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February 4

Symmetry

I am trying to derive a set of equations for how physics would behave in two large spatial dimensions (as opposed to our universes 3), I am trying to restrict myself to arguments from symmetry. I have isolated quantum and hamiltonian mechanics as the obvious generators for the laws (and since neither specify a dimensionality I think I am at liberty to do so), but am struggling to get a foothold in. How does one construct a hamiltonian, for eg. electrodynamics, from symettery. I managed to get an argument that the lagrangian (which is trivially related to the hamiltonian) would be a function ${\mathcal {L}}={\mathcal {L}}({\dot {\mathbf {x} }},\mathbf {A} ,\phi )$ for the velocity, vector potential and scalar potential respectively. From speaking to people, they seemed to imply that finding canonical momentum was simple, am I missing the point, or have they just assumed that the conserved quantities are the same in 2+1D as 3+1D? —Preceding unsigned comment added by 129.67.39.49 (talk) 01:45, 4 February 2010 (UTC)

I saw an argument somewhere that gravity would not work in a two dimensional universe. You may look into that for a proof by counterexmaple that physics as we know it won't work in 2D. Unless you'r aiming for something like the holographic principle. In any case, you'r not really asking a question about the real world here. EverGreg (talk) 11:17, 4 February 2010 (UTC)

In the truly awesome book "Planiverse" by A.R.Dewdney (which is a work of fiction about a 2D universe) there is an extensive appendix comprised of comments from scientists who contributed to the book after discussion of it in Scientific American. In there they talk about a wide range of things that makes 2D universes at best very boring places. I don't have the book with me right now - and I don't recall the conclusions about gravity - but one of the things I recall is that atoms cannot form in a 2D universe. SteveBaker (talk) 11:27, 4 February 2010 (UTC)

While not directly answering your question, I'd assume you can take pretty much the same equations as in three dimensions. Notice that the magnetic field becomes 1D; the electric field stays 2D as does the vector potential. Cut off the last row and column from the electromagnetic tensor (and B_z becomes the one-dimensional B). Icek (talk) 17:57, 4 February 2010 (UTC)

Constraining 3D equations to 2D would not work, the most obvious change for example is that flux density would tail off at 1/r not 1/r^2. —Preceding unsigned comment added by 129.67.119.199 (talk) 14:25, 6 February 2010 (UTC)

Yes, but that's not a fundamental equation - the fundamental equation is one of Maxwell's equations, $\nabla \cdot D=\rho$. In 2 dimensions, the divergence of D is zero (as it has to in charge-free space) for a 1/r field, not a 1/r² field. Other problems with electromagnetism: Faraday's law of induction is valid in the sense of:

${\frac {\partial E_{x}}{\partial y}}-{\frac {\partial E_{y}}{\partial x}}=-{\frac {\partial B}{\partial t}}$

I think Ampère's law will work the following way:

$c^{2}{\begin{pmatrix}{\frac {\partial B}{\partial y}}\\{\frac {\partial B}{\partial x}}\end{pmatrix}}={\frac {1}{\varepsilon _{0}}}{\begin{pmatrix}j_{x}\\j_{y}\end{pmatrix}}+{\frac {\partial }{\partial t}}{\begin{pmatrix}E_{x}\\E_{y}\end{pmatrix}}$

-Icek (talk) 19:04, 6 February 2010 (UTC)

Well no, because maxwells equations are for 3D, 2D isnt just a world where we go; ok so everythings the same except d/dz=0. Thats why in my question I explained I was starting from hamiltonian dynamics, as it is derived independentally of the dimensionality of the system. Unfortunately I couldnt think of a watertight argument for what a hamiltonian would be. Obviously T+V is of no help as conservation of energy is an empirical law of physics. Symmetry seems to be the only thing I can claim, but obviously more is needed to set up a system of dynamical equations. —Preceding unsigned comment added by 129.67.116.242 (talk) 01:10, 7 February 2010 (UTC)

For a 2D version of the Dirac equation, you can use the Pauli matrices instead of Dirac's α_k and β, so there will be 2-component spinors instead of 4-component spinors. For the 2D version of the γ^μ Dirac matrices in the covariant form, one representation would be $\gamma ^{0}=\sigma _{z}={\begin{pmatrix}1&0\\0&-1\end{pmatrix}}$, $\gamma ^{1}=\sigma _{z}\cdot \sigma _{x}={\begin{pmatrix}0&1\\-1&0\end{pmatrix}}$, $\gamma ^{2}=\sigma _{z}\cdot \sigma _{y}={\begin{pmatrix}0&-i\\-i&0\end{pmatrix}}$ Icek (talk) 18:24, 4 February 2010 (UTC)

concentrated alpha particles?

Could alpha particles be concentrated enough by compression or supercooling to form a liquid, and what would its properties be if this state could be achieved, for example, would it destroy any matter it came in contact with like an acid, or have explosive properties?Trevor Loughlin (talk) 05:10, 4 February 2010 (UTC)

Alpha particles are nothing more nothing less than helium nuclei. Nothing fency about them. 68.56.16.165 (talk) 05:19, 4 February 2010 (UTC)

If you squished them together with enough force to overcome the electrostatic repulsion, then you'd probably have enough energy for Helium fusion. If you allowed them to recombine with electrons and form neutral atoms, then you'd have liquid helium, (not alpha particles). Nimur (talk) 06:22, 4 February 2010 (UTC)

If you concentrate alpha particles, the pressure will increase dramatically from electrostatic repulsion, so they will not form a liquid. The electrostatic energy of a single particle in a sphere (or some other shape) of alpha particles of a certain density is proportional to the number of particles to the power of 2/3, the total energy is proportional to the number of particles to the power of 5/3. As you see, the energy content increases faster than the number of particles at constant density. Icek (talk) 06:25, 4 February 2010 (UTC)

You'd have to mix in electrons, in which case you get a nice Bose–Einstein condensate of helium-4. EverGreg (talk) 11:40, 4 February 2010 (UTC)

I think that if you squash them together hard enough, you might get a substance made entirely of neutrons. I'm not an expert in this area, though. 24.23.197.43 (talk) 02:32, 7 February 2010 (UTC)

Experimenting with an 18V wall wort

Hi all,

This may be an odd question, but I'd like to know how risky it would be to use the output of an 18V (800 mA) DC transformer (connected to the wall through a grounded, fused strip) to power circuitry? If one were to cause, say, a short circuit, what's the worst that could happen? Blowing a fuse? Electrocuting oneself?

Thanks, — Sam 76.24.222.22 (talk) 12:23, 4 February 2010 (UTC)

An additional fuse or circuit breaker, that is a bit larger than the current you actually want to use, should be installed in series with the output of the DC supply. A short with no such fuse could damage the transformer. Since 120 V or 240 V (depending on your country) is present within the transformer, a damaged transformer could be quite dangerous. --Jc3s5h (talk) 15:43, 4 February 2010 (UTC)

See the article AC adapter. I assume you are asking about a "wall wart" ac-to-dc adapter which is more than just an ac-to-ac transformer. These devices are not well standardised but should have a Certification mark such as UL, CE, etc., etc. Check also that the adapter is labelled with the ac input voltage of your supply and the dc output voltage. You may have to find out the output polarity or fit a different output connector. You can use the adapter to power your circuits but there is no specification of the output regulation or ripple. It may not tolerate short circuits or more than the rated current (800 mA). Generally these adapters are sealed and have an internal fuse. They are not intended to be repaired. The certification mark is your best assurance that the dc output is properly isolated from the ac supply and cannot electrocute you.Cuddlyable3 (talk) 15:50, 4 February 2010 (UTC)

A lot of them are not true DC devices - they are often half-wave rectified AC, which is plenty good enough for things like charging batteries - but hopeless for driving "circuitry" in general. Even the ones that do full-wave rectification are not generally filtered well enough to give you a rock solid constant voltage. SteveBaker (talk) 22:52, 4 February 2010 (UTC)

One bad thing which could happen is that the internal fuse fails to protect against an overload (they are sometimes sensitive to short circuits but not prolonged overloads) and the device heats up and starts a fire. Edison (talk) 15:39, 5 February 2010 (UTC)

film versus HDTV

Which is the best, and what are the relative costs of buying or hiring 16 mm or 35 mm cine cameras, including developing and video transfer costs, compared HDTV or even UHDTV digital movie cameras such as Red? Dark scenes such as dimly lit musicians on stage seem OK on my semi-pro HDTV AVCHD video camera.But very bright beach scenes or sodium lamps shining on trees at night somehow seem to lack "atmosphere" despite plenty of detail. I cannot seem to find much cost information about film based movie cameras on the web.Trevor Loughlin (talk) 15:04, 4 February 2010 (UTC)

Could you please expand greatly on your question "which is the best"? It's impossible to answer without knowing a lot more about your budget and requirements. A film movie camera will be the best for many situations, and an HD video camera will be the best for many other situations. Tempshill (talk) 18:23, 4 February 2010 (UTC)

Wikipedia has articles on Comparison of movie cameras (film-based) and Professional video camera (digital) that may help. Since a film camera consumes filmstock only once while a video camera can reuse (overwrite) a recording medium many times it is impossible to compare overall developing and video transfer costs without knowing how much you plan to use the camera. The light from a Sodium-vapor lamp is monochromatic while human Color vision is trichromatic (our retinal cones have 3 different bandpass responses). Colour photography makes an imperfect emulation of human vision and it has no way to adapt to sodium lighting. Cuddlyable3 (talk) 01:55, 6 February 2010 (UTC)

Four-dimensional universe

What would a four-dimensional universe be like in terms of physics, chemsitry, biology, etc.? --J4\/4 <talk> 16:50, 4 February 2010 (UTC)

It is common to refer to our universe as being four-dimensional: length, width, height, and time. Physics easily works with time as a dimension. So, there is no change there. Chemicals change over time without a problem. Biological things age without a problem. So, I can't really see much of a difference from what we experience every day. -- kainaw™ 17:11, 4 February 2010 (UTC)

Our article, Fourth dimension, contradicts you in paragraph #3. Comet Tuttle (talk) 17:27, 4 February 2010 (UTC)

That paragraph contradicts itself. It needs to be better written to state whatever it is attempting to state. -- kainaw™ 17:58, 4 February 2010 (UTC)

maybe that paragraph has changed already, but what it means (meant?) is that time is not a fourth dimension in an euclidean space, but it is a fourth dimension in a Minkowski space, i.e. time is distinguishable from the other three dimensions. —Preceding unsigned comment added by 83.134.175.84 (talk) 18:13, 4 February 2010 (UTC)

So, a smart-ass answer to the original question would be: It will make Euclidean space look like Minkowski space. -- kainaw™ 18:44, 4 February 2010 (UTC)

That's like asking what a cat would be like if it was really a dog. For all intents and purposes, our three-dimensional universe is the only one that ever could exist, so any speculation beyond that is mere fluff. Vranak (talk) 17:53, 4 February 2010 (UTC)

I meant what a universe with four spatial dimensions would be like. I know that some people have done something similar with two dimensions, predicting what its physics, chemistry, biology, etc. would be like. --J4\/4 <talk> 19:57, 4 February 2010 (UTC)

Read flatland, and extrapolate (it's basically required reading for anyone speculating about more dimensions). I have a feeling that the world is 3d because it's the lowest practical number of dimensions - going higher is "cool", but not necessary for a universe to exist. The universe usually chooses the lowest energy for anything. (This is just speculation, I don't have specific arguments.) Ariel. (talk) 20:07, 4 February 2010 (UTC)

NO! Please don't read flatland - it's a terrible book that not only doesn't describe a 2D world at all well - but completely messes up the few things it does describe. It's also painfully sexist, classist, elitist and just about every other kind of 'ist'. Some people claim that's a satire on the sociology of the times...but it's still horrible to read. Read Planiverse instead - that's a superb book - it's very consistent, it has characters and plot and stuff - and even contains a comprehensive appendix that describes where they had to cheat on the physics to make a workable story. The drawings are a lot of fun - you can spend ages looking at the 2D steam engine to try to figure out how it works. SteveBaker (talk) 22:48, 4 February 2010 (UTC)

What, Flatland might corrupt the mind of J4V4, so he shouldn't read it? I agree that it's probably not the most scientifically grounded examination of worlds with a different number of dimensions, but it is an entertaining read. And it's more a commentary on Victorian society and culture, rather than its "sociology" (not sure if you intended that word or not). Buddy431 (talk) 00:23, 5 February 2010 (UTC)

I don't think it would corrupt anyone's mind - but it would severely disappoint anyone who is trying to understand what a 2D world might be like. If that's what you're trying to understand then reading flatland is just a total waste of your time. Planiverse, on the other hand, really makes you think - and gives you a real feeling for the difficulties of 2D. In flatland, men are geometrical figures - the lower classes of society have few sides (triangles and squares) - higher classes more - all the way up to the circles. Women on the other hand are like needles - effectively 2-sided - lower than the lowest of the low men. If this kind of thing feels kinda nasty...welcome to flatland. Planiverse, on the other hand explains how a being from that world can eat and poop without falling in half (think about that!) - how fluids can circulate within it's body. How it is impossible for them to make practical wheeled vehicles - but how it's easy to travel by balloon. What music sounds like - and how the instruments work. How wars can be fought when only one warrior can fight at a time. It's an amazingly clever book. So, yeah - if you're interested in struggling through a turgid, wincingly nasty Victorian diatribe - you need flatland. If you want to get your head stretched into thinking in 2D and have an actual plot with characters and stuff - get Planiverse. SteveBaker (talk) 02:51, 5 February 2010 (UTC)

Drifting waaay off topic, but: Steve, I recently re-read Flatland, and it's clearly a satire against the 'traditional Victorian values' of its time, not an affirmation of them. I agree that Planiverse is better in several ways, but that's partly because it's able to build on both the pioneering example of Flatland itself and on a century of further thinking on the topic - "on the shoulders of giants" and all that.

While we're making recommendations to J4V4, may I nominate The Fourth Dimension, a non-fictional work by Rudy Rucker, himself a Professor of Mathematics, a successful (Science Fiction) writer and a fan of Flatland's author. [/sercon litcrit]. 87.81.230.195 (talk) 10:04, 5 February 2010 (UTC)

I didn't get a satirical feel from flatland. It didn't seem to be making fun of the concept at all - it was all delivered with a perfectly straight face and seemed to go out of it's way to demean women. I knew it was claimed to be a satire before I read it...but I just couldn't see that in the book - it seemed to simply be promoting this view of the world. I've read "The Fourth Dimension" too - it's not bad - but I found it a little disappointing. I guess it didn't tell me anything I didn't already know - but it's probably a good introduction for someone who hasn't thought a lot about 4D already. One book to avoid like the plague is "Flatterland - a romance in many dimensions" which kinda claims to be a sequel to flatland or something like that. It delves into 0D, 1D, 2D and 4D worlds as well as universes with non-Euclidian geometries, etc. It ought to have been interesting - but it really wasn't. For example, in the 0D world, he explains that there is only one entity in the world and it is the king of 0D-land. Well, no! How can you have a thinking being in a literal singularity - how could its brain possibly work...it's kinda getting across the rough idea of a zero dimensional world - but not explaining how anything whatever could possibly exist in such a place. Bleaugh! Simply awful. SteveBaker (talk) 14:49, 5 February 2010 (UTC)

Good Lord! You thought Flatland was supposed to be serious? No wonder you didn't like it. Did you take Gulliver's Travels at face value to? 86.179.145.61 (talk) 16:56, 5 February 2010 (UTC)

I have to disagree with your interpretation of Flatterland as well. It's more looking at the mathematics of different types of spaces, rather than the scientific plausibility of them. J4V4 is clearly interested in the latter here, so I agree that it probably wouldn't be the best book to read. But if someone is interested in a lighthearted, and not-too-painful introduction to non-Euclidean geometry and other fun math topics, Flatterland is worthwhile to read. Buddy431 (talk) 00:31, 6 February 2010 (UTC)

The OP asks about 4 dimensions, not 1, 2 or 3. SteveBaker thank you for your book reviews, but how often must your faulty grammatical contractions such as "within it is body" be rebuffed before you allow yourself to conform to this aspect of the English language? In mitigation you have occasionally used it's = it is correctly, if rarely on your web site to which you sometimes link. Cuddlyable3 (talk) 19:30, 5 February 2010 (UTC)

You would have some difficulty tying your shoelaces. Gandalf61 (talk) 20:28, 4 February 2010 (UTC)

I read in one of the literary excerpts from the Portable Atheist (I forget who) an interesting theory by one of the characters. I don't know if it's really supported at all by evidence but three dimensions is supposedly the only space in which you can tie a knot and not have it just all back apart. And so by some convoluted logic that's the only dimension that a universe could start itself up in and survive. -Craig Pemberton 04:47, 5 February 2010 (UTC)

Mathematicians can measure things in a 4-dimensional universe by using Quaternions. Non-mathematicians may find it strange that a solid object can have a different shape depending on which direction you look at it. Here is a video. Cuddlyable3 (talk) 20:42, 4 February 2010 (UTC)

Computer graphics tech tends to represent everything in four dimensions (4x4 matrices) and uses affine geometry and homogeneous coordinates to move stuff around gracefully. You might have fun learning linear algebra and how it views the concept of dimension. Also, we have some nice animations of stuff like hypercubes and four dimensional simplicies. We have a page on the fourth dimension. A 0 simplex (point) has 0 borders. A 1 simplex (line) has 0 borders (points). A 2 simplex (triangle) has 3 borders (lines). A 3 simplex (tetrahedron) has 4 borders (triangles). A 4 simplex (pentachoron) has 5 borders (tetrahedra). Look carefully at the animation and you can count all five. -Craig Pemberton 21:18, 4 February 2010 (UTC)

We do use 4x4 matrices and affine geometry - but that's not to represent things in 4D - it's so we can compute the effects of visual perspective using a single matrix operation. Also, it's convenient to use the same 4D hardware to store RGB colors with an 'alpha' field to approximate translucency. But we're not generally doing 4D geometry. SteveBaker (talk) 22:48, 4 February 2010 (UTC)

Right. I literally meant that the representation is four dimensional. The thing modeled is probably going to be three or two dimensions.-Craig Pemberton 04:40, 5 February 2010 (UTC)

I recall reading that in a 4-dimensional universe, gravitational and electromagnetic forces would diminish with the cube of the distance. The inverse-square law becomes the inverse-cube law. This may present some problems for atoms, molecules and stable orbits for planets. Please correct me if I'm wrong. 78.176.30.155 (talk) 21:26, 4 February 2010 (UTC)

Yes, that's a reasonable assumption. Also, in 4D it's much harder to enclose a hyper-volume - so making things like plant and animal cells and tubes for containing liquids and gasses is harder because you need a greater amount of material to enclose whatever is inside. Think about drawing a 2D circle on paper - the actual outline is a tiny amount of 'stuff' compared to what's inside. But in 3D, with like a balloon, there is far more 'skin' required to hold in the contents. This gets worse in four spatial dimensions and upwards.

