Deor (talk) 21:47, 7 December 2008 (UTC)[reply]

Long train journey

I had the misfortune today of having to catch a train from Preston to Southampton which took nearly six hours! I did a very simple calculation and worked out that the average speed of the train during the journey was 52 mph which seems very slow, particularly as it is supposed to be a main line service.

The first leg of the journey from Preston to Stockport via Bolton took 1:39 and is about 35 miles (according to a quick path-drawing excercise following the general route of the line in Google Earth). This averages around 21 mph although there were quite a lot of stops.

The main part of the journey, from Stockport to Southampton via Stoke, Stafford, Birmingham, Oxford and Reading (but with more stops than that, about 15 stops in total) took 4:09 and is about 214 miles. This works out at an average of 52mph.

The trains [[4]] are capable of doing 125 mph. I assume that not all of the lines it went on allow that speed and obviously slowing down and stopping at stations all wastes time but it stills seems very slow indeed to me. The Virgin Voyager trains seem to accelerate quite fast so I can't believe that and slowing down adds so much to the journey time.

If the train could average 80mph then it would easily do the journey in about 3 hours, which is a bit more bearable but why does going 250 odd miles take such a long time? I think I'll fly next time I want to travel such distances! Much quicker and usually cheaper too. —Preceding unsigned comment added by 62.249.220.179 (talk) 21:01, 7 December 2008 (UTC)[reply]

Slowing down, stopping, waiting in a station, and getting back up to speed again does take a significant amount of time. Say it adds on 5 minutes per station, you say there were about 15 stops on the main leg, that's 1hr 15 mins added on to your journey. There may also have been additional delays due to waiting for other trains to get out of the way or parts of track where the train had to go slowly (damaged rails, damaged bridges, sharp corners, etc.), which all adds up. --Tango (talk) 21:35, 7 December 2008 (UTC)[reply]
5 minutes per stop seems quite low. That might be how long they are actually stopped, but adding in the slow down and accel and you can probably double that. StuRat (talk) 22:15, 7 December 2008 (UTC)[reply]
Indeed, that was a conservative estimate. I was guessing at 3 minutes stationary and 1 minute breaking and accelerating (it will spend more than 1 minute doing those things, but it is moving, if slowly, so not all the time is lost). --Tango (talk) 23:21, 7 December 2008 (UTC)[reply]
It usually works out quicker although more expensive if you go via London. That's where the fast trains go. Very annoying for us provincials. Itsmejudith (talk) 23:29, 7 December 2008 (UTC)[reply]
Yes, it's just under five hours via London according to Traveline. It's eight hours by coach but that includes an hour's wait in Birmingham, giving you time to do some shopping.--Shantavira|feed me 09:05, 8 December 2008 (UTC)[reply]
The biggest problem with this sort of journey is that the rail system was never designed that way. In fact it wasn't designed at all, but grew somewhat organically depending where the railway companies (no national organisation in those days) thought that they could make some money. Presumably no-one thought that there would be much call for paying customers to travel your route, so you have to make use of the tracks that actually were built (and those not subsequently ripped up in the time of Beeching). Cross-country routes like this one are generally hampered by the need to use parts of the major routes and they have to wait their turn to fit in with the express trains. I've had my share of journeys like you describe, just try your best to feel noble about your reduced carbon footprint. Mikenorton (talk) 18:32, 8 December 2008 (UTC)[reply]
So lets say the train does 0 to 60 in ten seconds after every stop... not one for the old folks anyway. Wouldnt work the best if you were standing at the toilet. ~ R.T.G 12:50, 9 December 2008 (UTC)[reply]

Citrus identification

Can anyone identify this citrus tree? The fruit are about 3 inches (7.5 cm) in diameter, with orange skin and greenish pulp. The taste is like a lime, and very sour. [5] --Amble (talk) 23:18, 7 December 2008 (UTC)[reply]

Likely it's Mandarin limeCitrus limonia is a hybrid. Julia Rossi (talk) 01:07, 8 December 2008 (UTC)[reply]
Thanks. I considered that one but doubted it because of the flesh color; it's greenish-yellow instead of orange. --Amble (talk) 05:48, 8 December 2008 (UTC)[reply]
I found it tricky too, but it's the pulp that makes it different. The article could use more images. : ) Julia Rossi (talk) 06:01, 8 December 2008 (UTC)[reply]


December 8

Carbs from Vegetables

Sort of 3 questions:

1. Does anyone know of a place that lists the amount of carbohydrates, protien and fats in typical vegetables (brocolli, colliflower, protatoe, pumpkin, carrot, etc.)?

2. What is the scientific consensus on eating non-starch vegetables (ie no potatoe or pumpkin) as the only source of carbohydates in a diet (ie no bread/rice)? Not asking for medical opinion, I just want to know if scentifically the body can get all the carbs it needs from only non-starchy vegetables.

3.Before cultivation, what was the source of carbs for hunter/gatherers? And in what period did the majority of the earths population start eating mainly cultivated food instead of hunting/gathering for food. --Dacium (talk) 01:39, 8 December 2008 (UTC)[reply]

1. USDA food database
2. Humans don't need carbohydrates at all. See gluconeogenesis. If a chemical is classified as "nutritional fiber" that means that humans cannot digest it, and while human intestinal bacteria can digest some sorts of fiber, they (the bacteria) mostly live in the colon where monosaccharides cannot be absorbed into the body anyway. Icek (talk) 02:22, 8 December 2008 (UTC)[reply]
3. See Neolithic Revolution.
Icek (talk) 02:22, 8 December 2008 (UTC)[reply]
Thanks! About number 2, why is it that low carb diets seem to be not recommended scientifically? Upon reading most of the articles I could find here (such as low carb diets etc) it appears the lack of carbs itself is ok, but they don't recommend it because people eat to much fat or protien?

If a diet is just non-starch vegetables, eggs, nuts and lean meat (ie no excessive protien or fat), is it scientifically considered healthy?--Dacium (talk) 02:38, 8 December 2008 (UTC)[reply]

Actually, most recent science actually supports the low-carb, high-protein diet as the most healthy. The "low fat, high carb" diets of the past have been more recently shown to be quite a bit LESS healthy. This radio broadcast: [6] discussed in detail a recent Israeli study that compared 3 diets: The "atkins style" low carb diet, the "ornish-style" low fat diet, and the "mediterranean diet" seen as lying somewhere between the two. It found that the rank-order for healthful outcomes among practitioners of the diet was 1) Atkins 2) Mediterranean and 3) Low-Fat. Here is the original article, published in the New England Journal of Medicine: [7] Here's another article: [8] that cites two different studies from 2004 which show unequivocally that low-carb diets beat low-fat diets in lowering both blood cholesterol levels and blood triglyceride levels. We have a carry-over from the old days when "low fat" was everything, but most modern studies seem to be leaning more and more towards "low-carb" diets. --Jayron32.talk.contribs 03:47, 8 December 2008 (UTC)[reply]
The study you mention is a weight loss study. Even if a lot of people's health would benefit from losing weight, a healthy diet is a diet that keeps your weight the same, and that you can live on for years and years without suffering from any nutritial deficiencies. As for your claim that the high-protein diet is the most healthy, neither of the articles even discusses if people get enough vitamins and minerals when they eat low-carb, high-protein. I don't recommend eating rice or bread, but vegetables and fruit (= carbs) are important sources of vitamins and minerals. Lova Falk (talk) 20:56, 8 December 2008 (UTC)[reply]
When I hear people making such arguments about getting sufficient vitamins and minerals I wonder whether they don't realize that one can easily get these micronutrients in concentrated form e. g. as pills which is often more convenient than e. g. eating relatively large amounts of carrots for a little vitamin A. After all, scientists have figured out which chemicals are behind the vitamins; it's not like the 18th century when it was only known that lemons and sauerkraut prevent scurvy, it has been pinned down to ascorbic acid. So why not use modern science and technology? I don't want to say what's a healthy diet but that vitamin deficiencies are actually easily solvable problems (vitamin pills aren't expensive either).
By the way, it seems to me that the results from the NEJM article cited by Jayron32 has more to do with the psychology of eating habits than with healthy nutrition. Icek (talk) 01:31, 11 December 2008 (UTC)[reply]

This site has it all. -hydnjo talk 04:01, 8 December 2008 (UTC)[reply]

Non-starchy vegetables are generally high in sugars, so they do supply "carbs". They are generally also high in micronutrients and in fibre, which is why they are a useful part of the diet. If you fancy fish and broccoli for dinner, with no potatoes, go ahead, but adding one or two small potatoes won't kill you either. Itsmejudith (talk) 08:49, 8 December 2008 (UTC)[reply]

Mushroom Substrate

what makes a good mushroom substrate, that doesn't involve vermiculite? i can't find one on the internet so i'm asking u guys. —Preceding unsigned comment added by 76.14.124.175 (talk) 02:40, 8 December 2008 (UTC)[reply]

At Fungiculture we've got a substrate section[9]. And google has a range[10], but what is "good" needs someone who knowsJulia Rossi (talk) 02:48, 8 December 2008 (UTC)[reply]

thanks! —Preceding unsigned comment added by 76.14.124.175 (talk) 03:14, 8 December 2008 (UTC)[reply]

Fixed link – you're welcome,  : ) Julia Rossi (talk) 04:31, 8 December 2008 (UTC)[reply]
Penn & Teller ? StuRat (talk) 14:24, 8 December 2008 (UTC)[reply]

Compressing Water

I've heard that compressing water (like compressing air in an air compressor) is extremely difficult, borderline impossible. Why is this, when there is plenty of space between water molecules? [[User:Shane 42]] (talk) 04:09, 8 December 2008 (UTC)[reply]

There isn't much space between the liquid water molecules...when water changes from liquid to solid, it's volume actually increases! With most liquids the volume of the liquid and solid is the same - so most liquids are no more compressible than their corresponding solids. The molecules only separate out when they form a gas - ang from 20001 to 20002 atmospheres (perceived). Water is compressible, but only at pressures comparable to 20000 atmospheres. HTH, Robinh (talk) 08:14, 8 December 20d the volume of one gram of gaseous water (steam) is MUCH larger than one gram of liquid water or ice. Hence, steam is very compressible - but water and ice are not. SteveBaker (talk) 04:51, 8 December 2008 (UTC)[reply]
See equation of state#Other equations of state of interest (stiffened equation of state). Water is like air already under 20000 atmospheres, so changing from 1 to 2 atmospheres (real) pressure is like water changin08 (UTC)
Due to the hydrogen bonding between water molecules, there is actually little to no space between them - the formation of crystalline ice disrupts the hydrogen bonding, which is why water expands when it changes state to ice. Bobzchemist (talk) 18:07, 8 December 2008 (UTC)[reply]

UK DNA taken from criminals

How do the police get this? Kittybrewster 08:23, 8 December 2008 (UTC)[reply]

Usually with a cotton swab on the inside of the cheek.--Shantavira|feed me 09:10, 8 December 2008 (UTC)[reply]
"So Mr Jones - would you care to explain how we came to find your DNA all over that cotton warehouse down by the docks on the night in question?" SteveBaker (talk) 13:56, 8 December 2008 (UTC)[reply]

Human body voltage

I just held the leads of my multimeter, and sure enough, there was a 60mV difference between my left hand and my right hand (the right hand being the "ground"). Sure enough, when I switched hands on the leads, it read -60mV, and when I let go, it popped back to 0, so I doubt it's a fluke of the multimeter itself.

Does anyone know of any articles or external links as to what my be causing a measurable electric potential between a human's extremities? And is it actually normal, or am I turning into Elle Bishop? :) --Link (tcm) 08:43, 8 December 2008 (UTC)[reply]

60mV is an incredibly small difference - it could easily be caused by some kind of inductive pickup in the wires leading to the meter. I would do two things:
  1. Try doing the experiment while standing in different places in the room - also outdoors - and see if this number changes (I bet it does)
  2. Try reversing the leads an seeing if it still reads 60mV-ish...which would suggest an inaccuracy in the meter.
I'm pretty sure you aren't abnormally turning into "The Human AA". Be careful with measuring yourself with a meter...people have died trying to accurately measure their resistance on the ohms scale! (Although you should be OK on the volts scale).
SteveBaker (talk) 13:54, 8 December 2008 (UTC)[reply]
Indeed - be careful! Whatever you do don't pierce the skin, once you are through the skin your resistance is very low and the high voltage used to measure it can kill you (as Steve says, measuring voltage should be safe, it's a pretty passive test, but it's not worth risking it). --Tango (talk) 15:29, 8 December 2008 (UTC)[reply]
That'd be very difficult to do with a battery-powered meter, as the voltage cannot be possibly higher than the one provided from the batteries, and, the last time I tried that, even the resistance between the two sides of my tongue was several kilohoms. -- Army1987 – Deeds, not words. 15:35, 8 December 2008 (UTC)[reply]
The thing about measuring across the tongue is that your heart isn't on the path between the two probes - so it's relatively safe (I say relatively - because if one hand happens to be touching some metal part of the meter...and the other probe is on your tongue - then maybe you are still in trouble). But measuring resistance from one hand to the other puts your heart right in the firing line. The "I did it and got away with it" argument also applies to crossing freeways while blindfolded. SteveBaker (talk) 16:37, 8 December 2008 (UTC)[reply]
Nevertheless, it has happened. The voltage can easily be higher than that of the batteries, you just need a transformer, although actually now I think about it is probably current that is the risk, not voltage. --Tango (talk) 15:38, 8 December 2008 (UTC)[reply]
It's the current that's the danger, I think there was a Darwin Award for someone who killed himself with a multimeter - the electrodes pierced his skin, and the current caused a heart attack. DuncanHill (talk) 15:41, 8 December 2008 (UTC)[reply]
In this case, the current isn't enough to zap and kill a person. However, it is enough to cause fibrillation. The chance of fibrillation in a healthy adult is small. In a person with a pacemaker or heart disease, the risk is increased. Whenever I hear about the volt/current argument, I can't help but remember reading specs on a railgun that used a teravolt generator that had very low current. The warning was: "They say volts won't kill you. That is true. A few thousand teravolts won't kill you. It will vaporize you." -- kainaw 15:52, 8 December 2008 (UTC)[reply]
Yes, the current is the danger (or more precisely the charge, you need around 60 mC IIRC), that's why I mentioned my resistance. Assuming the ohmmeter uses 4.5 V, and a resistance of 30 kΩ, you'd get 0.15 mA, so you'd need to wait 400 seconds before any significant danger. YΩMV, but I don't think that in "normal" circumstances you could get a much higher current through your body with a "normal" multimeter. (BTW, are there really transformers working with DC?) -- Army1987 – Deeds, not words. 16:03, 8 December 2008 (UTC)[reply]
Every time I say this - we have the same debate - the fact is that more than one person has actually, for real, died from doing this. So if your theory says that it can't happen then you need to find a new theory because your old one just met with reality and didn't come off so well! SteveBaker (talk) 16:37, 8 December 2008 (UTC)[reply]
Where did you get the 30kΩ figure? Are you remembering that we're talking about the resistance of the inside of the body (you have to pierce the skin first) which is essentially salt water? Salt water has a pretty low resistance. --Tango (talk) 16:43, 8 December 2008 (UTC)[reply]
Sorry, but can we have a WP:RS that says that someone died from the electric shock of a passively used multimeter? I can easily imagine all kinds of accidents with a multimeter and live cables, but I have trouble believing in the lethal power of a bog-standard battery that is used in many millions of toys without adding in a lot of stupid-smart electronics. --Stephan Schulz (talk) 16:47, 8 December 2008 (UTC)[reply]
The award Duncan refers to is at http://darwinawards.com/darwin/darwin1999-50.html. I had not understood that the winner had done that. If you reach blood, resistance will be low enough. (But it's somewhat unlikely to happen accidentally, at both terminals. And measuring voltage as the OP was doing shouldn't be very dangerous.) -- Army1987 – Deeds, not words. 16:52, 8 December 2008 (UTC)[reply]
I haven't re-read the Darwin award, but I believe it was done intentionally. I agree it's not likely to happen by accident, but nevertheless caution is warranted. --Tango (talk) 17:06, 8 December 2008 (UTC)[reply]

← (e.c.) Also, if you have a pacemaker you can kill yourself with a smaller current, indeed those body fat measuring scales recommend that pacemaker users don't use them. -- Army1987 – Deeds, not words. 17:10, 8 December 2008 (UTC)[reply]

A factor that must be considered is the internal resistance of the voltage source. If the internal resistance is high, it will reduce the current for any given external resistance. That's why "shocking coils" do not harm people. —Preceding unsigned comment added by 98.17.46.132 (talk) 17:20, 8 December 2008 (UTC)[reply]

I think stun guns have caused death. Does anybody know the open-circuit voltage of a typical stun gun? ("Open circuit" means measured with a very high-resistance voltmeter. I don't think voltage can be measured without imposing some sort of load - shades of Heisenberg.) Some stun guns use body contact from 2 prods. Others use penetrating barbs on the end of wires; the barbs benetrate the skin and stick there to give the shock. The barb kind is obviously more dangerous, unless the prod type touches an open cut, mosquito bite, etc. Sweat on the skin also enters into it. —Preceding unsigned comment added by 98.17.46.132 (talk) 17:40, 8 December 2008 (UTC)[reply]

Does anybody know the internal resistance of a typical stun gun? If the internal resistance and open-circuit voltage are known, the current can be calculated for any given external load. If the external load is assumed to be zero, that will reveal the maximum current that the stun gun can impose. It should be less than lethal. —Preceding unsigned comment added by 98.17.46.132 (talk) 18:02, 8 December 2008 (UTC)[reply]
Are you claiming that a stun gun applied to the internal body (below the heavily resistant human skin) is in no way lethal? Much of this topic is discussing the possibility of harm or death by applying voltage/current below the skin - especially to the blood, which is highly conductive. -- kainaw 18:25, 8 December 2008 (UTC)[reply]
In general, the probes for a stun gun should be close together, which would make the current path relatively local. This would tend to reduce the risk of applying fatal current to the heart, and is rather different than applying a multimeter or other current source to both hands. Dragons flight (talk) 19:08, 8 December 2008 (UTC)[reply]
I don't believe the Darwin Awards story. Just because some guy from the US Navy says it's true doesn't make it true. Note the word "Unconfirmed" at the top of the article. Where is the original report? And if you can kill yourself with a 9-volt battery and two pins, why has it happened only once in recorded history? And why never with a 12-volt car battery, or a 9-volt plug-top transformer, or a PC motherboard with all those jumper pins sticking up?
Anyway, returning to the question, I can get very close to the same results as the OP if I repeat the experiment enough times. Most of the time, though, the readings are apparently random in polarity and magnitude. My guess is that the voltage across your fingers is some messy waveform related to the sinusoidal mains voltage that your body picks up like an antenna, and to your body position and skin resistance. A cheap DVM set to DC will probably convert this waveform into a more or less random reading depending on the shape of the waveform. If you've ever looked at the waveform on an oscilloscope when you hold a high-impedance scope probe in your finger then you'll know what I mean. Imagine that the DVM is taking samples at random points on that waveform, or at least trying to average it with a very poor averaging circuit. --Heron (talk) 20:50, 8 December 2008 (UTC)[reply]
Electrical current flow in the human body is 3-dimensional. Usually, we think of electrical current as electrons flowing between 2 points in a narrow stream through a wire - essentially a 1-dimensional flow. However, electrons repel each other, so the flow in a 3-dimensional conductor is different. The following simple demonstration will show this. Fill a cup or glass nearly full with tap water. Dissolve some table salt in the water. Put the two prods of an ohmmeter in the water and adjust the meter to show the resistance between the prods. Now move the prods closer together, then farther apart. There will be no noticeable difference in resistance regardless of the spacing of the prods. This is because the electrons can spread out and have a great many parallel paths between the two prods. Unlike a typical wire-resistance measurement (essentially one-dimensional), the width of the salt-water conductor is very large compared to the distance between the prods - hence the current path is 3-dimensional. (The current flow resembles, in 3 dimensions, the "lines of magnetic force" shown by iron filings on a sheet of paper placed over a bar magnet.) Some electrons in the salt water demo will actually move away from the positive electrical pole at first, then swing around toward it. Between the two electrical poles, electron distribution will have approximately an even density across all parts of a plane normal to electron flow. (The boundaries of the cup or glass, and the surface of the water, are the approximating factor, as compared to a container of infinite size.) In the human body, electrical current from an externally-applied voltage will flow in the same manner. If a voltage is imposed between two points on the torso on opposite sides of the heart, and the heart is not directly between those two points, the spread-out of current will still give the heart the full current of that plane. (A complicating factor is that different bodily organs will have a different specific resistance. The outer boundary of the body is another complicating factor.) If a voltage is imposed at two points on the same arm or leg, the heart will experience very little of the current. So it is torso-applied voltage, or hand-to-hand applied voltage, that is lethal when the voltage is sufficiently high and the internal resistance of the voltage source is sufficiently low. —Preceding unsigned comment added by 98.17.46.132 (talk) 21:06, 8 December 2008 (UTC)[reply]

A 60mV difference is nothing. There's about a 200 V difference in the air between your head and your feet: [11], due to the inherent potential gradient in the atmosphere... --Jayron32.talk.contribs 21:59, 8 December 2008 (UTC)[reply]

Hold on there. Between two points, vertically spaced with 2 metres, there might be a 200 volt voltage, but only until you connect the points with a human body or another conducting object. When you do that, you short-circuit the voltage you originally had. As an equivalent example, consider a 9 volt battery. What is the voltage between the electrodes? It's 9 volts, of course, but what happens if you connect them with a piece of wire? The voltage drops to essentially zero. —Bromskloss (talk) 13:05, 9 December 2008 (UTC)[reply]

This anecdote of death by Simpson 260 sounds like an urban legend, since the meter does not place a 9 volt battery in series with the two test leads. Instead it has circuitry including the calibration rheostat, perhaps scaling resistors, and the meter movement in series. The present Simpson 260 manual [12] says (p9) the maximum short-circuit current on the ohms times 10000 scale, where the 9 volt battery is used, is 75 microamperes. For the RX1 and RX100 scales, it uses just a 1.5 volt battery. The meter movement itself is 20,000 ohms per volt and 50 microamperes full scale. The short circuit current on the RX1 scale is 125 mA, but note that is for a SHORT CIRCUIT, which the human body is not. I have seen safety bulletins in the past which contained myths intended to scare readers away from doing things which might lead to injury, such as if a person did the meter experiment with a source of greater current at higher voltage, or with an ammeter and a high energy source. I do not deny that under contrived conditions such as implanted electrodes it might be possible to cause electrocution with a 9 v battery. Edison (talk) 04:02, 10 December 2008 (UTC)[reply]

The following site says there has been several hundred deaths from stun guns in Britain alone. It also says 50,000 is typical for a barb type stun gun. —Preceding unsigned comment added by 98.17.46.132 (talk) 06:39, 11 December 2008 (UTC)[reply]
Here is the web site I mentioned above:
http://www.csmonitor.com/2008/1211/p01s01-wogn.html
The voltage for the barb-type stun guns mentioned is 50,000 volts. The internal resistance of the voltage source is not mentioned. Also, the stun-gun deaths were 320 in the US and Canada.

Longevity

I was just wondering - even if we extend average life expectancy to beyond 90 or 100, wouldn't we spend a good chunk of those last years blind deaf and frail - as we haven't worked out how to fix age-based deterioration in sight and hearing amongst other things. Paul Austin (talk) 11:09, 8 December 2008 (UTC)[reply]

Well, my visual prosthesis and cochlear implants are working fine, but that doesn't help my ... other thing ...begins with "m" ... what was the question ? Gandalf61 (talk) 12:19, 8 December 2008 (UTC)[reply]
Actually - I think the reverse is true. We've made such improvements in fixing things like eyesight, hearing and such that now we find many people are dying while they still have a lot of productive years ahead of them. SteveBaker (talk) 13:48, 8 December 2008 (UTC)[reply]
Have we really? My aunt is slowly getting blind and there is nothing anybody can do about it (I don't know her condition). Anyway, instead of jokes and opinions, isn't there any research done? The quality of the last ten years of people's life now compared to a previous period. Should be possible to do, but has anybody done it? Lova Falk (talk) 16:51, 8 December 2008 (UTC)[reply]
Actually, I am going to disagree with SteveBaker here. In the U.S. at least (can't speak for elsewhere) we have the means to both extend the life and improve the quality of that extended life; however we lack the political will to do so in an effective and equitable manner for all people. Essentially, the haphazard manner in which healthcare is handled in the U.S. actually provides both problems (i.e. people dying while still productive AND people living well past the usefullness of their own bodies). Both are solvable with modern medical technology; but given the poor access most people have to health care, it is likely we won't see any widespread universal system for providing both kinds of care to all people. --Jayron32.talk.contribs 21:54, 8 December 2008 (UTC)[reply]
I know a number of people in their 90's, in the U.S., who live self sufficiently and participate in a variety of activities. Time eventually catches up with them, but many have had a "hale and hearty" lifestyle well past 90. I knew a lady of 104 who was in a wheelchair and in a nursing home, but who could see and hear fine and was apparently of sound mind. Certainly some people have a stroke or Altzheimers decades earlier, or become blind or deaf. Edison (talk) 03:21, 10 December 2008 (UTC)[reply]

Island of Stability

Does anyone know of any images representing the graph of stabilities of nuclei, other than the one linked on the article? Specifically I was looking for something showing the 'sloping' of elements towards stability.

Cheers,

Cyclonenim (talk · contribs · email) 14:27, 8 December 2008 (UTC)[reply]

In the first picture in the article Island of stability, height indicates stability, so you can really see that sloping towards the stable peak. Click on the picture to get a higher resolution, it was awfully hard to read on my screen at least. EverGreg (talk) 15:36, 8 December 2008 (UTC)[reply]
I agree that it's a good image and very helpful; however, I was looking for a kind of inverted image that showed the most stable nuceli in a sort of ditch. The reason for this was because the example we were given in class was like a ball rolling down a hill, and it'd be a good way to indicate it. —Cyclonenim (talk · contribs · email) 17:51, 8 December 2008 (UTC)[reply]

Wikipedia, Censorship and Child Pornography

I was reading about how the UK has banned the Wikipedia article on the Scorpion's Virgin Killer because the original album cover had a naked child. I understand that Wikipedia is not censored. But it made me wonder what images are in the child pornography article. I hesitate to look at the article because I'm at work (not to mention I personally might find it disturbing). Can an editor upload hard-core child porn and justify it by saying Wikipedia isn't censored and that's what the article is about? Or how about showing the images that Gary Glitter was imprisoned for? 216.239.234.196 (talk) 18:20, 8 December 2008 (UTC)[reply]

An editor can upload any image and make any claim he or she would like to make. That doesn't mean that the other users have to accept it. With far more people acting in a sane and reasonable manner, those who just want to be a dick are kept in check. -- kainaw 18:23, 8 December 2008 (UTC)[reply]
For the record, child pornography presently has no images of children or of pornography. Dragons flight (talk) 18:26, 8 December 2008 (UTC)[reply]
Also, I think you misunderstand the whole not-censored idea. If something is morally opposed, Wikipedia will not remove it as it is not censored to personal belief. The only circumstance in which something is removed is if it is against the law where the servers are held (I think it's Los Angeles but I could be wrong). Child pornography images (not potential images but explicitly proven images) would have to be removed by law in LA. —Cyclonenim (talk · contribs · email) 18:35, 8 December 2008 (UTC)[reply]
Actually the servers live in Florida, but your point is otherwise correct. Dragons flight (talk) 18:59, 8 December 2008 (UTC)[reply]
So if Florida rules that Virgin Killer album is illegal, then it will be removed? What about images that have not yet been ruled child pornography? What's to stop somebody from uploading child porn images to the child porn page and then (accurately) claiming that if they haven't been ruled illegal yet, then they must stay? I guess the other editors, right?
Also, I just realized that I accidentally posted this to the Science desk. I meant to put it in the Humanities desk. Is it OK if I move it? 216.239.234.196 (talk) 19:06, 8 December 2008 (UTC)[reply]
You can move the question, but it has already been answered. One user demanding that an image is legal and must be kept is not enough to keep it on Wikipedia. This is a community. One use cannot force an image to be on a page against the wishes of the community. So, the community will keep a user from exploiting Wikipedia policies to be an annoyance. -- kainaw 19:09, 8 December 2008 (UTC)[reply]
See the Miller Test. I think everyone would agree that an album cover has "artistic merit", and so is going to be legal in the US pretty much regardless. Though we don't have the finality of a court of law, I think in general Wikipedians are likely to apply a similar standard to Miller in deciding whether something should be included or not. Dragons flight (talk) 19:13, 8 December 2008 (UTC)[reply]
It also should be noted that the furor over this album cover is rediculous. I can buy this album, underage penis and all, at my local WalMart. I checked. The greater issues are legion, however:
  1. A non-governmental agency is allowed to control content for ISPs which cover 95% of Britain, without means for formal redress should mistakes be found.
  2. The method of censorship is unneccesarily disruptive (the use of transparent proxies) where other, less disruptive means are availible and easy to implement. The end result (preventing users from seeing the image) could have been achieved without funneling access from essentially all of the UK through 12 IPs. Furthermore, even using the transparent proxy method, the ISPs involved could implement an XFF standard which would essentially allow a users original IP address (and not the proxy's) to be seen by Wikipedia.
  3. The censoring of the image can be easily bypassed by using subtle variations on the URL, which means that the censorship of the image itself is both unreasonably disruptive to the free flow of information (see above) and entirely ineffective in actually censoring the image.
  4. The blacklist in question has blacklisted BOTH the image and the article about the album. One could make a justification for censoring the image which is consistant with "community standards" over child-pornography. However, the blocking of access to the text of the article, which contains nothing at all which could be construed as pornographic, is outrageous, and is again why problem #1 (having no means of redress) is such an issue.
  5. The parties involved (the ISPs individually and the IWF specifically) have been unreasonably flippant about working with Wikipedia or the Wikimedia Foundation to solve the problem, despite the relative easy with which a solution could be worked out, and the potential media shitstorm that could result by being so flippant. If the IWF or the involved ISPs responded to the problem in a reasonable manner, this would have been solved days ago. The fact that they seem to be uninterested in working out a solution has resulted in an unneccesary escalation of the problem in the media, which is NEVER a desirable outcome.
None of these problems have anything at all to do with the actual censorship of the objectionable image. Arguements could still be made that the image should be censored; however that is NOT the major issue at hand here. The major issue is the irresponsible manner in which the involved parties have handled the censorship. --Jayron32.talk.contribs 21:10, 8 December 2008 (UTC)[reply]
For further info about the IWF blocking problem see Wikipedia:Administrators' noticeboard/2008 IWF action. Gwinva (talk) 21:34, 8 December 2008 (UTC)[reply]
Also, didn't Wikipedia move its servers to San Francisco? (Also I think the Nevermind album also has a similar image if I remember correctly but it doesn't seem to be banned). ~AH1(TCU) 23:29, 8 December 2008 (UTC)[reply]
Servers still live in Florida. The administrative offices are in SF. Dragons flight (talk) 00:44, 9 December 2008 (UTC)[reply]
Yeah but the Nevermind album is a pic of the real life miracle of a babys ability to swim before he can walk. The other one is a picture of a little girl with something unusual looking around her vagina and, is it a picture of a "virgin killer" or a picture of what a "virgin killer" should or has targeted? Valid arguement against it but as per Wiki usual people will compare this picture to the Nevermind album, the added tasks and descisions regarding censorship, showing an oil painting of Mohammed and say "Oh if you censor that we wont be able to show anatomy or naked people kissing." Rubbish but hopeless to argue with. Well done for pointing it out anyway. It is a pity the word "pornography" dominates the debate about a picture which is obviously part of an artists protrayal of maliciousness towards a small girl. Sex is not evil but the creation of that album cover was certainly not all halos and polka dots. So long as people farm animals against their own animal cruelty laws, morals will be confusing unless directly affected in a negative way. Closed Community - 1 Wider Community - 0, Open to anything - 1 Open to everything - 0 ~ R.T.G 00:22, 9 December 2008 (UTC)[reply]

It is not proven despite numerous studies that the viewing of "real" child pornography, or violent pornography, leads to abuse or proves an intent to abuse. Therefore, anyone criminalized by viewing extreme material or mere nudity in the case of this image, is a victim of false abuse and imprisonment. Censorship is crime, as are visual pseudo-crime laws. It is interesting to conjecture the possibility of a libel action by those falsely accused of sexual criminality under these thought-crime laws. False abuse industry figures such as John Carr and Jim Gamble would be seriously out of pocket. This is nothing to do with protecting children from sexual predators-it is a moral crusade. —Preceding unsigned comment added by Trevor Loughlin (talkcontribs) 07:20, 9 December 2008 (UTC) Trevor Loughlin (talk) 07:21, 9 December 2008 (UTC)[reply]

Just as the word "pornography" is not the best description of the problem with this particular item, the claim of persecuting the viewer is not really a good part in this debate. Wise up Trev. You are defending the guy who breaks his ankle in a pot hole in case he is sued for the dangers the pot hole created... Censorship is a crime huh? Spitting on the phrase "moral crusade" in general... You probably have a low opinion of Mother Theresa. I am white. Bring back slavery I say. Two sugars please. Persons like you help to make drugs illegal because you prove that it may be absolutely neccesary because you do not respect the fact that some humans can be real evil fucks and we have all survived it. You would have it all go to crap and watch it just becase nobody has watched it going to crap for ages. Not one for the zoo or the carnival except a carnival of horrors. Sorry for the language. False abuse industry? Out of pocket? Stuff? Nonsense? Its as though some sort of group is trying to control our country by their own opinions. Prevent people having guns without a license? That would be a crime or a restriction or something. No difference between guns and candy floss. Every kid should want one. Blah. ~ R.T.G 12:45, 9 December 2008 (UTC)[reply]

You know, it brings up the question of "What is child pornography?". I don't find either image (Nirvana or Scorpions) remotely erotic. But maybe somebody else does? Out of 6 billion (or so) people on the planet, if one of them finds them erotic, is it child pornography? 216.239.234.196 (talk) 13:52, 9 December 2008 (UTC)[reply]

Unfortunately, that standard can never be applied with any sort of usefulness. There are people who get sexually aroused by pictures of clothed children, and yet we don't outlaw pictures of children altogether. In the U.S. the Miller test defines obscenity in all of its forms, though I can't speak to similar principles in other nations, I imagine some sort of "community standard" principle exists in many other nations. --Jayron32.talk.contribs 16:57, 9 December 2008 (UTC)[reply]
When I was small the film The Exorcist was banned. I thought there was too much hassle over films where people got hurt in similar ways you might see in an engineering mill or to much hassle over creatures which arent much more scary than your mild mannered dinosaur. As it turned out the film has stuff like a ten year old girl who when she is finished puking on hereself takes to stabbing her own vagina screaming "fuck me Jesus". The "Virgin Killer" piece is not the same as Nevermind. Again, talk about peoples ideas of clothed children... it's not quite hitting the button. The album definitly hits some sort of button. If it is not an erotic and/or abusive one... please go in to what it is because to be fair, what else is it? If it could be construed as something else it would be the first thing described rather than comparing it and defending it blindly. The only arguement here outside of quoting standards is that if one could watch paedophilia without joining in that it should be available to all. Who is up for that? I wonder. ~ R.T.G 00:11, 10 December 2008 (UTC)[reply]
Personally - I don't give a damn what sick shit people look at. What bothers me is what the kid went through in order for the picture to have been taken in the first place. We need laws that prevent those children from being involved - and to punish those who get the children involved. But once that has played out - what's done is done and the actual album cover is somewhat 'meh'. I don't have a problem with Wikipedia showing it in an appropriate context - just so long as we're not encouraging more people to do that kind of thing. The time to worry about this was when the album was released - and the people to hassle about it are the ones who commissioned, photographed, published, initially printed and violated the rights of that poor kid. They should all have gone to jail. SteveBaker (talk) 02:43, 10 December 2008 (UTC)[reply]
Yeah Gwinva but it is so weird the way Wikipedia debates this topic. The main concensus is that anything goes, had better go and questioning that is something wrong. How weird is that? That girl, now a 40 or 50 year old lady has to make the psychology of not giving a shit or she does give one and feels bad forever. It's indecent (that doesnt mention anything about sex, clothes, community groups, local law anything it's very plain in its own right "virgin killer" destruction of innocence, poison of the mind pure and by design). ~ R.T.G 06:32, 10 December 2008 (UTC)[reply]

Post-docs

When did post-docs become the common path of career progression in the sciences? Our article on the topic doesn't provide much history. My impression is that pursuing faculty positions immediately following one's PhD used to be much more common in the sciences than it is today. Dragons flight (talk) 19:02, 8 December 2008 (UTC)[reply]

That's probably correct. The American Physical Society probably has the statistics on that. --98.217.8.46 (talk) 01:37, 9 December 2008 (UTC)[reply]
My guess is it coincided with the increase in number of PhDs compared to available faculty positions. This combined with the greater mobility and perhaps larger number of places countries likely to be of interest to a scientist Nil Einne (talk) 12:32, 11 December 2008 (UTC)[reply]

Continuously-cooling device?

Apparently some people from Stanford created a zero electricity cooling device, which you use by heating it over a fire, and then it cools way down to refrigerator-like temperatures.

First, I'm wondering how the device works. I wasn't able to much out about that. I'm guessing that it's some long-running endothermic reaction (which thus sucks in heat), which is jump-started by heating the chemicals up until the reaction starts. Is that likely?

Second, I'm wondering if there's anything theoretically against having the same system (if it indeed works as described above), where the chemical reaction starts at room-temperature (specifics of the actual chemicals used aside)? If so, would it "yo-yo" back and forth between freezing, warming back up to room temperature, and then freezing again? And, since there is an energy gradient from which presumably you can draw energy, would this provide a continual "free" energy source, which would gradually suck up heat from the Earth? (Yay! Free energy until we all freeze to death!)

Thanks! — Sam 63.138.152.238 (talk) 20:14, 8 December 2008 (UTC)[reply]

This isn't a new concept. It most likely works on the same principles as an icyball which I believe predates modern compression refrigerators. Unfortunately the process wouldn't work at room temperature so no free energy here.-- Mad031683 (talk) 21:03, 8 December 2008 (UTC)[reply]
(edit)I should actually read the articles I link, It's from the 20's though still not new. -- Mad031683 (talk) 21:05, 8 December 2008 (UTC)[reply]
Absorption refrigerator? ~ hydnjo talk 22:22, 8 December 2008 (UTC)[reply]
But is there anything against there being a chemical reaction of this kind that takes place at or below room temperature, besides the fact that none has been found (or is likely to be found) with what we have at our disposal? — Sam 146.115.120.108 (talk) 03:51, 9 December 2008 (UTC)[reply]
The laws of thermodynamics are a harsh mistress. Certainly there are chemical reactions that do these kinds of things - but the energy in that case comes from (or winds up in) the chemicals. That doesn't give you 'free energy' that gives you energy from reacting chemicals...which isn't 'free'. SteveBaker (talk) 04:18, 9 December 2008 (UTC)[reply]
If at any point you reach the conclusion that something provides "free energy" there's an error in your reasoning. The laws of thermodynamics are pretty fundamental to our understanding of the universe, something that violated them would invalidate every theory we have, which is problematic since we have working technology and centuries of experiment prove the laws to be true. -- Mad031683 (talk) 17:31, 9 December 2008 (UTC)[reply]

Traction for tires.

Static (non moving) friction is stronger than kinetic (sliding) friction. This means that once an object (such as tires) start to slide, it has less friction strength to push in the opposite direction. This is demonstrated when our car gets stuck in snow. It's easier to drive slowly out of being stuck than by trying to spin our tires. So why is it that dragsters spin their tires? They should have less available traction and thus just sit and spin.

A corollary to this question, if I may. Once I have an explanation of why dragsters spin their tires for more forward movement, I will want to know if it is possible to stop faster with the tires driven in reverse (naturally, being aware that the tires spinning in reverse will lose directional control, but that is not my present question).

Thankyou.

Doug —Preceding unsigned comment added by 192.30.202.21 (talk) 23:51, 8 December 2008 (UTC)[reply]

I thought they melted the tires a little so that it would stick to the track, providing greater grip. I'm sure you can find the answer on the appropriate wikipedia page. 96.242.34.226 (talk) 00:06, 9 December 2008 (UTC)[reply]
Yep, that's basically it. Per our article on burnouts, tires have more traction at higher temperatures, and the friction of an intentional burnout is the fastest way to boost tire temperature. As for braking, eh... bearing in mind that there's a mechanical distinction in attempting to drive the wheels backwards and actually doing so, I think the answer is still "no". A dragster at speed can easily lock the wheels (and start slipping) by simply braking (thus the drag chute). Spinning the wheels backwards would have no further effect and could prove damaging to the vehicle. — Lomn 00:47, 9 December 2008 (UTC)[reply]
Rubber is weird stuff - and (as is fairly obvious) it gets sticky as it gets close to melting. So hot tyres are sticky - and sticky is good. So they heat the tyres up by spinning them (often with bleach poured on the track to help soften them still more). But for the actual launch at the start of the run - the idea is to NOT spin the tyres. In Formula 1 car racing, the pit crews keep replacement tyres in electrically heated jackets so that they are nice and sticky when they are put on the car at the next pit stop. SteveBaker (talk) 02:15, 9 December 2008 (UTC)[reply]
I wonder if releasing the clutch at super high revs might snap something. Formula cars do a lap to warm the tires and they would be the best gripping tires around but apparently if you spun one you would wreck its grip and unbalance the steering very easily. Rally cars were made at one time that could almost compete with formula cars but they were so dangerous and after a few races they would be burnt and seize up so they did away with them. ~ R.T.G 02:47, 9 December 2008 (UTC)[reply]

Hang on one second...I've often read that to get the best start off the line you basically have to dump your clutch at high enough revs that traction would just about be broken. This is to get the engine into the power band as quickly as possible. It is supposed to be a fine balance between trying not to spin your wheels endlessly (i.e. not moving) vs. not spinning at all and "bogging down" at low revs far below the power band of the engine. It is also given as a reason why four-wheel drive cars are so difficult to launch, the apportionment of torque to all four wheels makes it harder to break traction. This is just what I read on the net and in magazines, if anyone can explain it in finer detail I'd much appreciate it. Also, given the torque and power curves of a Honda S2000 (apparently a notriously difficult car to launch), what is the optimum RPM to dump the clutch at? Zunaid 16:51, 10 December 2008 (UTC)[reply]

Yes - you want the most torque possible at the wheels - consistent with them rolling (and therefore maintaining static friction) rather than slipping (and therefore getting dynamic friction). Since static friction is greater than dynamic friction for almost all materials - this is the best you can do for maximum accelleration. Dumping the clutch at this optimal RPM is certainly one way to reach that goal. Although...letting it out a little more gently to get the car rolling before ALL of the power is applied might be fractionally better for a turbo-charged car. With a turbo, you need enough engine RPM to generate enough exhaust to get the turbo spinning. If that RPM produces more torque than your tyres can stand without spinning - then you have a nasty problem. In that case - you might want to rev the engine to the higher RPM level to get that turbo going - then either briefly drop them as you dump the clutch (the turbo will take a while to spin back down again...) or you can let go of the clutch a little more gently to give the car time to get rolling before you let the full power of the engine get to the wheels. However, a car that demands that you do that could REALLY use a different gear ratio for 1st gear and/or some better tyres!
Differentials are the enemy of fast launches because they feed more power to the wheel that's moving the fastest. This is great for going around corners - but crappy when you are trying to launch quickly. If just one of your wheels starts to slip (maybe because the road is worn a bit more smooth on one side than on the other - or one tyre has a little less tread left) - the diff will apply more power to that wheel - robbing power from the wheel that's gripping and making the slipping one slip much worse. This is a problem in two wheel drive as well as four - but in a 4 wheel drive vehicle, you'll probably have a front diff, a rear diff and a center diff - all fighting hard to find the wheel that's LEAST able to make the car go fast and give it all the power! The fix for THAT is sophisticated "limited slip" differentials, lockable differentials and (best of all) fancy computer controlled differentials that are tied into traction control and yaw rate sensors. With those things, you can get a faster launch because power is given to the SLOWEST wheel instead of the FASTEST.
Sadly, on most cheap modern cars without fancy differentials, etc, there is "traction control" - which is supposed to prevent wheel slip on launch by artificially limiting your revs. This sounds like a good thing - but they are typically tuned to preven slip with not-perfect, not-sticky tyres and relatively poor road surfaces. Hence they limit the revs to something below what your nice new semi-slicks are capable of on clean, dry pavement - also, when they do drop the revs, it takes the engine time to get back up where you want it when the traction controller finally decides to give you back the right pedal. That means that to get the best launch speed you (ironically) have to turn off the very system the manufacturers put in place to help you do this!
As for a Honda S2000...the only thing I know about it is that the radio antenna is a nice short rubbery one that happens to fit perfectly onto the stock MINI Cooper'S antenna base and which produces considerably less drag and better FM reception than the one that came with my car! Thank you Honda! So there is at least ONE thing you make which I really like. SteveBaker (talk) 22:26, 10 December 2008 (UTC)[reply]


December 9

Coconut water as an IV

While perusing of our coconut article, I noticed that it said that coconut water can be used as an intravenous fluid. I'm a little curious about it. Would it be used to help dehydration, or what? bibliomaniac15 00:55, 9 December 2008 (UTC)[reply]

It would never be used IV: if you were on a island where you had nothing else to use, you wouldn't have IV tubing and an intravenous catheter; and any place that has IV tubing and an intravenous catheter would have a bag of saline, too. That said, coconut water is hyperosmolar/hypertonic: it is about 500 mOsmol/L in contrast with blood, which is about 290 mOsmol/L. So if infused, the effect would be to increase serum osmolality, resulting in retention of fluid. Since the statement in the article is unsupported by any citation, it needs to go. The one with the citation can stay :) - Nunh-huh 01:08, 9 December 2008 (UTC)[reply]
It can be, and has been, used as IV fluid, here is a link to an article discussing it. [13]. DuncanHill (talk) 01:12, 9 December 2008 (UTC)[reply]
And here's another [14]. DuncanHill (talk) 01:13, 9 December 2008 (UTC)[reply]
And a third [15]. DuncanHill (talk) 01:16, 9 December 2008 (UTC)[reply]
And another, [16]. DuncanHill (talk) 01:19, 9 December 2008 (UTC)[reply]
Still they keep coming [17]. DuncanHill (talk) 01:20, 9 December 2008 (UTC)[reply]
The fact that every time some clown uses it someone writes an article about it is actually pretty good evidence that it's not used except under extraordinary circumstances. - Nunh-huh 02:37, 9 December 2008 (UTC)[reply]

(outdent) I think it would be better to drink instead.--Lenticel (talk) 04:32, 9 December 2008 (UTC)[reply]

Extracting oxygen from ferrous oxide (FeO)

Could you? What resource would it drain? Does FeO actually contain O or is such a compound changed for ever? And why, if the moon has as much of this red stuff as mars... is it black and not red? ~ R.T.G 02:35, 9 December 2008 (UTC)[reply]

FeO (or iron(II) oxide) does indeed contain oxygen. It is actually a black solid, which would help explain the colour difference. DuncanHill (talk) 02:40, 9 December 2008 (UTC)[reply]
But FeO is rust right? And iron is definitely red unless you melt it... ? I thought it was iron that made Mars red and blood red, is ferrite not iron? Whats the difference? ~ R.T.G 02:51, 9 December 2008 (UTC)[reply]
FeO is only one form of rust. Iron(III) oxide is the common red rust that you were thinking of. 76.97.245.5 (talk) 03:33, 9 December 2008 (UTC)[reply]
The article on Mars surface color is a good place to start. You should read it and follow at least some of the links. Please ask if anything is still unclear. Now, regarding the extraction of oxygen on Mars: as far as I can recall, most projects involved extracting oxygen from CO2 in the Martian atmosphere rather than from iron oxides on the Martian surface; see Mars Surveyor 2001 Lander for example. Extracting oxygen from iron oxides is possible, of course; but probably not as convenient or not as economic. You can do a little research here - this is a good topic for a project. BTW, it is possible to extract oxygen from Al2O3, too. The "by-products" (carbon, iron, or aluminum, respectively) are likely to be of considerable use, as well, so you should take that into account. --Dr Dima (talk) 04:02, 9 December 2008 (UTC)[reply]
Another article you should read is In-situ resource utilization. Enjoy, --Dr Dima (talk) 04:18, 9 December 2008 (UTC)[reply]
Its a lot easier, in general, to extract the metal from metal oxides (basically by transfering the "oxide" part to another substance, and leaving behind the metal) than it is to extract the "oxide" as oxygen. The reduction potential of the O2 + 4e1- --> 2O2- half-reaction is quite high; to actually oxidize O2- you'd need a rediculously strong oxidizing agent, or to do it electrolyticly you'd need a rediculously huge amount of current. Neither is a particularly economical means of producing oxygen. Free oxygen is such a hard thing to produce, it required a massively complex and convoluted chemical system (photosynthesis) to actually make it on Earth. If we are going to produce free oxygen in situ on another planet we colonize, then its going to come from a biological source rather than from an industrial/chemical one. --Jayron32.talk.contribs 04:27, 9 December 2008 (UTC)[reply]
It is true that energy demands of restoring a metal oxide to metal and oxygen are relatively high. However, electric energy is pretty much the only thing that will not be lacking on the early stages of Mars or Moon exploration. Bringing and deploying solar panels is very much easier than bringing and sustaining, say, water-tanks with algae. Solar panels have 20-30% efficiency vs 5-6% for photosynthesis, and the working temperature range for the solar panels is much broader. This is of crucial importance on both Moon and Mars, where temeprature changes between day and night are quite extreme. So, on earlier stages of Moon & Mars exploration, the direct electro-thermal process seems the way to go. On the more advanced stages of exploration / colonization / terraforming, the photosynthesis will produce al least some of the breathing oxygen and food for the humans. --Dr Dima (talk) 05:47, 9 December 2008 (UTC)[reply]
Agreed. Even though producing industrial amounts of free oxygen on a foreign, uninhabitable planet will probably never be an easy feat, using biological means would probably be even more difficult than using electrical means. Of the photosynthesising organisms we know today, I doubt even one species would survive on Mars for a fair amount of time, let alone being able to produce reasonable quantities of oxygen. Genetic engineering is always an option, of course, but I'm going to go on a limb and say it's probably easier and more economically viable to create a durable, properly catalysed electrochemical oxygen generator than it is to genetically engineer an extremely hardy and efficient photoautotroph. What's more is that using the biological way, a steady and reliable source of liquid water is pretty much a necessity for the organism to even do anything other than just sit there as a planetary ornament. --Link (tcm) 06:12, 9 December 2008 (UTC)[reply]
Water tanks and algae may be unworkable, but there may be a promising future in certain forms of archaebacteria and other extremophile life forms which may prove to be useful in this endeavour, especially with a little genetic engineering thrown in. We may find that engineering some little archeon with the ability to extract oxygen from oxides is easier even still than dragging around solar panels. The ability of a wide-range of enzymes and other biological process to turn otherwise impossible or improbable chemical processes into workable systems is mind boggling, and it may simple require putting together the right biological system to make it feasible. --Jayron32.talk.contribs 06:02, 9 December 2008 (UTC)[reply]
Back to the original question, is there a solvent that can dissolve FeO, and when electrolyzed produces oxygen and Iron metal (rather than hydrogen)? Graeme Bartlett (talk) 10:43, 9 December 2008 (UTC)[reply]
And with Graeme Bartletts question, what amount of solvents would current technology want for creating plant supporting atmosphere on the moon including ozone and other nessecary stuff? Would it all float away before it was useful? ~ R.T.G 13:08, 9 December 2008 (UTC)[reply]
Iron oxides dissolve in phosphoric acid, see this patent, for example. I never heard of electrolytic extraction of iron, though. Iron is usually produced from oxide in presence of carbon or carbon monoxide in a blast furnace, see Iron#Production of iron from iron ore. I'd venture guessing that the process to be employed on Mars - if iron oxides are to be the source of oxygen there ar all - would be some modification of an induction furnace or an electric arc furnace that would thermally dissociate iron oxides into iron and oxygen. At near-zero pressure the dissociation will go more readily, and there are no consumable chemicals to be brought from Earth - a definite advantage over a chemical process. Regarding your second question (the one about retaining an atmosphere) - Mars has been losing its atmosphere over a few billion years now, and there is still some left; so if humans generate a new Martian atmosphere it will not "float away" any time soon :) . Moon has lower gravity than Mars, though, and is closer to the Sun; and Earth with its magnetosphere does not help either. So I don't know how long a lunar atmosphere may persist once generated. --Dr Dima (talk) 17:46, 9 December 2008 (UTC)[reply]

Time Travel

One idea about time travel is that when you exceed the speed of light, everything, relative you you, is going backwards. This will have zero scientific meaning because, as the nice old man with the funny hair tells us, you can't make matter go faster than the speed of light. Even if you are going fast enough to see light stop in its tracks, wouldn't the matter that it's coming from continue to move? You can't measure speed without comparing it to a unit of time, 100 km/hr, 40 ft/second, 3 light-years/minute, so would you bump into the still moving objects because all you would see is the light from 2 min in the past or an hour in the past. If we were an x-ray, which i believe goes faster than the speed of light, would you see the light hitting and bouncing off matter? Say you continue to go the speed of light, which would hurt when, relative you you, air molecules run though you like bullets, could you go to the Sun, and just go through it without getting hurt? Infrared is lower than light so could you run though it like your hand over a candle? Weird stuff, but I think it's interesting. --70.181.81.205 (talk) 03:20, 9 December 2008 (UTC)[reply]