Indeed, while sealing eg. a 3D jar, you need to seal the 2D circle between the jar and its cap. But for a 2D 'jar' you only seal 2 points. For 4D, you'll need to seal a 3D volume. Btw, I asked another question about dimensions before, and interestingly Steve had bashed 'Flatland' back then! 78.176.30.155 (talk) 23:53, 4 February 2010 (UTC)

What about hypercube and Roman surface? ~AH1^(TCU) 02:19, 5 February 2010 (UTC)

Since no one has answered yet, I'll have a go. A 3D cube consists of 6 squares and has 12 edges. To create an air-tight cube, one must seal these edges, which are 1 dimensional lines (please disregard my previous post saying that sealing the jar needing a 2D circle etc, my bad). A hypercube consists of 8 3D cubes (cells) and these are connected by 24 2D faces that need to be sealed, which is harder to do. I don't know what to make of the Roman surface as I, a non-mathematician, can't grasp how it is constructed. It looks like a Klein bottle which has no volume, so what to seal? It is not a useful container anyway! Then again, someone who is much more knowledgeable (read: Steve) can maybe enlighten us on these matters. 78.176.30.155 (talk) 15:26, 5 February 2010 (UTC)

The Roman surface is a realizable 3-D object. It has a real volume divided into 3 similar compartments and it could therefore be constructed as a container. Its 9 edges are all concave. Cuddlyable3 (talk) 19:41, 5 February 2010 (UTC)

Given the length of this section, it's odd how few people have actually tried to answer the question... You can easily change the number of dimensions in our physical theories and see what happens, since it is just a parameter that is determined empirically. As has been mentioned above, all the inverse-square laws would become inverse-cube laws, and that does mess everything up. Under Newtonian gravity, there would be no stable orbits - objects would either spiral in or out (if you know basic calculus, you can go through the standard derivation of Kepler's laws from Newton's universal theory of gravity changing the square to a cube and see what happens, it's easy enough to see that, while the maths works fine, the results are completely different). Under General Relativity, it apparently gets even worse - gravity wouldn't be able to extend outside a solid object (I haven't seen that derived, though). Under Quantum Mechanics, we find that atoms can't form. We also find that light can't exist (you can have electromagnetism, but it can't propagate as waves). Basically, a universe with anything other than 3 spacial dimensions (and the same fundamental laws of physics as ours) would be very boring (the problems I've mentioned apply to higher dimensions than 4 as well, and there are also problems with fewer than 3 dimensions, some the same as those I've mentioned, some different) and life couldn't arise (so we can use the anthropic principle to explain the number of dimensions we observe). You could, of course, come up with different laws of physics which would give interesting results with other numbers of dimensions, but if you are allowed the change the laws of physics you can do almost anything! --Tango (talk) 15:29, 6 February 2010 (UTC)

cyanide poisoning or other deadly poisonous gases & residue

Greetings!

I am gathering data because I believe I am being poisoned via gas. Are gases likely to leave a residue in the filtration in my home? I have kept sources to submit but do not know if they are worthwhile in proving my case.

Also is there a source for submitting prescriptions to verify if they have been laced with poison?

Anyones input would be greatly appreciated.

Thanks! —Preceding unsigned comment added by Vickie Bragg (talk • contribs) 18:40, 4 February 2010 (UTC)

If you suspect that you are being poisoned, go see a doctor. If you suspect someone is trying to intentionally poison you, as it sounds like, also go to the police. Asking for information to anonymous people on a reference desk about this stuff is probably not a safe way to handle the situation. Falconus^{p t c} 18:53, 4 February 2010 (UTC)

Please call your doctor immediately to ask these questions. I agree with Falconus that researching this on the Internet is not going to help you at all. Comet Tuttle (talk) 18:58, 4 February 2010 (UTC)

For the non-medical part of your question - no, a gas won't leave a residue on your filters - precisely because it's a gas. If the suspected substance were an airborne powder (such as the spores of something nasty or a very finely ground chemical agent) or perhaps even very fine liquid droplets - then maybe it would. SteveBaker (talk) 22:33, 4 February 2010 (UTC)

That's not necessarily true. Depending on the filter and the gas you may get a chemical reaction, or even simple adsorption, that leaves behind some residue. Dragons flight (talk) 18:11, 5 February 2010 (UTC)

This is not medical advice but an observation on probabilities. Some symptoms have many possible causes (e.g., itching) and no single diagnosis stands out as more probable without far more details and sometimes testing or treatment trials. Other symptoms are so specifically characteristic and have such a narrow range of possible explanations that a single diagnosis is far more likely than all others. In western societies the fear that one is being deliberately poisoned repeatedly or chronically by gas is not all that rare and in nearly all cases indicates a very specific problem for which there is a treatment. Fears will not be allayed by poison testing. The advice: Please see a doctor and explain your fears and follow through with seeing the specialist she or he refers you to. Good luck. alteripse (talk) 00:03, 5 February 2010 (UTC)

Name That Beetle

My friend lives in Berkeley, California. She has been finding some of these beetles in her house. I think they might be devil's coach horses, but she thinks they're too narrow and not the right colour. They're not earwigs: they don't have the pincers. Does anyone know what they might be, and whether they pose any sort of threat? Marnanel (talk) 19:49, 4 February 2010 (UTC)

Someone else has suggested Jerusalem crickets. Marnanel (talk) 20:04, 4 February 2010 (UTC)

Looks like it could be, but it's hard to tell with that image and the coloration is normally a bit redder? Get a better image. Try using [bugguide.net] to key it. The website is highly effective. -Craig Pemberton 21:27, 4 February 2010 (UTC)

BTW, in order to be a beetle it needs to have elytra (the front wings which have been modified into shields for the back wings). The scientific name for beetle is "coleoptera" which literally means "wing cover". So if you think it's a beetle look for them to make sure. -Craig Pemberton 04:53, 5 February 2010 (UTC)

Unless they only have a half-cover, in which case they are Hemiptera or true bugs. Also, the Devil's Coach Horse IS a beetle but flightless, and only has little residual wings and wing-cases that aren't really obvious. Alansplodge (talk) 16:21, 5 February 2010 (UTC)

I am reasonably certain that that is a Jerusalem cricket, not a beetle, and certainly not a rove beetle. Jerusalem crickets often wander into houses in California.--Eriastrum (talk) 18:52, 6 February 2010 (UTC)

Right hand exposed to gel extraction's UV ray for 2 minutes non-stop.

While having green UV ray on, I cut a gel using a blade with my bare right hand. I later found out that my hand for holding the blade and being exposed to UV during cutting the gel should be worn a glove. How serious of a damage might have this caused? —Preceding unsigned comment added by 142.58.43.215 (talk) 19:51, 4 February 2010 (UTC)

This is medical advice, which is against policy to answer here on Wikipedia. If you are concerned about it, the only advice that we are allowed to give is to consult a doctor or other medical professional. Sorry about that! Falconus^{p t c} 19:54, 4 February 2010 (UTC)

That's right; you are asking a bunch of anonymous people on the Internet; we cannot possibly give an accurate diagnosis. Please call your doctor. Comet Tuttle (talk) 20:03, 4 February 2010 (UTC)

Nonsense removed - Nimur (talk) 22:13, 4 February 2010 (UTC)

One question, how is a UV ray green? I thought UV was invisible or maybe purple? Googlemeister (talk) 22:04, 4 February 2010 (UTC)

Likely a secondary green light to indicate visually whether the UV light is on or not. Ginogrz (talk) 22:08, 4 February 2010 (UTC)

Or it may just be part of the spectra for whatever compound they use to create UV light (e.g., it radiates in green visible light and in UV, and possibly other energies such as infra-red - does the light feel warm?) --Ludwigs2 23:11, 4 February 2010 (UTC)

The types of damage that can be caused by ultraviolet light are well known, but to find out what may have happened in your particular case, you should talk to your local workplace safety officer or a doctor. --Carnildo (talk) 01:12, 5 February 2010 (UTC)

Incidently, I'd caution against using a bare hand for cutting a gel, especially if it's stained with ethidium bromide, which can cause heritable mutations. Use nitrile gloves; apparently the EtBr can get through latex. Other dyes (e.g. SYBR Green I) are also toxic, even if less so than EtBr. -- Flyguy649 ^talk 05:05, 5 February 2010 (UTC)

If you do talk to an outside doctor, you'll probably want to first figure out the type of light source, its power, and its wavelength spectrum. UV refers a large range of wavelengths and the potential hazard can differ by orders of magnitude depending of the particular wavelengths involved. A local safety officer might be able to tell you more, since he may already be familiar with the equipment and its hazards. Dragons flight (talk) 05:43, 5 February 2010 (UTC)

[Removed medical advice. 86.179.145.61 (talk) 13:57, 5 February 2010 (UTC)]

I must say that if you ask the typical MD about some physics question like the health effects of exposure to some particular UV wavelength at some intensity for some time, you might get a blank stare. Unlike TV shows would indicate, they are not all experts in every branch of science. Edison (talk) 15:36, 5 February 2010 (UTC)

What's the power rating of the UV source? If it's a relatively low-power UV lamp for fluorescence observations (like we use in our lab to check TLC plates), then you'll be fine -- we don't have to wear gloves or anything when marking the plates. If it's a higher-powered source, sunburn might happen on prolonged exposure -- but unless it's a very high-power source, a two-minute exposure prob'ly won't cause any harmful effects. The reason for wearing gloves was probly because of toxic/irritating chemicals involved, rather than UV exposure. FWiW 24.23.197.43 (talk) 02:52, 7 February 2010 (UTC)

life possible on other gas giant moons

Is this possible Callisto and Ganymede also have ocean underneath the black icy surface. And Encladeous the whitest moon on Saturn the artlce also said they have a ocena beneath the surface. Did any of article said Europa once had ocean without ice, if the information I had is original sorce.--209.129.85.4 (talk) 20:56, 4 February 2010 (UTC)

Speaking speculatively, life is possible on any number of bodies in the solar system. All that's required (even with the restrictive presumptions of terrestrial life) is trace amounts of liquid water as a medium and sufficient access to 'organic' compounds that could serve as building blocks for cellular processes, and those are fairly widespread in the system. However, no one has any idea what the necessary (much less sufficient) conditions for the commencement of life are - we can't even really define when more or less normal chemical reactions transform into more or less stable self-replicating chemical reactions (which is maybe the minimal quality that any living thing needs to have). --Ludwigs2 23:07, 4 February 2010 (UTC)

You must add to this that Life could be of a diffrent form than Organic life. It maybe a case were life is of Gas or any compound/substance it is just our understanding of Organic life that we currently refer to.Chromagnum (talk) 07:02, 7 February 2010 (UTC)

Where does the momentum go when I put on the breaks?

If I understand the conservation laws correctly, momentum is always conserved but kinetic energy can easily be lost when it is converted to other forms of energy. So when I am traveling along in my car and apply the breaks, I understand that the kinetic energy of the system (my car and everything in it) has been converted to heat (which is just undirected kinetic energy of the breakpad molecules, right?). Where did the momentum go? Isn't it an internal force that caused me to stop? Or was it an external force exerted by the earth? If I measured the earths momentum with arbitrary precision would I find the car's momentum had been transferred to the Earth? Thanks 128.223.131.109 (talk) 21:36, 4 February 2010 (UTC)

Hitting your brakes makes your wheels stop rotating. If you were floating in your car, they would stop rotating and your momentum would not change. You are focusing on the relationship between the road and the tires. The car has forward momentum. The tires try to move with the car (without rotating). The friction between the tires and the road tries to keep the tires and road as one body. Therefore, the car is trying to pull the road. The road pulls back with an equal and opposite force (assuming you don't start skidding). That is an instantaneous stop. For a slow stop, it is the same. Car pulls on wheels which pulls on road and road pulls back. Interestingly, busy intersections with stop lights often have rippled roads, cause by many vehicles stopping (pulling) on the pavement. -- kainaw™ 21:43, 4 February 2010 (UTC)

The momentum goes into individual atoms in the road, air, brakes, chassis, etc (heat). Also slightly into the rotation and momentum of the planet but such effects are swamped by the size of the Earth. And your acceleration would tend to cancel the effects of your deceleration. -Craig Pemberton 22:04, 4 February 2010 (UTC)

The momentum doesn't become heat; heat is more or less defined as molecular motion (kinetic energy) without (net) momentum. It's very quickly correct to say that the momentum is entirely sunk in the (rest of the) planet's net rotation (speeding it up or slowing it down, or turning its axis of rotation). --Tardis (talk) 23:10, 4 February 2010 (UTC)

Yes, that's right. Craig was thinking of the kinetic energy, not the momentum. --Anonymous, 02:02 UTC, February 5, 2010.

You are literally changing the rotation speed of the Earth. But because the mass of your car is utterly microscopic compared to the mass of the planet - the effect is too small to measure. Also, when you first speeded up, you altered the rotation speed of the planet in the opposite direction - so the net result is zero. There have been numerous uses of this for joke purposes - the Car Talk show on NPR advocated that everyone should live to east (or was it to the west?) of where they work so that the combined effect of commuters speeding up as they leave home and slowing down when they get to work would shorten the working day. (Yes, it's silly). SteveBaker (talk) 22:24, 4 February 2010 (UTC)

I have pondered this while driving more than a few times (Ohio roads are notoriously boring.) Say that if you take your car, accelerate in a straight line (pushing off on the planet) to get up to 60mph, then apply the brakes (grabbing onto the planet) until you stop, where exactly does all the energy come from/go to along the way? You accelerate using fuel, to increase the net difference in momentum between you and the planet. That makes sense. You stop by using your brakes, but what determines the relationship between heat generated through friction, and momentum exchange with the planet? Do you have to give back 100% of the momentum you took from the planet? If so, where does the heat come from (since we are 'conserving' energy)? --Jmeden2000 (talk) 14:09, 5 February 2010 (UTC)

You are getting confused between conservation of momentum and conservation of energy. Both things are perfectly conserved - but separately. Momentum is conserved because the planet is being slowed down or speeded up in the opposite direction to motion of your car. Energy is conserved because chemical energy in the gasoline is turned first into the kinetic energy of the car (as you accelerate) and then as you brake, the kinetic energy turns into heat in your tyres, in the road and in your brake disks/drums/pads. Eventually, that heat dissipates into the ground and into the atmosphere - and (because both are gigantic) ends up making very little difference to the overall temperature of the world. Both things are conserved but in totally unrelated ways. SteveBaker (talk) 14:28, 5 February 2010 (UTC)

So it is correct to say that 100% of the energy put into your car during acceleration (stored as a difference of momentum) is returned in the form of heat or other energy dissipated by your brakes? So, no material 'efficiency' is employed in determining how much heat energy your brakes need to dissipate, since it all has to go out this way? --Jmeden2000 (talk) 14:41, 5 February 2010 (UTC)

Nearly 100% yes. On a flat road your car would eventually stop without using the brakes because its kinetic energy is slowly dissipated in air resistance and rolling resistance (see article). Cuddlyable3 (talk) 19:57, 5 February 2010 (UTC)

Yeah - it all ends up as heat - but not necessarily in the brakes. The air resistance results in the air heating up, other internal bits of the car will get warm, some energy will go into distorting (and then heating) the tires and the springs and the oil in the shock absorbers. Some of it even winds up being absorbed by stretching the material in your seat belts. But the VAST majority of the energy ends up in the brakes. The only way it wouldn't would be if you started off at the bottom of a valley and drove to the top of a nearby hill and stopped at the top. In that case, some of the energy would wind up in the gravitational potential energy of your car...but as soon as you drive down the other side and stop again, that too has turned into heat. It's worth remembering that when you consume gasoline getting your car up to 70mph and then use your brakes to stop from high speed, the heat generated in the brake disks is about the same as if you poured the same amount of gasoline on them and set fire to them in some confined space!! Little wonder then that the brake disks of race-cars often end up glowing cherry-red by the end of the race - and failing to down-shift as you drive down a long hill can overheat your brakes to the point where the brake fluid boils and the brake disks warp from the heat! SteveBaker (talk) 23:14, 5 February 2010 (UTC)

February 5

How will Augmented Reality glasses work?