X-rays don't go "faster than the speed of light". -hydnjo talk 03:32, 9 December 2008 (UTC)[reply]
First see speed of light. Many of your assumptions about the speed of electromagnetic waves are simply wrong. -- kainaw 03:33, 9 December 2008 (UTC)[reply]
Sorry - all of your basic premises are incorrect - so your conclusions don't work.
  • In your first sentence: This idea that something unknown and interesting happens when you exceed the speed of light completely neglects the indisputable fact that you can't do that. If you plug speeds greater than lightspeed into the equations relating to time, length and mass, they end up producing something like the square root of -1. The square root of -1 is not -1 (which is what you imply by suggesting that time would go backwards)...go ahead and type -1 into your pocket calculator and push the square root button. What you get is "Error". The square root of -1 is not a number that can express a real world property of mass, distance or time. This makes it impossible to ever go faster than ligh - not just some kind of interesting unknown thing...IMPOSSIBLE. That impossibility means that we can't use math or science to speculate on what would happened if you somehow magically did do that. The impossibility lies at the heart of the very mathematics we use here.
  • In your second sentence: Einstein didn't just say you can't go faster than light - he actually said that you can't go as fast as light. So your idea of stopping light in it's tracks by moving alongside it at the same speed would be impossible even in a non-relativistic world. But the distinguishing thing (the utterly WEIRD thing) about light is that it's speed is always the same relative to you no matter how fast you're moving. So even if you are moving away from the Sun at 99.9999999% of the speed of light - if you try to measure the speed of that ray of sunshine, you'll find that it's STILL moving past you at the speed of light...not only does it not stop - it doesn't even slow down to the slightest degree! This is a deeply weird thing - but we've proven it to be true in numerous highly convincing experiments.
  • In your third sentence: You claim that one cannot measure speed without reference to time. In truth - the universe seems to be entirely dominated by this lightspeed thing - and it's arguably the case that we should treat speed and distance as fundamental things and make time be derived from speed and distance. In such a situation, you would indeed measure your speed (as a fraction of lightspeed) without reference to time.
From this point on, your statements pile incorrectness on incorrectness to the point where it's hard to comment on them. But as others have pointed out - infrared light isn't slower than visible light - along with ultraviolet light, radio, microwaves - they all move at exactly the speed of light.
The one thing you that you say which is SO true...is that this stuff is weird but interesting. But you need a better grasp on the underlying science...once you do, things are much weirder than you can possibly imagine.
SteveBaker (talk) 04:09, 9 December 2008 (UTC)[reply]
Furthermore, by combining the second law of thermodynamics with the law of special relativity as described by SteveBaker above, you could contruct a completely coherant and consistant system of mechanics and motion with no mention of time at all. By the second law of thermodynamics, the entropy of the universe increases continuously. Thus, if we take the idea of "absolute time" to mean the 0 point is the Big Bang and the end-point of time to be the heat death of the universe; then we could just as well look at the Big Bang as a perfectly ordered universe (0% entropy) and the end of the universe as 100% entropy, and you could deal with temporal measurements merely by saying "event A happened when the universe was at entropy = 50%" and "event B happened when the universe was at entropy = 50.1%" you would have an unambiguous means to order event A and B without resorting to any measurements of time at all. Time is a mathematical convenience we use more easily express the ordering of events, but its not a real physical "quantity" the way that mass and distance and speed are. --Jayron32.talk.contribs 04:44, 9 December 2008 (UTC)[reply]
Well, I give the OP credit for some original thinking. Perhaps what he says is true in a parallel universe which has its own physics and natural laws. As Shakespeare wrote, "There are more things in heaven and earth than are dreamed of in your philosophy". Even in this universe we may be looking at things in a way that distorts reality, yet which is "proven" by mathematics and physics. Einstein himself showed that the Newtonian way of looking at reality was wrong, even though it was supported by mathematics and physics. Perhaps Einstein, in his turn, will be proven wrong. Conventional wisdom sometimes turns out to be conventional foolishness. Great ideas sometims start as heresy. —Preceding unsigned comment added by 98.17.46.132 (talk) 06:15, 9 December 2008 (UTC)[reply]
This demands a little correction. Einstein didn't prove Newton wrong precisely. He amended Newton's laws to account for the strange things that happen close to the speed of light. Newton's laws are stunningly accurate for all 'reasonable' speeds - and over the entire range of conditions for which they had ever previously been tested. Einstein didn't formulate his equations in order to explain some horrible experimental discrepancy that had been found - he was seeking an explanation for the absolute nature of the speed of light and deduced by pure reasoning that this correction to Newton's laws were therefore required. Remember it was only YEARS later when super-careful solar eclipse experiments had been performed specifically to test relativity that we finally had any kind of experimental evidence for the error in Newton's laws. Any amendment to Einsteins laws would have to apply in situations that are stranger still - which have yet somehow evaded our ability to test them. It would also require some kind of new discovery about the nature of the universe - something as stunningly weird as the absolute nature of the speed of light. But since we've tested these laws at all sorts of extremes - and they seem to work just fine - the number of places where a 'correction' to Einstein could possibly be hiding are rapidly vanishing. Certainly any new 'Hawkins law of refined relativity' (or whatever) would have to show Einsteins laws as working just fine over an enormous range of conditions - and any loopholes it provided for potential time-travellers would (by necessity) be impractical in the extreme! Personally - I doubt that'll ever happen. We fixed the bug - and now it's right. SteveBaker (talk) 13:46, 9 December 2008 (UTC)[reply]
Such an enquiring mind deserves its own expression in a science fiction novel. Who knows where that would take you? Think on, 70.181... Julia Rossi (talk) 07:09, 9 December 2008 (UTC)[reply]
The phrase "time travel" is a double negative. The word time is similar to the word speed and the word motion. It has no size or shape. It is a scale with no measure which looks odd but is spot on. You can traverse a centimeter but not an instant lol. When Einstein says that such speed would slow you down he is refering to the fact you would be squashed so tight nothing could move similar to ice or the Earths core. ~ R.T.G 10:54, 9 December 2008 (UTC)[reply]
I respectfully disagree with Steve's comment "We fixed the bug - and now it's right." Einstein's general relativity models gravity and space-time. However it does not model quantum theory. Einstein's theory is a more accurate refinement of Newton's model, but it does not represent every situation. Many scientists have worked to create a more accurate model, and I expect that the scientific community will eventually agree on a new theory that models gravity more accurately than general relativity. Axl ¤ [Talk] 21:46, 9 December 2008 (UTC)[reply]
It's perfectly possible that that could happen - but (and here is the crucial thing) whatever this new theory is, it has to agree with relativity rather precisely over the entire range of measurements we've done to date that confirm relativity. So the new theory would pretty much HAVE to prohibit faster-than-light travel. Sure, it could say that gravity doesn't warp space - or that some different set of math applies at the scale of quantum events...but the math has to produce the same results as Einstein over the range of data we have...which is pretty much the entire range of human experience - and higher speeds out to lightspeed and masses up to black holes and down to atoms. SteveBaker (talk) 02:32, 10 December 2008 (UTC)[reply]
Indeed, if you want to allow time travel or faster than light travel you need to introduce something which we haven't been able to observe yet. "Exotic matter" is the usual way people construct such theories. --Tango (talk) 14:03, 10 December 2008 (UTC)[reply]
Yes...although that's about as meaningful as speculating that the magic time-travelling pixie will come along and tell us how. It's not like there are these mysteriously faster-than-light things that we're trying to explain - there is zero reason to expect or even imagine that exotic matter will do anything interesting whatever in terms of relativity. Of course Newton would have said the same thing if asked about the speed of light (he didn't even know that light HAD a speed) - but the state of experimental science was pretty poor in Newton's day. Apples falling from trees are rather blunt instruments when it comes to probing the secrets of the cosmos...we have cool toys like a computer-controlled telescope the size of a schoolbus in orbit around our planet and something the size of a shoebox that sits on your desk, contains all of human knowledge and can do simple arithmetic about ten billion times faster than Newton could manage. But - as I said in the post that triggered Axl's reply - "Personally - I doubt that'll ever happen." - not "I know for 100% sure it'll never happen." SteveBaker (talk) 21:52, 10 December 2008 (UTC)[reply]
Sure, given how much observing we've done, "something we haven't observed yet" means something that probably doesn't exist. It's still interesting to think about, though (at least, it is for me, I'm a mathematician, we rarely let such minor details as whether things exist in reality get in the way of interesting maths). --Tango (talk) 21:59, 10 December 2008 (UTC)[reply]
Just to clarify: I do not think that a new widely accepted theory will allow time travel to be possible. Rather I think that there will be a new theory that would be a better model than general relativity. Comment to Tango: I think that the Large Hadron Collider (and later particle accelerators) will indeed show new phenomena that have not yet been observed. Axl ¤ [Talk] 22:19, 10 December 2008 (UTC)[reply]
GR does allow for time travel, it just requires you to fudge things a bit (eg. with exotic matter). Finding such matter (or a way to create it) is rather unlikely, but not impossible. The LHC will almost certain show us things we haven't seen yet (that's why it's being built), but they are likely to be things we already know ought to exist, it will just help us fine tune our theories. Observing exotic matter would be a much more significant event than observing the Higg's Boson, say (which would be a pretty big event). --Tango (talk) 22:26, 10 December 2008 (UTC)[reply]

Containing a super-volcano?

Could a very large Kevlar bag contain a super-volcano eruption and prevent the consequent mass extinction of mankind? Could any conceivable structure contain the dust and gases?Trevor Loughlin (talk) 07:33, 9 December 2008 (UTC)[reply]

Although I'm no expert on the subject, I know supervolcano eruptions are extremely energetic events. Containing the actual explosion would require unobtainium. As for the gas and dust, supervolcanoes eject over 1000km³ of tephra alone - not to mention the enormous volumes of gas that are released. I'd think your options are limited to damage minimisation, luck, and - unlikely but possibly - prevention of eruption. Containment is all but impossible as far as I can imagine. In any case, it would probably be more feasible to construct domes over all the major cities and harness geothermal and nuclear energy to stay alive. You'd also need to create artificial sunlight for greenhouses and the like. --Link (tcm) 08:17, 9 December 2008 (UTC)[reply]
Kevlar is seriously weakened by heat, so it stands no chance against lava or a volcanic bomb. Graeme Bartlett (talk) 10:31, 9 December 2008 (UTC)[reply]
Perhaps an Operation Plowshare sort of endeavour could relieve the pressure and prevent an explosive eruption. Or at least make an awesome Jerry Bruckheimer movie. --Sean 13:42, 9 December 2008 (UTC)[reply]
That might work, yes. On the other hand, it might just set it off early. Which would, kinda, suck. —Ilmari Karonen (talk) 18:15, 10 December 2008 (UTC)[reply]

Stellar Classification

I've read the article, found it a little confusing, but finally think I've got it. However, I wanted to check my understanding....

If a star is rated G1V in its wikibox, it means

  • G - about the same size, temperature and brightness as the sun
  • 1 - a bit hotter than the sun, though, since the sun is G2V
  • V - about the same size as the sun.

Hmm. I mentioned 'size' twice. Maybe that's ok. Have I got this right? mike40033 (talk) 07:58, 9 December 2008 (UTC)[reply]

The classifications are explained in Stellar classification. G will be the Harvard spectral classification. I think the number (in this case 1) relates to the absolute magnitude and V is the Yerkes spectral classification, all of which are explained in the article I cited. Jdrewitt (talk) 15:43, 9 December 2008 (UTC)[reply]
Yes, that's the article I mentioned, that I read, and found confusing, and wanted to check my understanding. Have I got it right? mike40033 (talk) 00:35, 10 December 2008 (UTC)[reply]
Hello, well the Harvard classification indicates the temperature of the star's atmosphere, so strictly speaking G will stand for a star which has a comparable temperature to the sun. I think though since the sun is a main sequence star, you can infer the size and other properties from the temperature (This would not be the case for a red giant though). The number relates to the luminosity of the star, so 1 will stand for a star that is simply brighter than the sun, not necessarily hotter though. Then the Yerkes sectral classification relates the luminosity to the size of the star, so V will indeed represent a star about the same size as the sun. That's my interpretation of the article anyway. Jdrewitt (talk) 15:45, 10 December 2008 (UTC)[reply]
You are wrong about the arabic number. As the article says: "The spectral classes O through M are subdivided by Arabic numerals (0–9)." Hence, the spectral type of the star is G1 as opposed to the sun's G2. This means that the star is a little hotter and therefore has a spectrum closer to type F than the sun. This agrees with what the original poster stated. Indeed, the designation G1V has two parts (not three as one might suspect), in agreement with the Hertzsprung-Russell Diagram being a two-dimensional representation of properties. The spectral type is essentially given by temperature, the luminosity class (as indicated by the Roman numeral) by luminosity, although the boundaries between the luminosity classes are different for hot O type stars than for cool M type stars. The variation of size and mass can also be traced on the Hertzsprung-Russell diagram, but that is a little more complicated. --Wrongfilter (talk) 18:40, 10 December 2008 (UTC)[reply]
Thanks for pointing that out, it is not clear from the article by any means. Yeh, that makes sense now. Jdrewitt (talk) 10:46, 11 December 2008 (UTC)[reply]

Energy crisis

HI pple, I wanted to know whether its feasible to convert IR radiation to electricity..and use it ,say, for mobile charging ... If so, can you just tell me how.. —Preceding unsigned comment added by 59.163.146.11 (talk) 08:36, 9 December 2008 (UTC)[reply]

Well, for starters you can use IR radiation to heat things, so if you had enough of it you could use it to run a boiler to power a steam generator, but I'm almost certain there would be more efficient ways to do it. Gunrun (talk) 10:06, 9 December 2008 (UTC)[reply]

Possible? Definitely. Feasible? Apparently, not quite yet. --Link (tcm) 12:06, 9 December 2008 (UTC)[reply]
The boiler/steam generator concept has been implemented here, although it's not exactly a mobile solution, and the power it generates is currently still more expensive than conventional methods. Gandalf61 (talk) 13:27, 9 December 2008 (UTC)[reply]
There is research work going on in the field of infra-red 'solar panels' that would collect radiant heat and convert it to electricity. There are all sorts of interesting applications for them. However, if they exist at all - they are lab experiments - not something you can go out and buy. SteveBaker (talk) 13:30, 9 December 2008 (UTC)[reply]

Speed and mass

I remember reading somewhere that the faster an object goes the more mass it has. Is this right? Assuming it is does this mean that if you could accelerate a 9mm bullet to massive speeds (possibly using magnets?) you could demolish a house with it? Also would it be possible to accelerate an object to such speeds that its mass would be more than its atomic structure could withstand causing it to collapse in on itsself and form a black hole? Is this the reason nothing can move as fast as light? Gunrun (talk) 10:01, 9 December 2008 (UTC)[reply]

This is right, mass increases with speed. But no, a thing cannot be made to collapse into a black hole this way. See our article on mass and relativity. As for destroying a house with a single bullet, to get any really noticeable increase in mass, you would have to accelerate the 9 mm bullet to such a velocity that it would not hold together for an instant flying through the atmosphere. If the house were in a vacuum, however, then you could do a lot of damage with a single bullet, although it wouldn’t require a relativistic velocity, just plain very, very fast would do. This sort of thing is a problem for stuff in outer space in general, and especially for delicate instruments and space vehicles in orbit; we’ve managed to pile up quite a lot of junk up there in the past fifty years.--Rallette (talk) 10:49, 9 December 2008 (UTC)[reply]

There are a few things to note here:
  1. The mass of the bullet is no different from the perspective of the bullet. It's only heavier for outside observers. But since the house is an outside observer - the bullet would indeed seem heavier.
  2. The bullet's energy is kinetic energy - which is given by 1/2 M v2 - so when you double the speed, you quadruple the amount of energy. So even without the relativistic effect, a bullet moving close to the speed of light would do an insane amount of damage.
  3. However, the bullet won't collapse or break apart or anything - as far as it is concerned, it's just sitting there minding it's own business, being the same mass it always was. So providing it's moving through a good, hard, vacuum - it'll be just fine. Of course in air there would be severe problems - the heating due to friction would evaporate the bullet at just a few thousand miles per hour - LONG before it got remotely close to gaining mass noticably!
  4. Note that the energy it would take to get something as big as a bullet moving that fast would be horrendous.
  5. When we're talking about relativistic effects, there is an ENORMOUS difference between going at (say) 99.999% of the speed of light and going at 99.9999% - adding that extra '9' causes enormous differences in the mass we'd perceive the bullet to have attained - and spectacular increases in the damage it could cause.
  6. You can work out the change in mass quite easily. Take the mass of the bullet and multiply it by (where v is it's velocity and c is the velocity of light) - then, you can calculate the energy by multiplying that mass by v2 and dividing by two.
So if we take a 6 gram 9mm/17 Browning round and push it up to 99.9999% of lightspeed, we have a mass of 6g / sqrt ( 1-(99.9999x99.9999)/(100x100) ) which is 4242g - about 4 kilograms. At 99.9999% of 299,792,458 meters per second (light speed) that bullet would release 1,900,000,000,000,000,000 joules - which is about 500 megatonnes of TNT. About ten times more than the biggest nuclear bomb ever detonated! The bullet wouldn't just destroy the house - or the city that the house was in - it would stand a good chance of destroying an entire european country. That's at 99.9999% of light speed. Make that 99.999999% (six nines after the decimal point) and the amount of energy goes up by another factor of ten and most of the planet would be at risk from your 9mm bullet!
Of course the amount of energy you'd need to get the bullet up to that speed in the first place would be...exactly the same...so to get your bullet up to 99.9999% of the speed of light - the propellant would have to be something with about the power of ten decent size hydrogen bombs.
SteveBaker (talk) 13:24, 9 December 2008 (UTC)[reply]
Actually, the city would probably be fine, in fact the house would probably survive. In order to do any damage that energy would have to be absorbed somehow, I would expect the bullet to just go straight through barely slowing down. --Tango (talk) 13:59, 9 December 2008 (UTC)[reply]
So it seems it would actually do less damage to humans as an ordinary 9mm bullet does. Yes, it will make a hole, but not turn and/or deform. --131.188.3.20 (talk) 14:42, 9 December 2008 (UTC)[reply]
I think it depends on how it impacts. If it came in at an angle and hit the ground - I don't see how it could keep going for long. You'd have a large crater and an enormous amount of material ejected into the atmosphere - nuclear winter...all of that stuff. If it came in horizontally - then maybe it's a different picture.
Let's consider your "pristine bullet" scenario. The tip of the bullet touches the wall at 99.9999% of c. The molecules of brick immediately in front of the tip do...what?
  • Suppose the tip of the bullet is a shallow cone. The molecules of the brick either have to move out of the way laterally (which means accellerating to maybe a tenth the speed of light from a standing start - and then continuing at that speed through the brick above, below and to the sides of the bullet - with maybe 50 Megatonnes of energy between them.
  • ...or the molecules have to accellerate to 99.9999% of the speed of light to stay in front of the bullet and fly out of the 'exit wound' on the far side. The force required to do either of those things has to be imparted by the bullet itself...so it has to apply a SPECTACULAR amount of force to the material of the brick...there is no way for it to do that without shedding a lot of energy (and in truth - evaporating into a cloud of relativistic particles.
  • More likely is that the atoms of the bullet act like particles in the large hadron collider and convert the material they impact into who-knows-what exotic particles - which in turn shoot off at relativistic speeds...but we're not talking about a small cloud of a few dozen protons at near light speed - we're talking about an avagadro's number (or so) of protons doing that! The amount and energy of the resulting sub-atomic debris would vaporize a city...no problem.
So, no - I don't see how the bullet can go right through without releasing an enormous amount of energy. If you think it can - tell me in detail what happens to the cylinder of material immediately in front of the bullet - it can't just "go away" - and it can't gently move to one side because it doesn't have enough time. So it either accellerates to near lightspeed itself (causing secondary, tertiary, etc damage in the multi-megatonne range) or it's converted to other particles - which form a VAST amount of hard radiation with similar consequences as it's absorbed by surrounding materials.
Nope - I'm pretty sure we get our big satisfying explosion...not just a neatly drilled hole. SteveBaker (talk) 15:03, 9 December 2008 (UTC)[reply]
I'm not sure exactly what would happen, but let's consider the possibility of the cylinder of matter just being pushed forward ahead of the bullet and see what happens. That requires a spectacular amount of force, certainly, but we have that. Let's assume we have a perfectly inelastic collision, what we need to work out is the energy lost in that collision because that's the energy that's going to go into destroying things (the bullet and cylinder of brick will head of into space if they don't hit anything else first (we'll assume there is just one house and nothing but desert to the horizon), so that energy doesn't go anywhere interesting). We have 4 (relativistic) kg of bullet colliding with a thin cylinder of brick (we'll ignore the bonds between that cylinder and the rest of the house because I'm a mathematician and that's what we do - the energy to break them is probably trivial compared to the energy of the bullet anyway). Most of the house is air, so we'll ignore that, let's say we have two external walls and an internal wall to get through, we'll say that's 2 metres of brick (it's something of that order). According to Brick, the density of brick is about 2000kg/m3. The diameter for the bullet is 9mm, so that's a volume of 9mm*2m=0.018m3, so a mass of 36kg. Now we get to calculating the energy lost in a relativistic completely inelastic collision, and I'm not entirely sure I've done it right, but this is what I got: The bullet and brick are now moving at 0.11c (much slower than I expected, brick is heavier than I thought!), so you have an object of rest mass 36kg moving at 0.11c, that's an energy of, well, 1/2 mv2 (0.11c isn't very relativistic), so 2*1016J, or 5 megatonnes of TNT, so we have 495 megatonnes left to destroy the world, so ok, that's pretty nasty. Out of interest, I did the same sums for your even faster bullet and got that the bullet and brick after the collision are now going at 0.74c, giving an energy of (using relativistic formulae this time) 1.6*1018 or about half a gigatonne of TNT, leaving 4.5 gigatonnes left. So, the moral of the story is not to shoot houses with relativistic bullets (and that Steve has a better intuition about relativistic physics than me)! --Tango (talk) 16:49, 9 December 2008 (UTC)[reply]
I can't calculate the volume of a cylinder... hang on while I revise all that... --Tango (talk) 17:32, 9 December 2008 (UTC)[reply]
Ok, it's 1kg of brick (I thought 36kg was a bit much!), so the final speed is 0.97c (far closer to what I was expecting), which corresponds to an energy of 2.8*1017J, or 67 Mt, leaving 433 Mt left. So, still a massive bang. For the faster case we have a final speed of 0.9997c, and an energy of 3.6*1018J or 0.86 Gt, leaving 4.14 Gt, so again, still a massive bang. Oh well, the final conclusion is the same, but not by quite as much as I my first calculations showed. --Tango (talk) 17:44, 9 December 2008 (UTC)[reply]
Since the proportion of energy left is decreasing as speed increases, I've done it again for 99.9999999999% c to see what happens. This gives a final speed of 0.99999997c and an energy of 3.6*1020J, or 86 Gt, from an initial energy of 500 Gt, leaving 414 Gt left, exactly the same proportion as last time, perhaps this is an asymptotic thing? 0.86 is about , could that be the limit? --Tango (talk) 17:52, 9 December 2008 (UTC)[reply]
No, that would be stupid, while the brick weighs a nice round number the bullet doesn't, so we wouldn't expect a nice answer. It's probably coincidence. --Tango (talk) 17:54, 9 December 2008 (UTC)[reply]
The problem with the bullet pushing a neat cylinder of brick out of the wall is that the particles of brick have to accellerate from zero to 99.9999% of the speed of light (minus a little bit) in the time it takes the bullet to travel maybe a couple of millimeters at most. At lightspeed, a nanosecond is a foot - 300mm - so the brick molecules would have to accellerate to a significant fraction of lightspeed in just a few picoseconds - it's a very, very VERY short period of time. Classically F=ma - and for the relatively small mass of the brick, and an accelleration of zero to lightspeed in a few picoseconds...that's a PHENOMENAL amount of force that the bullet has to apply to the brick. Worse still - the brick cylinder is being accellerated to relativistic speeds - so the energy it needs is pretty much the same as the amount of energy it took to get the bullet up to that speed in the first place. So the energy of the bullet would have to be divided roughly equally between brick and bullet post-collision. So the brick accellerates from zero to maybe half the speed of light in maybe 3 picoseconds - and the bullet slows down by about the same amount just as quickly. Just think of the g-forces on the bullet! We're talking g forces comparable to a neutron star. How can a lump of lead or brick suffer that much force without being utterly annihilated? It's just inconceivable that this can end in anything much short of two thousand quadrillion joules(!) of spectacularly high energy gamma rays...which will cook everything out to the horizon and to a depth of a few kilometers into the ground. A few thousand square miles of everything would simply vanish - the resulting debris would likely be thrown up into the upper atmosphere and would probably shut out the sun for a few years - maybe plantlife dies - then animal life dies - then it's game over for humanity. SteveBaker (talk) 02:23, 10 December 2008 (UTC)[reply]
It doesn't matter if the bullet and brick are completely annihilated, as long as the remnants continue to travel on at relativistic speeds and take a large chunk of the energy isn't space with them. However, my calculations show that it wouldn't be a large enough chunk and we would still be looking at an explosion big enough to wipe out all life on Earth. (Although, I've realised I still can't calculate the volume of a cylinder, I used the diameter instead of the radius, so it's actually 0.25kg of brick. That doesn't seem to make a significant difference to the end result though.) --Tango (talk) 13:58, 10 December 2008 (UTC)[reply]
You might be interested in the Oh my god particle, a relativistically-fast micro-bullet From Beyond! --Sean 13:46, 9 December 2008 (UTC)[reply]


This whole bullet scenario is pretty silly. You're applying a physical model which is designed for elementary-particles to macroscopic objects. There are so many problems - like, bullets would not remain in solid-form when their individual particles attain kinetic energy many orders of magnitude above their intermolecular binding energies. Once again, when you pose a ridiculous physical scenario, there's no good scientific-model to apply, so throwing equations at it will not conclusively answer anything. Maybe we should move this question to the Science Speculation Desk For Crackpot Theories Applying Quantum Mechanics and Special Relativity to Unlikely Scenarios. I don't think it does a service to the "uninitiated" readers who are unfamiliar with advanced physics when we use inapplicable theories on non-physical situations. It's bad physics, even if the math is flawless. Nimur (talk) 16:17, 10 December 2008 (UTC)[reply]
But the bullet's kinetic energy is zero in the only reference frame that tells you anything about what state of matter the bullet is in. --Tango (talk) 16:56, 10 December 2008 (UTC)[reply]
It's hard to say where to begin in shooting down Nimur's post! Firstly, the 'physical model' is Einsteins special relativity theory - which most certainly does apply to macroscopic objects. The bullet is PERFECTLY able to retain it's solid form (so long as we're in a vacuum) precisely BECAUSE relativity says that the laws of physics are the same for all inertial frames of reference - so the bullet is able to consider itself to be stationary - and if it's stationary in a vacuum then it's certainly not going to fall apart due to some mysterious binding energy issue. The same is true for the building...and in fact, this is just as much a question of what happens when a building that's moving at 99.9999% of lightspeed hits a completely stationary bullet...because that's the EXACT same question. Bullets don't usually spontaneously disintegrate just before something hits them! Until bullet and building actually meet, neither of them is in the slightest bit inconvenienced. If you don't know this (and given what you just said - it's hard to see how you do) then you should sit back and read some of the things posted here rather than complaining about them because there is a strong possibility that you'll actually learn something. The equations I was throwing at the problem are all perfectly acceptable for this kind of situation. It's hardly "advanced physics" - the equations have been around for 80-some years. Lorentz, F=ma, E=1/2 mv2 are all taught in any good high school - and those are the only equations I've used. This is a perfectly legitimate way to discuss the question as asked. If you're going to start whining about the nature of the questions that are asked here - then you are on a slippery slope. SteveBaker (talk) 21:37, 10 December 2008 (UTC)[reply]
You were taught special relativity in high school? I didn't get taught about Lorentz factors until Uni. (I'd read about them in books before then, of course, but that's just because I'm a geek.) --Tango (talk) 21:56, 10 December 2008 (UTC)[reply]
Again, I won't contest your equations, I don't doubt relativity. When anyone can show me an experimental setup which tests bullets at relativistic speeds, (or stationary bullets and relativistic brick walls), I'll start worrying about the details. In the meantime it's an irrelevant gedankenexperiment - you apply relativity to something which has never been observed in a relativistic context... you may as well start throwing the Theory of Evolution at the brick wall (again, a perfectly sound and scientific theory - but only applicable to the correct context!) My only point is that you can't take a scientific model and expect it to be universally applicable, no matter how rigorously verified it is in a specific context... Science must be based on experiment first and foremost. No relativistic bullet/brick-wall experiments exist, so you are blindly speculating that these equations which have only been verified for muons (and their ilk) hold for walls and buildings. You are "pretending" without any scientific evidence that Relativity is the Grand Unified Theory, and you're implanting that idea into other people who don't yet have enough training to decide for themselves. Nimur (talk) 14:47, 12 December 2008 (UTC)[reply]

Sequence line-ups

I am starting a project involving the use of computer programs (BLAST, ClustelW, AlignX) to line-up the genes of different clades of the same enzyme in two species of flatworm. I don't know where to begin, however, as I have no experience in this area. Can anyone guide me where to go to find information about how such a project may be undertaken or a link to a paper or two that have used the same method before? 143.117.157.60 (talk) 11:35, 9 December 2008 (UTC)[reply]

This paper covers a lot of relevant tools: [18]. Another resource is CDD. TreeFam seems relevant: [19]. Some of these I found Googling "alignment orthologs flatworm", etc. BioEdit is a nice, free (Windows) sequence editor that has plenty of built-in tools. HTH --Scray (talk) 11:54, 9 December 2008 (UTC)[reply]
You might also want to consider using Psi-BLAST, and it has a nice tutorial. --Scray (talk) 11:57, 9 December 2008 (UTC)[reply]
I also find ClustalX much friendlier than ClustalW. --Scray (talk) 11:59, 9 December 2008 (UTC)[reply]
There are several pretty decent Wikipedia references that you might want to read through. If you already have your sequences in hand, you can assemble them into FASTA format and run them through Clustal (use version ClustalX as suggested above, since it's a graphical user interface) to generate your multiple sequence alignment. ClustalX can also export the alignment file as in a format that can be used to generate a phylogenetic tree or dendrogram (which is what I assume you are trying to do). As mentioned above, Bioedit is very useful for modifying/annotating your alignment file from ClustalX into a form that can be published.
If you don't already have sequences in hand, then you need to use BLAST ([20]) to find all of the sequences that are significantly similar to each other in the sequence database. To do this, take your known enzyme sequence and blast against a particular flatworm genome. There are a few variations that you need to be aware of:
1) BLASTN - nucleotide blast, searches a nucleotide database using a nucleotide sequence query
2) BLASTP - protein blast, searches a protein database using a protein sequence query
3) TBLASTN - translated blast, searches a translated nucleotide database using a protein sequence query
Any given enzyme will probably have fairly high identity at the protein level between closely related species, but the nucleotide conservation will be much lower. For that reason, I would recommend starting from a protein sequence and searching your different species using BLASTP to pull out the homologous enzymes. Note that this will only identify annotated protein sequences (or in some cases predicted protein sequences). You can extend your search using TBLASTN against the whole genomic sequences to find unannoted nucleotide sequences that could encode the enzyme you're interested in. If you find a piece of genomic sequence that seems to contain a protein-coding gene, you can run it through a gene prediction program. It can get a little complicated sifting through genome data, but it's a good exercise to see if you can find intron/exon junctions, etc. Have fun! Medical geneticist (talk) 20:14, 9 December 2008 (UTC)[reply]

Why does light refract upward at cold temps?