Glasses or Contact Lenses where images are electronically displayed on the surface: how will it be possible for the wearer to focus on what's being displayed when the image is less than an inch from the eye? I cannot make out the individual hairs and dusts on the surface of my eyeglasses: all I see is a blur. --※Cōdell 23:48, 4 February 2010 (UTC)

A head up display projects a picture onto the screen eyepiece focussed at infinity (collimated); I've no idea how they'd get it to work if the AR was just an OLED embedded in the glasses (I rather suspect you're right). The projection thing is okay if it's augmenting things that are at optical infinity (as is the case for pilots looking out of their aircraft), but if someone was proposing to superimpose AR objects on my (real) desk, that'd be an issue too. -- Finlay McWalter • Talk 00:51, 5 February 2010 (UTC)

Ah, the AR article pointed me at virtual retinal display, where the image is lasered right into your eye. That article isn't super-clear about how it handles the current focal length of your eye. -- Finlay McWalter • Talk 01:06, 5 February 2010 (UTC)

I'd just like to point out that I think that particular "concept" image is totally unencyclopedic. Basically it's just a (crude) Photoshop job that someone did on their blog. It has no bearing on how actual devices might look or work. It should not be on Wikipedia. There are, I am sure, plenty of alternatives out there for illustrating how this technology does work, or how actual engineers/scientists imagine it would work. (On top of that, the "concept" image is a horrible idea from both a design and practical standpoint—a huge, clunky phone type thing that sits over your face, requires both ears, and you can awkwardly dial from the reverse side of it by poking yourself in the eye... imagine actually trying to use that, under even ideal conditions. Now compare that with a Bluetooth earpiece+regular phone interface that you keep in your pocket when you aren't dialing.) --Mr.98 (talk) 01:17, 5 February 2010 (UTC)

It's also worth mentioning that, for both a collimated or VRD type AR system, other people looking at you wouldn't be able to see what you're seeing (which that mockup seems to show). -- Finlay McWalter • Talk 01:24, 5 February 2010 (UTC)

Correct. That markup is just Hollywood junk. I worked on VR helmets a long time ago. When I started, the top of the line helmet weighed a lot and had screens set far away from the eyes. So, you had to practically bolt the helmet to the back of your head to keep it from sliding off. The reason for the design is that the human eye will not focus well on small detail that is closer than a foot or so from a person's face. A perfect VR helmet needs the image to be about an inch from the eye. So, I built a very small lens system to make the image appear to be two feet away and much larger than it really was. Going back to the markup - the lady would just notice a red blur in front of her face. It wouldn't be anything useful. -- kainaw™ 02:11, 5 February 2010 (UTC)

And it also makes you look like you're having a thousand mile stare. ~AH1^(TCU) 02:08, 5 February 2010 (UTC)

The professional ones that people actually USE for virtual reality work are generally huge - and would cost you about the same as a new Ferrari! Take a look at this beauty: http://www.link.com/img/AHMD_F16.jpg (which I used to work on). The large curved plastic gizmos are semi-silvered mirrors - in a flight simulator, they let you see your real hands and real instrument panels - but by draping the area around cockpit with black velvet, you prevent other light sources from interfering with the graphics. The graphics system uses the head tracker to estimate which parts of the virtual world it's generating would be occluded by the physical cockpit out here in the real world - and blacks those bits out so you can't "see through the airplane"). Those mirrors are that large so you get a wide field of view - they use exotic coatings to avoid reflections from other things around you. You'll notice that lens built into the side of the helmet - that's a holographic lens that collimates the light so it appears to be coming from infinitely far away - behind that is a video projector that pumps out a bright, better-than-HDTV image. The lenses have to be adjusted to the individual wearer. The biggest problem is keeping it lightweight and balanced so it doesn't hurt your neck. Because pilots each have their own custom-fitted helmet, this gizmo fits over the top of their regular flight helmet. There is a head-tracker built into the back of the helmet. It also comes in a version where the mirrors are fully silvered so you only see the virtual world. The resulting image quality is stunningly good. (...or you could buy a Ferrari...a nice shiney red one!) One interesting reason why the lenses have to be so far from your face is that you get really weird psychological issues when you can't see your own nose! SteveBaker (talk) 02:17, 5 February 2010 (UTC)

Good. So the concept art like in the image I found are not feasible then? So how would these AR contact lenses work then (or not)? Virtual retinal display isn't used, I think. --※Cōdell 03:27, 5 February 2010 (UTC)

The other method for doing augmented reality is not to have a see-through screen, but an opaque helmet and a pair of cameras. I've been experimenting with this recently. This actually has the advantage of making lag [i]less[/i] noticeable in some situations, because the real world (as seen through the cameras) will lag the same amount as the simulated world. However, this approach has many other drawbacks. You need surprisingly high-quality cameras (expensive ones) to give you enough visual quality as you move your head around, even in a situation with well controlled lighting. If you try to replace your eyes with off-the-shelf consumer web cams, (Even the slightly pricey HD ones.) and you'll just make yourself sick. Even with the nicest cameras we were able to reasonably get our hands on it means that you take a serious loss of visual acuity when you put the helmet on.

While this approach isn't nearly as pricey as the military rig that Steve links to above, it's not exactly cheap either. The only headset we've found under five grand that isn't laughably poor (optical) quality is the eMagin z800 which will 'only' set you back $1500. But it's still only 800x600x2 and I'm not at all impressed by the (build) quality of the units. If you don't think 800x600x2 is good enough resolution then you'll really need to open your wallet, assuming you keep tens of thousands of dollars in your wallet, that is. (Fun fact : 800x600 is not good enough resolution to comfortably read a book, and I don't think you'd pass a DMV eye exam either. )APL (talk) 06:28, 5 February 2010 (UTC)

Using cameras just to avoid lag is kinda silly - you're just adding more lag to the background. The trick for avoiding lag is to know precisely how much lag you have and to build fancy extrapolation algorithms that know about the dynamics of the human head - how fast it accelerates and decelerates. Then you can predict where your head will be when the graphics will eventually be displayed and calculate the appropriate view direction when you start rendering it. This worked great on the L3 system. The only time there would theoretically be noticable latency would be when you accelerated your head really fast (eg because you needed to jerk around suddenly to see something) - but in those case, your eyes tend to lead the head motion and fast eye motion causes a 'saccade' - during which your brain shuts off the 'video feed' from your eyes until the scene settles down again - and by then, our extrapolation algorithm was caught up. Net result - no noticable lag. SteveBaker (talk) 14:18, 5 February 2010 (UTC)

Oh, I agree with everything you just said. I was trying to put a positive spin on things. Actively compensating for lag (if it works) and using the lowest latency equipment and software you can get your hands on, will always be better than merely hiding lag.

The real advantage to AR system with cameras is that you're more flexible with what you do with the real-world background. But this comes at a serious cost of visual quality. APL (talk) 15:57, 5 February 2010 (UTC)

Just why are these systems so expensive? I'd have thought I'd be using one on my PC by now?Trevor Loughlin (talk) 05:42, 5 February 2010 (UTC)

Small markets. The market for people who want to put on a helmet the size of a football helmet and wander around playing with simulated objects is low. On top of that, the technology intrinsically isn't cheap. (Putting a high resolution display in an area the size of a postage stamp isn't easy.)

Worse, Not only are the markets small, they're made of people willing to shell out big bucks. The z800 I mention above was launched at $500. When they realized that their biggest customers were all defense contractors they promptly tripled the price!

So, you've got a difficult to manufacture piece of technology that is needed by only a small number of people, most of which have very deep pockets. APL (talk) 06:41, 5 February 2010 (UTC)

Yep. And just take a look at the photo I posted that link to...it even LOOKS expensive. The projectors were custom made, the lenses were super-fancy lightweight holographic lenses that cost a small fortune. The curved plastic mirrors have all kinds of exotic coatings on them (and incidentally, those coatings are destroyed and have to be replaced if someone touches them without gloves on). The low latency head-tracker is pretty fancy technology. These things are inherently expensive - and are way too fragile for mass-market use. That means they only get short production runs (I doubt that L3 sells more than a couple of dozen a year) and without economies of scale, they aren't going to get cheap. The only thing that is getting better is that PC's are now fast enough to drive them. However, the cost and danger of flying a real F16 in these kinds of training scenario dwarfs the price of the simulator - so even at these outrageous prices, it's a bargin for the military. SteveBaker (talk) 14:18, 5 February 2010 (UTC)

Actually, what that silly image shows is more of a HUD than actual Augmented Reality. HUDs are not ridiculously expensive, especially if you're willing to settle for a low resolution "red eye" display. Heck you could probably make a usable one out of a pocket TV and an R-Zone. APL (talk) 06:41, 5 February 2010 (UTC)

This article give a critical view of the "LED-contact lens" idea. The developer claims "If the pixel [the microLED] is close enough to the micro-lens, it will generate a virtual image that could be 30cm or more away from the surface. Our eyes can focus on this now." but quotes a critic "There would have to be some projection technology for it to appear at a distance that you could then focus on. I can't really see them generating a projection through a contact lens." My own view (pun) is that such a lens would need to carry a dense array of pixels that can be modulated in both brightness and phase to give an illusion of a scene at a greater distance. We are unable to do that at present. Cuddlyable3 (talk) 18:39, 5 February 2010 (UTC)

Thank you, that was helpful. --✚Cōdell 23:45, 6 February 2010 (UTC)

Fingernails?

We all get little white spots on our fingernails occasionally. Is there any official term for them? Nyttend (talk) 00:29, 5 February 2010 (UTC)

Uncle Cecil wrote in 1990 that they're called "punctate leukonychia", which he described as "medicalese for white spots." Comet Tuttle (talk) 00:53, 5 February 2010 (UTC)

Don't forget that if they're unexplained you can tag them as idiopathic punctate leukonychia.... TenOfAllTrades(talk) 03:47, 5 February 2010 (UTC)

And if you've had them for a long time they're chronic idiopathic punctate leukonychia. Richard Avery (talk) 15:30, 5 February 2010 (UTC)

And if they aren't causing you any medical problems, then they are benign chronic idiopathic punctate leukonychia. --Jayron32 18:22, 5 February 2010 (UTC)

And depending on where they are - on fingers or toes, on one hand/foot or the other and at the base or tip of the nail, they could also be either Anterior, Posterior, Dorsal, Ventral, Lateral, Medial, Proximal or Distal...benign chronic idiopathic punctate leukonychia. SteveBaker (talk) 23:01, 5 February 2010 (UTC)

Mustard pain

Why does eating too much hot mustard, such as English Mustard, cause pain inside the nose? And why does this pain only last two or three seconds and not longer? 78.146.193.0 (talk) 02:10, 5 February 2010 (UTC)

Allyl isothiocyanate is a potent lachrymatory agent. As to why the action is only brief - I do not know, but it may well depend on dose and personal sensitivity. --Dr Dima (talk) 02:22, 5 February 2010 (UTC)

steam

PC Game related, Moved to Computer Desk --220.101.28.25 (talk) 06:03, 5 February 2010(UTC)

three low pressure systems near each other? how do they interact?

as of time of writing, I'm referring to the weather.com map -- I don't know where else to get such a convenient summary on one map, and am afraid to save a copy of my own for fear of copyright issues. Firstly I'm wondering if low pressure systems have a tendency to merge -- or maybe repel or attract each other depending on the circumstance (like gravitational bodies)?

Also, where the heck is all this moisture coming from? Isn't it in the middle of winter? Isn't hurricane season over? Also I know it turns to snow very sharply near the mountain regions? This interests me because Charlottesville usually doesn't get a lot of snow at all because of the same mountain range effect (right?) but now we're getting 28 inches which must be shattering records left and right; certainly not 50 inches in one season (ignoring smaller snowfalls, we had a 22 inch blizzard last Christmas). John Riemann Soong (talk) 03:41, 5 February 2010 (UTC)

Well, I think what you're looking for on how low pressure systems interact is Fujiwhara effect...as for moisture, it can come from the most unlikely sources...when summer thunderstorms form in Alberta and Saskatchewan, the moisture to feed those thunderstorms is being transported from the Gulf of Mexico, over 1,500 miles away...it just depends on the atmospheric setup as to where the moisture originates. Ks0stm ^(T•C•G) 03:59, 5 February 2010 (UTC)

Yes but how is the Gulf warm enough to support such a massive storm with so much energy? I mean, half the country is essentially going to get 2 feet of snow... that's a lot of water.... John Riemann Soong (talk) 16:02, 5 February 2010 (UTC)

It might be as little as 2" of water. That's still quite a lot - but not unprecedented. SteveBaker (talk) 03:15, 6 February 2010 (UTC)

I've been tracking the progression of this winter's weather, and I've saved images of sea surface temperatures from Weather Underground since early December. Don't be afraid to save the images on your computer, as the copyright only applies to using the images elsewhere. Take a look also at Winter storms of 2009–2010 and Winter of 2009-2010 in Europe. Many storms have drifted over the North Atlantic, in the absence of the North Atlantic Gyre, and underwent frontal cyclogenesis. There was an earlier discussion here about this. As more storms such as the North American Blizzard of 2010 head out into the open Atlantic ocean, this will serve to "nudge" the existing lows in the North Atlantic, spinning more of the Gulf Stream in different directions. By the way, the earlier storm you described was the 2009 Christmas winter storm. Some of these storms are so large that they're simultaneously drawing water from the Pacific and Atlantic oceans. Leaves me wondering what the 2010 Atlantic hurricane season will be like. ~AH1^(TCU) 22:00, 7 February 2010 (UTC)

Evolution

Resolved

What's that type of evolution called when two very similar looking species have evolved completely separately in different locations? —Preceding unsigned comment added by 82.43.89.14 (talk) 09:40, 5 February 2010 (UTC)

http://en.wikipedia.org/wiki/Convergent_evolution —Preceding unsigned comment added by 157.193.173.205 (talk) 09:53, 5 February 2010 (UTC)

Thank you!

Find the average velocity

Between two train stations a train travels the first $1/n$th of the distance with uniform acceleration, then with uniform speed v, and for the last $1/n$th of the distance with uniform deceleration. What is the average velocity in terms of v and n?

--220.253.218.157 (talk) 11:11, 5 February 2010 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. --Tagishsimon (talk) 11:13, 5 February 2010 (UTC)

OK, please help me. My understanding is that average velocity is displacement divided by time, but I don't see how to find either displacement or time from the question. Perhaps you could help me with that?--220.253.218.157 (talk) 11:25, 5 February 2010 (UTC)

Yes, average velocity is displacement/time. As the train is always moving in the same direction, the displacement is the distance travelled by the train - let's call this d. Let's divide the time up into three parts. There is the time t1 taken to travel a distance d/n while accelerating uniformly from rest to velocity v - note that the average velocity during this part of the journey is v/2. Then there is the time t2 taken to travel a distance (n-2)d/n at a constant velocity v. There is the time t3 taken to travel a distance d/n while decelerating uniformly from velocity v to rest - this is the same as t1. Work out t1, t2 and t3, add then together to find the total time for the journey t, then average velocity is d/t. Gandalf61 (talk) 11:44, 5 February 2010 (UTC)

$t=$${2s(v-u)} \over {v^{2}-u^{2}}$ so t1 and t3 are ${2d} \over {nv}$. t2 is ${(n-2)d} \over {nv}$, so total time is ${4d+(n-2)d} \over {nv}$.d/t is therefore ${dnv} \over {4d+(n-2)d}$ = ${nv} \over {4+(n-2)}$ = ${nv} \over {n+2}$. Is this the correct answer?

Great answer, but where do you get $t=$${2s(v-u)} \over {v^{2}-u^{2}}$? It is valid, but simplifies to $t=$${2s} \over {v+u}$ which intuitively is the displacement divided by the average velocity (assuming constant acceleration). Why the more complicate form? 58.147.58.179 (talk) 15:50, 5 February 2010 (UTC)

Having gotten the answer, you can now look for the intuitive meaning of your result. Had the train traveled at a constant velocity v, each of the n segments of the trip would have taken the same time period. The trip as presented in the problem takes the same time period for each of the n-2 segments in the middle, but each end segment takes twice as long (because of constant acceleration between 0 and v), so a total of 2 + (n-2) + 2 = n+2 time periods are required, as opposed to the constant velocity v trip of n of those same time periods. Thus the average velocity of the trip as stated is n/(n+2) as fast, or nv/(n+2).58.147.58.179 (talk) 16:05, 5 February 2010 (UTC)

Potassium supplements

I notice at the drugstore that all potassium supplements (pills, capsules, etc.) only have 3% daily value of potassium. From this, I infer that to take all 100% of my daily value of potassium at once would be dangerous somehow.....? Can someone explain this to me? What is the point of these supplements if the provide so little of the nutrient? --The Fat Man Who Never Came Back (talk) 15:12, 5 February 2010 (UTC)

Er, sorry about that. I guess I should have read the article first. Still, 3% seems awfully low. Also, I'd like to know more about the injuries that large concentrations of potassium could cause.--The Fat Man Who Never Came Back (talk) 15:18, 5 February 2010 (UTC)

(EC) I suspect it's to prevent potassium toxicity. High serum potassium will cause problems with muscular contraction, particularly of the heart. It is important that the heart, being a rather important muscle, beats normally. -- Flyguy649 ^talk 15:20, 5 February 2010 (UTC)

Potassium in biology says "Although hyperkalemia is rare in healthy individuals, oral doses greater than 18 grams taken at one time in individuals not accustomed to high intakes can lead to hyperkalemia. All supplements sold in the U.S. contain no more than 99 mg of potassium; a healthy individual would need to consume more than 180 such pills to experience severe health risks". Gandalf61 (talk) 15:27, 5 February 2010 (UTC)

Potassium chloride is used for lethal injection. Potassium-sodium exchange is an important part of biological function. See Na+/K+-ATPase. At resting potential, potassium is "supposed" to stay within the cell and remain at low levels outside the cell. Sodium is supposed to remain at low levels inside the cell and remain at high levels outside the cell.

Well ... if you ingest lots of potassium (without giving it chance to be taken into cells gradually while being exchanged for Na+), you'll suddenly cause lots of potassium ions to flood into your body's cells without Na+ having a chance to leave those cells, i.e. the membrane potential of the cell goes up. Effectively your entire body depolarises.

Since sodium is supposed to stay at high levels outside the cell, ingesting lots of Na+ (Cl-) is less of a problem... the cause of death is usually chronically-induced, via kidney failure.

John Riemann Soong (talk) 22:17, 5 February 2010 (UTC)

For that little potassium you might as well eat a few more bananas. 67.243.7.245 (talk) 23:30, 5 February 2010 (UTC)

Bananas make me fat.--The Fat Man Who Never Came Back (talk) 02:56, 6 February 2010 (UTC)

Really? Bananas are not really that high-caloric, compared to their potential to make you feel full. I generally have no reservations about allowing myself a banana when I'm hungry.

Of course if you eat them Elvis Presley-style, that's another matter entirely.... --Trovatore (talk) 03:03, 6 February 2010 (UTC)

If your adiposity is normal and we are supplyng approximately your daily K needs by iv feeding, we would give you about 2 meq per kg per day. The reason your pills have so little is that almost no one needs K supplementation because it is ubiquitous in both animal and plant foods (unless you are living off minerals). The only people who need it are those who have unnatural losses, like those who take a diuretic. On the other hand, if your kidneys do not work, excess K cannot be excreted and will be among the first things that kill you if you do not have access to dialysis. Eat food and stay away from the supplement shelves. alteripse (talk) 08:42, 6 February 2010 (UTC)

Hawking radiation

Hawking radiation according to the article appears to be radiation which exits the event horizon and does not fall back in. Would not such a phenomenon require some form of replacement energy, perhaps from radiation which had not already fallen in been absorbed? 71.100.13.180 (talk) 15:42, 5 February 2010 (UTC)

Assuming that you mean that there must be an energy source for the radiation, then the answer is that it comes from the mass which the black hole loses. JamesBWatson (talk) 15:50, 5 February 2010 (UTC)

You mean rather than from the mass it gains? 71.100.13.180 (talk) 18:34, 5 February 2010 (UTC)

The mass of a black hole doesn't have to stay constant. It's continuously leaking away some of its mass through Hawking radiation. On the other hand, usually there's also new mass that's getting sucked into the black hole. If the amount of mass lost from Hawking radiation exceeds the amount being sucked up, then the black hole will get smaller and eventually disappear. If the amount of mass being sucked up is greater then the black hole will grow. The two effects don't have to balance out. Rckrone (talk) 21:29, 5 February 2010 (UTC)

Yes but if you add water to a boiling pot of water which is not itself of a temperature high enough to boil then the pot of water not only gains mass buts is coolded to a point that there is less water in the pot being converted to water vapor by the reduced temperature of the water in the pot, i.e., more incoming mass of lower temperature --> less outgoing radiation : more incoming mass of equal or higher temperature and more outgoing radiation. Right? 71.100.13.180 (talk) 23:18, 5 February 2010 (UTC)

No, not right. The intensity of the Hawking radiation depends only on the total mass of the blackhole, not in the temperature of the mass from which it was formed. 68.56.16.165 (talk) 23:48, 5 February 2010 (UTC)

"is" or "was" formed? 71.100.160.128 (talk) 00:10, 6 February 2010 (UTC)

If more matter is added, the total mass will change and so will the radiation intensity (The blackhole radius, temperature, entropy will all also change accordingly). 68.56.16.165 (talk) 00:44, 6 February 2010 (UTC)

Interestingly, the Hawking radiation goes down as the mass of the black hole goes up - or in other terms, it goes up as the mass of the black hole goes down. Unless something fancy quantum-mechanical happens that we don't yet understand, the last few kilos will go off like the biggest boom Dr. Strangelove or any Mad Scientist could wish for. On the other hand, for stellar-sized black holes (and larger) the incoming cosmic microwave background is larger than the outgoing Hawking radiation, so it will take a few billion years of dilution of the universe before "normal" black holes have a chance to shrink at all. --Stephan Schulz (talk) 08:39, 6 February 2010 (UTC)

Yes, Blackholes have negative heat capacity and warm up as they radiate energy away. Just keep in mind that negative heat capacity is the rule - not the exception - for gravitationally bound objects that have virialized whenever non-gravitational interaction between its components can be neglected. For instance, interstellar clouds also warm up as they radiate energy away. Dauto (talk) 15:16, 6 February 2010 (UTC)

Supposing a radiating black hole was surrounded by a Dyson sphere to stop energy being sucked in, but with some means of extracting the energy coming out. Would this defeat the Second Law of Thermodynamics?Trevor Loughlin (talk) 15:14, 9 February 2010 (UTC)

The Dyson sphere itself also has a temperature and emits radiation as well

If I step on a Mormon cricket....

Will it go to the Celestial Kingdom?--The Fat Man Who Never Came Back (talk) 15:46, 5 February 2010 (UTC)

That depends if the number of angels that can dance on the head of a pin is a prime number or not. Googlemeister (talk) 15:49, 5 February 2010 (UTC)

The Common Quaker remains silent on this matter.--Shantavira|^{feed me} 17:26, 5 February 2010 (UTC)

Meanwhile, the Great Mormon hies to Kolob in a twinkling of an eye.--The Fat Man Who Never Came Back (talk) 17:40, 5 February 2010 (UTC)

Wikipedia has an article about the Mormon cricket which is neither a Mormon nor a cricket. In the unlikely event that you step on a Mormon Cricket match they would likely worship you as a pre-Columbian giant. Cuddlyable3 (talk) 17:38, 5 February 2010 (UTC)

QUESTION-can magnetron be used as an amplifier

This question was put up in the class by my professor. i have read so far & gathering all sort of information i cud get that it is an oscillating device which produces electron according to the resonant frequency. This is the sole reason that it cant be used as an amplifier is there any other reason. —Preceding unsigned comment added by 61.1.100.54 (talk) 16:00, 5 February 2010 (UTC)

Reading the article on the Magnetron might actually help. Question remains what sort of amplifier you exactly mean. But very generally speaking: Yes, it can be used as an amplifier. NoisyJinx (talk) 16:23, 5 February 2010 (UTC)

Electrons are emitted from the heated cathode in the magnetron. They are supplied by the current through the magnetron (i.e. the magnetron does not manufacture electrons). The magnetron is usually used as an oscillator to convert dc input power into microwave radiation at the resonant frequency determined by the anode cavities. For a microwave amplifier use a different device such as a klystron. Cuddlyable3 (talk) 17:52, 5 February 2010 (UTC)

Bio-gas

how is bio-gas produced with waste products of oilpalm processing —Preceding unsigned comment added by Liemenam (talk • contribs) 17:01, 5 February 2010 (UTC)

Our Biogas article discusses this, though it doesn't specifically talk about palm oil at all. Comet Tuttle (talk) 18:55, 5 February 2010 (UTC)

light

could the dopplar shift in light be caused velocity only ie blue shift being faster than 186000mps while the red shift being slower —Preceding unsigned comment added by 82.22.255.246 (talk) 17:45, 5 February 2010 (UTC)

Wikipedia has an article about Doppler shift. The speed of light in space does not change. Doppler shifting of light is due to its source moving relative to the viewer e.g. the light from a star moving away from Earth is red-shifted. Cuddlyable3 (talk) 17:58, 5 February 2010 (UTC)

Cuddlyable3 is correct. "The speed of light in space does not change". Only the frequency and wavelength of the light changes. Only if light enters a more dense medium, ie air/ water/ glass will it slow down. — 220.101.28.25 (talk) 06:27, 6 February 2010 (UTC)

Let us be clear that the slowing of light in transparent media is not accompanied by a colour (frequency) shift although a different phenomenon Dispersion (optics) can be observed. Cuddlyable3 (talk) 13:43, 6 February 2010 (UTC)

Study which shows that some People will not change their minds

I read a Wikipedia article a while back which was about a study by 2 college professors who divided people into two groups. One group of people would not change their minds even when presented with evidence which shows that their belief was incorrect and would not even consider the possibility that they might be wrong. The other group accepted the possibility that they might be wrong even when in the end they turned out to be correct. If I remember correctly, the first group might even become hostile when their ideas where challenged. I'm looking for that article because it has details which I do not remember (like the two college professors names). —Preceding unsigned comment added by Saxonwg (talk • contribs) 18:22, 5 February 2010 (UTC)

It seems a waste of "study" effort to confirm such a common observation. There are two kinds of people: those who divide people into two kinds and those who don't. Cuddlyable3 (talk) 18:43, 5 February 2010 (UTC)

That was unhelpful, Cuddlyable3. The original poster is asking for a specific article and you blew him off. Comet Tuttle (talk) 18:53, 5 February 2010 (UTC)

Confirmation bias? Comet Tuttle (talk) 18:53, 5 February 2010 (UTC)

Or potentially Primacy effect? 20:39, 5 February 2010 (UTC)

Bigots? 78.146.215.222 (talk) 23:44, 5 February 2010 (UTC)

Global warming denial? ;-) ~AH1^(TCU) 21:48, 7 February 2010 (UTC)

Why does Pluto's status as a Dwarf Planet bother so many people?

The Definiton provided by the IAU is clear enough, and Pluto is strange enough (just look at the orbit) that it is obviously not like the other traditional planets. Does it matter? Pluto didn't go anywhere. We didn't know about 100 years ago, and kids these days know the new classification. So it's just three generations that have this problem. Is it just that we don't like change? Aaronite (talk) 18:30, 5 February 2010 (UTC)

It's because we were taught that Pluto was a planet when we were children. To suddenly say it is not a planet... it's like saying Washington was not a President, based on a technicality! Pluto was always presented as the most obscure, the most foreign, the most futuristic. Pluto is also the dinkiest and loneliest of the planets—and who doesn't like an underdog? (And three generations of Pluto-lovers is enough, to paraphrase an infamous quote. Four generations ago—my grandmother's mother—women couldn't vote in the USA. It's not an inconsequential amount of time on a human scale.) --Mr.98 (talk) 18:37, 5 February 2010 (UTC)

Artistic comparison of Pluto, Eris, Makemake, Haumea, Gonggong (2007 OR10), Sedna, Quaoar, Orcus, 2002 MS₄, and Salacia.

Pluto was thought to be the expected Planet X responsible for observed perturbation of the gas giants' orbits, see the article Planets beyond Neptune. Disqualification of Pluto means that Planet X must be sought all over again among the objects in the picture. Sheesh. Cuddlyable3 (talk) 19:00, 5 February 2010 (UTC)

I don't know - but if you followed the latest astronomical observations then it was clear since the 1990s that Pluto was just one member of some kind of outer asteroid belt (Kuiper belt). And I think from current observational data (especially since the Voyager probes visited Uranus and Neptune) there doesn't seem to be the need for Planet X (does anyone know what the original mistake was that lead to the assumption of Planet X?). Icek (talk) 19:12, 5 February 2010 (UTC)

Did you look at the article? Cuddlyable3 (talk) 20:01, 5 February 2010 (UTC)

I know about the 0.5% mass discrepancy, but why was there an error in the mass determination in the first place? If you derive the mass from Triton's distance and orbital period, then an error about 1/600 in Triton's distance from Neptune (less than 600 km, or about 0.03 arcseconds) could cause that, but there must have been a systematic error if they were so sure that there is a discrepancy in the orbits. Icek (talk) 08:25, 6 February 2010 (UTC)

It is just that we don't like change. (why do you think all the signs along the highway near my house have miles-per-hour on them? It ain't for any logical reason) 128.223.131.109 (talk) 20:29, 5 February 2010 (UTC)

There are plenty of other cases where science has changed the definitions of things - for example: mushrooms are no longer plants, bird are now dinosaurs, glass was (for a while) a liquid - but now it's not again, viruses were once "lifeforms" - and now they aren't. I could go on for hours. Yet other illogical classifications still stand (Why is Europe a continent?). Other terms change completely (a "computer" is no longer someone who computes, a "typewriter" is not someone who types - and a 'calorie' magically became a 'kilocalorie'). And thoughout all of those changes - the general public either ignored the change in status - or went along with it without complaint. Given our usual flexibility - why it is that people made such a fuss over Pluto is really hard to understand! SteveBaker (talk) 22:52, 5 February 2010 (UTC)

I think it has always retained the "Planet X" fascination—Pluto is sci-fi fodder at its best. Mushrooms are not. There is something wonderfully fundamental about what planets there are in the solar system—to have that yanked out from under us by a cabal of wrinkly astronomers... why, it's just not right! I will go to my grave insisting that not only is Pluto a planet, it is the most awesome planet. Dictionary definitions be damned. A better comparison with the redefinition of Pluto would be the argument over whether T-Rex was a fierce king of the jungle or a lowly scavenger. I mean, we all know T-Rex is bad-ass, right? He's no scavenger, whatever those irritating paleontologists say. --Mr.98 (talk) 23:40, 5 February 2010 (UTC)

In this case, there wasn't even an existing definition of "planet". They belatedly but very sensibly rectified that omission. That is, it was sensible to rectify the omission; whether the new definition itself is a sensible one - that's a different question, but it was done by what was effectively a scientific consensus, a concept not unfamiliar around here. It was decided to draw the line at a certain point, and Pluto fell outside the line, because to continue to have Pluto as a planet would have meant including Eris and some other bodies as planets, and that was undesirable for various reasons. It wasn't like "We all hate Pluto, so let's contrive a definition of planet that's sure to exclude it". -- Jack of Oz ... speak! ... 23:48, 5 February 2010 (UTC)

My apologies for editing anyone's contributions, but from this point onward in the discussion the posts were indented so many times that they eventually got shifted off the screen. I have only moved them leftwards.

If Pluto were a planet - then so should our moon be (the Moon is much bigger than Pluto and it's path around the sun is much more normal than Pluto's). That makes the Earth/Moon system into a dual-planet and means that we have to find another name for our twin planet because you can hardly call something "Moon" when it's not a moon. The astronomical convention would have to be to call it Earth-b or something. If you think people were pissed at the astronomers for demoting Pluto...would you want to be the one telling them that we have to change the name of the Moon?!?! Just think of the trouble romantic song-writers would have finding a rhyme for that! SteveBaker (talk) 03:08, 6 February 2010 (UTC)

My view is, of course the Moon is a planet. Why change its name? It can be a planet, and still called the Moon.

This actually goes to the heart of why the IAU definition is a terrible one. Their definition is based, not so much on the intrinsic characteristics of the body, as on where it's located (that is, its orbital characteristics). But these are much less interesting than the intrinsic ones!

Just to take an example, as I understand it, if the Earth were in Pluto's orbit, it would not yet have "cleared its neighborhood" either. Should the Earth cease to be a planet, just because it were transported to Pluto's orbit? Or what about rogue planets, torn loose from the grip of their parent stars?

On the other side of the coin, it's only a historical accident that the gas giants were ever grouped with the rocky planets. They're clearly a different sort of thing; you can't land on them and establish a base! But you can on some of their moons.

By any rational standard, the Moon would be a planet, and so would Ceres and Ganymede and Europa and Titan, but Jupiter would not be. --Trovatore (talk) 03:18, 6 February 2010 (UTC)

I desire to be/with you under Earth-B/Just you and me/in the light of Earth-B/doing it like a flower and a bee - I see untold possibilities for poets! --Stephan Schulz (talk) 08:53, 6 February 2010 (UTC)

"By any rational standard" - well, one rational counter to that proposition is that planets orbit stars, not other planets. If a body orbits a planet, it might be a satellite, or an asteroid, but not itself a planet. -- Jack of Oz ... speak! ... 22:05, 6 February 2010 (UTC)

Why? As I say, that seems to be basing planethood not on any characteristics of the body, but simply on where it is and how it's moving. To me those seem irrelevant. Would a sufficiently large moon *become* a planet, if you set it in a different orbit? Or would Earth cease to be a planet, if you set it in motion around Jupiter, or if you ripped it free to wander through interstellar space? Is that really how you think of the word? For me it is certainly not. --Trovatore (talk) 22:28, 6 February 2010 (UTC)

Lots of astronomical terms depend on where an object is found. An asteroid becomes a meteor when it enters our atmosphere and becomes a meteorite when it hits the ground. SteveBaker (talk) 23:55, 6 February 2010 (UTC)

That's fine; I just wanted to disabuse you of the notion that anyone who sees things differently than the way you see them is not employing a "rational standard". -- Jack of Oz ... speak! ... 22:39, 6 February 2010 (UTC)

So, presumably, you've been considering Eris, and probably Ceres as well, planets, just like Pluto? APL (talk) 07:06, 8 February 2010 (UTC)

Besides - even if you decide that (say) Io is not a planet because it's orbiting a planet - you still have to leave open the possibility of binary planets (analogous to binary stars). If a body is large enough to be a planet but is not given that designation because it orbits another planet - what are you going to do when some exoplanet hunter finds two bodies of equal mass orbiting each other? Do you flip a coin and arbitrarily label one of them "moon" and the other one "planet"? That's a pretty stupid definition! So if you use mass or diameter or roundness or almost any other "obvious" criteria for saying "Planet" then you have to either exclude Pluto or include the Moon. As it happens, the IAU's definition covers that situation by declaring that if the point about which the two objects orbit lies within one of the two bodies then you have a moon - if it lies outside of both of them then you have a binary system. So in fact, the Moon doesn't count as a planet (not even a "dwarf planet") for that reason. The thing that excluded Pluto wasn't its size - it was that crazy orbit. My point is that if you want to come up with clean definitions for words used in a scientific context then you have to make tough "bright line" definitions that sometimes result in different meanings for words than in common English usage. People didn't stop using the word "Bird" and start to talk about "putting up a dinosaur feeder for the winter" when that determination was made. In common English usage, mushrooms are still plants - although they haven't been taxonomically a part of the plant kingdom since the 1930's. People persist in calling tomatoes "vegetables" when they are really "fruit", peanuts are called "nuts" when they are really "legumes" and spiders are still called "insects" by many people. So it really doesn't matter if people continue to talk about "The planet Pluto" in informal circumstances if it makes them happy. But in scientific usage - particularly in publications - it's essential that we use language precisely - and for that we need a solid definition, and the IAU did exactly that. Popularity or otherwise does not matter one iota in the achievement of this purpose. SteveBaker (talk) 23:50, 6 February 2010 (UTC)

I'm having trouble following whom you're addressing here, Steve — you seem to be agreeing with Jack and disagreeing with me, but I wasn't the one saying Io's not a planet because it orbits a planet. I was saying the opposite — maybe not about Io, it's a tad small,whoops, I take it back — Io's plenty big enough. I thought it was smaller than that. but I would certainly include Ganymede and Europa as planets. And the Moon, for sure.