Was out snow shoeing earlier, have always wondered why at colder temperatures (<-25C) light refracts upward way into the sky? The only info I could find about this was instead for forming ice plates and cooler temps, when its real cold the ice crystals for a more vertical shape? Does air density have to do with this as well? —Preceding unsigned comment added by Oilsandsfj (talkcontribs) 12:50, 9 December 2008 (UTC)[reply]


http://en.wikipedia.org/wiki/Mirage#Superior_mirage This should help you I think. Gunrun (talk) 14:01, 9 December 2008 (UTC)[reply]

Cheese and intestinal blockage.

Is there anything in cheese that makes it cause constipation? I've noticed with myself and friends, whenever we eat a meal with quantities of cheese, our bowels get blocked up. I've eaten tons of dairy and lots of fatty foods in meals without any similar problems. But what is there about cheese that seems to act like intestinal concrete? --69.149.213.144 (talk) 14:31, 9 December 2008 (UTC)[reply]

The bigger issue is that when you are eating cheese, you are NOT getting as much dietary fiber as when you eat other foods. Try the experiment and see if eating some high-fiber foods alongside cheese doesn't improve the situation for you... --Jayron32.talk.contribs 16:51, 9 December 2008 (UTC)[reply]
Or get your fiber in your cheese, with caraway cheese: [21]. (Actually, this is low on fiber, so you'll still need other sources.) StuRat (talk) 05:01, 11 December 2008 (UTC)[reply]
What, no article ? Now I'm really cheesed off ! StuRat (talk) 05:03, 11 December 2008 (UTC)[reply]

Will road salt kill grass? Grsz11 16:49, 9 December 2008 (UTC)[reply]

It can yes, if too much of it gets on grass it can burn it, the same way over fertilizing it can. -Djsasso (talk) 16:51, 9 December 2008 (UTC)[reply]
Oh well, I rent. Thanks, Grsz11 17:13, 9 December 2008 (UTC)[reply]
See Salting the earth... --Dr Dima (talk) 17:15, 9 December 2008 (UTC)[reply]
Instead of sodium chloride, potassium chloride is sometimes used to melt road ice. Would potassium chloride be less harmful to grass and to the metal parts of cars? —Preceding unsigned comment added by 98.17.46.132 (talk) 14:37, 10 December 2008 (UTC)[reply]
A very good question. Googling for KCl NaCl plant toxicity returns plenty of fascinating stuff, including a great 1908 paper on wheat root growth in solutions of several metal chlorides at various concentrations. Skimming conclusions from a few sources, the somewhat surprising answer is: KCl is not necessarily less toxic than NaCl for grasses. So please don't salt your garden! That is, unless Menelaus is calling ;) . --Dr Dima (talk) 18:47, 10 December 2008 (UTC)[reply]

How do you use microwaves to find out if there's foil inside butter tubs?

I've just started a new project with school and Dale Farm that we have to detect the foil inside butter tubs without taking the lid off. Microwaves work at finding out if there's metal there or not but I can't work out how to make a circuit that will tell me without looking at every current coming out. Anyone know of any useful websites? —Preceding unsigned comment added by C ocean (talkcontribs) 17:39, 9 December 2008 (UTC)[reply]

Puting metal in a microwave is contraindicated (don't do it!) for several good reasons. First, the potential for fire or other hazards is quite great, and secondly the presence of metal could damage the magnetron (the working bit) of the microwave as well. It would actually be quite easy to, using stuff lying around the house or availible at the local SuperMegaHardware Store, create a rudimentary Metal detector. this google search turns up literally hundreds of sites which show how you can do this. Good luck! --Jayron32.talk.contribs 18:01, 9 December 2008 (UTC)[reply]
It sounds like what you want is a radar setup. I agree, though, a metal detector is much more practical for the typical school project (unless this is a particularly unusual sort of school). 198.29.191.149 (talk) 19:08, 9 December 2008 (UTC)[reply]
Butter+foil+microwave oven=fire, don't do this combination. Graeme Bartlett (talk) 20:21, 9 December 2008 (UTC)[reply]
Although the flaming result would certainly reveal the foil. Fire extinguisher recommended. --—— Gadget850 (Ed) talk - 20:47, 9 December 2008 (UTC)[reply]
I don't see the word "oven" anywhere in the original question; C ocean, can you clarify what you are trying to do? Beyond that, I have seen microwave ovens with metal racks, so clearly the whole "never use metal in a microwave!!!111" meme is overwrought. --LarryMac | Talk 20:47, 9 December 2008 (UTC)[reply]
You can use metal in a microwave oven— such as a rack —under certain circumstances. You get some electric current induced into any metal, but pointed edges cause arcing and heating. A spoon would not arc, but a fork would. I suspect the the edge of the foil cover would arc, and melted butter is flammable. This would occur in a standard microwave oven or if it was just focused microwaves such as from radar. --—— Gadget850 (Ed) talk - 21:00, 9 December 2008 (UTC)[reply]
I've seen microwaves specifically designed to be safe with metal, but only one piece of metal and it needs to be pretty flat (eg, a piece of foil covering a bowl would be fine). If you have two pieces, of one piece that bends, then you can get arcs from one bit of metal to another, but if you only have one bit there is nowhere for the arc to go. I think the way they do it is to not have any metal around the edge of the oven so nothing can spark from a bit of metal inside to the edge. --Tango (talk) 22:10, 9 December 2008 (UTC)[reply]
Wait, wait, wait...are we over-thinking this? Are they talking about some foil contaminant buried deep inside the butter (seems unlikely) - or are they simply asking whether the foil that is SUPPOSED to be sealing the butter under the lid has somehow not been put there or perhaps was subsequently removed? If THAT is the question our OP has to answer then perhaps it's as simple as rotating the lid and seeing how stiff it is? Or tapping on the top of the lid and listening to the sound it makes (or having your computer listen to it)? Or weighing it? ...or...lots of REALLY simple tests! SteveBaker (talk) 01:51, 10 December 2008 (UTC)[reply]
The OP indicated some aspect of the project involved circuitry, so I assume that an electronic device is supposed to be built which will detect the presence of metal. Rudimentary metal detectors, involving simple inductor circuits, can easily be built using household materials, so I still think that's the easiest way to go. --Jayron32.talk.contribs 03:32, 10 December 2008 (UTC)[reply]
Or do a biopsy stick in a needle and take out a sample, too bad about the little hole though. Graeme Bartlett (talk) 03:46, 10 December 2008 (UTC)[reply]
This sounds VERY much like a common electronics class lab (sometimes used in physics as well). The point of the lab is to build two variable oscillator coils. Put one in the middle of the other and get them on the same frequency. Connect a tiny speaker between them. Everything should be fine until something interferes with the magnetic waves (not microwaves - magnetic waves). Then, the frequencies get messed up and get out of sync - causing an audible signal over the speaker (the beep that metal detectors make). I've seen it printed up many times for many different schools. The test is always "detect (some metal object) inside (some opaque container)". -- kainaw 03:51, 10 December 2008 (UTC)[reply]

If a cosmic string passed through the Earth, what would happen? Assuming they exist. --140.247.10.18 (talk) 19:10, 9 December 2008 (UTC)[reply]

For a long cosmic string (kilometres or bigger), I expect the Earth would be destroyed by tidal forces before it got too close, so it wouldn't be able to pass through the Earth. For a very short one (smaller than an atom) it would be much like a micro-blackhole and would pass straight through with little effect. I'm not sure about ones inbetween. --Tango (talk) 19:48, 9 December 2008 (UTC)[reply]
How to destroy the Earth: Whipped by a cosmic stringDanielLC 01:52, 10 December 2008 (UTC)[reply]
Theoretically we can calculate many results, but one thing should be noted the concept of cosmic string is still in a hypothetical stage. Otolemur crassicaudatus (talk) 10:35, 10 December 2008 (UTC)[reply]
The interesting thing about cosmic strings is that they have no gravitational field at all! At least, straight sections of them don't. The metric of a straight cosmic string can be written ds² = dr² + r² dθ² + dz² - dt², which is exactly the same as the metric of Minkowski space in cylindrical coordinates (r,θ,z,t). The only difference is that the range of the angle θ is smaller than 360°. To put it another way, you get the cosmic string metric by starting with Minkowski space, deleting a wedge-shaped region from it, and gluing the two sides of the wedge together. There are no tidal forces and not even any gravitational attraction—you can hover at any fixed distance from a cosmic string without firing your engines at all. But two comoving objects that pass a cosmic string on opposite sides will end up moving towards each other at an angle equal to the angle of the wedge you removed (the defect angle). The deflection is the same regardless of the speed of the objects and the distance from the string.
I can't remember reading anything about the effect of a cosmic string passing through an object, so what follows is just idle speculation—but I suppose it would be like slicing the object into two pieces and sending them crashing into each other at a relative velocity that depends on the defect angle and the speed of the string through the object. With a small defect angle and a low speed you would get compression waves radiating outward from the collision plane, like an earthquake. With a large enough defect angle and/or a high enough speed I suppose the object could be compressed enough to form a black hole. In intermediate situations there would be massive devastation of some kind. But nothing will get "sucked in" to the cosmic string; it has no gravity at all. -- BenRG (talk) 06:41, 13 December 2008 (UTC)[reply]

Native Americans and Atlantis

How plausible is the information in the link here? http://www.redicecreations.com/specialreports/2006/05may/atlantisDNA.html --Emyn ned (talk) 19:20, 9 December 2008 (UTC)[reply]

"Genetic researchers determined that 96% of Native Americans fell into one of the four A-D haplogroups and while these mtDNA types were also found in Asia they are not present in Europe or Africa. This too indicates that Asia was the ancestral region of most Native American tribes. Then in 1997 another lineage was discovered, which geneticists dubbed X. This discovery ignited a storm of controversy that has not died down to this day. The X haplogroup needs careful,thoughtful, and deep historical analysis because this group may well hold one of the most important keys to unlocking the secrets of our collective past. ......

Moreover, the vast majority of tribes contained no X members. In fact, it was not found in any native tribes in Central or South America. Again, what did these patterns mean? Independent researchers associated with the Edgar Cayce Association (A.R.E.) quickly pointed out that the data supported some of the material found in the Atlantis readings that the 'sleeping prophet' had given in the 1930s. Cayce noted that some Atlantis refugees had immigrated to the northeastern region of the United States and later formed the Iroquois nation. It was in those tribes that the highest concentration of the X haplogroup was found." --Emyn ned (talk) 19:25, 9 December 2008 (UTC)[reply]

No comment on the genetics, I'm just amused by the concept of a mass migration from the Mediterranean to New England. I wonder how many Atlantians survived their first winter. APL (talk) 20:17, 9 December 2008 (UTC)[reply]
There are certain persistant cultural traditions and artifacts among Native American peoples which raise some questions as to how "isolated" they were. The Quetzalcoatl/Kukulkan myth in Central America has some depictions of the "feathered serpent god" as a bearded, pale-skinned man; neither traits were common among native American peoples, leading to speculation that the myth had European connections. Additionally, certain artistic traditions of the Olmec people show subjects with decidedly African (and not really Central American) features, suggesting contact there. Beyond that, there is the Vinland settlements circa 1000 AD, speculation over Chinese exploration of the N. American west coast, and other evidence of possible pre-Columbian contact between the hemispheres. While the celebrated, the well funded "expeditions" had the benefit of being ventures supported and historically recorded by the power elite, and so show up in the historical record. There may well have been fisherman plying the coasts of North America and other, less celebrated contacts, between the hemispheres that disappeared from the formal historical record. There are many, simpler, Occam's razor-compliant explanations for genetic anomalies among Native American populations than "Mega continent disappears without a trace, and leaves no evidence except genes among the Native Americans". --Jayron32.talk.contribs 22:18, 9 December 2008 (UTC)[reply]
Is anyone willing to comment on how this ties in with the reported descent of Native Americans from the lost tribes of Israel? CBHA (talk) 22:37, 9 December 2008 (UTC)[reply]
Sure. There is no such descent, at least as the Mormons or Atlantismaniacs tell it. See Human mitochondrial DNA haplogroup for a map of the travels of the peoples bearing Haplogroup X. - Nunh-huh 00:21, 10 December 2008 (UTC)[reply]
To be precise, Mormons (more correctly known as Latter-day Saints) do not claim that Native Americans descend from the "Lost Tribes" of Israel. Lehi in the Book of Mormon was a descendant of Manasseh (Alma 10:3). Thanks to other references such as Alma 46:23-24, it is traditionally inferred that Ishmael, who joined Lehi's group with his family, was a descendant of Ephraim.
But that's probably not what you're referring to. A good answer to the assertion that it's *impossible* that Native Americans descend from Middle-Eastern heritage can be found [here[22]]. I probably would have worded it "There is no *proven* descent...." Kingsfold (talk) 14:01, 20 October 2009 (UTC)[reply]

Does lemon juice damage your teeth?

All over the internet it is suggested that it does; but one can't always believe the internet. Nothing about the matter on Wikipedia, as far as I can see. I've recently taken to drinking green tea with lemon, which is very refreshing; and I suppose I'm going through about the juice of one small lemon a day. But if I'm damaging my tooth enamel, I'd better stop. 92.8.198.137 (talk) 23:16, 9 December 2008 (UTC)[reply]

Lemon juice is somewhat acidic, and the acid could damage your teeth, but the final pH of the liquid is what matters. Even highly acidic drinks like orange juice or pop don't really make much difference, the enamel damage comes from sugar that feeds bacteria that stay on the teeth, not the acid that just passes right by into your already acidic stomach. These bacteria produce acid that remains in contact with the enamel for a long time and can cause real damage. You might theoretically be damaging your teeth, but chewing on a piece of bread is probably worse. SDY (talk) 23:42, 9 December 2008 (UTC)[reply]
Here is a good reference. Otolemur crassicaudatus (talk) 00:05, 10 December 2008 (UTC)[reply]
Can't get access to the full article. I assume they were soaking the teeth in the liquid? Again, the final pH of "tea with lemon" is probably in the 4-5ish range at best unless it's "do you want some coffee with your sugar?" amounts of lemon juice. SDY (talk) 00:10, 10 December 2008 (UTC)[reply]
This is another interesting article (although orange rather than lemon). Axl ¤ [Talk] 22:51, 10 December 2008 (UTC)[reply]
Thanks for your help, everyone. I'm still confused a bit, though. Sure, orange juice, on the scale that people drink it, is bad for your teeth; but I was hoping that the juice of one lemon a day would not be a problem. Quite a few internet sites claim that even lemon water may be bad for the teeth. Anyway, I'm reducing to the teeniest squeeze of lemon per cup of tea. 92.8.198.137 (talk) 22:23, 12 December 2008 (UTC)[reply]

December 10

Tea and diabetics

I was in my local tea market and they had a sign warning of the dangers of drinking tea if you are a diabetic. It warned that it can increase blood sugars. I've never heard of such a thing. Obviously, if you take your tea with sugar, that's a problem. But unsweetened plain tea? Is there any truth to this? --69.149.213.144 (talk) 04:15, 10 December 2008 (UTC)[reply]

According to this article, which appears to quote a reliable source, rat studies suggest that tea may be of benefit to people with diabetes. [23]. DuncanHill (talk) 04:32, 10 December 2008 (UTC)[reply]
Here is a reference according to which "Tea catechins, especially (-)-epigallocatechin gallate (EGCG), appear to have antiobesity and antidiabetic effects". Otolemur crassicaudatus (talk) 11:22, 10 December 2008 (UTC)[reply]
Tea does not worsen blood sugar. Axl ¤ [Talk] 18:29, 10 December 2008 (UTC)[reply]
Unless, of course, you add sugar to your tea... – ClockworkSoul 19:06, 10 December 2008 (UTC)[reply]
Caffeine is a diuretic. This means that it makes you pee. Depending on the type of tea, it can make you pee, which reduces your water proportion (and I mean the percent of water you are composed of). This, inturn, will increase your blood (glucose) sugar level, because the water that is excreted in the urine will be immediately from the blood. (urinary system for more). Then nephrons of the kidneys take the toxins from the blood and in urinary tubes (it's been a while since i last did biology) funnels it to the bladder for excretory storage. Mind you, water is the solvent in the medium of these toxins. So tea may increase blood glucose levels in this way.96.53.149.117 (talk) 07:58, 11 December 2008 (UTC)[reply]
Interesting. But this market also sold coffee and there was no warning sign about coffee and diabetics. --70.167.58.6 (talk) 16:12, 11 December 2008 (UTC)[reply]
If it were a tea market, I'm guessing there would be a lot of fancy teas some of which may contain sugars natural or otherwise. This may be directed at those. Even more so if you're a Brit in which case you may be thinking of several cupsof tea within a few short hours Nil Einne (talk)

Caffeine is indeed a mild diuretic. There is some evidence that a large quantity of caffeine intake can impair glucose control. However the caffeine load is equivalent to over a litre of tea drunk, with 75 grams of sugar at the same time. Axl ¤ [Talk] 11:30, 12 December 2008 (UTC)[reply]

Fleeting bad memories

Sometimes out of the blue I suddenly remember a bad memory and makes me feel bad. My knee-jerk reaction would bedoing an intellectual na! nanana! I can't hear you! by focusing on something else (tapping my fingers for example) until it goes away. What do you call that resurgence of memory and my suppression of it.--Lenticel (talk) 04:45, 10 December 2008 (UTC)[reply]

There's a wiki article Flashback (psychological phenomenon) which is too stubby to be of great help, but it's a start. Suppression of it, repression, is a defense mechanism. Julia Rossi (talk) 05:04, 10 December 2008 (UTC)[reply]
Take also a look at Rumination_(mental). --Mr.K. (talk) 09:51, 10 December 2008 (UTC)[reply]
The finger tapping block is mechanical, not the same thing as a subconscious repression. Try Thought suppression for the deliberate conscious one. Julia Rossi (talk) 22:34, 10 December 2008 (UTC)[reply]
I find swearing at the people who caused the bad memories to be beneficial. Of course, only do this out loud when you're alone, or you'll have to tell everyone you have Tourette's Syndrome. StuRat (talk) 04:48, 11 December 2008 (UTC)[reply]

Jets flying over populated areas

Do fighter aircrafts have to fly over populated areas? Civil aircrafts probably have to, but why do military jets do it?--Mr.K. (talk) 09:37, 10 December 2008 (UTC)[reply]

If a military aircraft flies over populated area, that does not mean it will use its weapons system. It becomes quite tough and the route becomes quite complex if it avoids civilian areas. If there is short air route available by flying over a civilian area, the fighter may take that route. Otolemur crassicaudatus (talk) 10:41, 10 December 2008 (UTC)[reply]
I would assume the question is motivated by the F/A-18 that crashed into a house in San Diego recently, and not by concerns over weapons systems. In this case the fighter was on approach to Miramar which is surrounded on three sides by populated areas. Dragons flight (talk) 11:07, 10 December 2008 (UTC)[reply]
It is not uncommon for military bases to be surrounded by populated areas. It is not reasonable to ask the fighter jets so somehow create a wormhole through space and teleport from outside the populated area to the military base without flying over all the homes that were built around the base - usually long after the base was built. -- kainaw 13:38, 10 December 2008 (UTC)[reply]
It's very unusual for fighter jets to land on houses, so it doesn't make sense to give the issue much attention in their routing. You'll probably save more lives by having the houses near the base, which will reduce the number of person-miles the base workers will drive on their daily commute. --Sean 13:42, 10 December 2008 (UTC)[reply]

Why should military aircraft be held to any standard other than civilian ones, given the latter are larger, not designed as ruggedly vs things that could happen in the air (747 doing a barrel roll and getting hit during a dog-fight?), and are owned by companies deep in bankruptcy vs the cash cow that some claim US military spending is. DMacks (talk) 14:02, 10 December 2008 (UTC)[reply]

"Why should military aircraft be held to any standard other than civilian ones..."
There are dozens of reasons:
  • Different aircraft design, including size, speed, type of fuel, maneuvering capability
  • Different flight capabilities
  • Different engines (louder, noise-complaints over populated areas)
  • Different training methods and selection criteria for pilots
  • Different aircraft manufacturing (materials, hazardous components)
  • Different safety regulations regarding pilot state (hours of sleep, for example)
  • Different ground support crew (maintenance, air traffic control, personnel supervision)
  • Psychological impact due to the presence of an ejection seat on a pilot in an emergency over a populated area
  • Potential to carry weapons systems
  • Overall different philosophy regarding the role and operation of military vs. civilian aircraft
The result is that there is a different standard, implemented in the form of air space - there is restricted military-only airspace; there is restricted civil-only airspace, and shared airspace. The F-18 that crashed this week had already declared an engine malfunction while over the ocean, and was being routed to Miramar (instead of the aircraft carrier where it was based), because it was probably thought safer to fly overland than over water [24] - "Several experienced pilots said that if there's a nearby landing field ashore, an inexperienced pilot wouldn't attempt a dangerous, engine-out landing on the pitching deck of an aircraft carrier." Pending the full investigation, it is not clear why the pilot ditched the aircraft, but assuming his judgement was sound, a serious equipment failure may have rendered it uncontrollable. Alternatively, the pilot may have misjudged or panicked. Nimur (talk) 16:36, 10 December 2008 (UTC)[reply]
Thanks for the knowledgeable reply! I might add in reply to the question "Why should military aircraft be held to any standard other than civilian ones...", that they are already held to much lower standards. To be exact, 750 feet lower. At least that was the case in Germany, where US jets (mostly Phantoms) crashed on civilian houses on a regular basis when I lived there - they were allowed to fly at 250 feet at supersonic speed, according to de:Tiefflieger (for which there seems to be no translation. Can it be that they only did that in Germany?) I can tell you - it all fun and games when they fly slowly over you on Fourth of July, but it's brute force when they blast over your head every other day at random times. — Sebastian 18:07, 10 December 2008 (UTC)[reply]
Tieflieger trained not only in Germany, but they were a particular problem there for a number of reasons. First, Germany is simply small and full. There are few areas without significant population, particularly not for an aircraft at Mach 1 or above. Secondly, Germany was seen as a likely battlefield in the Cold War. Hence, for realistic training, Germany was preferred. And thirdly, as a result of the WW2 capitulation, the allies got fairly far-reaching military cooperation agreements that allowed them to use German airspace for training purposes without alienating their own voters. --Stephan Schulz (talk) 19:28, 10 December 2008 (UTC)[reply]
Can you define "regular basis"? Was it daily? Who's house is going get destroyed today? Was it weekly? Was it monthly? Was it yearly? Did it happen 3 times over 20 years? It is difficult to relate this singularity in the U.S. with Germany without something better than "regular basis". -- kainaw 18:13, 10 December 2008 (UTC)[reply]
Ah, found it: de:Starfighter-Affäre. The plane was the Lockheed F-104G, a.k.a. "Starfighter". There were hundreds of crashes. According to the German article, alone in 1965, there were 27 accidents with 17 casualties. And as I remember, this dragged on for years. — Sebastian 18:24, 10 December 2008 (UTC)[reply]
Looking at our own article Lockheed F-104, which says "flying at high speed and low level over hilly terrain, a great many accidents were attributed to CFIT or Controlled Flight Into Terrain ...", I learned a wonderful doublespeak way to say "crash"! — Sebastian 19:33, 10 December 2008 (UTC)[reply]
"Controlled flight into terrain" isn't doublespeak, it's a term of art describing a specific type of crash. Other types of crash include runway overruns, mid-air collisions, and structural failure. --Carnildo (talk) 22:34, 10 December 2008 (UTC)[reply]
But of course! It's a "controlled flight into building", as in "Controlled demolition hypothesis for the collapse of the World Trade Center". ;-) — Sebastian 23:18, 10 December 2008 (UTC)[reply]
I see, I wasn't aware of that term. But it's still strange, and it doesn't seem to be common in aviation, at least not here at Wikipedia. Even our article Aviation accidents and incidents only mentions Controlled Impact Demonstration, which uses the term in the way most people would: "Controlled" meaning "keeping things under control". — Sebastian 00:16, 11 December 2008 (UTC)[reply]
I used to work in flight simulation - it's a common enough aviation term with a very precise meaning. It means that the plane didn't hit the mountain because it was damaged or because the pilot had blacked out...the aircraft was perfectly flyable - and the pilot was fully in command of the controls - but the plane smacked into a mountain anyway. Hence it means things like flying into a mountain because of reduced visibility - or some kind of nighttime navigational error - or because the altimeter was mis-calibrated...something like that. SteveBaker (talk) 06:21, 11 December 2008 (UTC)[reply]
And I should point out that I, despite having never heard the term before nor any experience in the airline industry was able to guess more or less what it meant Nil Einne (talk) 12:20, 11 December 2008 (UTC)[reply]
My point was for User:SebastianHelm's sake, he said "I learned a wonderful doublespeak way to say "crash"!" - but it's not doublespeak (it's not a euphemism) and it doesn't mean "crash" - it means a very specific kind of crash. At any rate - no mention of the Starfighter would be complete without the saying that was prevelant in the USAF at the time: "If you want to buy a Starfighter - get a piece of land in Germany and wait!". SteveBaker (talk) 18:07, 11 December 2008 (UTC)[reply]

(undent) Out of curiosity, how unstable was the F-104? Modern fighters are designed with relaxed or absent static stability for maneuverability or other reasons with the plane kept under control by computer correction. Stealth was a future concept, but was there intentional instability in the F-104 design for maneuverability? For that matter, is an F/A-18D particularly stable? SDY (talk) 18:43, 11 December 2008 (UTC)[reply]

The Starfighter was bought because the producer bribed several politicians in europe to buy it, so they bougth the bird which was a good weather high speed high altitude intercepeter and used it for what it was needed in europe an allweather allround fighterbomber. The bad training and the design which was not for turbulent valleys and small hills made it the a dangerous witwenmacher widdowmaker.--Stone (talk) 20:45, 11 December 2008 (UTC)[reply]

Reducing fat

There are a myriad of products on the market that promise to reduce the fat in your body. In a series of them, the effect is from outside the body (heat waves, cream, vibrations, small electro-shocks). Excluding surgery, is there any possibility to reduce fat through this way or fat can only be reduced from inside?--Mr.K. (talk) 09:47, 10 December 2008 (UTC)[reply]

Dieting may help. Physical exercise is the best option to reduce fat. It depends on the amount of body fat a person has. There are anti-obesity drugs also available. In extreme cases where the person is too overweighted, surgery is generally required. Otolemur crassicaudatus (talk) 10:47, 10 December 2008 (UTC)[reply]
The question is actually about ways of reducing fat with an external procedure (not diet, exercise, ...) and excluding surgery. Is it possible?Mr.K. (talk) 11:08, 10 December 2008 (UTC)[reply]
Well exercise is arguably an "external procedure", and likely to be effective. In principle, electrical muscle stimulators should be capable of improving muscle strength and tone in a way that is similar to (but probably inferior to) that of exercise. That would probably have an indirect effect on fat. I have also seen some studies (in rats) supporting the notion that vibration reduces fat deposition, though that is not the same as removing existing fat deposits. The best thing for reducing fat though is almost certainly dieting. Dragons flight (talk) 11:17, 10 December 2008 (UTC)[reply]
In the case of exercise, our body burns the fat to obtain energy, definitely a natural process of our body. --83.40.248.171 (talk) 11:39, 10 December 2008 (UTC)[reply]

Clockwork Toy (Homemade)

I'd like to make a gear-based toy, but I don't know a good source for cheap gears and such. Any suggestions? Preferably plastic. Black Carrot (talk) 10:56, 10 December 2008 (UTC)[reply]

McMaster-Carr has all sorts of those kinds of bits and bobs. --Sean 13:48, 10 December 2008 (UTC)[reply]
Lego Technic? SteveBaker (talk) 21:19, 10 December 2008 (UTC)[reply]
You may also consider the Meccano toy sets, which (if childhood memory serves me) had all sorts of cogwheels and related bits for technical models. --Cookatoo.ergo.ZooM (talk) 20:28, 11 December 2008 (UTC)[reply]

LPG

At what temp. does LPG turn to vapor for use on a furnace in a camper?```` —Preceding unsigned comment added by Raytrudell (talkcontribs) 13:34, 10 December 2008 (UTC)[reply]

Assuming good faith that it is not a homework question, the answer to your question is -42°C. Otolemur crassicaudatus (talk) 13:50, 10 December 2008 (UTC)[reply]
This temperature is appropriate for propane, however in case of LPG it may vary from -44 ºC to 0 ºC. Otolemur crassicaudatus (talk) 14:01, 10 December 2008 (UTC)[reply]
Doesn't pressure have something to do with it? —Preceding unsigned comment added by 98.17.46.132 (talk) 14:03, 10 December 2008 (UTC)[reply]
Yes, it is in "normal" atmospheric pressure. Otolemur crassicaudatus (talk) 14:20, 10 December 2008 (UTC)[reply]
LPG in a cylinder is at a higher pressure than atmospheric. When an appliance connected to the cylinder is turned on, the pressure in the cylinder is reduced somewhat and the liquid boils, thereby releasing gas. It will always boil, regardless of the temperature of the LPG liquid, unless the ambient temperature makes the temperature of the liquid LPG in the cylinder extremely low. LPG is mainly butane; in winter months, LPG suppliers mix some of the more expensive propane with it to ensure it will boil. —Preceding unsigned comment added by 98.17.46.132 (talk) 15:00, 10 December 2008 (UTC)[reply]
Yes it will boil in any temperature above 0 ºC which we see in our every day life, but it needs the minimum temperature -44 ºC in "normal" atmospheric pressure to boil. Otolemur crassicaudatus (talk) 15:16, 10 December 2008 (UTC)[reply]
"LPG" and "vapor pressure" in Wikepedia have information on this.