As for the need for a uniform definition of the word "planet", I sharply disagree there. No one has presented a convincing argument as to why the lack of a definition was a problem, except for people who like nomenclatural neatness for its own sake. Usually you need a definition of foo when you start creating a theory of foos in general. I have seen no evidence that the IAU definition in any way enables the study of planets in general (indeed, they specifically limited it to our solar system, so it's virtually usesless-by-design outside the particular list of eight). --Trovatore (talk) 00:09, 7 February 2010 (UTC)

It's not a matter of nomenclatural neatness for its own sake. Just what does anyone mean when they say "planet"? Or "broccoli", or "camel", for that matter. You can call the big oak tree in your front garden a "planet" if you like, and nobody's going to get too upset about it - unless you start teaching your theory to school children, say, or telling people on the WP ref dek that the Solar System includes your big oak tree. That's not gonna happen, obviously, but surely you can see that in scientific contexts there has to be agreement about the meanings of scientific terms, otherwise we're likely to descend into an abyss of chaos and despair (to be slightly melodramatic about it). There was an implicit understanding of "planet" for a long time, and that served its purpose, until it started becoming unclear which bodies were planets and which weren't. That's when it became necessary to settle the matter, definitionally. So we now have a formal definition of "planet". But, as I say, feel free to apply that term to whatever non-planets you like - just don't expect to do so in any sort of formal environment and get away with it, because you'll be told in no uncertain terms "Keep up with progress, Trovatore, and let go of old ideas, otherwise stay out of the kitchen". -- Jack of Oz ... speak! ... 03:24, 7 February 2010 (UTC)

The IAU has no authority (nor does anyone else) to establish the "formal" meaning of words. --Trovatore (talk) 03:34, 7 February 2010 (UTC)

That's only slightly true. Their only authority is measured by the degree to which their decision is respected. It's pretty clear (by the mere fact that people are complaining that "Pluto isn't a planet anymore") that the public accept that authority whether they like it or not. Everyone could just say "Silly IAU! Of course Pluto is a planet!" - and that would be that. But that's not what happened. Also, many prestigious scientific journals are going to start requiring "correct" use of the word in papers that they publish. This is not unusual - laws set by governments are only obeyed to the degree that the people accept them - or they have police and a judicial system to enforce them. If a particularly horrible law was passed, the police or the courts might simply refuse to enforce it. If the IAU made a particularly horrible decision, then the journals might not use their definition in their editorial policy. The IAU have the same authority to define "planet" as the government has to ban cellphone use while driving. More actually - they aren't even asking the general public to use the new definition - only scientists who are working within fields of study where IAU is considered to be the authority in these matters. SteveBaker (talk) 05:15, 7 February 2010 (UTC)

"Their only authority is measured by the degree to which their decision is respected." Exactly so. And I am arguing that we should not respect it. --Trovatore (talk) 05:46, 7 February 2010 (UTC)

I think that what everyone else is arguing is that that ship has sailed. The IAU has set themselves up as the official entity capable of changing this formal definition, and the scientific community has widely accepted it.

You can speak casually anyway you like, but you can't (correctly) claim to be speaking "formally" while using your own personal definition, however much more correct your definition is. That's what formally means : "Official" and "being in accord with established forms". (Unless, of course, you disagree with the dictionary's authority to provide an authoritative definition of the word "formal", in which case precise, logical communication with you is far more trouble than it's worth.) APL (talk) 07:06, 8 February 2010 (UTC)

See, you keep on changing your position, Trovatore. First, you say the decision was a bad one because it was based on the orbital characteristics of celestial bodies, rather than intrinsic ones. That's a substance argument. Then, you said the IAU had no authority to determine a formal definition. This is a principle argument, and it means that, even if you thought the definition was perfect in every way, you'd still reject it on the grounds that they had no authority to make such a ruling in the first place. Now, you've gone back to saying you don't respect their decision - which implies that you're no longer denying their right to make such a decision, just arguing with the decision they actually made. You're back to a substance argument again. You cannot have it both ways, but you're trying to. -- Jack of Oz ... speak! ... 05:59, 7 February 2010 (UTC)

Hmm? Why not? The IAU was wrong on both substance and principle, so I address both. --Trovatore (talk) 06:00, 7 February 2010 (UTC)

I just don't think you can do that. If you say they had no authority to impose a definition, then as far as you are concerned it should be completely and utterly irrelevant what the text of the definition is, because you reject it out of hand, sight unseen, on principle alone. Having completely rejected the definition on principle, you can't then readmit it only to criticise it on its substance - unless, of course, you're trying to have it both ways. -- Jack of Oz ... speak! ... 08:10, 7 February 2010 (UTC)

I disagree. They had no authority to impose a definition, and the one they chose was also bad. Both of these points are relevant to the discussion. --Trovatore (talk) 08:16, 7 February 2010 (UTC)

But if the definition they chose had been a "good" one (meaning, one you agreed with), then presumably you'd still be rejecting it on principle ...... or would you? If you hold to the principle, what possible difference could it make whether the definition was good, bad or indifferent? -- Jack of Oz ... speak! ... 08:22, 7 February 2010 (UTC)

If they had chosen a definition I liked, the principles would still apply, but it probably wouldn't bother me as much; I'm a human being, not some Randian superhero. That's descriptively. Prescriptively, should it make a difference? Of course — the damage is greater if it's a bad definition. --Trovatore (talk) 08:37, 7 February 2010 (UTC)

Wouldn't it be Goofy without Pluto in the Universe? Cuddlyable3 (talk) 01:18, 6 February 2010 (UTC)

The reason was because it might force George Lucus to release another round of Stars Wars films with updated dialog: Tarkin will now say to Leia, "You're far too trusting. Dantooine is too small and too remote. Although it has sufficient mass for its self-gravity to form a hydrostatic equilibrium, Dantooine has failed to clear the neighborhood around its orbit, and won't make an effective demonstration."A Quest For Knowledge (talk) 01:20, 6 February 2010 (UTC)

Fortunately, StarWars is set in a far distant galaxy a long time ago - hence either (a) the IAU had not made that determination at the time of those events - or (b) speed of light considerations would ensure that the IAU's decision cannot possibly have yet reached the Federation. SteveBaker (talk) 03:08, 6 February 2010 (UTC)

T h e s e a r e n o t t h e a n s w e r s y o u a r e l o o k i n g f o r . Cuddlyable3 (talk) 13:39, 6 February 2010 (UTC)

Federation? Surely you mean the Empire, or perhaps the Republic? APL (talk) 07:06, 8 February 2010 (UTC)

The mention a Trade Federation (the group with all those robots) In those crappy new Star Wars movies. Googlemeister (talk) 14:53, 8 February 2010 (UTC)

Menstruation

How would a hypothetical human female go about stopping her annoying periods indefinitely? —Preceding unsigned comment added by 82.43.89.14 (talk) 18:59, 5 February 2010 (UTC)

See the article Hysterectomy. Cuddlyable3 (talk) 19:02, 5 February 2010 (UTC)

See also Extended cycle combined hormonal contraceptive, and the hypothetical women should talk to her doctor. -- Flyguy649 ^talk 19:17, 5 February 2010 (UTC)

She should consult her doctor who will be able to point her in the right direction - not some geek on the internet! --TammyMoet (talk) 20:20, 5 February 2010 (UTC)

Well, duh, she isn't going to get a hysterectomy or birth-control pill off of wikipedia - but she can get all the information she wants here. Why are we assuming that the OP is a female? The OP clearly stated that the subject of discussion is a hypothetical human female, thus heading off the inevitable "Wikipedia is not the place to ask for medical advice" response. 128.223.131.109 (talk) 20:42, 5 February 2010 (UTC)

Merely appending those magical words is neither a necessary nor a sufficient condition to come to a conclusion about what is and what is not a medical question. SteveBaker (talk) 22:24, 5 February 2010 (UTC)

No, but Kainaw's Superimposition tells us that since we are not being asked to give a medical diagnosis, this isn't a prohibited medical advice question. Comet Tuttle (talk) 23:10, 5 February 2010 (UTC)

Someone suggested that menstruation besides being unwelcome is an exceptional or even "unnatural" state since it involves Endometrium (uterine lining) cells failing to perform the function for which they grew and that a more natural state for a female is to be continually pregnant throughout her fertile life. Could that be achieved? Cuddlyable3 (talk) 01:07, 6 February 2010 (UTC)

This rivals the famous feminist nonsense "the only difference between men and women is a uterus" assertion of the 1970s. You have documented a new low in ideologically twisted physiology. alteripse (talk) 08:34, 6 February 2010 (UTC)

It's actually a pretty well accepted fact that, premodern times, most women spent most of their adult lives pregnant and/or lactating. The exceptions would be the celebate, for whatever reason. On top of that, it can't have been too unusual to have so little fat that menstruation stopped. This doesn't mean that spending your adult life pregant is a good thing (life expectancy of women was low due to the shocking mortality rate associated with giving birth), but it does suggest that monthly periods for 30 years may not be ideal or natural. Many young women spend years slightly aneamic thanks to the regular bleeding (if I weren't on this sodding iPhone I'd get you some references). In any case, there are loads of options if a hypothetical woman takes herself to her doctor. They range from a repackaged version of The Pill to more drastic surgical options, and would probably involve talking about what specifically is problematic about her periods. If the hypothetical woman has a male doctor and wishes to discuss it with a female doctor, they can usually just ask and people understand why. 86.179.145.61 (talk) 13:20, 6 February 2010 (UTC)

All true (except your apparent misunderstanding or misuse of "natural"), but none of those facts makes menstruation an "exceptional" or "unusual" or "pathologic" or "unnatural" state for a woman of reproductive age. alteripse (talk) 13:55, 6 February 2010 (UTC)

By "natural" he/she just means the state that humans have evolved to cope with. (How else would you define it in this context?) If the typical state through most of human development was for women not to be menstruating as often, then it may be that humans are not well equipped for that. Rckrone (talk) 18:29, 6 February 2010 (UTC)

Sorry, if you are correct that that was the intended meaning of natural then your understanding is equally flawed. "Natural" does not mean "optimized for human health": that misunderstanding is hard to distinguish from intelligent design and Platonic idealism. Please review biology 101. alteripse (talk) 18:36, 6 February 2010 (UTC)

I never said that natural meant "optimized for human health." You have order of causation wrong. Also, the question in parenthesis was not meant to be rhetorical. How would you define "natural" in this context? Because I really don't see what sort of meaning you're trying to hint at that you found offensive. Rckrone (talk) 18:56, 6 February 2010 (UTC)

My objection is to (1) use of a fantasy idea of an "ideal human state of nature" as a support for a specific social policy preference, or (2) sloppy use of the usually-denotatively-meaningless term natural as if it were an objective attribute of an argument or product someone is advocating or selling. I think the anonymous IP poster 86... was misusing the term in both senses, and I read your comment as endorsing it and failing to understand my objection. Someone can (and usually has) argued that virtually anything a human can do or experience is ipso facto "natural". Use of the term natural to endorse one preferred condition, experience, or behavior over an alternative usually signals an intellectually or semantically sloppy argument or a poor understanding of human evolution. Is that clearer? If the shoe doesnt fit, then feel free not to wear it. alteripse (talk) 20:09, 6 February 2010 (UTC)

Maybe some people think about the concept of "natural" in terms of some nonsense about Platonic ideals or artificial flavoring, but doesn't mean the word itself is tainted. It's still useful to think about the circumstances that a species has evolved to cope well with, contrasted with relatively new circumstance that it hasn't had time to adapt to. We have a perfectly good adjective to communicate that distinction concisely. e.g. a species' "natural habitat". Rckrone (talk) 23:54, 6 February 2010 (UTC)

I agree the word has a relatively precise and useful denotative meaning in some contexts. I think it a suboptimal word to use to designate an environment in which an organism is more adapted in comparison to another. Perhaps suboptimal enough to qualify as intellectually and semantically sloppy, but that is my opinion and you are free to be Humpty Dumpty and have it mean just what you choose it to mean. alteripse (talk) 01:42, 7 February 2010 (UTC)

Some (but not all) women stop menstruating while lactating. Lactation is far less drastic than a hysterectomy and one does not even have to get pregnant to get started. So our hypothetical human female might want to try Erotic lactation, maybe in alternating combination with the more booring alternative of milking her self by her hands or a breast pump. :-) —Preceding unsigned comment added by 89.8.105.190 (talk) 04:37, 6 February 2010 (UTC)

article on time deprivation

I am looking for an article on experiments where people are not given any cues as to what time it is and seeing the effects on their internal clocks, but have not had much luck looking around here for it. Googlemeister (talk) 20:29, 5 February 2010 (UTC)

I would start here: Circadian rhythm. There is a section on rhythym disruption. CoolMike (talk) 21:43, 5 February 2010 (UTC)

I also found Chronobiology CoolMike (talk) 22:18, 5 February 2010 (UTC)

The gambling industry in places such as Las Vegas has practical experience of eliminating time cues because "the standard casino is windowless so as to control a patron's concept of time"[1] [2]. Cuddlyable3 (talk) 00:47, 6 February 2010 (UTC)

Did they get that idea from the Soviet KGB? 24.23.197.43 (talk) 03:46, 7 February 2010 (UTC)

Yes it was a KGB Russian roulette secret. Cuddlyable3 (talk) 20:52, 7 February 2010 (UTC)

There's a wee bit of information in the last paragraph of Circadian rhythm sleep disorder#Normal circadian rhythms. This looks pretty good, and you can find more by Googling for circadian +"temporal isolation" and similar sets of terms. Deor (talk) 01:21, 6 February 2010 (UTC)

Just to add a bit of info, the technical term for a time cue is zeitgeber, so the thing to look for is information about zeitgeber deprivation. Looie496 (talk) 17:47, 6 February 2010 (UTC)

See sleep#timing and perception of time. ~AH1^(TCU) 21:46, 7 February 2010 (UTC)

February 6

How prevalent is magical thinking among university graduates of the western world?

(And how about among the western world's adult, general population?)

One glossary of psychiatric terminology (http://www.abess.com/glossary.html) has the following definition of the term:

Magical thinking A conviction that thinking equates with doing. Occurs in dreams in children, in primitive peoples, and in patients under a variety of conditions. Characterized by lack of realistic relationship between cause and effect.

Children, primitives, patients... Hmm!

I used to think that magical thinking, among adults in the western world, was a rather rarely occuring phenomenon, but now I wonder...

Might it be frighteningly more prevalent?

I have found this:

Periodical: Psychology Today,
Article: "Magical thinking"
By: Matthew Hutson, published on March 01, 2008 ( http://www.psychologytoday.com/node/21263 )

Speaking about 'magical contagion' it says:

[...] In one study, 80 percent of college students said there was at least a 10 percent chance that donning one of Mr.Rogers' sweaters, even without knowing it was his, would endow wearers with some of his "essence" — improve their mood and make them friendlier.[...]

I have also found an article claiming:
"Research shows that the frequency of magical thinking and superstitious behavior increases under conditions of stress."

(Title: "The Effects of Stress and Desire for Control on Superstitious Behavior"
Journal: Personality and Social Psychology Bulletin, Vol. 28, No. 1, 102-108 (2002)
DOI: 10.1177/0146167202281009
http://psp.sagepub.com/cgi/content/abstract/28/1/102 )

I do not have access to more than the abstract of that one, so I have no way of finding out whether it gives any prevalence numbers or whether it says anything at all about university graduates' beliefs.

Personal, subjective, experience, though, shows that EVEN some HIGHLY EDUCATED university graduates sometimes resort to magical practices.

When pressed into a tight corner (figuratively speaking) during a heated argument, where they are fighting and desperately wanting to win an argument, then they will sometimes clearly show this strange belief:

It seems that -- when all the facts, circumstantial evidence and plausible reasoning seems to stack up against them -- then, as a last resort,even some highly educated people will desperately cling to the hope and belief that they can MAKE a statement (claim) of theirs, BECOME TRUE -- just by strongly wanting it to be true and/or by stating (saying) their claim in a sufficiently "strong" and "convincing" manner.

I can imagine that this belief may have originated as a post hoc ergo propter hoc logical deductive fallacy, from situations where they had misunderstood something and then received a stern correction from some authority (parent?), whereupon they (wrongly), maybe unconsciously, perceved that it was reality itself that was changed by the correction, instead of just their personal view of the reality at hand.

Well...
I would really like to have some numbers on the prevalence and frequency of this.
Preferrably with some specific scientific references backing it up.