Test your microwave with a mobile phone?

On a recent episode of the Gadget Show it was claimed that you can test the shielding on your microwave oven by checking whether a mobile phone will receive a call when inside the oven [25]. I have tried this on two microwaves so far, and in both cases the phone could receive the calls. I have also read elsewhere that the shielding should not stop mobile phone calls because the frequency differs too much from those used by the microwave. Can anybody clarify this please? Larry Mystery (talk) 15:21, 10 December 2008 (UTC)[reply]


The question you are asking is, roughly restated, "does the microwave have a shield?" It should be more properly restated, to be very precise, as "What is the non-linear anisotropic attenuation-vs-frequency characteristic of the microwave casing, and what frequencies of attenuation overlap those frequencies used by the cellular phone?" First of all, let's clarify a few details:

  • Microwaves and cell phones commonly do operate at the same or similar frequency band (for example, 2.45 GHz). But, maybe your microwave and cell phone operate at different frequencies... it depends on whether your phone uses GSM, where you bought your microwave, etc. You can check this with the marshmallow test, or if you're smart, just read the label on the back of the microwave oven.
  • Microwaves commonly include a few features, such as a wave guide or horn to guide the microwave energy in a specific direction (towards the food)
  • After the microwave energy is "in the oven", it bounces around, off the walls, maybe even setting up resonant waves. So, any "shielding" should really be surrounding the entire oven, with strongest protection at the places of strongest electromagnetic fields (typically, directly opposite the "horn" where the waves come in.
  • Microwave ovens probably use a "crappy" but generally single-frequency tonal magnetron to create the electromagnetic waves. So, the shielding is quite probably a "notch filter" (isolating out that single frequency and preventing it from passing).
  • By the second law of thermodynamics, any (passive) shielding should be bidirectional - that is, if the energy can't get out, then energy can't get in, either.
  • Shielding is also not measured as "all or nothing" - it's measured as an attenuation. That means that the shield lowers the intensity of the radiation, but does not make the signal disappear completely. Now comes the non-linear part. The case in consideration compares two very very very different orders of magnitude - nearly one kilowatt of oven radiation, blasting from eight inches away, compared to a few milliwatts transmitted by the phone and maybe nanowatts (picowatts even!) received from the tower. (Depending on "details," your phone may need bi-directional communication to initiate the reception of a call; or it may just need to receive a single incoming message from the tower). So it may not be safe to say that the shielding materials attenuate by a fixed amount over this entire range of power levels. It's possible that very-low intensity signals, like those from the phone, are not attenuated much at all; while high-power signals are brought down to safe intensities (and no further)
  • Cell phones use very complicated modulation to make sure that the data can be deciphered even when the signal is very very weak. This is what advertisers often mean when they say "fewer dropped calls" (though they might also be talking about density of towers). Specifically, some of the QAM spread-spectrum coding schemes are particularly insensitive to single-frequency interferers. So if the So even if the microwave shielding is "pretty good" at notching out (stopping) that single frequency that the oven operates at, the cell phone data may be fairly undeterred.
  • And the anisotropic part makes a huge difference! The cell-phone probably has a crummy antenna, which may mean it has a weird angular reception pattern. And, the microwave oven shielding is probably not uniform either (presumably concentrated on blocking regions of highest radiation while cooking!) So, if you rotate the phone, you may get dramatically different reception patterns. And this is totally assuming that there is no resonant coupling between the 2.4-GHz resonant chamber of the oven, and the 2.4-GHz dipole antenna inside the phone. Who knows what may happen to the reception pattern if that effect is non-negligible! In summary, the orientation of the phone with respect to the oven, and the orientation of the oven with respect to the nearest tower, will dramatically change the results. (see Radiation pattern for more graphical explanation).

So, it can actually be fairly complicated to say whether a given microwave will "shield" a given cell-phone from a call. Irrespective of the result of that test, it is not really a good way to determine whether the oven casing effectively blocks out the microwave energy used during cooking. Nimur (talk) 17:00, 10 December 2008 (UTC)[reply]

paper mache external fuel tank

I attended a lecture at the Naval War College by Dr. Paul Kennedy of Yale University where he stated that during the second World War, the British developed paper mache external fuel tanks for the P-51 Mustang. He showed a picture of two Brits unloading one such tank from a stack. At that time, the Americans were using aluminum external tanks and the Germans were picking them up off the ground after they were dropped in Belgium and then they (the Germans) would reuse the metal. The paper mache tanks, however, when hitting the ground would become unusable. I have not been able to find any reference to paper mache tanks on the internet or in published materials I have on planes of the second World War. East5426 (talk) 15:58, 10 December 2008 (UTC)[reply]

Mildly related: the Tom Clancy movie Clear and Present Danger featured a paper bomb/missile that was used to blow up a drug kingpin's house such that it could not be traced to the US source by the shell fragments. Or something like that. --Sean 16:52, 10 December 2008 (UTC)[reply]
I've looked around on google a bit, and mostly all I see are modeling sites selling tanks for use on static models and discussion board posts, none of which meet WP:RS. Definitely happened, but you may need a bricks and mortar and, ironically, paper library to find references. SDY (talk) 16:59, 10 December 2008 (UTC)[reply]
It's possible the professor was making a vague allusion towards early research in composite materials, which now make up an entire class of aerospace engineering materials research because of their light weights. I don't know that any such materials were in use in research labs, let alone combat, in World War II. Nimur (talk) 17:12, 10 December 2008 (UTC)[reply]
In early 1943, the Eighth Air Force was looking for ways to escort B-17's to Germany and back. The YB-40's were no match for the German fighters, and once the B-17's had dropped their bomb load, the YB-40's were too heavy to keep up with the lightened bombers. Ira C. Eaker began looking at adding drop tanks to P-47 fighters. The U.S. was then using 200 gallon paper tanks for ferry flights, but these were mostly useless for combat, they added a great deal of drag to the airframe, tended to leak if filled with fuel for more than a few hours, and could not be used at altitudes greater than 23,000 feet.
Eighth Air Force fighter command, with the help of British engineers, designed a 108 gallon metal tank suitable for combat operations that was tested in May of '43, but a steel shortage prevented production. The Brits would begin supplying a paper 108 gallon tank which they had developed for their own use in September of '43. The British 108 gallon tanks extended the P-47's combat range radius from 190 to 375 miles.
The U.S. began manufacturing a 200 gallon paper tank (which was only half-filled on the P-47) that became available 28 July (260 mile rangeradius), and an 85 gallon (photo) (referred to as 75 gallon tanks, but actually held 85) metal tank (340 miles). On 27 September '43 the eighth flew it's first escorted mission to a target inside Germany using a mixture of the 85 gallon metal tanks, as well as the British 108 gallon paper and metal tanks. Levine, A. J. (1992). The Strategic Bombing of Germany, 1940-1945.] pp. 90-1. OCLC 25131830
Still looking for paper tanks for the P-51.—eric 21:17, 10 December 2008 (UTC)[reply]
This is a longshot but the search might work better in some search environments using "papier mache" instead of "paper mache". CBHA (talk) 21:28, 10 December 2008 (UTC)[reply]
[26] [27] w/ photos of the 108 gal. paper tanks.—eric 21:55, 10 December 2008 (UTC)[reply]

Diamonds Part 2

A few days ago, I posted a question about Diamonds. For the original question and discussion above, see this link: Wikipedia:Reference desk/Science#Diamonds. A follow-up thought (and question) came to mind after reading the input from my original question. So, we now have "real" (natural) diamonds that one can purchase for, say, $1000. And we have the "same exact thing" (synthetic) that one can purchase for, say, $100. Much of the discussion centered on purchasing the cheaper synthetic diamond, because it is exactly the same thing as the more expensive natural diamond. The only real difference is purely psychological and is a product of emotion and of clever marketing. But, what about looking at this issue from another perspective? Let's say that I indeed want to buy the "real thing" (natural diamond). As a consumer ... when I purchase what I think is the $1000 "real thing" … how do I know that I am not, in fact, being swindled and getting the $100 synthetic one in its place? Thank you. (Joseph A. Spadaro (talk) 18:23, 10 December 2008 (UTC))[reply]

Via grading and certification services such as the Gemological Institute of America. — Lomn 18:40, 10 December 2008 (UTC)[reply]
A related issue is how one is able to know that a natural diamond is not a blood diamond. Although there are industry procedures in place to ensure that synthetic diamonds or blood diamonds are not misrepresented, as an end consumer, you ultimately have to rely on your trust in the vendor. Past that, the article section Diamond#Synthetics, simulants, and enhancements notes that "Today, trained gemologists can generally also distinguish between natural diamonds and synthetic diamonds." It also mentions several machines/methods to distinguish them (DiamondSure & DiamondView). Additionally, most synthetic diamond producers are upfront about the nature of their wares. Many even visibly (under a loupe) mark their gem-quality diamonds with logos or other such items which shows who produced them. I believe DeBeers has even started marking natural diamonds in a similar fashion, to show that they are "real" diamonds. Natural diamonds from Canada are routinely marked, e.g. with the "CanadaMark" service. High carat diamonds may be marked with a serial number, and registered with institutions like the Gemological Institute of America, which record their provenance. (Unfortunately, I can't seem to find an article about diamond marking.) -- 128.104.112.113 (talk) 19:15, 10 December 2008 (UTC)[reply]
Could crooks put counterfeit certification markings on diamonds? Even if a serial number on a natural diamond is registered, how would a person know which diamond is the natural one? A record of all sales and purchases of a natural diamond would have to be kept as well. —Preceding unsigned comment added by 98.17.46.132 (talk) 22:09, 10 December 2008 (UTC)[reply]
Artificial gem diamonds aren't identical to natural gem diamonds. If made without further intervention, a lab diamond is (scientifically) superior - there are no almost impurities and a much lower incidence of flaws. To compete in the gem market, the lab people have to add impurities (mostly metals) to allow them to control the colour and clarity of their product; in particular they produce lab gem diamonds in colours that occur infrequently in nature. For now (because they don't feel the need not to, and to avoid stirring up a war with DeBeers) they do so in a fashion that simulates a natural diamond to casual (and fairly close) inspection, but isn't intended to deliberately appear entirely natural. DeBeers has a number of technologies to distinguish any of these from the "real" thing (as 128.104.112.113 notes above, they sell equipment to dealers for this purpose). Some other synthetic gems (such as emeralds) are made with deliberate un-natural additions that assist detection. If the lab people really wanted to, I imagine they'd be able to "improve" the growing process to produce the adulterations and defects that the gemologists and their machines look for. I guess (were that to happen) a technological tit-for-tat would ensue for a while (much like CAPTCHA) but eventually the lab ones would be sufficiently imperfect as to be entirely indistinguishable. Diamond marking is (in part) a recognition of this inevitability (the blood diamond thing is also a factor). But it's not much of a solution - numbers can always be cloned, and many gem diamonds turn over in the market so infrequently (decades) that the cloning won't be detected. Even if it is, if ten people all have identical diamonds with the same number, whose is the real one? And if a major player (say Russia or China) decided to mass-produce indistinguishable lab gem diamonds and tag them as coming from a mine that they really only bother to run when the inspector comes, they can produce fully certified artificials. And a major production of such diamonds could lower the price of all diamonds (except the truly exceptional ones with a provenance) as to make chasing after suspected "fakes" uneconomic. The only thing stopping this all from happening is that it's not in the interest of the artificial makers to ruin the market they've just joined - they want to be competitive, but they don't want to end up making diamond so cheap that there's only a decent profit when you make it by the ton. So they have a gun to DeBeers head (once they don't want to use) and DeBeers have one back - they can dump their (reportedly huge) reserves onto the market which zaps the artificial guys profit margins and makes their venture capital dry up (it's a Phyrric victory, as it also ruins DeBeers market for years to come). This stalemate won't last forever, I think. All those new members of the Chinese and Indian middle classes have a taste for things that the western middle classes already enjoy. Sooner or later someone will decide he can make his fortune selling a nice 1 carat artificial to 100 million people, and the game's up. 87.114.128.88 (talk) 23:08, 10 December 2008 (UTC)[reply]
...which, incidentally, is (in the long term) an unalloyed good for the Human Race. Diamond, like gold, is amazing stuff, and it's a shame it's been wasted in gaudy frivolity. The same technological improvements that will lower the artificials' prices so that everyone in India can have one will (hopefully) improve the diamond makers' abilities to the point where they can make affordable diamond an engineering material. Diamonds as bearings and bushings and joints, diamond coatings to metal components, diamond elements in aircraft wings and car engines, maybe even diamond beams holding up a three-mile skyscraper. 87.114.128.88 (talk) 23:19, 10 December 2008 (UTC)[reply]
I agree. Debeers has had people paying insane prices for shiny baubles for too long now. It's time that diamonds were made available to everyone at reasonable prices. An interesting side-effect will be that diamonds, once no longer rare or expensive, will no longer be valued in jewelry. Other gems will take over that position, like pearls, at least until they can be exactly replicated in the lab. StuRat (talk) 04:21, 11 December 2008 (UTC)[reply]
It's possible for diamond to remain popular in jewellery even after you can pick up a one carat rock for a buck and a half. They make excellent stones for decorative purposes because they don't get damaged (diamond being spectacularly hard) - and they have this HUGE refractive index which is what makes them sparkle so alluringly. Perhaps the trend will merely be for jewellery sales to trend towards much bigger and more perfect stones while the price remains pretty much stable. It's hard to predict when human emotion is so tied up in what happens. SteveBaker (talk) 06:14, 11 December 2008 (UTC)[reply]
I fear that super-cheap diamonds would suffer a "bling" problem (with gaudy people festooned in them like some kind of insane pearly king) that diamonds would become gauche; I guess it's much the same as how wearing purple was once such an indicator of success and thus prestige, but with the advent of synthetic dyes anyone can wear purple so it has no cachet whatever anymore. 87.114.128.88 (talk) 13:30, 11 December 2008 (UTC)[reply]
Also remember that when first isolated, and for many decades afterwards, aluminium was fantasticly expensive. During most of the 18th and 19th centuries, it was more expensive than gold and was used decoratively and in jewlery! These markets definately fluctuate greatly depending on availibility and public perceptions... --Jayron32.talk.contribs 13:37, 11 December 2008 (UTC)[reply]
It would be amazing what we could do with tons of cheaply mass/produced diamonds. Construct buildings from it. Unbreakable windows. The possibilities are nearly endless.
An interesting note: I remember reading a science-fiction book from the end of the 19th century, where the Austro-Hungarian Empire develops some kind of highly advanced, completely bullet-proof armored suit for their soldiers, and goes to war with Russia. The russians have a huge numerical advantage, but they lose every battle because they cannot even harm their enemy. So a great (economical) sacrifice has to be made: they gather all the diamonds they can get hold of, and forge bullets for their rifles out of diamond, this being the only material which can penetrate that armor. --131.188.3.20 (talk) 14:00, 11 December 2008 (UTC)[reply]
Let's all not get collective hardons (excuse the pun) over the potential applications of diamonds. The high refractive index makes them unsuitible for windows, for example. Also, diamonds, being flamable, are not very well suited for high temperature applications; I wonder if a diamond bullet wouldn't just burn up in the cartridge at ignition! Diamonds do have quite important industrial and commercial applications, but they are not a miracle substance and there are practical limits to their use... --Jayron32.talk.contribs 14:16, 11 December 2008 (UTC)[reply]

Flammable?? Really??

That's a helluva factoid! So, got any pictures of flaming diamonds? --DaHorsesMouth (talk) 23:59, 11 December 2008 (UTC)[reply]

Diamonds are carbon, the same basic material as coal, and are equally flamable. Our article on Material properties of diamond notes that "they can burn in the presence of oxygen if heated over 800 °C (1500 °F)." This google search as well as this one show enough links that this is a real phenomenon. Several sites agree with the 800 deg C/ 1500 deg F roughly. It is enough of a concern that jewlers need to be careful when soldering jewlery with diamonds on them, see this page with instructions on the problem. --Jayron32.talk.contribs 05:47, 12 December 2008 (UTC)[reply]

Hardly indestructible

Despite the assertion that "diamonds are forever", they aren't particularly tough. While they are extremely hard, that makes them more likely to chip than softer materials, like steel, which can deform to absorb an impact. Consider that glass is also very hard, although not quite as hard as diamonds. So, is glass difficult to break ? Not at all. Why isn't every diamond chipped, then ? Because small, roughly spherical shapes aren't all that likely to be chipped. Most glass marbles survive without chips, even though they are quite a bit larger than the average diamond. StuRat (talk) 17:28, 12 December 2008 (UTC)[reply]

Graphite is actually more stable, which is highly ironic given that saying "a pencil is forever" is precisely contrary to the primary advantage of a pencil over a pen... SDY (talk) 17:32, 12 December 2008 (UTC)[reply]

Thanks to all for your input ... I really appreciate it. This discussion was very informative. (Joseph A. Spadaro (talk) 15:47, 13 December 2008 (UTC))[reply]

I was reading about Travis Pastrana. During an athletic competition, he sustained an injury in which his spine was separated from his pelvis. While I was continuing to read about him, I was assuming that this injury would have left him paralyzed. Seemingly, it did not. Why / how could that be? Thanks. (Joseph A. Spadaro (talk) 19:43, 10 December 2008 (UTC))[reply]

By not damaging his spinal cord, or otherwise causing significant nerve damage. This is one reason why the common advice is not to move an accident victim: if the spine is damaged, moving the victim can indeed lead to spinal cord injuries and, potentially, to paralysis. 198.29.191.149 (talk) 20:11, 10 December 2008 (UTC)[reply]
In an adult human, the spinal cord only extends about 2/3 of the way down the back. Below that point, there are several nerves that travel the remaining distance through the vertebral column and exit at various lumbar and sacral segments. Without knowing much about the injury you describe, I would assume that a separation between L5 and S1, while painful and probably dangerous, could plausibly fail to sever any of the sacral nerves that exit from the sacral region. He may well have suffered some stretch-induced injury (similar to a brachial plexus injury) that might include temporary numbness or weakness of the lower extremities. -Medical geneticist (talk) 20:16, 10 December 2008 (UTC)[reply]

Thanks for the info ... much appreciated. (Joseph A. Spadaro (talk) 15:47, 13 December 2008 (UTC))[reply]

Washing up

When washing up, does one get better results if one puts the Fairy liquid in the bowl before filling it with hot water, or after? And if so, why? DuncanHill (talk) 22:36, 10 December 2008 (UTC)[reply]

I doubt you'd get much (if any) difference by placing the washing up liquid in the bowl before or after. There might be a slight difference as the splashing of water on the liquid when placed before the water may increase the 'bubbliness'. That said, I imagine the best results in those terms would come if you placed the liquid in during the fill-up process. —Cyclonenim (talk · contribs · email) 23:28, 10 December 2008 (UTC)[reply]
Agree with Cyclonenim, definitely during. And for the foreigners here, it's Fairy liquid  :) hydnjo talk 02:53, 11 December 2008 (UTC)[reply]
Towards the end is better, because the earlier you add it, the more foam you get. While a bit of foam is good as a thermal insulation, it doesn't drain as well when you dry your dishes. — Sebastian 08:58, 11 December 2008 (UTC)[reply]
I always rinse the dishes with hot water, so lather is not a problem. DuncanHill (talk) 13:08, 11 December 2008 (UTC)[reply]
How about omitting the Fairy liquid and just leaving the dishes in the sink and waiting for Elves to wash them up? Edison (talk) 20:09, 11 December 2008 (UTC)[reply]

Lonely inventor builds working cyborg girlfriend in own home - malarkey or effective way?

Just read a news story where this is claimed to be the case.

Any thoughts on the matter? I'm immediately suspicious of his claims, as the videos presented in the article only show a working head and working hand. There is nothing showing the entire femmebot up and about and performing the tasks he says that it can perform (which, to my mind would be the vids that would really wow everyone). The still photos kinda look like he's just posed a rubberised mannequin in various places.

Also, the story appears in The Sun - which, as any fellow Brit will know, doesn't exactly have the best reputation as a newspaper for fact-checking.

So, what do you think? BS or not BS? --Kurt Shaped Box (talk) 23:38, 10 December 2008 (UTC)[reply]

Well, leaving aside The Sun's unassailable history of quality reportage, the official website of the project is at [28]. DuncanHill (talk) 23:42, 10 December 2008 (UTC)[reply]
Dunno about you - but programming the gynoid to violate the First Law of Robotics (she can apparently slap humans) seems like a really bad idea to me. --Kurt Shaped Box (talk) 01:07, 11 December 2008 (UTC)[reply]
It's a pretty impressive project for a one-man hobby effort - but it's FAR behind the state of the art. He's got together a large collection of miscellaneous bits of software and wedged them into the computer that drives the robot - but look at the movements of mouth and eyes in the video - they are laughably pathetic. A lot of the claims on the web site are of the form "In theory she could be programmed to..." - meaning he hasn't done these things and in all likelyhood is unable to do so. Move along - nothing to see here. SteveBaker (talk) 06:08, 11 December 2008 (UTC)[reply]
It was also claimed that this robot was built on a budget of $21000, which is pretty low-cost for a research robot prototype. I know of at least five or six robotics projects around here (e.g. [29], [30], [31] ) with a budget orders of magnitude larger - and it shows, in terms of equipment quality, manpower available, and total "advances" on the cutting edge. I would put this robot into the regime of "advanced enthusiast hobbyist" project - clearly the designer is very skilled but he's not a professional robotics engineer. On the one hand, "kudos" for doing a low-cost, low-budget innovation; on the other hand, if there was anything really innovative, then why isn't this guy doing it professionally? Nimur (talk) 15:16, 12 December 2008 (UTC)[reply]

December 11

Yerba mate

Does yerba mate have any caffeine? If not why does it seem to have that effect? —Preceding unsigned comment added by 63.165.5.103 (talk) 00:34, 11 December 2008 (UTC)[reply]

The article you linked seems to have quite a detailed answer: Mate contains xanthines, which are alkaloids in the same family as caffeine, theophylline, and theobromine, well-known stimulants also found in coffee and chocolate. Mate also contains elements such as potassium, magnesium and manganese. Caffeine content varies between 0.3% and 1.7% of dry weight (compare this to 2.5–4.5% for tea leaves, and 1.5% for ground coffee). Mate products are sometimes marketed as "caffeine-free" alternatives to coffee and tea, and said to have fewer negative effects. This is often based on a claim that the primary active xanthine in mate is "mateine", erroneously said to be a stereoisomer of caffeine. However, it is not chemically possible for caffeine to have a stereoisomer, and "mateine" is an official synonym of caffeine in the chemical databases. 76.97.245.5 (talk) 01:10, 11 December 2008 (UTC)[reply]

plants

is there a way to keep a plant or seed alive fo a couple months without letting it grow? —Preceding unsigned comment added by 76.14.124.175 (talk) 00:49, 11 December 2008 (UTC)[reply]

Seeds can remain viable for a very long time indeed. Our article seed hibernation mentions seeds which have grown into plants after ten thousand years or so of hibernation. Algebraist 00:53, 11 December 2008 (UTC)[reply]
so you have to freeze the seeds? —Preceding unsigned comment added by 76.14.124.175 (talk) 01:21, 11 December 2008 (UTC)[reply]
I think that's not necessary. As long as you store it in a clean, cool, dry and dark place then the seeds should be indefinitely dormant. Basically you don't want to trigger germination due to moisture and sunlight and avoid spoilage from fungi and bacteria.--Lenticel (talk) 01:58, 11 December 2008 (UTC)[reply]
Yea, just refrigerate them in a dark container. Freezing could actually damage seeds from tropical plants that aren't adapted to such conditions. StuRat (talk) 04:08, 11 December 2008 (UTC)[reply]

Laser cooling

What's the application of laser cooling? Is it only able to cool atom? Could it cool molecule? And do they provide data about the coolest temperature reach for each atom? Thanks for your responses. roscoe_x (talk) 01:19, 11 December 2008 (UTC)[reply]

Laser cooling might be of help to you. As for the coolest an atom can be, have a look at Absolute zero. - Mgm|(talk) 09:52, 11 December 2008 (UTC)[reply]
See Laser_cooling#Minimum_temperature for details on the minimum temperature that can be achieved by laser cooling. To cool large molecules is more difficult, but a method called Sympathetic cooling achieves this too. EverGreg (talk) 10:29, 11 December 2008 (UTC)[reply]
I was fascinated to learn today that Steven Chu, who won a Nobel Prize for work on laser cooling, is the leading contender to be Barack Obama's Secretary of Energy. What a 180° turnaround from the current attitude toward science in the Executive branch! --Sean 21:07, 11 December 2008 (UTC)[reply]

Crystallisation esp. seen in ice... what is the magic of the hexagon?