Could you please help me? —Preceding unsigned comment added by 89.8.105.190 (talk) 05:21, 6 February 2010 (UTC) (Subsequent signature-> Seren-dipper (talk) 01:03, 7 February 2010 (UTC)

100% of normal adults and children engage in magical thinking. It is how our brains are wired. For many citations of studies in college students that confirm this, see the recent popular book on how badly we intuitively understand probabilities and causation that will probably prevent you from ever asking this question again, see The Drunkard's Walk by Leonard Mlodinow. alteripse (talk) 08:05, 6 February 2010 (UTC)

Perception is reality. Moreover, a person's attitude is crucial to determining their relationship to something. So having 'magical thoughts' does in fact shape how things work out. So it's not really magical at all. Vranak (talk) 11:37, 6 February 2010 (UTC)

A lot of otherwise intelligent people still believe in the supernatural (eg religion, God) which is not quite what you asked. 78.146.77.179 (talk) 12:25, 6 February 2010 (UTC)

Now you have 3 meanings, but the essence of magical thinking is imagining a causal relationship between 2 events that does not exist in any objective, verifiable, predictable, practical sense. To the extent that attitude can positively affect something (like other people's behavior), it no longer fits the definition, so I think Vranek's answer is somewhat off the point. Whether you consider belief in a deity to be an example of "magical thinking" depends entirely on whether you think God exists. Cognitive science shows that the way human brains work is to imagine causal connections between nearly all the combinations of events we experience; the core of scientific thinking is to recognize we are always prone to this and to devise ways to prove or disprove these possible connections. alteripse (talk) 12:53, 6 February 2010 (UTC)

It's not off the point, because the question itself is based off inaccurate conception of human nature. My answers addresses that mistake rather than try to answer directly, which would be building error upon more error. Vranak (talk) 17:30, 6 February 2010 (UTC)

Wikipedia has an article Dreamtime which I describe as the magical half-life of some Australian Aborigines . Cuddlyable3 (talk) 13:29, 6 February 2010 (UTC)

Abstract thinking, intuition, morphic resonance, self-reference, perception, mind-expanding, psi (parapsychology), prayer, metaphysics, oneness and if a tree falls in a forest may be of interest. ~AH1^(TCU) 21:42, 7 February 2010 (UTC)

Clarification of my magical thinking question

User:Alteripse said:

100% of normal adults and children engage in magical thinking. It is how our brains are wired.[...]

Well, that may certainly be true for decisions and actions affected by "Instinctive drift" and "the Unconscious mind".

Nevertheless, what I gather from conversations with the people I have met, is that a significant proportion (hopefully the majority) of the western world population, will probably consider it to be, maybe a bit amusing, but still a blatant display of outright stupidity when they, for example, see someone who quite seriously, deliberately and consistently uses the magic incantation "Knocking on wood" along with its ritual knocking, because of a feeling or belif that it might just help "a little bit".

(I am not talking about the sporadic knockers who know for sure that the knocking and incantation itself is in vain, but who still does knock, sometimes, because it evokes a comforting memory of their late, kind, grandmother who used to 'knock on wood').

There must surely have been done scientific research (sometime, somewhere ?) focused on the prevalence of this kind of noticeably stupid behaviour!

So, can anyone please help me with some prevalence numbers and/or references?        Seren-dipper (talk) 09:32, 7 February 2010 (UTC)

Oops! I have to correct myself: To say that magical thinking is: "noticeably stupid" is itself not a very bright thing to do. When scrutinized, magical thinking turns out, on the whole, to be a valuable survival tool. Therefore: "remarkably irrational" makes a much better formulation!
  --Seren-dipper (talk) 21:04, 7 February 2010 (UTC)

life question

have scientist been able to create life in lab from non living components? (Dr hursday (talk) 08:48, 6 February 2010 (UTC))

See synthetic life. --ColinFine (talk) 09:53, 6 February 2010 (UTC)

hello this is hursday again i read the article but i cannot understand it or at least the part of it being cheap and close but also in the article lead me to belief life has not be created maybe i am not understanding article could you please tell me if life has been created by scientist. thank you (Dr hursday (talk) 10:03, 6 February 2010 (UTC))

It may depend on your definition of Life. See Miller–Urey experiment and Abiogenesis. Off the top of my head I believe that some amino acids, precursors to 'life' may have been made experimentally. --220.101.28.25 (talk) 10:30, 6 February 2010 (UTC)

The simple answer to your question is No. No scientist has been able to create a living thing in a laboratory. They are able to construct more and more complicated molecules of living things-- way way past amino acids, but no cells that can respond to environment and reproduce. I did not see anything in the synthetic life article that would suggest it is impossible, just that it has not yet been done. alteripse (talk) 13:03, 6 February 2010 (UTC)

It is a fertile subject for fiction, fiction and research Cuddlyable3 (talk) 13:20, 6 February 2010 (UTC)

We are seeing breakthroughs at an amazing rate and while nobody has yet claimed to produce an entire working lifeform - we are really close to seeing that. I give it less than 5 years. Here are some of the announcements that lead me to that conclusion: [3][4][5][6]. This guy [7] claims to have actually managed it (although close reading suggests not)...and this guy [8] is also very close.

There is a measure of disagreement about what constitutes "success" in this field. Someone has already moved a strand of DNA from one species of bacteria to another and had it successfully reproduce. Does that count? We have scientists who have synthesised a copy of the (already known) DNA of a real bacterium from chemical feedstocks and inserted that into a bacterium whose DNA had been destroyed and ended up with a living bacterium. That's synthetic - but it's only an exact copy of an existing living creature made synthetically. There are people who are trying to design a DNA sequence from scratch - but how much of that DNA has to be "designed" by the scientist? Is it OK to steal the design of a gene that makes a protein that allows energy to be extracted from sucrose from a natural lifeform and merely glue those genes together to make an organism? Do you maybe have to design all of the proteins yourself, then design the DNA to create those proteins? Is using DNA at all "cheating" ?

I know where the ball is - but I'm not sure where the goalposts are - which makes it hard to tell whether a goal has been scored or not!

SteveBaker (talk) 18:18, 6 February 2010 (UTC)

particulate fluidisation

what are the practical industrial applications of particulate fluidisation ?or how particulate fluidisation is helpful to chemical industries ? —Preceding unsigned comment added by Snair0122 (talk • contribs) 08:49, 6 February 2010 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. -^Avic_ennasis @ {{subst:CURRENTTIME}}, {{subst:#time: xjj xjF xjY }} / @ 10:31, 6 February 2010 (UTC)

While doing your homework, you might find the article fluidized bed helpful. However, the texts you were given for the course are probably going to be more relevant. 86.179.145.61 (talk) 11:23, 6 February 2010 (UTC)

The big advantage of fluidization is that it allows the discrete (solid) phase (catalyst and/or reactant) to mix better with the continuous (gas/liquid) phase (reactant(s)), thus increasing the reaction rate. (See Dust explosion for an extreme case of exothermic reaction occurring in an (unintentionally) fluidized state.) This is why all the cat crackers at our refinery are of the fluid-bed type -- we get a faster reaction (and hence better throughput) with the same amount of catalyst! 24.23.197.43 (talk) 04:00, 7 February 2010 (UTC)

Reptiles, snakes or evnous snakes

Steebe Backshall's Deadly 60 states the following: Most eople of the UK live their whole lives without ever seeing a reptile in the wild, and are certainly surprised to hear six of them." Are there only six kinds of reptiles in the UK or is said about snakes or vernous sakes? The Hungarian translator of the book. --Ksanyi (talk) 09:57, 6 February 2010 (UTC)

To the best of my knowledge, the only reptiles in the UK are grass snakes, slow worms and adders, of which only the adder is venomous. I (a 20-year-old who occasionally ventures into open grassy areas, heaths etc) have seen a slow worm and a couple of adders. I'd be surprised if more than half the people in the UK hadn't seen at least one of the three during their lives. Maybe city-dwellers skew things a bit. Brammers (talk) 10:03, 6 February 2010 (UTC)

Woops! Looks like there are six after all. Brammers (talk) 10:14, 6 February 2010 (UTC)

It's certainly rare to see those things in the UK. I would be surprised if "most" people never saw any...but they certainly aren't common there. SteveBaker (talk) 02:32, 7 February 2010 (UTC)

Despite spending long days walking far from habitation in the UK, I've never seen a reptile in the wild, so they must be rare in the areas where I walk (mainly Northern England) I often see wild deer, red squirrels etc. so it can't be because I'm too noisy or unobservant. I haven't any documentary evidence, but it seems quite likely to me that the majority of UK residents never see a reptile in the wild, as claimed, though there are warmer areas of the UK where reptiles are more commonly seen. Dbfirs 22:30, 7 February 2010 (UTC)

I'd say a significant minority of all people in civilized cities don't see reptiles, or even know what they are. Of all people to know what a bandicoot is, I was with an Australian over the weekend and when I asked him if he has ever heard of it, he replied, "Yeah, that's a little squirrel-like rodent thing." Now if there exists even one Australian who doesn't know what about the indigenous marsupials, it's no wonder that New Yorkers have no idea the difference between reptiles and amphibians. DRosenbach ^{(Talk | Contribs)} 00:40, 8 February 2010 (UTC)

Where on the r/K selection theory scale do social insects like ants and bees fall?

Where on the r/K selection theory scale do social insects like ants and bees fall? They seem to exhibit K traits of altruism and social organization, yet investment in offspring is low. It is complicated by the fact that they operate like a superorganism.

Are they primarily on the r or K side of the scale? --Gary123 (talk) 10:05, 6 February 2010 (UTC)

It certainly depends on which factors you base it on, but both the fact that offspring counts are immense and, as you said, investment in offspring is quite low would imo outweigh the social organization, therefore putting insects on the near r side, certainly not as far as bacteria or, for that matter, flies. NoisyJinx (talk) 13:45, 6 February 2010 (UTC)

further, there's no real evidence that the social organization in social insects is learned - it seems to be largely genetic. one of the rationalizations to K-selective species is that parents must spend time with each offspring teaching required behaviors. --Ludwigs2 19:58, 6 February 2010 (UTC)

sleep

hello this is hursday. it seems to be that an organism going into sleep state is would be heavily selected against by evolution that is animal may be eaten by predator also time spent in sleep is time that could be used gathering food or mating with and yet almost all animals sleep why is this? is there some evolutionary advantage to having sleep? wouldnt a creature without need to sleep have advantages over creature that does need sleep? (Dr hursday (talk) 11:50, 6 February 2010 (UTC))

You are essentially asking why sleep is necessary and we simply do not know. We know that is seems to be universally necessary among animals, we know some of the beneficial things that happen during sleep, and we know some of the bad things that happen when someone is deprived. See our article on sleep. It seems to be the way living things work. alteripse (talk) 12:58, 6 February 2010 (UTC)

Unihemispheric slow-wave sleep might be of some interest --Digrpat (talk) 14:30, 6 February 2010 (UTC)

We don't know why sleep is necessary? It's neccessary because parts of the body, particularly the brain, benefit greatly from being in a regular rest state. It's as straightforward as charging your cell phone battery. If you don't do it, it dies. Vranak (talk) 15:34, 6 February 2010 (UTC)

I've read that the military has experimented with drugs that keep people alert without sleep without any apparent side effects. 67.243.7.245 (talk) 15:40, 6 February 2010 (UTC)

Yes,we know that it is necessary, but why did we evolve to require sleep? As the OP states, clearly it'd be better for survival to always be alert, and have the "regeneration" going on constantly in the background. -- Aeluwas (talk) 16:17, 6 February 2010 (UTC)

Plainly it is not optional. And regeneration cannot occur when your neurons are in use. It's like trying to remodel your kitchen while cooking Christmas dinner. It simply does not work. Vranak (talk) 17:27, 6 February 2010 (UTC)

I don't think anyone but the OP has suggested that sleep may be optional. What everyone is saying is that although we know it isn't optional, we don't really know why (there are lots of theories sure, but none of them really have the strength of evidence for us to be able to say this is why). Saying 'your brain needs rest' may be a good enough answer for a lay person, but this is the science desk. And we do know why rechargable batteries need to be recharged, so that example doesn't work. The 'remodel your kitchen' doesn't particularly work either, for example I would question whether you really can't remodel your kitchen when it's in use (it may not make sense to do it, but that doesn't mean it's impossible) and in any case the brain isn't a kitchen (many modern file systems can be defragmented while in use fairly well which is likely a far better comparison then a kitchen although also still far from good) and there is the 'half the brain sleep' and lots of other credible things that seem they may work, but all we really know is that they don't seem to because few organisms have them. Nil Einne (talk) 10:36, 7 February 2010 (UTC)

(after edit conflict) The fact that all animals mammals and birds sleep, even after a long hibernation, suggests a strong evolutionary advantage that outweighs the disadvantages you mention, but we still don't fully understand the processes involved (as Alteripse said above). Evolutionary adaptations include sleeping with only half the brain at any time, and not sleeping during the first month of life (as in killer whales), but these seem to be rare. Some humans need less sleep, and this adaptation has a possible link with a genetic change, BHLHB3, but the rarity of these adaptations suggests that sleep is an essential function in a healthy brain. You might like to read, also, our articles on Sleep (non-human) and Sleep disorder. Dbfirs 14:46, 6 February 2010 (UTC)

Do you mean to imply that birds are not animals?? Dauto (talk) 15:02, 6 February 2010 (UTC)

Oops! I thought "mammals and birds" and stupidly wrote "animals". Sorry! I've corrected my error. Dbfirs 23:06, 6 February 2010 (UTC)

Although sleep clearly has multiple functions, I personally believe that the most compelling explanation is the "synaptic homeostasis" theory that Giulio Tononi has been defending in recent years, in articles such as Tononi G, Cirelli C (2006). "Sleep function and synaptic homeostasis" (PDF). Sleep Med Rev. 10 (1): 49–62. doi:10.1016/j.smrv.2005.05.002. PMID 16376591. {{cite journal}}: Unknown parameter |month= ignored (help). Looie496 (talk) 17:38, 6 February 2010 (UTC)

See sleep deprivation for the effects of a lack of sleep on humans. ~AH1^(TCU) 21:38, 7 February 2010 (UTC)

Less Deep Injuries cause Less Pain?

Hello I recall being told that A less deep injury whould cause more pain then A deep one, due to there being more nerves at the surface layer then deeper down.

Any info on this being true? 94.172.41.229 (talk) 15:12, 6 February 2010 (UTC)

Seems unlikely - you have to go through the surface nerves to get to the deeper ones. How would the surface nerves "know" that the wound goes down deeper. The closest this might be to being true is that deep wounds are (in some cases) no more painful than shallow ones...but even that seems unlikely. However, I don't have any solid information - there may be more to this than meets the eye. SteveBaker (talk) 15:40, 6 February 2010 (UTC)

The more severe burns aren't all that painful (Well, in comparison to one of less severity), but that's because they destroy the nerves. Vimescarrot (talk) 16:15, 6 February 2010 (UTC)

The paper cut article says that the shallow cuts don't bleed much, so pain receptors are left open to the air where they can continue to cause pain. Some of the references in that article might be worth looking at, especially the first one. Buddy431 (talk) 18:05, 6 February 2010 (UTC)

Testicular trauma would fit in a different category, I think. ~AH1^(TCU) 21:31, 7 February 2010 (UTC)

Good Book on analog filter design

I'm studying Digital filter design in DSP now. But most books assume that you know analogue filter design, concept of ripples, polynomials and such. Which is a good book to start on the most basics of analogue filter design starting with polynomials and image impedances and builds upto stuff like butterworth, chebychev response, const-K, m-derived, realisations like foster forms etc? Books on network theory does filter design abruptly just listing the different response standard forms, their properties etc. 59.93.33.156 (talk) 16:19, 6 February 2010 (UTC)

Another thing is those attenuation(Cosh(xxx)), and phase responses which look nothing like actual responses. 59.93.33.156 (talk) 16:22, 6 February 2010 (UTC)

The book Active Filter Design by Carson Chen, 1982 Hayden Book Co. Inc. leads one from filter basics up to Butterworth, Chebychev, Bessel (and a little on Elliptic/Cauer) forms. Cuddlyable3 (talk) 01:46, 7 February 2010 (UTC)

I'm assuming active filter design is not much different except for few amplifiers and principles still apply 59.93.33.177 (talk) 03:51, 7 February 2010 (UTC)

Yes. I found Chen's little book to be weak on active analog filters despite its title. It's good for the analogue filter basics though. Cuddlyable3 (talk) 20:40, 7 February 2010 (UTC)

Manufacturing process for Methylene Blue Injection 1%

Feb 06, 2010

To Whom It May Concern ,

It would be my honor and privilege to know you .

It was great to visit your website and learn much from you .

Would you please teach me the MANUFACTURING PROCESS FOR METHYLENE BLUE INJECTION USP 1% from METHLENE BLUE TRIHYDRATE POWDER ((MW: 373.90, CAS# 7220-79-3)

Dilute Methylene Blue trihydrate with water and mix well.

Assay for solution strength per USP procedures .

How to sterilize ( decomposition temperature ) and pack .