The chemistry of crytallisation is the usual topic but what about the physics? Especially seen in Snowflakes and on the poles of Saturn but also seen to create exotic type forces when freezing water (such as expanding its own mass without external reactions and creating linear faces). The stuff on snowflakes and Saturns poles... although non-solids convecting will form hexagonals naturally filling out the available space... what is going on with the hexagonals in snowflakes or on Saturns pole where there is ample space to be some random shape? Although the hexagonal pole of Saturn is peculiar, not even crop circles have a patch on snowflakes. Is this hexagonal a manifestation of the genetics of non-living items? How does a crystal create a smooth face over an area and how does a crystal without boundaries in size create a hexagon in an open space? If somebody travels through space and time, will they use a hexagonal stargate? Are some liquids actually a sub-viral life bound in a hexagonal skin? ~ R.T.G 02:00, 11 December 2008 (UTC)[reply]

well, ice is typically hexagonal due to the Hydrogen bonds in water. its not exactly random.--Lenticel (talk) 02:32, 11 December 2008 (UTC)[reply]
I don't think anyone has adequately explained why snow flakes have so many shapes. The water vapor, it is said, condenses on a dust particle and the shape initially established grows. I think there is a theory that impurities in the water vapor establish the original shape. Some information might be obtained if a snowflake can be grown on a solid particle of known size and shape and extremely pure water vapor is supplied for the growth material. "Snowflake" and "Wilson Bentley" in Wikipedia provide interesting information, photos, and leads to other information about snowflakes. —Preceding unsigned comment added by 98.17.46.132 (talk) 02:53, 11 December 2008 (UTC)[reply]
Yeah, the pictures I was talking about are on Wilson Bentley who learned a method to photograph snowflakes in detail. Although possibly related to hydrogen bonding, a ball is similarly related to a ball park. Look at the pictures close up, they are nothing unusual but they are amazing every time, symmetry across distances based on a hexagon much larger than a hydrogen bonded molecule and also the pole of Saturn is probably bigger than the Earth itself. Hey, its not random at all!! ~ R.T.G 03:05, 11 December 2008 (UTC)[reply]
Snowflake growth is actually fairly well-understood. Different combinations of humidity and temperature favor different growth patterns (growth from corners vs. growth from faces vs. growth from edges, linear growth vs. branching growth, plates vs. rods, etc.). On a molecular scale, the six-fold symmetry comes from the hexagonal lattice of ice; on a macroscopic scale, the symmetry continues because as the snowflake forms, it moves around within the cloud, exposing all parts of of the snowflake to a given environment at the same time. --Carnildo (talk) 23:34, 11 December 2008 (UTC)[reply]
Included among the Bentley snow-crystal photos shown at http://www.bentley.sciencebuff.org/collection.asp?page=1
are some snowflakes of unusual shape. At first glance, a few of them do not even seem to be hexagonal - but they are actually irregular hexagons. —Preceding unsigned comment added by 98.17.46.132 (talk) 03:14, 11 December 2008 (UTC)[reply]
Honeycomb (see Honeycomb geometry) might shine some light at the phenomenon. I assume you already did read Crystal, Crystal habit and Crystallization. Crystal shapes depend on the material (see the Insulin crystal pix, no hexagon) but hexagons are pretty efficient shapes, so it's not surprising or magic to encounter them in nature. 76.97.245.5 (talk) 15:28, 11 December 2008 (UTC)[reply]
Another strange hexagonal snowflake form obstructing the reference desk
Honeycombs are not surprising in an enclosed space such as the pattern of convection also seen in rock at the Giants Causeway but this doesnt cover snowflakes and the poles of Saturn which exhibit hexagonals in free form as though you just dropped something and it landed in the shape of a crop circle. Although it is not covered exactly, the best I can gather from what is available, regarding the snowflake, is that perhaps two molcularly bonded which are theoried to form a six sided shape, might grow around one single one to form a huge hexagon but this would not sufficiently describe the scale of it or the intricate yet intricately symmetrical patterns and even this goes no ways toward explaining the enormous Saturnian pole which exists in the fastest flowing wind known (12000 km per hour i think). One thing that is interesting regarding the hexagonal in particular is the fact that snowflakes and the Saturnian pole form themselves in a free flowing wind. I doubt there is much to explain some crystalline forms but they are simple and amazing. Would love to study them if there was anything to go on but seems like pretty pictures only. Wonder do snow flakes form hexagons in a weightless vacuum? ~ R.T.G 23:28, 11 December 2008 (UTC)[reply]


For more information on the cause of the different shapes flakes take, check out this excellent graphic, which is the last slide in a gallery of incredibly detailed images of snowflakes. --Shaggorama (talk) 07:47, 12 December 2008 (UTC)[reply]
Great pics Shaggo, especially numbers 1 to 4. I have trained up on machining steel and can't get over how some of the details are symetrical, just as though machined to high spec. The missing link between fractals and organisms I reckon or the gene pool of Gaia. ~ R.T.G 14:30, 12 December 2008 (UTC)[reply]

Inhabitable planets larger than the Earth?

Assuming mankind either explores other solar systems or perfects terraforming within this system, how much larger than Earth could a planet be before it caused serious problems for the human colonists? And could a planet with a core of low density materials such as lithium or aluminum be much larger than Earth but have normal gravity? Since Ringworlds and Dyson spheres are unphysical even with advanced nano-materials, would a pressurized sphere of hydrogen gas be capable of making a terraformed "Earth" with normal gravity, but on a much larger scale? —Preceding unsigned comment added by Trevor Loughlin (talkcontribs) 02:57, 11 December 2008 (UTC) Trevor Loughlin (talk) 02:59, 11 December 2008 (UTC)[reply]

One possibility for living on a planet with higher gravity is to live some distance under the surface, where the gravity would be significantly less. Unlike the Earth, though, such a planet must not have a molten core. StuRat (talk) 04:02, 11 December 2008 (UTC)s[reply]
I guess it's possible - but the technology for digging that deep doesn't remotely exist - and remember that you'd have to start all of that constuction - as well as build things like solar power plants on the surface of the planet - so much of the work involved would still be high-g.
As for alternative construction approaches - RingWorlds and Dyson spheres are indeed problematic for all sorts of reasons. You didn't mention the other fictional star-encompassing idea from the book "The Smoke Ring" it's sequel "The Integral Trees" (an awsome piece of imaginative world-making - and actually rather more feasible than "RingWorld"). But why bother - if you have the engineering skills and the raw materials - then just make spinning cylindrical mini-worlds - each a few kilometers in diameter and a few tens of kilometers in length (think "Rendezvous with Rama")...you could make them in stable solar orbits - in vast quantities (if needed) with none of the theoretical issues you'd have with the more exotic designs. Your pressurized sphere of hydrogen would be an interesting concept - but I don't see why you'd choose hydrogen versus a big pile of asteroids. SteveBaker (talk) 06:00, 11 December 2008 (UTC)[reply]
Considering it is a hypothesis, why couldn't it be entertained?96.53.149.117 (talk) 06:06, 11 December 2008 (UTC)[reply]
I think the idea behind using hydrogen is that it is lower density so you can get a larger surface area without having the gravity be too strong for humans to live there. I'm not sure how well that would actually work, anyone want to do the calculations? What would the pressure be like in the centre? The more hydrogen you have the higher the density would be, so there may be a practical limit on how big such a "planet" could get (obviously it would become a star at a certain point, but there may be a limit before that). There is also an issue with the pressure needing to be at least a certain value to keep the shell from collapsing in on itself (that would depend on your choice of building material, of course), it may well turn out to be an over-constrained problem. --Tango (talk) 14:24, 11 December 2008 (UTC)[reply]
Much more serious is the question of how you'd construct it! If you start with a ball of hydrogen - the depth into the ball at which the surface could be suspended by the internal pressure would be pretty deep down - and you'd have to somehow blow away all of the hydrogen outside of your surface in order for it to be supported by internal pressure alone. If you plan to build the 'shell' first - and then fill it with hydrogen, how do you keep the thing suspended against it's own gravitation before you pump the hydrogen in? If it's strong enough to stay put before the hydrogen goes in - then why did you need the hydrogen in the first place? Since the hydrogen acts much like the star at the center of a dyson sphere (both in terms of gravitation and pressure - although in the case of the star, it's photon pressure) - you'll have the exact same stability problems as a dyson sphere...which is known to be fundamentally unstable. So I don't think this 'design' can work. SteveBaker (talk) 17:58, 11 December 2008 (UTC)[reply]
How about this: You pump hydrogen in from who knows where (a nebula, maybe?) and use the reactive force from the pumps spaced around the shell to hold it up as you build it (sure, the hydrogen you pump in before it's finished will escape, but that's not a problem, you just pump in more). I don't think there's a problem with stability because there isn't a massive star at the centre that you need to keep central so it doesn't matter if the whole thing moves about a bit, in fact, you probably want it to orbit a star. --Tango (talk) 18:55, 11 December 2008 (UTC)[reply]
I had a better idea! You start off with a small sphere of steel (or whatever your 'crust' will be made of) - maybe a few meters across. You bring it close to the star and set it spinning. Pretty soon it's molten from the heat of the star. Now, you take a tube made of something that won't melt at that temperature and insert it into the sphere of liquid steel - pushing it in from the stationary point at the 'north pole' of the spinning sphere. Now you pump hot liquid hydrogen (you're going to need a LOT of pressure!) into the center of the sphere through your tube - and simultaneously add more steel into the molten sphere. As the hydrogen enters, it inflates the steel sphere like a soap bubble - and you can control the thickness of the 'crust' by altering the rate at which you add metal or the rate at which you pump hydrogen. When your sphere is large enough - you have to tow it out to the orbit you want it at (very carefully because you don't want it to pop(!!) and then wait for a few millennia for it to cool down (you could actually tow it further out so it would cool faster). As the iron and hydrogen cool - they'll both shrink - so you'll have to keep on pumping hydrogen into or out of it to keep the pressure at the designed level. (NO - I really don't think this would work - the stability issues are still problematic.) A gigantic steel soap bubble! SteveBaker (talk) 20:19, 11 December 2008 (UTC)[reply]
You may have problems with tidal forces making it asymmetric, you wouldn't get a perfectly spherical bubble. As long as it is close, though, it will probably work well enough. I'm also unsure how molten steel would behave in a vacuum - you may have to work quickly to prevent it boiling off. I don't see what stability issues you would have, though, it's just a balloon, balloons have been pretty stable at every birthday party I've been to. --Tango (talk) 21:41, 11 December 2008 (UTC)[reply]
We can avoid the worst of the tidal issues by picking an outragously hot star and doing our construction a nice long way away from it. Balloons (at 'human scale') are stable because they are entirely a matter of air pressure fighting elastic forces in the envelope. For our planet-sized bubble - we also have gas pressure - but instead of elastic forces to counter it - we have gravity. (There is no possible material that would be strong enough to keep the thing together with elastic forces at the size of a planet. The trouble with that is that the force of pressure only cares about the volume of the container - and the pressure will be more or less equal everywhere - no matter how the envelope moves relative to the high density gas at the core. However, gravity is different - it's an inverse square law. So if the dense core of our gas ball should ever move away from the center by a teeny-tiny bit - the side of the envelope that's now a bit closer will be attracted more strongly and the side of the envelope that's further will be less strongly attracted - so instead of the situation sorting itself out - it gets worse. So this is an unstable equilibrium...and that's never a good thing. For enthusiasts of the Larry Nivan "Ringworld" series - you'll have noticed that in later books he had to invent huge rocket motors for his ring that would fire to keep it perfectly in balance. This is the same problem - and it's the (sad) reason why Dyson Spheres, Ringworlds and now Bubbleworlds are not likely to be sustainable. It's a shame because this makes a great story. You fly nickel-iron meteors in from outer orbits - let the the sun melt them for you to make your crust. Any rock you are left with you keep for decorative features like mountains and fijords. Icy cometary stuff can be boiled into steam (do we really need hydrogen? Well - if so, we have to make a big solar-powered electrolysis cell to get hydrogen from the water (and keep back some of the left-over oxygen for atmosphere - and also keep some water for your oceans. Everything you need is right there. But the time involved is crazy - and the stability problems are (I believe) gonna kill the project. SteveBaker (talk) 23:40, 11 December 2008 (UTC)[reply]
Meh, a Matrioshka brain makes for better stories anyway. And you get to use the phrase 'sufficiently godlike'.Algebraist 23:44, 11 December 2008 (UTC)[reply]
As a Slashdot regular - I have to say "Can I get a beowulf cluster of those?"  :-) SteveBaker (talk) 23:55, 11 December 2008 (UTC)[reply]
Pressure won't be constant it will be higher nearer the centre. If one side of the shell moves towards the centre both gravity and pressure will increase. At first, gravity will increase quadratically and pressure linearly (I think), so it's unstable, but beyond a certain point that will change because the gas is becoming less and less spherically symmetric as the shell moves and sooner or later you can no longer reasonably model it as a point mass. With your model, you eventually get the highest pressure point being at the surface, but that doesn't seem plausible to me, the pressure must surely overcome gravity at some point. While gravity at the surface (which is what's important) may not be constant, it's going to stay within certain bounds as long as the external influences do. Even if it is too unstable, you can just have taps strategically placed around the shell and release hydrogen in order to push the shell in the opposite direction (like a balloon flying round the room when you let go) - you would need some way to replace the hydrogen, but if you managed to get that much to start with, surely you can find some more. --Tango (talk) 00:12, 12 December 2008 (UTC)[reply]
Exactly...the linear increase in pressure with depth versus the square-law increase in gravity is what ensures that the structure won't be stable. When it moves off-center, there is no restoring force - only a force that tends to push it even more off-center. Hence the structure is doomed without some kind of active control system (big rocket motors basically). SteveBaker (talk) 13:36, 12 December 2008 (UTC)[reply]
But what I'm saying if that it's only linear vs inverse-square for small displacements, after that it becomes something more complicated that I imagine will set up a restoring force. The question is how extreme the variations in surface gravity will be by that point. And you don't need rocket motors, as I said, you can just use the pressurised gas inside the shell for thrust. --Tango (talk) 13:46, 12 December 2008 (UTC)[reply]
The core of a planet is almost always going to be made up of heavier elements because they sink down to the centre over time. The only way the core could not contain lots of iron is if there wasn't much iron on the planet at all, which would mean the colonists were very limited in resources for building. You could get a planet quite a bit larger than Earth without too much trouble, though - while the extra mass increases gravity, the extra distance from the centre reduces it so surface gravity only increase linearly with radius (assuming constant density, which isn't quite true, so it will be a little more than linear). That means you can get double the surface area of Earth with only 41% more gravity, which is probably survivable (especially with the advanced medical technology that will almost certain exist by the time we have the technology necessary to reach other solar systems). --Tango (talk) 14:24, 11 December 2008 (UTC)[reply]
Well, there are also other considerations, such as how gravity will affect no only the density of the atmosphere, but on its composition. Higher gravity planets will tend to "hold on" to different gasses at differing ammounts, further complicating the 'livability' question.... --Jayron32.talk.contribs 14:30, 11 December 2008 (UTC)[reply]
Indeed, there are all kinds of things to consider, most of which will depend on far more than just the size of the planet - distance from (and type of) the star and the presence of life will probably have a greater influence on the atmosphere than 41% extra gravity. --Tango (talk) 16:48, 11 December 2008 (UTC)[reply]
Start with and existing gas giant such as Jupiter. Send the construction robots down to the correct depth and build an expandable shell at that depth. The robots themselves are gigantic drigibles supported by heated hydrogen. Then, gradually remove the gas from above the shell by launching it at escape velocity. We have lots of energy available for this effort: just fuse some of the hydrogen. The only theoretical problem I can see is where to get the material with which to build the shell. -Arch dude (talk) 02:25, 12 December 2008 (UTC)[reply]
That doesn't work though - your robots swoop down with a 10km x 10km chunk of 1km thick 'crust' material...what do they nail it to? They can't just let go of it because it'll just fall to the center of the 'gas ball'. Until you have the spherical shell 100% complete, it won't hold pressure - so it'll just collapse. That being the case - how can you build the shell? My proposal to start with a liquid 'drop' of steel and to gradually inflate it like blowing a soap bubble solves that problem completely. SteveBaker (talk) 05:33, 12 December 2008 (UTC)[reply]
You can hold the crust up with balloons filled with hydrogen (they may need to be quite large balloons, since Jupiter is mostly hydrogen anyway, to it's only a slight lifting gas, or you would need to heat it which requires energy, although with some kind of heat exchange system it wouldn't need too much). Then, once you've eliminated the gas above the shell, the pressure can hold it there. Your glass-blowing style method sounds cool, but would probably be much more difficult to achieve - this method is actually possible with today's technology (almost), if we only had the resources available to devote to it. --Tango (talk) 10:36, 12 December 2008 (UTC)[reply]
Consider the moment before the last piece of crustal material is bolted into place...at this moment the ENTIRE crust of a large gas-giant is being held up by balloons?!? We're talking trillions of tons! Now when the last piece is bolted in place - the structure is still not self supporting (because it relies on a pressure differential from the gasses inside the planet versus outside - and your "outer" atmosphere is still there. So with balloons holding up your entire planet your next step is what?....Oh yes - remove the outer atmosphere. Oh - but wait - the buoyancy of those balloons is all that's stopping the crust from collapsing! So as you pump away the upper atmosphere, your balloons will start losing lift...although admittedly you won't need as much lift. Anyway - imagining a reasonable thickness of crust (a kilometer maybe?) - consider the amount of Hindenberg-sized balloons it would take to support a Jupiter-sized crust containing 6 x 1010 cubic kilometers of steel! (8 grams per cc - so 8000kg/m3 - 8,000,000,000,000 kg per cubic kilometer - 480,000,000,000,000,000,000 tonnes for the entire crust. The Hindenberg could lift 3,000 passengers and 160 tons of freight - let's call that 200 tonnes. So you'll need 2,400,000,000,000,000,000 Hindenbergs. At 8 billion tonnes per square kilometer - every square kilometer of crust will need 20 million Hindenbergs to support it during construction - each with a volume of 200,000 cubic meters! Oh - but wait - that was a hydrogen balloon in a dense oxygen/nitrogen atmosphere. You have a hydrogen balloon in a mostly hydrogen atmosphere - so you have to heat the gas in order to get any lift...MANY more balloons - and some means of keeping them all hotter than the surrounding atmosphere. Good luck with that!
SteveBaker (talk) 13:28, 12 December 2008 (UTC)[reply]
Why use steel? There are far lighter things, and I don't see why it needs to be a kilometre thick, there isn't supposed to be any significant force on the crust (gravity and pressure should balance out) so it doesn't need much strength. A couple of centimetres of carbon fibre or something should do it. Far more feasible than a pump that can operate at temperatures hot enough to melt steel. --Tango (talk) 13:53, 12 December 2008 (UTC)[reply]
Actually, the construction robots are gigantic hot-gas balloons, as I said. What I did not say is that the shell they are constructing is merely an entire shell of joined hot-gas balloons glued together. After we complete the shell, we begin removing the outer atmosphere, and at the same time we gradually increase the tensile strength of the shell by adding more and more kevlar straps. This gradually increases the weight, but this is counterblanced by the gradually increasing pressure differential. -Arch dude (talk) 20:51, 12 December 2008 (UTC)[reply]

Erection

I know that heterosexual rapists, some of them, get erections when rape is the form of sexual intercourse. Is this also found in homosexual rapists?96.53.149.117 (talk) 05:32, 11 December 2008 (UTC)[reply]

I'm almost certain they do, rapists rape for the same reasons whether they go for the same gender or not. —Cyclonenim (talk · contribs · email) 08:03, 11 December 2008 (UTC)[reply]
I'm sure I'm missing something here, but isn't it impossible to commit rape (as defined by the OP) without an erection? Zain Ebrahim (talk) 11:02, 11 December 2008 (UTC)[reply]
I think he meant that rapists can only get an erection when sex is non-consensual. Belisarius (talk) 11:51, 11 December 2008 (UTC)[reply]
In simple terms, I think this might also be part of what is being asked. It's layman's guess only, so take it as you will:
There's probably a general consensus that a significant part of rape (perhaps the most significant part), is often the acting out of power or fantasy over another person. As such, the physical act of rape will probably elevate a wide range of bodily systems related to bodily arousal, excitement, aggression, and the like - as best I can recall (layman's information only) these will involve factors such as neurotransmitters and/or hormones (for example, endorphins, or epinephrine (adrenaline)), excitation of the autonomic nervous systems related to bodily arousal) generally, emotional excitement, and so on. The same bodily chemicals and factors are broadly involved in sexual arousal. (See also erection#Autonomic control.)
Again as a layman, the response to these would probably be felt as sexual and physically arousing for the person involved, regardless of the nature or gender of the target they were directed to (see rape of males) -- and regardless even of the gender of the rapist (rape by females exists too, see our article on rape by gender). FT2 (Talk | email) 15:01, 11 December 2008 (UTC)[reply]

1 calorie

Why is 1 calorie defined as the heat required to raise the temperature of 1g of pure water through 1 degree celsius from " "14.5 degree & not from any other temperature"? —Preceding unsigned comment added by 118.95.40.140 (talk) 07:30, 11 December 2008 (UTC)[reply]

Good question. The temperature needs to be indicated since the specific heat of water changes with temperature. Consequently, as our article calorie explains, there are different definitions for different temperatures, and the 15 °C calorie (cal15) is just one of them. But why anybody would want to use just that definition, I'm not sure. To me, the 20 °C definition makes more sense, since that is room temperature. Maybe it's because 15 °C is closer to the average outside temperature in moderate climates. — Sebastian 08:47, 11 December 2008 (UTC)[reply]
To expand on Sebastian's excellent answer; raising the temperature of water from, say, 14 degrees to 15 degrees actually takes a different amount of energy than does raising the temperature from say 20 degrees to 21 degrees. Thus, while we often say that "The specific heat of water is 1 cal/g * deg C or 4.184 J/g * deg C" that is an approximation. The actual value varies depending on the temperature. The correct way to calculate specific heat at any given temperature requires some rather complex differential calculus.
Given that we want the units we measure in to remain constant (having the value of the calorie change based on temperature wouldn't be all that useful) we need to pick a temperature to define it at. The actual temperature we use is rather arbitrary, and for some unknown reason, it was decided that 15 deg C was the choice. The same thing happened when choosing 0 deg C for "STP" or 25 deg C for "standard conditions" for thermodynamics. Since the functions are ALL temperature dependent, we have to keep temeperature constant; but beyond that it really doesn't matter what constant number we choose. --Jayron32.talk.contribs 13:32, 11 December 2008 (UTC)[reply]
You might also find the Mpemba effect interesting. 76.97.245.5 (talk) 14:51, 11 December 2008 (UTC)[reply]
True, but not directly applicable in this case. The cited effect has to do more with heat transference rate effects (such as the insulating effects of ice, convection currents, etc. etc.). That is, it depends on how fast or slow the heat is removed from the substance. Specific heat, which is the basis for defining the calorie as a unit, is about the quantity of heat energy actually transfered, not how rapidly that heat is transfered. --Jayron32.talk.contribs 19:09, 11 December 2008 (UTC)[reply]

Spinal injury

I'm looking for information on spinal injuries, especially fuzing of vertebrae and conditions requiring this, etc. Got a friend who may need most of their back fuzed, and I'm looking for information on what it involves, what the impact might be long term, and (very much secondarily) what sorts of issues might medically lead to such a requirement. Mostly an article on spinal fuzing, or whatever the correct medical term is.

I can't find a relevant article. Do we have any, and if so what are the title/s? (If we don't, what are the correct medical terms and any suggested resources, for a wider search?)

Thanks.

FT2 (Talk | email) 13:05, 11 December 2008 (UTC)[reply]

Well, I was going to recommend the article tilted Vertebral fusion, but that is basically a dicdef and nothing else. Hm. Have you tried websites like WebMD or something like that? Google? --Jayron32.talk.contribs 13:20, 11 December 2008 (UTC)[reply]
This site is quite comprehensive. And this article may be useful. -hydnjo talk 14:41, 11 December 2008 (UTC)[reply]
Two good reviews of lumbar spine fusion:
Rutherford EE, Tarplett LJ, Davies EM, Harley JM, King LJ (2007). "Lumbar spine fusion and stabilization: hardware, techniques, and imaging appearances". Radiographics. 27 (6): 1737–49. doi:10.1148/rg.276065205. PMID 18025515. Retrieved 2008-12-11.{{cite journal}}: CS1 maint: multiple names: authors list (link)
Leone A, Guglielmi G, Cassar-Pullicino VN, Bonomo L (2007). "Lumbar intervertebral instability: a review". Radiology. 245 (1): 62–77. doi:10.1148/radiol.2451051359. PMID 17885181. Retrieved 2008-12-11. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
Hope those help you. Good luck to your friend, too. —Cyclonenim (talk · contribs · email) 17:20, 11 December 2008 (UTC)[reply]

Duck question

About 2 years ago I found out that our super markets sell deep frozen duck and I ate up to 4 dishes a week -- excellent stuff! I was crazy about it. The duck came deep frozen on an aluminium dish and packed airtight vacuumed in plastic. Now and then there were small air pockets and where you could eat all of the duck including skin (there were no bones) from the airless packed, those with air pockets often had not so good a taste and I found the skinny parts frequently tough and non-delicious to impossible to eat. Then the oil price rose and, due to the bio-diesel-madness (I put your tortillas in my tank), the food prices, too. In an attempt to make the inflation not to show, the super markets didn't rise the price but reduced quality. Suddenly they sold other brands, and they were not vacuumed and thus did not only have air pockets but were regularly filled with air. With those, I have to discharge about one third of the duck as inedible. Now that the economy is crashing and the oil price has dropped they sell the same low quality stuff at slightly lower prices.

Now the question: does anyone know how exactly the air renders the duck, and especially the skin, inedible? 93.132.132.239 (talk) 19:53, 11 December 2008 (UTC)[reply]

Probably it allows the moisture to evaporate out of the meat - but it's possible it also alters the rate at which the meat freezes - or there was once something in those gaps that is no longer present which is responsible for the problem. It's hard to know which. SteveBaker (talk) 19:56, 11 December 2008 (UTC)[reply]
What I object to is the poor quality of fruit in the supermarkets. It looks good. They dowse it with insecticide while growing so there are no blemishes on the skin. Some of it is waxed to further enhance the appearance. But it has very little flavor. It is almost always unripe as well, including canned peaches and other canned fruit. Farmers' markets just have supermarket stuff. If you want good fruit you have to grow it yourself if you have the space, not using commercial varieties of fruit trees. America has good meat in the markets, but poor fruit. There is good opportunity for fruit and vegetable stores - what the British call a "greengrocer". —Preceding unsigned comment added by 98.17.46.132 (talk) 21:12, 11 December 2008 (UTC)[reply]
Our article on freezer burn may be of interest to your original question. As to the later stuff, I am not sure the reference desk is much of a place to air your greivances against your local supermarket. --Jayron32.talk.contribs 21:15, 11 December 2008 (UTC)[reply]
It is common for air-packed food to be packed with nitrogen (or some other rather inert gas), not just "air". That is why food will last a long time in the bag, but spoils quickly after you open it. So, you need to know if these are packed with plain air or not. As for fruit, this is America. There is choice. I can buy cheap nasty fruit from Food Lion. I can get slightly better fruit from Piggly Wiggly for about the same price. I can get even better fruit from Harris Teeter for more money. I can spend even more and buy fruit from local farms at the farmer's market (though, there isn't much there other than peaches). I can go broke and get organic fruit from Earth Fare at a cost slightly higher than a new luxury sedan. When I travel to other countries, I am always surprised by the lack of choice. For example, when I was in Norway, you could buy Br0d (bread) - one brand. You could buy Melk (milk) - one brand. You had two choices of cereal: wheat or oat. However, there were at least 30 choices of beers and similar alcoholic beverages. -- kainaw 04:05, 12 December 2008 (UTC)[reply]
Hold on, Kainaw, this is plain nonsense. One type of bread? Are you sure that was a grocery store you visited, and not vinmonopolet? You're closer to the mark with regard to milk, the milk market used to be a monopoly called "Fellesmeieriet", now Tine, but there are a couple of smaller competitors. Anyway, Tine do of course produce more than one kind of milk (various levels of fat, several types of fermented milk). And your claim about cereals is also incorrect, regardless of how you disambiguate it. Where the heck were you, anyway? --NorwegianBlue talk 17:02, 12 December 2008 (UTC)[reply]
As far as I know, I was in a grocery store. It was in Bardufoss (I don't really know how to spell it). I'm not claiming that I disliked anything there. In fact, I spent a lot of time trying to figure out a way to stay in Norway. I worked out a place to stay in Tr0mso. I just had difficulty because every official I talked to said that I had to basically have a job offer before I could stay there. Now, I just can't afford to return because the difference in purchasing power between the U.S. and Norwegian economies is terrible. -- kainaw 01:42, 13 December 2008 (UTC)[reply]
Wikilinks: Bardufoss, Tromsø. Bardufoss is tiny (2200 inhabitants), and has a large air force base, and I suppose shops to a large extent would cater for the needs of the military, which might explain the large selection of beers. --NorwegianBlue talk 13:09, 13 December 2008 (UTC)[reply]
On the other hand, in America you pay for such choices. Most of the cost in "name brand" products is to cover the cost of marketing, since there are so many brands to choose from, each brand must distinguish itself by spending gobs of cash on advertising, and thus pass that cost onto you, the consumer. In many cases, "store" or "generic" brand products are made in the same factories as the name-brand foods, but at a lower price since there is no advertising on said products... --Jayron32.talk.contribs 05:37, 12 December 2008 (UTC)[reply]
I don't think these two anons are the same person. One IP looks up to Germany the other US. It seems like a semi-random complain tacked on to me Nil Einne (talk) 10:40, 12 December 2008 (UTC)[reply]
I should point out that how significant the demand for biofuels was the cause of the 2007–2008 world food price crisis is an open-ended question. It definitely doesn't seem to be the only factor and may not have even been the primary factor. (One recent suggestion in the case of corn anyway is that it may have partially been an economic bubble perhaps mostly due to speculation of biofuel demand but even in that case it's questionable if you can really blame it on the demand for biofuels as opposed to the stupidity of humans) Nil Einne (talk) 10:40, 12 December 2008 (UTC)[reply]

Thank you, I think freezer burn is what I was looking for. (And I'm not really interested in fruit as long as there is other food available.) 93.132.146.73 (talk) 10:54, 12 December 2008 (UTC)[reply]

Energy generating floors

This report [32] talks about using piezo-electrics to extract electrical energy from the footsteps of people walking through the tokyo subway.

Are they truly capturing energy that would otherwise have uselessly turned into sound/heat energy - or are they actually making the people expend more effort in walking?

I kinda suspect at least some of the latter - in which case I wonder whether there is a legality to be answered - if you are making people work for you to generate your electricity - don't you have to pay them minimum wage while they do it? (...well, that last part isn't a science question - so I'd better not ask it here!)

SteveBaker (talk) 19:53, 11 December 2008 (UTC)[reply]

I have seen lame-brained "something for nothing" "free" energy gimmicks for years, like connecting turnstyles, stairtreads or revolving doors to generators, or building little piezo generators into shoesoles. These ideas likely spring from the notion that a generator merely turns effortlessly, without a conservation concept, that it is effectively the prime mover pushing all the motors etc connected to its output. I expect that walking on a surface which extracted energy would be a bit like walking up a slight incline, and that the walker's pulse rate would be a bit higher than on a normal floor, if he walked at the same pace. Edison (talk) 20:03, 11 December 2008 (UTC)[reply]
I guess it depends on what the floor was made of before. If it was a very hard floor that barely moved (concrete, say) and now it has some give in it, then it will be more tiring to walk on (think about what it is like to walk on sand - it takes more effort because the sand moves underfoot). If it already had some give in it (eg. floorboards) then they might be able to add their piezo-electrics without making it harder to walk on. (Of course, I doubt the tokyo subway has floorboards, concrete is far more likely.) As for the legality of it, I doubt anyone thought of such things when writing the laws, but that won't stop a skilled lawyer digging out a 400 year old law that could, under a very warped interpretation, ban such things. --Tango (talk) 20:11, 11 December 2008 (UTC)[reply]
I disagree that a floor with give to it is more tiring to walk on. The spring effect is actually quite beneficial, reducing the impact stress from walking. Dance floors, for example, are almost always made of wood, because dancing on concrete causes pain and injuries. StuRat (talk) 17:03, 12 December 2008 (UTC)[reply]
There is a difference between stress and energy, though. You have to lift your feet higher with each step, which uses more energy. --Tango (talk) 17:16, 12 December 2008 (UTC)[reply]
While it's possible that the piezo-electrics may generate some electricity for "free", it's likely to be an extremely small amount. This small amount probably won't justify the cost of installing the system. There may be an exception for places which are "off the grid" and where only a tiny amount of electricity is needed. For example, using such a method to power a pedometer that measures how far you've walked might be reasonable, if the price is similar to a button cell battery. StuRat (talk) 17:08, 12 December 2008 (UTC)[reply]
I believe that Tokyo subway stations are AMAZINGLY jam-packed with people - so there would be an awful lot of footstep-generated energy. So I don't doubt that they can extract a useful amount of energy (they must surely have done small-scale experiments to prove that). My question is whether they truly are (as they claim) harvesting 'waste energy' and turning it into something useful - or whether they are causing the general public to expend more energy as they walk in order to power their systems. I think people would object to being put into a giant hamster wheel in order to generate power for the subway company...is this really any different? SteveBaker (talk) 17:35, 12 December 2008 (UTC)[reply]
I would guess it's just using energy that would otherwise become heat. I still doubt if it's worth the money to install it, though. If you've ever tried the bicycle hooked up to a light bulb, you need to work amazingly hard just to light one bulb, so the tiny amount they get out of a footstep would do far less than that. For argument's sake, let's say they can get 1 watt from each person who walks by, but only while they are on the unit. To get one watt-hour, you would need a continuous stream of people to walk over the one device for an hour.
Now, as for the argument that they're stealing your energy, let me give an example. Let's say some government agency comes and removes all the sod on your lawn because they suspect it may be contaminated with lead. That would be objectionable, right ? Now say they come and take one blade of grass to test it, instead. Who would care ? It's just too little to matter, just like the energy from your footsteps. StuRat (talk) 00:04, 14 December 2008 (UTC)[reply]

Vanadium foil is used in cladding titanium to steel

I found the statement: Vanadium foil is used in cladding titanium to steel. over and over again, but it looks all are quoting the rubber bible (CRC Handbook). Has anybody ever heard of this method? I now that welding steel to titanium is nearly impossible and they do explosion welding friction, welding and many other things to combine the two. A scientific article publishes the results on using copper for cladding, but vanadium is nowhere mentioned except on simple websites or in the introductions of some articles about vanadium which have also only one sentence about it, without source. Thanks.--Stone (talk) 20:33, 11 December 2008 (UTC)[reply]

Would this one help? [33] - - 76.97.245.5(talk) 15:36, 12 December 2008 (UTC)[reply]
Thanks! I have to read it when I have access to it on monday. Is there vanadium mentioned in the text?--Stone (talk) 22:26, 12 December 2008 (UTC)[reply]
The article specifically states "The best intermediate metal for welding steel to titanium lining is vanadium," - it also cites additional sources to corroborate the idea. Alternatively, the article discusses silver and other filler metals; it also details two techniques which use vanadium as the intermediary metal. Nimur (talk) 20:45, 13 December 2008 (UTC)[reply]

December 12

cactus

are all or most Echinopsis cacti phycedelic? —Preceding unsigned comment added by 76.14.124.175 (talk) 01:57, 12 December 2008 (UTC)[reply]

Hi – it looks as though almost all are psychedelic. At Echinopsis pachanoi, Echinopsis macrogona, Echinopsis scopulicola and Echinopsis lageniformis it mentions psychedelic effects. On a quick reading, they could be mistaken for other closely related cacti that may not have the same properties. There's a list of species at Echinopsis if you'd like to check through the blue links in the species section. Julia Rossi (talk) 02:36, 12 December 2008 (UTC)[reply]

Detecting bullets and Improvised Explosive Devices

Could a 360 degree angle, super fast, super high definition video camera with a computer vision system continuously comparing images help soldiers if Afghanistan by (1) detecting tiny changes in landscape features such as soil disturbance in the case of IED's and (2) detect the direction bullets come from so the soldiers know where to return fire and avoid getting shot or killing the wrong people? I make the assumption that for IED detection multiple drone or airships regularly update the data. Could some sort of radar or lidar be used to detect the source of flying bullets? —Preceding unsigned comment added by Trevor Loughlin (talkcontribs) 04:08, 12 December 2008 (UTC) Trevor Loughlin (talk) 04:09, 12 December 2008 (UTC)[reply]

Bullet detection systems (which basically tell you where the bullet came from) are already in use in the military: [34].
A 360 degree camera would need astounding resolution AND an incredible frame rate to be able to detect things as small and fast as bullets. Hence, the Qinetiq system uses sound.
UAV's look down on the scene from high altitude with cameras that have a narrow field of view and very high precision. Whether the people who analyse these photos can use them to detect an IED seems rather unlikely though - they are often placed under existing roadside features like trash piles and so forth.
SteveBaker (talk) 05:24, 12 December 2008 (UTC)[reply]
I've always wondered why they don't go all the way with the sniper detection systems and wire them into a weapon on top of a Humvee. If anyone shoots a bullet towards you, their location gets an RPG in return. --Sean 14:50, 12 December 2008 (UTC)[reply]
Because putting fire control in the hands of an automated system is a very touchy proposition. Consider that a system like Qinetiq cannot distinguish who fired a round or where they aimed, or often even how far away they are -- only a bearing to point of origination is provided. — Lomn 15:24, 12 December 2008 (UTC)[reply]
Fire control tightly couples into the rules of engagement. In many combat situations, even humans are not allowed to fire on a target without explicit case-by-case permission from a superior officer. As for the "super-high-resolution visual detection" problem, there's a variety of issues - the quantity of data processed becomes immense. Covering a large amount of ground with cameras increases the amount of data to process. Detecting "events" becomes a very hard computer vision problem; distinguishing "threat" events from "non-threat" events becomes a very hard artificial intelligence problem; and then, what to do as a response? If every square inch of a city is covered with a surveillance system, that does not necessarily mean there are adequate resources to respond to all detected threats. These topics are definitely under research; I've seen presentations on various technologies which aim to assist in this direction. It's pure speculation whether these systems will ever become functional and cost-effective enough to see common usage. However, if you think of the technological augmentations like RADAR and night-vision, which fifty or eighty years ago were "crazy ideas", they are now common-place in a lot of militaries... Nimur (talk) 15:35, 12 December 2008 (UTC)[reply]
I think that the reasoning is even more simple than that. It's the 'what if it malfunctions and starts firing indiscriminately at everything that moves?' factor that makes people jittery about deploying what basically amount to automatic sentry guns. --Kurt Shaped Box (talk) 16:33, 12 December 2008 (UTC)[reply]
This system actively identifies objects as small as RPGs using radar. I think it's on the edge of what radar can do right now. My friend is just preparing to head off to his second tour in Afghanistan. He said that one of the major problems with finding underground IEDs was that most areas of Kandahar relied on artificial irrigation agriculture. There were always holes and piles of dirt and people walking around with shovels. I'll bet a probability-based-system could be designed to give soldiers good estimates of where soil-buried IEDs could be. But IEDs tend to find themselves under piles of rubbish, in broken down automobiles or other already "irregular" features in the terrain. NByz (talk) 08:17, 13 December 2008 (UTC)[reply]

A UAV looking down and using thermal imagery would often show the location from which shots were fired. I have seen cop helicopter videos wherein a gun tossed from a moving car shows up glowing brightly in IR imagery lying in the weeds, and the heat given off by a human makes him show up clearly as well. The gun and the bullets would show up nicely via infrared. If the command and control forces knew where friendly forces were, it would be simple for the UAV to fire missiles at the source of the enemy firing. The downside is that mistakes are frequent, such as a US pilot bombing Canadian soldiers in Iraq, or US helicopters firing missiles at US light armored vehicles in Iraq. This also only works in conflicts where high-tech forces are up against poorly equipped forces, since a state-of-the-art military would promptly shoot down an enemy UAV, or if friendly forces had beacons of any sort to identify themselves to friendly aircraft, a state-of-the-art enemy would target missiles on those beacons. Edison (talk) 16:14, 12 December 2008 (UTC)[reply]

I know it's minor, but being Canadian, I wanted to mention that Canada wasn't involved at all in the invasion of Iraq. I think that you're thinking of the Tarnak farm incident in Afghanistan. Interestingly, according to our article on Iraq War (search "canada") Canada had one blue-helmet observer in Iraq in 2006... fancy that. NByz (talk) 08:21, 13 December 2008 (UTC)[reply]
It's really not much different than wearing a uniform: it doesn't have to transmit anything, it just has to be identifiable to a friendly unit. SDY (talk) 17:27, 12 December 2008 (UTC)[reply]
Soldiers wear camo when in combat, not (in modern times) gaudy uniforms. U.S. and allied forces sometimes had strobes on their persons and vehicles so that airborn gunships could tell them from hostiles forces in Iraq. If the enemy had modern technology, and aircraft the strobes or many RF identification methods would have been a death sentence. Edison (talk) 19:11, 12 December 2008 (UTC)[reply]

Water waste

I don't really understand why using lots of water is considered an environmental issue. The earth is a closed circuit, and as I understand it, most of the water from showers gets run off into the water system, purified, and reused, right? So how is it an environmental issue to take longer showers or water one's lawn (when it isn't an immediate drought)? 140.247.152.90 (talk) 05:07, 12 December 2008 (UTC)[reply]

Its not, apart from usually electricity (and hence coal) is used to pump the water. Many places actually have limited amount of water that because their damns only hold so much. When there is alot of water people use rediculous amounts for pratically anything. I believe it something like 5000 tonnes of water to make a laptop for example.--155.144.40.31 (talk) 05:30, 12 December 2008 (UTC)[reply]
(EC with above) The issue is not in the global use of water, it's in localized use of water. While on the whole, water is recycled via the water cycle, at the local level there are limited clean water resources in any one place. Wasting water lowers the amount of availible water, in say your local resevoir or underground aquifer and thus is of concern to the other people who share that water supply with you. In many places prone to drought conditions on a semi-periodic basis (such as the American South since about 2000) municipal water supplies dwindle to dangerously low levels on an annual basis. In other places, such as the American Midwest, the drainage of major underground water suplies, such as the Ogallala Aquifer is a serious concern, since such aquifers are slow to replenish; the annual removal of water from such aquifers frequently exceeds natural processes ability to replace them. The earth as a whole is not running out of total water, but the amount of potable (i.e. usable) water supplies is quite small, and subject to major problems if not managed well. --Jayron32.talk.contribs 05:33, 12 December 2008 (UTC)[reply]

Thanks. So, followup. This question arose cause the dining hall I eat at at college is considering going "trayless" (no trays to put your plates on) as a way to save, among other things, about a half gallon of water used to clean each tray. But we're in upper east coast America in a major city. Is running out of potable water a serious issue? Or is that a "waste" that's really meaningless? Thanks again, 140.247.152.90 (talk) 05:50, 12 December 2008 (UTC)[reply]

Not sure what "upper east coast" you are, bu the Mid-Atlantic states head towards drought nearly every year that I can remember, with lawn-watering and car-washing restrictions to conserve reservoirs. Some years I remember use restrictions in Manhattan (not lawn-watering, obviously:) and even up into Connecticut. Even little things that seem innocuous apparently make a big difference...first sign of drought, restaurants start serving water only when requested rather than by default when you are seated. DMacks (talk) 06:05, 12 December 2008 (UTC)[reply]
(EC with Dmacks response)Well, the other issue I neglected to mention is that waste water itself (the stuff that goes down the pipe at the bottom of the sink) all must be treated before being released back into the environment to remove all the nasties (like poop and soap) from it. This waste, even after being removed, must be dealt with as well. Reducing water usage also has the added benefit of reducing the amount of waste-water that need to be treated. Cleaning trays requires soap, which must be removed from the waste-water, and thus produces additional enviornmental stressors.
Additionally, there is the concern over short-sightedness. Even if, right now, the specific location you live in is not currently under water shortages, there is no reason to suspect that it will continue to lack those problems; no one ten years ago forsaw the current drought in Georgia and the Carolinas. Additionally people in America are highly mobile, and it seems reasonable to encourage good habits across the board, given that you may find yourself living in Atlanta or Phoenix or Kansas City some day; all of which are places facing serious water problems. --Jayron32.talk.contribs 06:07, 12 December 2008 (UTC)[reply]
Some people have made some good points although no one has linked to virtual water yet (which will a little simplistic at least helps you think about the issues). And one key point which Jayron hinted at but I will emphasise in a different way is that just because the water is still present on the earth doesn't mean it's easy for us to use. For example if the water all ends up in rivers that are extremely polluted that's a problem. And perhaps a far bigger issue is that while we can desalinate water, it remain an incredibly expensive process. Therefore if a significant proportion of our fresh water ends up in the sea we start to have problems. While yes, this water should eventually make it back to land (somewhere) as fresh water this may not happen as fast as we used it depending on the source. Not surprisingly then may have suggested the number of wars fought over water is going to increase in the 21st century. The water article has numerous links that may be of some interest, e.g. water politics and the water cycle also has this "the water cycle to continue to intensify throughout the 21st century, though this does not mean that precipitation will increase in all regions. In subtropical land areas — places that are already relatively dry — precipitation is projected to decrease during the 21st century, increasing the probability of drought. The drying is projected to be strongest near the poleward margins of the subtropics (for example, the Mediterranean Basin, South Africa, southern Australia, and the Southwestern United States)." Nil Einne (talk) 10:23, 12 December 2008 (UTC)[reply]
Half a gallon of water to clean one tray? They don't need to stop giving you trays, they need to use more efficient cleaning methods. All you need is a damp cloth... --Tango (talk) 10:30, 12 December 2008 (UTC)[reply]
Aramark's promotional literature for trayless dining (oh well, soon I guess) for the higher-ed market states "on average, a tray conservatively requires one-third to one-half gallon of water to wash." DMacks (talk) 11:15, 12 December 2008 (UTC)[reply]
I'm was with Tango, but out of interest had a bit of a look into it...If we say the average commercial dishwasher uses 6 gallons per cycle (http://www.hrwet.org/b&i_guide/cafe.htm) that'd mean putting through 12 trays per cycle, which is probably reasonable for a commercial dishwasher to handle (from my restauranter kitchen porter days!). As per the above it is the energy (and chemicals) required to re-clean water that's the best reason to minimize waste where feasible, this seems like a plausible way to reduce waste water. 194.221.133.226 (talk) 11:47, 12 December 2008 (UTC)[reply]
A commercial dishwasher is overkill for cleaning trays. There won't be food stuck on them and people won't be eating off them. A quick wipe with a damp cloth, maybe with some antibacterial soap on it (and then another wipe with a plain damp cloth) should be plenty. --Tango (talk) 12:38, 12 December 2008 (UTC)[reply]
I would assume that a school will not wash these things by hand. What you suggest would no doubt be enough but I suspect that they are put through the machine like other dishes. Essentially if we say there are 500 students using 1 tray per lunch time you've got a hell of a lot of trays to deal with. If you use a machine you can stack that, put it on (industrial ones i've used take a minute or two) and be doing something else while that does it, then switching to the next. I think they'll put them through the machine more often than not. 194.221.133.226 (talk) 14:13, 12 December 2008 (UTC)[reply]
Wiping a tray only takes marginally longer than putting it in a dishwasher - they need to decide which is worth more, an extra second of somebody's time or half a gallon of water. --Tango (talk) 14:17, 12 December 2008 (UTC)[reply]
Food service industries are regulated heavily by most states WRT dish cleaning procedures, for sanitation purposes. Most require that all dishes and utensils handled by customers and reused are washed according to certain standards (trays are not exempt); for example that they are washed at a certain temperature water, and according to certain procedures. While dishwashers are one option, and handwashing is another, but it is usually a far more extensive procedure than "wipe with a rag". The regulations exist for sanitation purposes; honestly, I am not sure that I want to eat off of a tray if I knew that hundreds of people ate off that tray before me, and the best it got was a half-assed three second wipe with a damp rag! If the trays are washed properly by hand, it may use somewhat less water, but it would also require significantly more work; more work costs more money; and the added cost of paying several extra people who essentially work to keep trays clean just for you will be added into the cost of the food. Given that option, it is just easier to forgo the tray... --Jayron32.talk.contribs 14:42, 12 December 2008 (UTC)[reply]
You don't eat off a tray, you eat off a plate. Paper serviettes could be issued for food items that don't come on a plate (fresh fruit, say), and for cutlery. There is no need for food you are going to eat to ever touch the tray. --Tango (talk) 14:46, 12 December 2008 (UTC)[reply]
Exactly... So the tray is superfluous. Good to see you understand that! --Jayron32.talk.contribs 15:12, 12 December 2008 (UTC)[reply]
Yes, Jayron, whatever you say, Jayron. --Tango (talk) 16:14, 12 December 2008 (UTC)[reply]
They are superfluous for people not purchasing a beverage or side dish. APL (talk) 05:35, 13 December 2008 (UTC)[reply]

You also don't eat off a toilet seat (I hope!), but it's a good way for germs to get around because they get on hands and hands get on food which gets... you gets the point. Part of the reason for the "always wash your hands after using the toilet" advice. Institutional settings are notorious for disease outbreaks because of shared stuff, and it's much easier to clean trays than it is to clean tables (which would otherwise have many of the same problems). Cleaning trays is certainly a secondary concern, but it's not irrelevant, especially in high-risk settings like hospitals. SDY (talk) 15:44, 12 December 2008 (UTC)[reply]

Which is more "environmentally friendly" - disposable cutlery or reuseable cutlery that must be washed? This depends on so many factors, such as rate of consumption, quantity used; etc. It's not immediately obvious which has less total environmental impact. Nimur (talk) 15:42, 12 December 2008 (UTC)[reply]
How many hands does the typical student have? Because carrying a main course, pudding, piece of fruit, drink, cutlery, and then paying at the till may prove somewhat difficult if they typically have two hands each. DuncanHill (talk) 15:47, 12 December 2008 (UTC)[reply]
The first reply to this query says something about wasting 5000 tonnes of water to make a laptop...? Wha..? ~ R.T.G 16:01, 12 December 2008 (UTC)[reply]
Who does anything more than wipe their toilet seat clean? --Tango (talk) 16:14, 12 December 2008 (UTC)[reply]

Suppose the previous Diner A has an infectious disease ("the bug") whose germs or virus can survive for an hour on an environmental surface like a tray. He eats, and transfers the bug from his saliva to his spoon and fork, which he leaves on the tray, contaminating it. The cafeteria worker wipes the tray with a rag which picks up the bug, and which leaves some on the tray. As the worker wipes other trays, he leaves the bug on them. Diner B places his silverware on the tray, contaminating them with the bug, which he then transfers to his mouth, as do diners C, D, .... from their trays which the cafeteria workers rag has spread the bug to. Some of the subsequent diners get sick. Thanks, but I will be dining in a place where the trays (if any) are sanitized per health department regulations. Our local health department forbids any wiping of dishes for this reason. They must air dry even after coming out of the dishwasher. Edison (talk) 16:06, 12 December 2008 (UTC)[reply]

Antibacterial soap in the water the cloth is dipped in between each tray would do a pretty decent job of killing such bugs. Wrapping the cutlery in a (recycled) paper serviette, as I suggested, also helps mitigate that problem. --Tango (talk) 16:14, 12 December 2008 (UTC)[reply]

(ec) While I think Tango's heart is in the right place, it's asking for trouble to trust that a once-over with a damp cloth (soapy or not) will be sufficient. (Are we also prepared to trust that a minimum-wage cafeteria slave – one who's too low on the totem pole to operate the deep fryer or ladle out mystery-meat stew – is going to do a thorough and comprehensive wipedown of each and every one of hundreds of trays every day?) While (most) people won't eat food directly off the tray surface, you don't need direct transfer from tray to food to harm a consumer. Trays are regularly handled by diners who fail to wash their hands after eating, sneezing, picking their noses, etc. If I touch that tray and then my hamburger or sandwich, I'm screwed. The health-conscious guy who buys an apple and lets it roll around on the contaminated tray is in for a world of hurt. A number of unpleasant infectious diseases can be transmitted this way, including – but by no means limited to – influenza, hepatitis A, and norovirus infection. (Worth noting is that all of those are viral rather than bacterial infections, and that even against bacteria the use of so-called 'antibacterial' soaps is not a magic wand.) A warm, damp, frequently-reused tray strikes me as one of the more effective vectors to spread these illnesses from person to person. (The tray-washer's wet rag is probably a good vehicle, too.) Finding a cleaning strategy that uses less than a half-gallon of water but doesn't incur excessive costs (disinfectant cost, cost of employee time, physical hazard to employees, risk of allergic or other toxic reaction for consumer, risk of transmission of infectious diseases) is a nontrivial challenge. TenOfAllTrades(talk) 16:41, 12 December 2008 (UTC)[reply]

Um, how much water is used up by a salmon growing up in the sea? 93.132.146.73 (talk) 16:23, 12 December 2008 (UTC)[reply]

Before deciding to get rid of trays, we first need to list the purposes of trays. I can think of two:
1) To allow you to carry many items at once. How can you carry a plate of food, bowl of soup, drink, utensils, napkin, and maybe a desert with just two hands ?
2) To catch spills. My soup regularly jostles a bit as I carry it, and spilling those drops on the tray seems far better than on me, the floor, and the table. This could possibly be addressed by putting lids on all the containers, but there goes the dish-washing savings. You could also put disposable lids on the containers, but that's not good for the environment, either. StuRat (talk) 16:51, 12 December 2008 (UTC)[reply]
You could, ya know, go up more than once, so that you don't have to take all the food back at once. Many university cafeterias are "buffet" style, where you pay an entry fee, and then its all-you-can-eat. In these situations, another problem with trays is that it encourages people to overload, which then results in food wastage. With a tray, you load up as much food as you think you may eat, and then if you don't finish it, it all goes in the trash... If you have to go up and get your soup, sit down, eat it, go up and get your salad, sit down, eat it, get up and get your chicken, sit down, eat it; you are MUCH less likely to take more than you want... Again, another side benefit of forgoing the tray. Again, NO system is foolproof, and trays come with as many problems as the benefits they provide. The question is if we are ready to forgo the benefits to also avoid the problems. Such is life. There is no perfect sitution ever which allows you to have a perfect system where the choice is obvious. Hence, TAANSTAFL... --Jayron32.talk.contribs 17:29, 12 December 2008 (UTC)[reply]
Based on a recent news story about a local university cafeteria which had gone trayless, it seemed to me that the "people take/waste less food if they don't have a tray" was the real reason administration had for the switch, with "it uses less water, so it's better for the environment" being marketing to help convince students to go along with it. -- 128.104.112.113 (talk) 19:45, 12 December 2008 (UTC)[reply]
To be fair, having people take (and waste) less food is also better for the environment. This page notes that it takes about 150 gallons of water to produce one pound of wheat. Depending on the location, some substantial fraction of that may come from natural rainfall.) Saving a half gallon of water by not washing a single tray allows one to grow an extra 1.5 grams (about a twentieth of an ounce) of wheat. Trimming the use of meat has an even bigger environmental savings. Reducing portion sizes slightly has a tremendous environmental benefit far beyond the water and energy savings associated with abandoning trays. TenOfAllTrades(talk) 23:14, 12 December 2008 (UTC)[reply]
"Trimming the use of meat has an even bigger environmental savings." Depending on what the meat is and where it was raised... 79.66.58.154 (talk) 23:47, 12 December 2008 (UTC)[reply]
Although most of the Earth is water, only about 1% of that water is accesible fresh water, and even less is used for safe drinking water. If our water goes into the sewage, it may eventually make it back into our drinking water, but that will take a while to purify. When it rains, water often runs into storm drains and do not get purified, and run directly into the lake. Also, we may not run out too soon, but with looming issues such as global warming and environmental change, drought and other factors could reduce our available water supply even further. Consider that half a billion people rely solely on the water supply from the Himalayan glaciers...and those glaciers could all melt before the century is out. Most of the consequences from not conserving are usually indirect and unintended. While it's true that the Earth is a closed system, that doesn't mean we'll always have the same amount of accesible, clean, safe drinking water. ~AH1(TCU) 00:07, 13 December 2008 (UTC)[reply]
I'm somewhat doubtful of that. While the effiency of raising meat varies greatly, it's always going to be an incredibly expensive process compared to agriculture. You can probably get some decent stats from global warming related studies which although focusing on CO2 likely have relevance to water too. For the person who asked about 5k tonnes for a laptop, again I suggest you take a look at virtual water which while as I said a little simplistic concept (as the article states) begins to address the issue. I suspect 5000 tonnes is wrong. Perhaps 5000 litres. According to our article a car takes between 400k to 1 million litres so 5k tonnes or 5 million litres for a laptop definitely seems excessive. (Although these things are difficult to quantify, definitely agricultural based goods use a lot e.g. 3k4 litres for 1 kg of rice) Nil Einne (talk) 00:38, 13 December 2008 (UTC)[reply]

Question about Recursion

Background: On a Pet Milk can label, when I was a child, there was a picture that contained a picture of itself -- which suggests abstractly that the picture contains an infinte number of ever-smaller copies of itself. No graphic representation nor physical manifestation of this concept is possible, of course; but it is abstractly logical. QUESTION: What is the TERM for the underlying concept, in abstract mathematics, whereby an image may contain itself, such that it is rendered abstractly to be an infinitely iterative reductive series; and where would I find a source offering a rigorous mathematical treatment of this abstract concept? Gggiiillllll (talk) —Preceding undated comment was added at 19:29, 12 December 2008 (UTC).[reply]