Thank you so much . —Preceding unsigned comment added by Haunguyenmd (talk • contribs) 16:33, 6 February 2010 (UTC)

Here is a data sheet for Methylene Blue Solution for Injection that may help. Cuddlyable3 (talk) 01:37, 7 February 2010 (UTC)

light (bis)

has the speed of light been measured after it has travelled a billion years or do people still take it for granted that einstein was right without checking.i am asking this question has i have been told he lied about lightspeed being constant to make his theory of relativity work even though he knew lightspeed is varied. —Preceding unsigned comment added by 82.22.255.246 (talk) 16:43, 6 February 2010 (UTC)

Not even a scientist as famous as Einstein is assumed to be right "without checking" - that's just not how science works. In fact, the predictions of Einstein's theory of general relativity have probably been checked more precisely and more thoroughly than almost any other scientific theory - imagine how famous someone would be if they managed to prove that Einstein was wrong ! We can certainly observe light that has been travelling for billions of years - light from the quasar 3C 273, for example, has been travelling for over 2 billion years before it reaches us. There used to be a theory of tired light in the 1930s, but it could not be made to fit all the cosmological observations that we now have from distant galaxies, so its is no longer thought to be correct. Gandalf61 (talk) 17:37, 6 February 2010 (UTC)

Also, nothing in science is taken for granted. Everything is always under scrutiny, including things most people would take for granted. -- Aeluwas (talk) 19:03, 6 February 2010 (UTC)

Of course nobody has measured the speed of light as light was travelling a billion years - humans didn't exist a billion years ago. But what can be measured is that the speed of light in a vacuum does not depend on the movement of the observer (that's a key insight that special relativity is based upon). For understanding objects that are far away, we need to make some assumptions (like physical laws are the same everywhere at all times) which should be as simple as possible (see Occam's razor). BTW, the tired light hypothesis mentioned by Gandalf61 is not about the speed but the energy of the light. And by the way, Einstein was wrong about quantum mechanics in assuming that there are hidden variables (see Bell's inequality). Icek (talk) 19:27, 6 February 2010 (UTC)

Bad answer! Light from an object that's a billion lightyears away that arrives on earth today has been travelling for a billion years. We know a lot about the laws of physics in the time (and distance) of it's source because we can measure spectra from those places and see familiar emission lines in them with exactly the expected redshift. We can look at the rate that distant galaxies rotate and deduce that the laws of gravity haven't changed. There is a lot we can tell...not one of those measurements have indicated that the laws of physics were different when that light was emitted. Measuring its speed produces the same answer as you get from a flashlight that's within a few light-nanoseconds of your detector. There are plenty of astronomical objects that we can collect light from that are a billion lightyears away and I'm sure this experiment has been done many times. Einstein was indeed wrong about quantum mechanics - but he didn't author any widely accepted theories about that. He passionately didn't want it to be true and threw up a large number of really interesting objections that forced proponents of quantum theory to think very hard about what they were saying. Quantum theory might well not be as well accepted as it is now if a mind as sharp as Einsteins hadn't pushed the theory to its limits and yet failed to break it. However, we aren't talking about Quantum theory - this is a matter of relativity theory - and Einstein appears to have been 100% correct about that since there are no experiments that indicate that it is not valid and an enormous number that demonstrate that it is. SteveBaker (talk) 23:27, 6 February 2010 (UTC)

How can one know exactly the redshift to expect from a source before one measures it? And when are you going to stop posting bad English such as "of it is source"? Cuddlyable3 (talk) 01:30, 7 February 2010 (UTC)

See Is The Speed of Light Constant? and Have physical constants changed with time? for some information about this. It's not possible to check the speed of light over large distances by dividing distance by time, because we have no independent way of measuring the distances or times involved and because spacetime is curved anyway. What can be checked is that light's speed is independent of frequency over very large distances and times (since there's no apparent "rainbowing" of distant transient light signals) and that the laws of physics are identical, or nearly so, out to the edge of the visible universe and back to shortly after the big bang. Redshifts can be compared with other measured properties as a test of cosmological models in some cases—see cosmic distance ladder. Einstein's 1905 paper on the photoelectric effect (for which he won the Nobel Prize) was one of the most important steps in the development of quantum theory. There was nothing wrong about that. -- BenRG (talk) 08:34, 7 February 2010 (UTC)

I suggest you ask the person who "told" you that Einstein lied about it for some reliable sources. Exceptional claims require exceptional references. --ColinFine (talk) 11:12, 7 February 2010 (UTC)

I suspect that the person who told you this was reporting a distorted version of Einstein's problems with the "Cosmological constant" - which he described as "his biggest blunder". His original relativity theory predicted that the universe would either collapse or expand forever. But because (he assumed) the universe could "obviously" not be doing either of those things - he kludged his equations by adding in this constant to make everything come out right. Subsequently, when it was proven that the universe is indeed expanding, it became apparent that he was wrong. So he didn't lie (except, perhaps to himself) but he did kludge an equation rather than more honestly standing by what his theory appeared to be saying. But that was nothing to do with the speed of light so if this is what's behind this story, it's horribly distorted from the truth. SteveBaker (talk) 16:17, 7 February 2010 (UTC)

Measuring snowfall when there are many drifts

I'm taking a lunch break from shovelling out of the North American blizzard of 2010. While it's not as bad here in west-central Ohio as it is farther east in the USA, it's still bad, and there are plenty of drifts: part of my lawn has several feet, while I could see the grass in other parts when I got up. In conditions like this, how is it possible to measure snowfall? Is it simply an issue of measuring in many different places and using standard deviation? Nyttend (talk) 18:13, 6 February 2010 (UTC)

I'd take the average (rather than the standard deviation) and check the results against the ones from the nearest Wx station provided by the National Weather Service. Northwest Pennsylvania got an inch, barely noticeable amongst all the lake-effect ;-) ​​​​​​​​Niagara ​​^{Don't give up the ship} 18:47, 6 February 2010 (UTC)

What I'm meaning is how the meteorologists measure it, not how I'm supposed to figure out how much I got; sorry for the unclear wording. Nyttend (talk) 19:33, 6 February 2010 (UTC)

That's pretty much it. Average measurements from different locations and check official results to make sure there isn't a significant amount of error in your results. No high tech or complex methods. There are, however, specially-designed snow gauges that try to minimize blown snow. ​​​​​​​​Niagara ​​^{Don't give up the ship} 19:50, 6 February 2010 (UTC)

More storms are coming but the Great Lakes region look set to miss the major snowfall. Blame the El Nino, Pacific-North American teleconnection pattern and Arctic oscillation. ~AH1^(TCU) 21:26, 7 February 2010 (UTC)

Camping trailers HVAC energy efficiency

Group of 40 camping trailers ranging from 12' to 40' camp all summer on a river bank at a club and share the same electric bill. Is it cheaper to leave on the air during the day while we're all out boating or turn off the air and turn it back on in the evenings when we return to the campground? —Preceding unsigned comment added by Qcliffy (talk • contribs) 18:21, 6 February 2010 (UTC)

That's chiefly a function of how good the insulation in the trailers is. The thing to do is to buy a couple of plugin power meters, and run one trailer with the all-day method and the other with the as-needed method, on the same day. -- Finlay McWalter • Talk 20:15, 6 February 2010 (UTC)

No. No matter how good the insulation, you will need less energy if you switch aircon on and off as needed. It may be less convenient, but energetically there is no question. The speed at which the trailers heat up depends on the difference between inside and outside temperature. So the closer to the outside temperature you get, the slower you heat up. And indeed, given that trailers usually have lousy insulation, I would suspect that they equalize after a few hours, in which case no further heat is gained. Financially, it may depend on wether you pay peak prices or a flat rate, of course. --Stephan Schulz (talk) 20:33, 6 February 2010 (UTC)

Yep - I agree. The insulation provided in camping trailers is a disaster. There is no doubt about it - you need to turn the A/C off when there is nobody in the trailers. SteveBaker (talk) 23:07, 6 February 2010 (UTC)

This question comes up so many times - usually in relation to central heating. 78.146.77.179 (talk) 01:08, 7 February 2010 (UTC)

The situation in a house or other large structure is a little different. A house takes much longer to get back to a comfortable temperature after it's been cooking all day - and with better insulation, there is more justification in leaving the A/C turned on with nobody in the house so you don't have to wait an hour for it to cool when you get home. But with a camping trailer, there is virtually zero thermal inertia and it'll get cool pretty rapidly after you've turned it back on. Combined with the terrible insulation (making it expensive to air condition), there is really no justification for leaving it turned on. It's a more debatable point with a large and well-insulated house. For example, my house has foot-thick concrete walls that act to provide huge thermal inertial - it's also extremely well insulated. That means that it takes a long time to heat up after you turn off the A/C - but once it is hot, it takes a long time to cool down again. Hence, we don't generally turn off the A/C unless we're going to be away for a long time - it's a net win though.

"My house has foot-thick concrete walls". Is it a former missile silo or other military structure? 89.242.43.246 (talk) 13:27, 7 February 2010 (UTC)

Nope - it's a house I designed myself that is as energy-efficient as I could cost-effectively make it. Actually, I kinda phrased that misleadingly - the walls are indeed a foot thick and they are predominantly made of steel-reinforced concrete but with layers of insulating foam and brick...Brick+Foam+Concrete+Foam+SheetRock = 12 inches total. It was built using Insulated concrete forms. (It's for sale too! Blatant advert is at: http://www.fmbaker.com/). SteveBaker (talk) 16:03, 7 February 2010 (UTC)

Looks very impressive - it would cost ten times as much in the UK. 89.242.43.246 (talk) 20:59, 7 February 2010 (UTC)

Yep - the land alone would cost that much - that's one of the reasons we live here. SteveBaker (talk) 13:49, 8 February 2010 (UTC)

Private non-profit camp grounds shower & toilet facilities EPA

We have a private campground/club grounds for boating club with about 50 persons spending weekends from June - October. In late October, the camp is shut down for the winter. 1 winter out of 3, the river comes up and covers the campground for several weeks. We have well water (tested OK for consumption) and a septic system that serves our 2 showers and 4 toilets for the 5 months we occupy the camp ground. The EPA says that because the river comes up and covers the campground sometimes, we have to shut down our bath house and collect our grey and black water to dispose of at an approved dump site. Is there a way to build some type of composting toilet system that would serve our group? Can we set up outdoor shower facilities that would drain into our current septic system (put only grey water into the field bed?) or put showers on a base of rock that would allow the shower water to trickle down into the sand below? We don't want to contaminate the Ohio any more than it already is, but we have limited funds. —Preceding unsigned comment added by Qcliffy (talk • contribs) 18:32, 6 February 2010 (UTC)

Portable toilet? Cuddlyable3 (talk) 01:21, 7 February 2010 (UTC)

What do astronauts do when there's nothing to fly?

I was just reading an article at CNN about how NASA's Constellation program will be eliminated in the 2011 budget if it passes. It quotes an expert at MIT who says that the proposal calls into question the career tracks of astronauts.

"The astronauts like to fly and anything that reduces the number of opportunities to go into orbit is going to discourage both current and future astronauts" he said.

"But we've been through dry periods before -- before the shuttle was developed and then after the [Space Shuttle] Challenger accident -- and we lived through it."

What do astronauts do when there's nothing to fly? Training all day? Do they ever get bored? 71.57.126.233 (talk) 20:24, 6 February 2010 (UTC)

Not being an Astronaut or NASA employee, from what I have read about Astronauts they already spend the majority of their time training. After all there are not that many spaceflights. Basic training is 20 Months. They are already very qualified (Bachelor's Degree +), and experienced, therefore very employable people.

Each mission is different, requiring more very specialised training especially, I imagine for Mission Specialists. EVAs are practiced to a high degree, everything is planned and practiced over and over (that might get boring!)

Commander and Pilots are already highly qualified as pilots and will need to keep their skills, so they will be kept busy doing that. If not they will almost certainly have no trouble being employed outside NASA if they can't wait around for a spaceflight that may not come for years, thought even up to now they wait years to 'fly'. Not the ideal situation as far as skills retention, but nowdays even Astronauts suffer from fiscal probelms like most of us do.--220.101.28.25 (talk) 23:37, 6 February 2010 (UTC)

Of course the ISS will continue to be manned until at least 2015...so there are still jobs for actual, active Astronauts until then. But the stunning success of recent robotic missions doesn't bode well for their long-term careers. SteveBaker (talk) 15:54, 7 February 2010 (UTC)

But from 35 flight slots on the space shuttle in 2009, we will only get about 6 slots for the Space station next year. So we should lay-off about 80% of our astronauts! Rmhermen (talk) 20:37, 7 February 2010 (UTC)

February 7

Scurvy - 133 year delay

The scurvy article says that in 1734 a book was published which said "scurvy is solely owing to a total abstinence from fresh vegetable food, and greens; which is alone the primary cause of the disease". But the Rose's lime juice article says "The Merchant Shipping Act of...[1867]... required all ships of the Royal Navy and Merchant Navy to provide a daily lime ration to sailors to prevent scurvy." Why was there a 133 year delay? 78.146.77.179 (talk) 02:01, 7 February 2010 (UTC)

The difficulty of carrying enough fresh veggies on a long ocean voyage (and keeping it fresh) meant that even though they knew the cause of scurvy, they didn't know what to do about it. It wasn't until MUCH later that it was realised that citrus fruit were sufficient to prevent this horrible disease - and not until it became possible to preserve that citrus juice for long enough that it became possible to prevent it in practice. Science in the 1700's wasn't what it is today! They didn't have the knowledge or tools to understand what it was in the composition of fresh veggies that prevented scurvy - and they didn't know how to find that in a portable, long-lasting form. SteveBaker (talk) 02:06, 7 February 2010 (UTC)

Also, there is a difference between knowing a remedy, and prescribing it. People knew that child labor was bad for kids forever, but the first laws restricting it were the Factory Acts in 1878. I think the Royal Navy started carrying and distributing limes and lime juice on long-time missions back in the Napoleonic wars. --Stephan Schulz (talk) 08:04, 7 February 2010 (UTC)

There is also a difference between prescribing a remedy and mandating it. As you point out, limes were used in the navy before the law was passed. alteripse (talk) 14:43, 7 February 2010 (UTC)

And of course the very first time they suspected that carrying limes would help with scurvy would have been a bad time to pass a law mandating it. First they needed more evidence - and since scurvy takes a long time to develop, it only appeared on the longest sea journeys. Even after it was well established that lime juice worked, it would have been reasonable to assume that Merchant navy ships would have adopted it voluntarily. No wonder that there was such a delay between suspecting the cause and passing the law. SteveBaker (talk) 15:51, 7 February 2010 (UTC)

On last week's edition of "Empire of the Sea" on the BBC, Dan Snow claimed that scurvy was virtually unknown among the officers on board ships, and this was due to their having a better diet than normal ratings. There was a resistance towards improving the diet of ratings, even though it had been proved to be of benefit, because of the negative attitudes towards the lower ranks from the Admiralty. However, since the BBC website on this doesn't contain any additional information, I can't cite his sources for this assertion. --TammyMoet (talk) 10:55, 7 February 2010 (UTC)

The Royal Navy experimented with stuff called Portable soup, which was dehydrated vegetable stock. Sadly, most of the Vitamin C (which they didn't know about) was lost in the processing, so it didn't help much. Alansplodge (talk) 15:05, 7 February 2010 (UTC)

Yeah - and that would be exactly the kind of thing that would leave them wondering whether they had the cause right in the first place. SteveBaker (talk) 15:51, 7 February 2010 (UTC)

From the mid to late 1700s Capitan James Cook used to take Sauerkraut as a preventative to scurvy. The article states that germany still took sourkraut even after england changed to limes, which gave the brits the nickname "Limey" and the Germans "kraut". Vespine (talk) 05:19, 8 February 2010 (UTC)

Weird TV interference

My wife is currently watching Before Sunrise on TVOntario via Rogers Cable. We have traditional analog TV. A few minutes ago, an unusual form of interference began appearing on the screen. It takes the form of narrow streaks appearing diagonally on the screen, sloping down from upper left to lower right, about 20° from horizontal. Each streak is slightly wiggly, not straight, and about 8 inches long. They vanish after a moment and new streaks appear. Perhaps due to persistence of vision, it seems as though there are about a dozen streaks on the screen at any particular time, spaced 2-3 inches apart. The overall effect is like rather watching the TV through a blizzard (for those in warm climates, that's a snowfall combined with a strong wind).

We switched on a VCR whose tuner is better shielded than the TV's, and using that tuner the interference disappeared. Switching back to the TV tuner, I see that the interference seems to have gone away while I've been typing this message (although TVO still seems to be more fuzzy than usual).

But I'm curious what sort of signal would generate this interference pattern, because I've been watching TV for decades and I've never seen this effect before. --Anonymous, 02:04 UTC, February 7, 2010.

Does this guide help? Mitch Ames (talk) 12:06, 7 February 2010 (UTC)

Nope, but thanks for trying. None of those has the sort of diagonal streaks I described. Whatever it was, a frequency close, but not identical, to the horizontal scan frequency must have been involved. --Anonymous, 20:21 UTC, February 7, 2010.

While you use cable TV you have no control over signal quality. However your cable company is large enough to have a complaints department that serves millions of subscribers and you can contact them via the website www.rogers.com. If you can send them a phograph of what you describe happening to your picture there is a good chance that they can explain and/or prevent it happening again. It may have been a disturbance caused by servicing their own equipment.Cuddlyable3 (talk) 20:08, 7 February 2010 (UTC)

Since changing to a tuner with better shielding eliminated the interference, it's clear that it wasn't originating from the cable system. (The signal was also weaker than normal, which is a cable system problem and I'll take it up with them if it persists.) --Anonymous, 20:21 UTC, February 7, 2010.

Multiple vertical streaks are given by interference at a multiple or "harmonic" of the horizontal scan frequency. Slight offset from a harmonic gives slanting streaks. Thus the interfering frequency may lie far from the horizontal scan frequency. Cuddlyable3 (talk) 13:24, 8 February 2010 (UTC)

Animal/plant hybrid

http://www.wired.com/wiredscience/2010/01/green-sea-slug/

Since it was an animal, but it's evolved to produce chlorophyll and carry out photosynthesis like a plant, which kingdom is it? --75.28.169.54 (talk) 02:30, 7 February 2010 (UTC)

It's still an animal, since the vast majority of its genes are inherited from its evolutionarily recent ancestors, but if the researchers are right (I haven't read the paper, so I don't know how solid their methods were) then it may have picked up a couple of algal genes by horizontal gene transfer. Exchanging genes in this manner is actually pretty common among microbes, but far less so among most complex organisms, so if this turns out to be real then it's incredibly cool. – ClockworkSoul 02:38, 7 February 2010 (UTC)

The animal undeniably originates from a less exotic species, so this is 100% animal. What makes a plant a plant is the cell structure, not just one gene. 67.243.7.245 (talk) 02:41, 7 February 2010 (UTC)

But how many other animals photosynthesize? None. --75.28.169.54 (talk) 02:42, 7 February 2010 (UTC)

Which is exactly why cladistics makes a better basis for taxonomy than single body characteristics. alteripse (talk) 02:52, 7 February 2010 (UTC)

Precisely. After all, is a bird no longer a bird if it can't fly? Does a mammal become a reptile when it lays eggs? – ClockworkSoul 02:59, 7 February 2010 (UTC)

Then the headline of the Wired article I linked to is wrong. --75.34.66.111 (talk) 03:03, 7 February 2010 (UTC)

They often (usually) are... that's what happens when science articles are written by non-scientists, which are headlined by even less science-savvy editors. It's good that you noticed that though; most people never do. – ClockworkSoul 03:17, 7 February 2010 (UTC)

Concrete/abstract knowledge

Why is it that students have so much trouble understanding concepts like electric/magnetic fields, algebra limits, and derivatives (to give only a few examples)? The universal answer I've heard is that children start by thinking in concrete terms and become more capable of abstract reasoning as they age. This message is echoed in Wikipedia's articles about child development.