Recursion, like in the title I just added for your question. Or, as you can see in the article, the Droste effect. Also, please sign your posts, using ~~~~. --LarryMac | Talk 19:36, 12 December 2008 (UTC)[reply]
Infinite regression might also be a topic of interest. -- 128.104.112.113 (talk) 19:41, 12 December 2008 (UTC)[reply]
Actually, there is a physical manifestation: The Infinite Cat Project! --Sean 20:53, 12 December 2008 (UTC)[reply]
I'm very sorry, but you cannot understand recursion unless you understand recursion. -Arch dude (talk) 21:08, 12 December 2008 (UTC)[reply]
I think the pertinent article is the Droste effect, and its cousin, mise en abyme. Follow the external link to Escher and the Droste Effect, and from there to The Mathematical Structure of Escher's Print Gallery.. - Nunh-huh 09:46, 13 December 2008 (UTC)[reply]
Also, fractal. —Preceding unsigned comment added by DanielLC (talkcontribs) 17:20, 13 December 2008 (UTC)[reply]
Man, user:SineBot's fast. I went back about five seconds later to sign that. — DanielLC 17:22, 13 December 2008 (UTC)[reply]
You can replace SineBot's signature with your own - no-one will notice (feel free to delete this message if you do)! --Tango (talk) 17:39, 13 December 2008 (UTC)[reply]

Pump type

Not sure if this question is "scientific" enough. If you think it should go in miscellaneous, plse. move it. I'm looking for a very low voltage pump (about 9V or thereabouts) to set up at a leak in our basement. I want to rig it so that it starts when there's water down there and turns off once most/all of it has been pumped off. The circuit is easy enough to whip up. I know that I need a suction pump, and one that can run dry for a while without getting ruined. That seems to rule out aquarium pumps. But I wouldn't know what to start looking for. Anyone a name for such an animal? (Finding how the water gets in seems to develop into a long term and costly project of elimination by trial and error. 2 possible causes down, no improvement, many more to go:-( 76.97.245.5 (talk) 20:51, 12 December 2008 (UTC)[reply]

Why 9 volts? Building centers/hardware stores have lots of utility pumps with water sensors which do this task. If the water contains dirt or mud or grit, it will quickly destroy pumps designed to pump clean water. Some aquarium pumps are rated to run dry for a time. A conductive sensor or float switch should be used to avoid the running dry problem. Maybe you could make a little dam around the leaking spot, out of Mortite or expanding foam or something to collect the water and make the mump's job easier. Hydraulic cement or other products could be used to fix the crack, rather than the fix proposed. Edison (talk) 20:58, 12 December 2008 (UTC)[reply]
http://www.google.com/search?hl=en&q=battery+powered+sump+pump&btnG=Google+Search -Arch dude (talk) 21:10, 12 December 2008 (UTC)[reply]
The water is seeping in along a wall, and maybe up through the foundation, not through any detectable crack. I've actually not yet caught it early enough in the process to find out more details. It only does that when we have one of those famed Georgia thunderstorm downpours, not when we get ordinary rain. We got a new roof, new gutters with gutter guards and the next step is going to be putting hydraulic cement and water barrier landscaping tarp along the sidewalk and wall on the outside. If that won't do, we'll have to get a drain pipe in the garden dug up and looked at. Failing that it get's real expensive with digging up the foundation form the outside and having it insulated. (People frequently get killed doing that unprofessionally, so we won't do that. which automatically means it'll cost oodles of money. I can't even get my hubby to understand why having water coming in through your wall and foundation is s.th. that needs to be remedied. He's not doing the wet-vacing.) Getting the water to collect at one spot would require more of an engineering effort than a quick fix would merit. I've put up a barrier along sections of the wall but some of it is under some built-ins. (more work -just what I need). I want the pump to suck up as much water as possible, so it's going to do an "last of the beverage through the straw" effect for a bit till the cut off doesn't have enough water for the circuit to close. I'll have a look at the sump pumps Arch dude linked. I hope they'll have some that are the right size. When I hear sump pump I think lots of flow, all liquid and dirt. What I need is little flow but no problem gargling up the silty water that comes in mixed with some air. My wet vac does that, but it's 120V and I don't want to mess with mains circuitry. Our electrical is my next project. (This Old House could have shows for ages in this place. It comes with a money drain.) Thanks for yall's help. 76.97.245.5 (talk) 23:08, 12 December 2008 (UTC)[reply]
Sump pumps like to have the water in a sump. If the water is of negligible depth, like a thin trickle, it is hard on a pump to sit there and basicall run dry much of the time. It should be possible to install a low dam a couple of inches inside the wall and catch all the trickles, and pump them out when the depth is half an inch or more down to perhaps 1/4 inch. If the depth is negligible, then a wetvac is the best solution. There are also absorbant rolls like the PIG which can be placed as a barrier, to catch occasional trickles. Another method is to have a contractor saw a groove in the floor an inch from the wall, which lets the water flow to an actual sump with a sump pump. Edison (talk) 20:48, 13 December 2008 (UTC)[reply]
Sump pumps are designed for situations like yours. They can detect water and turn on and off as needed. Beware that the water seeping through the walls will slowly erode them, however. StuRat (talk) 23:46, 13 December 2008 (UTC)[reply]

travertine

hello there i was just wondering if travertine is found in new zealand —Preceding unsigned comment added by 124.198.133.239 (talk) 21:56, 12 December 2008 (UTC)[reply]

Hi 124.198, you might find something in the Journal of Sedimentary Reseaerch, here[35] by going through the abstracts etc, but seems it could be connected to hot springs in the North Island. Julia Rossi (talk) 08:49, 13 December 2008 (UTC)[reply]
The only thing I could find except for someone claiming that their holiday pic showed travertine is the following: ...travertine deposits are common ... ."On the other hand, mixed silica-carbonate hot spring deposits are much more rare (Campbell et al., 2002). Among the best-studied silica-carbonate hot spring deposits, those from Waikite (Jones and Renaut, 1996; Jones et al., 2000b) and Ngatamariki (Campbell et al., 2002), New Zealand." This doesn't exactly rule out there is any travertine being deposited in those springs, either. Dendritic calcite crystals are reported to be a component of travertine. The former are found in hot springs at Waikite, North Island. You could maybe find more details with http://www.onegeology.org with another layer than the ordinary lithography. (That one only has things like "calcareous siltstone" and "limestone" so they may just not have travertine as a category.) 76.97.245.5 (talk) 18:03, 13 December 2008 (UTC)[reply]

December 13

In looking up an answer for the Travertine question above I came across the above page. I googled it and came up with dictionary links most of which went back to our page. I'm beginning to seriously doubt that such a term is in actual use in English. The page seems to have been translated from the German (Kalk-) Sinter page. That one's o.k. but I think what they are talking of is tufa or limestone (a limestone cave would be called a Kalksteinhöle in German.) Could s.o. with a geology background plse. see if this is a valid term. 76.97.245.5 (talk) 00:16, 13 December 2008 (UTC)[reply]

It's in Webster's Online [36]. DuncanHill (talk) 00:22, 13 December 2008 (UTC)[reply]
And here's an example of its use by John Davy. [37]. DuncanHill (talk) 00:23, 13 December 2008 (UTC)[reply]
Not exactly current usage then. The Webster mentions Calcite. Would you think that is the modern term for it or are the two terms merely related? 76.97.245.5 (talk) 02:40, 13 December 2008 (UTC)[reply]
Not all Calcium carbonate minerals are calcite - depends on the crystal structure. DuncanHill (talk) 22:09, 13 December 2008 (UTC)[reply]

Small children and names

Is there a reason why young children sometimes have trouble realizing there can be two people with the same name? A classic example might be the child who is upset because some other child in his or her class has the same name. Is it a feeling of uniqueness, that they fear not being special anymore? Or, is there something that actually makes them think, "Wait, this can't be right, there can only be one of 'x' in the world." (Such as the child I read about who was, admittedly, much younger, about 20 months. He was holding his comfort object, happened to open a drawer where his mother stored 3 more just like it for when one needed washed...he closed the drawer very slowly and didn't open it for weeks, as if he thought, "This drawer causes anomalies worthy of Star Trek."Somebody or his brother (talk) 00:47, 13 December 2008 (UTC)[reply]

I wonder how it might relate to the Lacanian concept of the "mirror stage"? It first happens between six and 18 months so that's about right – it involves ego-structuring, mastery, the Imaginary and the Real, the "thing" as symbolic object Das ding an sich. There's nothing to say it doesn't continue. There was an earlier observation by Henri Wallon. But I like the Star Trek anomaly best, Julia Rossi (talk) 09:10, 13 December 2008 (UTC)[reply]
When you consider all of the other things that a child has to learn - this is really one of the more minor ones. That the sound "apple" is actually a label for a thing - is a tough thing to just "realise"...but then to realise that it stands for a whole class of things - where the label "Mummy" doesn't. Then you have to know that "Mummy" when you say it means something different than when your friend says it...but when your mummy says it, she can either be talking about herself or HER mother. This is insanely complicated. That there can be more than one person with the same name is really just a small subset of the overall problem. SteveBaker (talk) 02:58, 14 December 2008 (UTC)[reply]

What's the cause of an inability to distinguish an actor from a character?

Do people who are unable to distinguish the two suffer from some inability to distinguish fantasy from reality? From the question I asked about the Wii earlier, I considered immersion one possible reason; but, one is not actively participating in a television show or movie, except in the case of trying to solve a mystery. Besides, it seems like there would be more of this problem if it were *only* immersion causing it. this isn't just a question about seeing actors only as capable of playing a certain role, of course, but of thinking the actor *is* the character.Somebody or his brother (talk) 01:13, 13 December 2008 (UTC)[reply]

It seems to me the answer to this, if there is one, must be multi-faceted. One facet might be "how many different characters has the person in question seen the actor play?" E.g., if someone's only knowledge of Lisa Kudrow is in the role of Phoebe on Friends, they may not distinguish the personalities of Lisa and Phoebe. If they have seen Lisa in multiple roles, they likely will see her quite differently. CBHA (talk) 02:17, 13 December 2008 (UTC)[reply]
Agree – publishers of TV magazines don't help when they write in-universe stuff about "soap" characters "tying the knot" on the show for example. Though it doesn't relate exactly to the mentally you ask about, see also Typecasting (acting). Julia Rossi (talk) 09:14, 13 December 2008 (UTC)[reply]
It must have something to do with learning and experience. For example, in my grandparents village in the first few years the TVs were introduced, everyone freaked out when they saw an actor in a movie who had already died in another movie. After that however, they get accustomed to it. --131.188.3.20 (talk) 19:24, 13 December 2008 (UTC)[reply]
The phenomenon you describe is not quite limited to TV actors. A name is just one part of how we identify an individual. If you meet s.o. at a party you may refer to that person as the girl/guy who was at Jo's party, when talking about that individual. New family members are often referred to as Bob's wife, Meg and Mel's baby etc. for quite a while. Equally actors will be referred to within the context that we know them from, even when we see them in a new setting: Isn't that that guy from NYPD blue? In the evolution of our social interactions it's always been important to know where in the hierarchy to place someone. Sorting out two different identities for one individual has just not come into the picture until most recently. 76.97.245.5 (talk) 21:36, 13 December 2008 (UTC)[reply]
It's not surprising when you consider all the effort the producers of a TV show or movie put into making people believe the actors really are the characters. Those people who aren't too bright tend to fall for it. StuRat (talk) 22:40, 13 December 2008 (UTC)[reply]

Schrödinger's Particle Accelerator

My little cat, Mr. Cuddlypants, is sound asleep on his cot. The cat on the cot happens to be the terminal focus of bundles of protons sent hurtling at 99.999999% the speed of light by a gargantuan particle accelerator. I'm in bed gazing at the little cot, and only just realized the presence of the particle accelerator. Should I bother to get up and move Mr. Cuddlypants or just turn over and go to sleep? Sappysap (talk) 01:21, 13 December 2008 (UTC)[reply]

So what's the question? Would high speed protons be harmful to a cat? The answer to that is almost certainly "yes" (assuming there is a significant number of them). Protons are charged, so would be a form of ionising radiation, which at the very least risks causing cancer. At those kind of speeds, though, the energy alone would be harmful. The cat would probably be vaporised by any significant number of protons at that speed. --Tango (talk) 01:38, 13 December 2008 (UTC)[reply]
No, it's a reference to the the cat in this thought experiment, which can be considered neither alive nor dead until observed. --Bowlhover (talk) 04:42, 13 December 2008 (UTC)[reply]
Thats Schrödinger's cat, I don't think Sappysap is Schrödinger. Not to mention Mr. Cuddlypants has a very well defined state with little quantum uncertainty. Mr. Cuddlypants is asleep on his cot rather than maybe dead in box. I think Tango's explanation is reasonable.--OMCV (talk) 05:56, 13 December 2008 (UTC)[reply]
I know what Schrödinger's cat is, but I don't see a connection to that beyond the presence of a cat and the name "Schrödinger" in the section header. --Tango (talk) 14:24, 13 December 2008 (UTC)[reply]
Although I have a cat I don't know whether I'd be willing to move it out of a particle accelerator. Although I do love my cat, I love myself more. A better bet would be to try and get it to move itself (shouldn't really be a problem with most cats) and if that fails well start looking for a new cat Nil Einne (talk) 12:16, 13 December 2008 (UTC)[reply]
According to the LHC article, dumping all of the stored protons (which would happen if you suddenly stuck your cat in the middle of the beam) would result in the release of 362 MJ, or the same as burning 8 kg of oil. Given that the protons are moving at 99.999999% the speed of light, and that the ring is "only" 27 km in circumference, the beamline would empty in about 90 microseconds. Mr. Cuddlypants would probably be flash-boiled instantly. However, I doubt your reaction time would be fast enough to save him from his fate. (I wouldn't roll over and go back to sleep, though. I'd probably crack a window first - I can't imagine vaporized cat would smell all that good.) Note this assumes that the accelerator vacuum chamber terminated directly at your cat. Having to pass through air and walls would probably dissipate a lot of the energy before it reaches the cat. Also note that it depends on how many protons the accelerator is putting out. The LHC will use 3×1014 protons - smaller accelerators would use less. Theoretically, it would be possible to build a very small accelerator whose beam would produce only a mild warming sensation. I'd still stay out of the way, though, due to radiation-induced DNA damage.) -- 128.104.112.113 (talk) 22:46, 13 December 2008 (UTC)[reply]
Actually, Mr. Cuddlypants would probably survive (not counting radiation damage, cancer, or other long-term effects). It is rather hard to stop ultra-relativistic particles, and even if you dump it into a solid object, that 300 MJ would be deposited over several meters. In fact, most of the energy is deposited not at the initial contact, but a few meters further in after each ultra-relativistic initial particle is converted into a shower of mildly-relativistic daughter particles (1 particle at 99.99999% c is less dangerous and far harder to stop than 1000 particles at 99% c). Incidentally, a loss of beam containment at a particle accelerator will usually not deposit enough energy into the beam line wall to actually damage the accelerator (though it can make an audible thwwump sound). So, assuming Mr. Cuddlypants is a normal size for a cat, and he has the privilege of being the first thing the beam hits, he will probably receive much less than 1% of the total beam energy and come away singed but intact. Dragons flight (talk) 00:08, 14 December 2008 (UTC)[reply]

Faster means lower pressure?

Isn't the Coandă effect just an example of viscosity? Further more (ignoring the Newtonian component) is it best to say lift results from low pressure on the top of an airfoil as described by Bernoulli's principle or does the airfoil experience drag from the viscosity of the air which pulls on the top of the wing. That is to say does the outer or inner surface of the top of the wing experience force? Although both forces are in the same direction surely it possible to distinguish defamation resulting from a push from inside versus a pull from above. Which side of the metal is having more force exerted on it?--OMCV (talk) 05:06, 13 December 2008 (UTC)[reply]

Not exactly. Viscosity is due to cohesion, that is the property of a substance to stick to itself. The Coanda effect is due primarily to adhesion, the property of different substances to stick to each other... --Jayron32.talk.contribs 22:15, 13 December 2008 (UTC)[reply]

Determining the sex of a seagull?

Is it possible to visually determine whether a seagull is male or female? Without seeing it mating or laying an egg I mean. --84.66.45.248 (talk) 13:31, 13 December 2008 (UTC)[reply]

Its easy. If you see two seagulls walking down the beach, and one is going "Sqawk sqawk SWAWK" and looking annoyed, while the other one is just walking away silently; the first is the female... --Jayron32.talk.contribs 22:11, 13 December 2008 (UTC)[reply]
Sounds like you got that email, too. StuRat (talk) 22:28, 13 December 2008 (UTC)[reply]
Our resident seagull expert, User:Kurt Shaped Box, should be around to answer that soon. StuRat (talk) 22:28, 13 December 2008 (UTC)[reply]
Hokay. The following is true for Herring/LBB/GBB gulls. It may not be true for all gull species. Pretty much the only way of visually sexing them is to observe two gulls that are obviously paired-up when they're stood close together. Most of the time (I'd say eight times out of ten), the male gull will be longer and wider than the female - perhaps with a longer skull, shallower slope to the forehead and a chunkier beak (this is not always obvious, or even noticeable at all). Beyond that, it's almost impossible to determine the sex unless you physically have the gull in your hands - females have (as you might expect) a wider pelvis (not that I'd know what I was supposed to be feeling for if I was to do that...). In an area where the gulls are well-fed and relatively safe from predators, there will probably be loads of undersized adult gulls that were originally the 'runt of the litter' and gulls which are basically fat, which complicates things somewhat. --Kurt Shaped Box (talk) 23:48, 13 December 2008 (UTC)[reply]

Pills

I happened to observe this characteristic about pills, and it caused me to wonder. In my (limited) experience, most prescription pills come in an oblong-shape. Some pills (such as aspirin), however, come in a round/circular shape. Is there any reason at all -- scientific? financial? -- why the maker of a pill would select one shape over another? Thank you. (Joseph A. Spadaro (talk) 15:54, 13 December 2008 (UTC))[reply]

Not a very good source but it makes some good points: http://www.nowfoods.com/?action=itemdetail&item_id=40088Cyclonenim (talk · contribs · email) 18:03, 13 December 2008 (UTC)[reply]
You've completely lost me... what does a 12oz packet of Apple Fibre have to do with anything? Was that the wrong URL, by any chance? --Tango (talk) 18:35, 13 December 2008 (UTC)[reply]
Definitely the wrong link... fixed now. —Cyclonenim (talk · contribs · email) 19:08, 13 December 2008 (UTC)[reply]
Ah, that's a far more relevant link, thank you! --Tango (talk) 19:10, 13 December 2008 (UTC)[reply]

Thanks ... but I am still lost. That link is a compare/contrast of tablets versus capsules. My question was about round-shaped tablets versus oblong-shaped tablets. Any clarification? Or did I miss something in the above link? Thanks. (Joseph A. Spadaro (talk) 21:56, 13 December 2008 (UTC))[reply]

Don't know why they're shaped that way, but the oblong ones are sometimes called caplets (a portmanteau of capsule and tablet). -- 128.104.112.113 (talk) 22:00, 13 December 2008 (UTC)[reply]
This is a WAG, but my speculation is that the shape is purely for identification purposes; the wider variety of shapes and colors allows for easier differentiation between different medications. Without looking it up, you can probably easily identify a pill such as Advil (oblong brown cylander) or Viagra (blue diamond) or the like. The shape probably serves little purpose beyond that... --Jayron32.talk.contribs 22:10, 13 December 2008 (UTC)[reply]
That's correct. And, since early pills got their choice of shapes and colors first, we ended up with a simple white, round pill for aspirin. At the rate at which new (and often questionable) drugs are approved, we will soon be up to plaid and paisly dodecahedrons. StuRat (talk) 22:20, 13 December 2008 (UTC)[reply]
StuRat ... are the pill makers required to select a unique shape/color? From my memory, all the pills I have ever taken were essentially white and oblong, although perhaps of different size. (Joseph A. Spadaro (talk) 23:43, 13 December 2008 (UTC))[reply]

Ocean floor water temperature

What is the average temperature of water at the bottom of the ocean, in particular the bottom of Challenger Deep? —Preceding unsigned comment added by 89.167.221.3 (talk) 16:46, 13 December 2008 (UTC)[reply]

Away from deep trenches, the bottom zone of ocean is the Abyssal zone, according to that article, "The abyssal zone has temperatures around 2 to 3 degrees Celsius, but 13-15°C in the Mediterranean Sea." In trenches, you get into the Hadal zone, but that article doesn't mention temperature. According this this book, the temperature at the bottom of pacific trenches ranges from 1.1C to 3.3C. --Tango (talk) 17:13, 13 December 2008 (UTC)[reply]
Doesn't that match the temps at which water is the most dense ? Not a coincidence, I bet. StuRat (talk) 22:12, 13 December 2008 (UTC)[reply]
It roughly matches the temps at which fresh water is the most dense, I don't honestly know much about the density of salt water... (or even what the salinity is at those depths). --Tango (talk) 23:33, 13 December 2008 (UTC)[reply]
It is a good thought. Freshwater is most dense at 4 C. Unfortunately it is also wrong. Water containing as much salt as the ocean does actually increases in density without limit all the way down to freezing point, around -1 C. The strange little density inversion shown in freshwater goes away when you add enough salt. It is true though that deeper waters are usually colder because colder water is denser (assuming the salinity stays constant). Dragons flight (talk) 03:00, 14 December 2008 (UTC)[reply]

ESPVR curve shift

Hi:

Which way would the End Systolic Pressure Volume Relationship (ESPVR) curve shift, left or right, after Ca++ channels are blocked by Ca++ blockers?

Thanks.

74.12.39.128 (talk) 17:46, 13 December 2008 (UTC)[reply]

The ESPVR is shifted by inotropy, and calcium channel blockers are negative inotropes. Here's an illustration (fig 2.14 on page 27): [38]. The cardiovascular physiology article has relevant links for those interested in more info. --Scray (talk) 20:30, 13 December 2008 (UTC)[reply]

TOOLS/HARDWARE IE:Europian style "cup hinges".

Hello and thank you for considering my request.I am a some what experienced carpenter but my when it comes to cabinet work my skills are seriously lacking in some respects.Modern hardware is one of those areas.I have designed and created a door for a certain client and to keep the hinges hidden and create an "inset",as opposed to an "overlay" or "half overlay",appearance I'm using the cup hinges.I got them at my local big box but they didn't come w/ instructions. My home library mentions them in several of my books but none of them offer a clear,with measurements and everything,"how to" to installing them.I went on line to the manufacturer ,they are brand name,but wile they offered templates and jigs for using their products I couldn't find any instructions.Perhaps one of y'all could offer some help or even know a source that I can get the "instructions" I seek.I'll be conducting some experiments this wknd. but am still looking forward to what other help and "how-to" information is out there.Any and all suggestions will be greatly appreciated.Thank you.RCW —Preceding unsigned comment added by 76.68.73.149 (talk) 18:16, 13 December 2008 (UTC)[reply]

My gut instinct tells me it may be better to telephone the manufacturer and ask to have instructions emailed/faxed to you. Exxolon (talk) 19:09, 13 December 2008 (UTC)[reply]
If you told us the mfr and model or scanned the item and included a picture we might be able to provide more help. Edison (talk) 20:39, 13 December 2008 (UTC)[reply]
Also try to explain how you would like to use them. Are you certain the type you got is suitable for creating an "inset" look? Meanwhile you might want to see if you have these things available (or can borrow them) to make your life easier: a Forstner bit and one of these things [39] (mobile drill stand / drill guide?) not necessarily this make. You can do without, but it will take a lot more fiddling.76.97.245.5 (talk) 21:03, 13 December 2008 (UTC)[reply]
Also try asking at the big box store where you bought it. StuRat (talk) 22:08, 13 December 2008 (UTC)[reply]
A standard router can be used to create the recesses for the fitting. Much better: You also get standard drill bits for the round recesses in every hardware store (well, in Europe, which may require a spot of expensive shopping). As opposed to Forstner bits, they have the advantage that you can only drill to the required depth. The hinges you can get in any IKEA store in two types (angle of opening 125 degrees or 153 degrees for slide out / roll out bits behind the front cover) costing about € 3.00 to € 4.00. They also stock air brakes which can be clipped onto the hinges to make the door close gently without a bang.
BTW, we have no article on cup hinges but one on Martina Hingis. Unfortunately it does not say anything about what size cups she wears and it certainly does not mention any hinges in her underwear. --Cookatoo.ergo.ZooM (talk) 01:52, 14 December 2008 (UTC)[reply]

Freezing hot water

Why does hot water freeze faster (assuming that what i heard is true)? --212.120.246.219 (talk) 19:48, 13 December 2008 (UTC)[reply]

See Mpemba effect 93.132.189.30 (talk) 19:52, 13 December 2008 (UTC)[reply]

Chemical depilatory

Since most chemical depilatory brands (Veet, Nair) seem to be alkaline (tell me if I'm wrong), it would seem to me that something like vinegar could neutralize the residue after use and help prevent burns. there are commercials neutralizers on the market--are they just slightly acidic solutions to do the same thing? EdwinHJ | Talk 20:59, 13 December 2008 (UTC)[reply]

If you are asking if vinegar is safe and effective to prevent burns after the use of a depilatory, I believe that would fall under the category of medical advice, which the reference desk doesn't give. Sorry. Talk to your doctor or a pharmacist(US)/chemist(UK) instead. -- 128.104.112.113 (talk) 21:57, 13 December 2008 (UTC)[reply]
In the UK you would want to talk to a pharmacist. DuncanHill (talk) 22:05, 13 December 2008 (UTC)[reply]
Without wanting to give any extra medical advice, I only want to note that those commericial neutralizers are likely buffered solutions; as such they are probably MUCH safer than using an unbuffered acid, such as straight vinegar, to neutralize the depilatory cream. But as noted, if you are experiencing problems, please seek medical advice from a professional... --Jayron32.talk.contribs 22:03, 13 December 2008 (UTC)[reply]
To explain that point further - if you just add acid - you won't know whether you've added too much or not enough. You could even make matter worse. But these buffer solutions are mixtures of chemicals that resist change in pH - so they'll just exactly cancel out any imbalance between acid and alkali. This would obviously be much safer...and that's probably what the commercial neutralizers are. SteveBaker (talk) 02:47, 14 December 2008 (UTC)[reply]

Temporal Fenestra

Most mammals have one unbroken opening that the eye and the mandible fit into, but humans don't, they seem to have a bone separating the eye hole and hole for the mandible. What am I missing? 24.77.21.240 (talk) 23:26, 13 December 2008 (UTC)[reply]

Tuberculosis

Does Tuberculosis cause paranoia/affects the mental health of patients? How often does this happen? I'm not asking for medical advice because I was reading a memoir in which the author described the mental instability of his father who later died of tuberculosis. Coolotter88 (talk) 00:05, 14 December 2008 (UTC)[reply]

Our article Tuberculosis says that the central nervous system can be affected - so presumably there could be consequences for mental health. SteveBaker (talk) 02:43, 14 December 2008 (UTC)[reply]

Effect of various pH levels on pepsin hydrolysis

At school, we did an experiment testing the effectiveness of pepsin on the hydrolysis of a wheat protein. We masses the pieces of protein at the beginning and then at the end to determine the change in mass. The protein in the beaker with the acidic solution lost the most mass and that, I hypothesize, is due to the fact that pepsin works best in an acidic environment and hydrolyzed the protein the best. But the mass went up in the basic solutions. Why is this? Could someone point me in the correct direction? The Ayatollah (talk) 01:43, 14 December 2008 (UTC)[reply]

cacti

how can u make cacti grow rediculusly fast? or at least fast? and also is it true u can cut a cactus in half and plant it and it will grow...so u then have two cacti? —Preceding unsigned comment added by 76.14.124.175 (talk) 02:30, 14 December 2008 (UTC)[reply]

I have no answer to your second question, but to make cacti grow quite fast, you might give the plant excessive vitamins and minerals. Or, you can gentically engineer the cacti.--Archaeopteryx (talk) 03:00, 14 December 2008 (UTC)[reply]