I've never understood how this could make sense. Very young children understand concepts like love, emotion, time, and protection. Those are obviously more abstract than electric fields or the concept of using "x" to represent an unknown; I can explain what an electric field is to somebody who's never heard of it, but how do you even begin to explain time or love? Why is it that five-year-olds have no trouble at all understanding all these abstract things that they can't be felt, seen, or imagined, yet high school students struggle with "abstract" physics and math? --99.237.234.104 (talk) 04:10, 7 February 2010 (UTC)

Are you sure they understand love, emotion, time and protection? Well, perhaps they do. But those things have been around for millions of years - we've evolved to be able to pick up on the things we need in early life very quickly - the ability to learn language just by hearing the sounds made by other people for example. The other things you listed have been around for maybe 100 years - they are a recent invention - we certainly aren't evolved to be able to understand electric and magnetic fields. SteveBaker (talk) 04:34, 7 February 2010 (UTC)

Children may well have experienced love and protection from their parents, emotions of their own, and time. But do children understand those beyond "this is what it is?" Ask a child how time, love, emotions or protection actually work...By the same token, a child could probably understand magnetism in general (hold this up to the fridge and it sticks), but explaining how it works is a different matter. Vimescarrot (talk) 10:12, 7 February 2010 (UTC)

I believe the key is that mathematical equations, electrical fields, and things of this nature are neither compelling nor real to high school students (or most people for that matter). So long as the TV turns on and the coffee machine works, your typical person, myself included, is quite content to let the men of science worry about polarities and resistances. These other 'abstract' things you speak of that children do understand are not so abstract at all. Are you really telling me that love is not felt? Then it is not love at all. And time is of course not perceived, but everyone has experience with boredom, or at least having to wait. Protection you say is abstract, but to a five year old this is not abstract at all – surrounded by strange and sometimes gruesome adults, not to mention malefactors their own age, it is comforting to have adult parents looking after your interests. Vranak (talk) 12:42, 7 February 2010 (UTC)

You are comparing apples with bananas. For instance, three year olds can speak grammatically without much dificulty. These very kids will have trouble later with high school grammar. These are two very different forms of understanding you are talking about here. Dauto (talk) 15:06, 7 February 2010 (UTC)

I also would echo that the types of love, time, and protection, etc., that a child (or a person) understands are the practical types. Who doesn't understand protection from a practical standpoint? We know what it is to be threatened and to be out of it. Understanding it from an abstract or theoretical standpoint is much harder—requires knowledge of psychology, sociology, etc. We know love because of how it makes us physically feel (hence we associate it with hearts, redness, heat—all physical symptoms relating to our emotional state), not because we abstractly understand what it is (which we don't—unless we study a lot of abstract science). Time we only understand as it is lived. The physics and philosophy of time are mind-boggling abstract and very hard to teach (the idea that time and space are linked, for example, takes forever for even clever undergraduates to grok). --Mr.98 (talk) 15:10, 7 February 2010 (UTC)

I'm sure I understand love, emotion, time, and protection, but shall I ever understand electric/magnetic fields, algebra limits, and derivatives?

File:Ape shaking head.gif Cuddlyable3 (talk) 19:53, 7 February 2010 (UTC)

Bringing this back to the realm of reference desk , as in lets give some references for further reading, there are some classic psyshologists and sociologists and other similar minded people who have worked on this, and have provided some of the classic frameworks for understanding some of these ideas. Consider reading up on:

• Jean Piaget's Theory of cognitive development and later theories based on this, or in refutation of this, proposes that people move through predictable modes of learning, and that one cannot learn abstract ideas (which Piaget calles the "Formal operational stage") if one is not developmentally ready for it.
• Kohlberg's stages of moral development, which expands Piaget's ideas into the moral realm.
• Erikson's stages of psychosocial development yet another "stages of development" based on Piaget's model.
• Bloom's Taxonomy, a pedagogical tool for meeting children's cognitive needs in a variety of modes, both concrete and abstract.
• Maslow's hierarchy of needs, which deals with some of this, noting that people need to have their basic physical needs met before they can work on meeting their metaphysical needs. So, if someone is worried about where their next meal is coming from, they aren't spending a lot of time pondering algebraic matricies...

IN general, one could learn a lot about these ideas by studying topics like pedagogy and Child development and the like. --Jayron32 05:00, 8 February 2010 (UTC)

Erikson is based on the Freudian model, not the Piagetan model

to the point, though: for piaget, it's not concrete vs. abstract, it's concrete vs. formal. concrete understandings are simple, direct, and usually physical/experiential. a child understands love or protection in concrete terms of what s/he feels at any given moment, and what his/her parents do (hug, entertain, approve, shield, prevent). It's why you get those classic adolescent "I hate you!" episodes - the child is caught up in the immediacy of a given feeling, and has (quite literally) forgotten the feeling of love. it takes an adult mind to be capable of viewing love in formal terms (as an object that exists independently of current situation and mind state). the reason it's called formal reasoning is that (in piaget's terms) the the concept can be conceived of in formulaic terms, to which formal laws of logic and reasoning can be applied. Thus, adults can adapt their relationships to all sorts of conditions and circumstances that adolescents literally can't even imagine (because if they did imagine them, they'd lose track of the feeling of love)

in terms of something like electromagnetism, most everyone can see the concrete effects of a magnet, but in order to understand the theory one needs to be able to forget about any concrete effects and imagine an entirely formal system of rules that define a universe of potential effects. even visualizing that is a serious exercise in formal reasoning; working with it and manipulating it to produce effects is even harder. --Ludwigs2 06:46, 8 February 2010 (UTC)

Hmm, that doesn't quite seem to fit the Piaget I read. Might this be a matter of different translations? On the emotional side, while it is dangerous to extrapolate from our own experience, I distinctly remember being about 4 and being told off by my mother. She then said "You know that doesn't mean I don't love you, don't you?" and I was puzzled, because of course she still loved me. Her telling me off or being cross with me didn't change the fact that she loved me, and I didn't know why she'd think she had to tell me. Now, 4 year olds are not adolescents, and not everyone is me, but I'd want to see some extremely convincing studies before I bought into this model of emotional development. 86.179.145.61 (talk) 12:34, 8 February 2010 (UTC)

How common is the lack of understanding of the probability concept?

They might even be capable of performing enough probability calculation to be able to pass an exam at a college level course: "Introduction to probability and statistics".
Still, many of them seem completely unable to really grasp the basic concept of probability.

Has there been any scientific research on exactly how common this lack of ability is?       Seren-dipper (talk) 06:03, 7 February 2010 (UTC)

lots. social psychology had a fair-to-middling-sized interest in this back in the 80s. In general, people over-estimate small probabilities, fail to appreciate conditional probabilities, and are largely incapable of appreciating stochastic processes or other weighted or patterned random events. --Ludwigs2 09:28, 7 February 2010 (UTC)

Hmm. I am not quite sure. Are we talking about the same thing?
One thing is making errors in the assessment of exactely how great or small a probability or likelihood of something is. Another thing entirely, is the inability to comprehend the probability concept itself.
It is this latter scenario that I am searching for numbers and hard facts about.        --Seren-dipper (talk) 10:35, 7 February 2010 (UTC)

So, can you explain what exactly you mean by "the probability concept itself" ? Or maybe give some examples of situations in which you think it is not comprehended ? Gandalf61 (talk) 10:45, 7 February 2010 (UTC)

Sure! I can give you an illustrating example of someone not comprehendig it:
I had a disagreement once, where I argued that if I were to end up in a situation where I had tossed a (regular) coin and five times in a row it had landed "heads up", then there would still not be any better chance of winning a bet by betting on that the next toss would give "tails up". My 'friend' would not believe me! After I had explained everything, to the best of my ability, then my 'friend' just mumbled: "But you can not KNOW that for SURE!". %-)        --Seren-dipper (talk) 11:46, 7 February 2010 (UTC)

What you describe is the Gambler's fallacy. Gambler's fallacy#See also lists related articles that might be of interest. Mitch Ames (talk) 11:57, 7 February 2010 (UTC)

inductivists would bet the opposite way. 81.131.60.13 (talk) 18:59, 7 February 2010 (UTC)

I already gave you a precise reference and answer above. Go to your nearest bookstore and look at The Drunkard's Walk by Leonard Mlodinow. As I said when you asked the question about magical thinking, it gives you a full answer to both questions and many citations. alteripse (talk) 08:05, 6 February 2010 (UTC)

There are many levels to this misunderstanding. The "coin lands on a head 5 times in a row - what is the probability of a 6th head" issue is one of them - but there are both deeper and shallower versions of this. Even people who think they understand this stuff quite well often fall foul of the classic Monty Hall problem...and at the opposite end of the scale, pointing out the astounding improbability of your Toyota's gas pedal sticking and killing you isn't helping Toyota's stock price out in the slightest! (During the last year only 19 people have died due to sticky gas pedals - yet 100 people die on the US roads every single day. Driving a Toyota is having an utterly negligable effect on your probability of having a car accident - so why are you worried?). People really suck at statistics and that's that. In all likelyhood this problem is hard-wired into our brains because we're strongly driven to make conclusions from scrappy bits of data. If I'm a stone-age hunter and I know that there have been nice fat deer down at the waterhole the last 5 times I visited - then I should certainly go there next time I need a meal. In that environment there would be no way to reason between random events and non-random ones - was it random that the deer happened to pick that waterhole instead of another one - or is there something statistically significant going on here. So our "common sense" leads us astray sometimes. Perhaps the coin isn't a fair one? Maybe it does come down heads more often than tails? It takes a conscious effort of willpower not to apply that instinct to the tossed coin problem - and if the coin had come up heads a thousand times in a row - I can't imagine any statistician, however anal, betting on tails for the 1,001th toss. So there is some number of coin tosses where everyone will 'break' with strict logic and pick heads - for your friend that number is 5 - for me, it's maybe 10 - the odds of this being random luck versus it being a biassed coin are very high because coins are overwhelmingly fair - but are they better than one in 1024? I suspect that even people who get that right are not doing so at the level of "gut feel" - but by knowingly overriding that gut feel. I would bet that even people who are good at statistics and understand it fully could be fooled into making the wrong decision if you wrap it up sufficiently that they stop thinking consciously about it. SteveBaker (talk) 15:38, 7 February 2010 (UTC)

To be fair, Toyota accounts for only about 15% of current U.S. auto sales. If we assume that the number of Toyotas currently on the road is a similar fraction (I couldn't find those numbers in a hurry), and if we assume that automobile deaths are roughly uniformly distributed across cars and manufacturers (kind of hand-wavey, but a passable first approximation) then about 15 deaths per day are in Toyotas. Adding an extra 19 annual deaths is an extra 0.3%. Therefore, if you're killed in a Toyota (conditional probability!) then there's about a 1 in 300 chance that it will be due to a sticky gas pedal.

Another way to look at the situation is to look at the number of recalled vehicles – about 2.3 million in the U.S. [9] – and compare that to the total number of registered vehicles in the United States: about 250 million. If the affected Toyota models represent about 1% of the cars on the road, then they should also represent about 1% of the deaths — call it about 1 per day, or three to four hundred per year. Nineteen deaths represent five percent or more of that total. I further assume for the purposes of this discussion that your risk of dying in all vehicles is otherwise roughly equal (an approximation that almost certainly needs tweaking). In that case, if you're killed in a Toyota covered by the sticky-pedal recall then there's about a 1 in 20 chance that it was the sticky pedal that killed you — and that's starting to get into the realm of legitimate concern. Ain't statistics grand? TenOfAllTrades(talk) 16:55, 7 February 2010 (UTC)

The following was written as a reply to

user:alteripse's comment of 08:05, 6 February 2010 (UTC) 

(But I spent so much time typing it in, that two other posts got in between).

Yes! and Thank you! (The book: [Drunkard's Walk: How Randomness Rules Our Lives] went straight to my reading list and I am really looking forward to getting hold of it! :-) (Unfortunately I will probably have to wait a couple of weeks, while the book is shipped overseas).
But your previous answers, abowe, and the wikipedia article about Mlodinow, and the reviews at amazon.com, they all seem to indicate that this book talks about how we, everybody, (to a greater or lesser degree) do make mistakes in our assessment of the probability and likelihood of this or that, in our daily lives.
Which is something slightly different from whether or not an individual is able to grasp the concept of probability! For example:
An older person who do not understand the probability concept, might still do better probability assessments in his unconscious mind, on account of helpful instincts combined with a long life's worth of experiences, than a young person who do understand the concept of probability, but lacks the lifelong experiences of the older one.

Well. As for my other question, which you referred to (I tried to clarify it here), about "magical thinking" I believe I still have not gotten quite the answer I am looking for. Because I am interested only in the conscious usage of magical thinking (and maybe half conscious after it becomes a habit).
This article (link below), from which I only have access to the abstract, seem to indicate that there are substantial differences between conscious and unconscious magical thinking.

© 2007 by JOURNAL OF CONSUMER RESEARCH, Inc. • Vol. 34 • April 2008; DOI: 10.1086/523288

"Conscious and Nonconscious Components of Superstitious Beliefs in Judgment and Decision Making" by Thomas Kramer and Lauren Block
So, I am still not quite confident that I have found scientific research telling of the prevalence of conscious use of magical thinking. Nor of the prevalence of what we now may refer to as "immunity to 'the gamblers fallacy'" (By comprehending the concept of probability).
  --Seren-dipper (talk) 18:34, 7 February 2010 (UTC)

Another book you might like (I certainly do) is The Black Swan by Nicholas Taleb. He talks a lot about the reverse of your observation, how people commonly apply the rules of probability when they absolutely shouldn't. For most things in real life, we have no idea what the "rules" are and so probability is useless - probability as we learn in highschool and university is only useful in casino games and the like. In fact he uses your coin flipping example exactly: he asks "Doctor John", a scientist, what the chances of him flipping another head after 99 tail flips, and he says "50% of course. The prior flips have nothing to do with the probability of the next." He asks "Fat Tony", a street-smart trader from Brooklyn (a place that holds a strange fascination for Taleb) the same question and he answers "tails. You're telling me that you flipped 99 tails in a row and got them every time, and that coin ain't loaded? Getouddahere" or something along those lines. TastyCakes (talk) 18:51, 7 February 2010 (UTC)

Well, the trouble with that example is that you have to specify in advance whether the coin is known to be fair or not. The probability of getting 99 tails in a row with a fair coin is 2⁹⁹:1 against. So if you aren't told that the coin is fair, you have to ask yourself which is more probable - a running streak of 99 tails - or an unfair coin? Now, I would reason thusly: Has there ever - in the entire history of coinmaking - been an unfair coin? The answer to that is obviously "Yes". Have more than 2⁹⁹ coins been minted since the dawn of time? The answer to that is clearly "No". So the probability of this being an unfair coin is clearly much larger than the chances of 99 consecutive tails...and Fat Tony is right to choose tails. The statistician is clearly a moron. On the other hand - if you are told that this is definitely a fair coin - then even though you've just witnessed the most astoundingly unlikely thing in the entire history of the universe, the probability of the next flip being a head is still 50:50. In that case, the statistician is right to say it's 50/50. Personally, I'd pick tails even though I was assured it was a fair coin because the probability of the rules of statistics themselves being correct is probably less than 2⁹⁹! SteveBaker (talk) 19:45, 7 February 2010 (UTC)

I think that is exactly what Taleb is getting at, and he uses the coin flipping as a simple example. He expands it to other, more consequential, areas like, say, economics. While the Dr Johns of the world will try to apply probability to things, the Fat Tonies of the world do not believe the underlying model and so disagree. The "scientist type" mistakes "the map for the landscape"; they put so much faith in their model that they leave themselves vulnerable to all the things that they could not possibly predict and incorporate into their model, the so called "unknown unknowns". He argues that this makes quants, for example, underestimate the risks in some investments, because they are applying probability to a system where they don't know the rules, they don't know the likelihood of terrorists crashing into downtown New York or a global banking collapse. They don't know what tiny event is going to be a "black swan" and radically change things, for the positive or negative, and overshadow (by many magnitudes) the type of probabilities they (and others) do expect and build into their models.

He's not arguing against the bell curve outright, he's just saying that it only describes some things, natural phenomena and the like. In systems where a small part of the population accounts for a large part of the total impact (one elephant can't be a million times bigger than another, but one human can be a million times richer than another), the bell curve does not suitably describe it, and can lead the user far astray.

Anyway, I don't think everyone likes or agrees with his ideas, but I thought it was an interesting read. TastyCakes (talk) 01:39, 8 February 2010 (UTC)

What about probability theory? ~AH1

^(TCU) 21:20, 7 February 2010 (UTC)

Like most of science and mathematics, probability works just fine - but only so long as you specify your initial assumptions correctly. The probability of a tail after a run of 99 tails FOR A FAIR COIN is indeed 50/50 just like probability theory says. However, without knowing that it IS a fair coin, you can use probability theory to show the overwhelming likelyhood that this is NOT a fair coin and hence the probability of getting a head on the 100th toss is more like 2⁹⁹:1 against...which (as near as dammit) means that the next toss will come up with a tail. There is nothing wrong with probability theory - PROVIDING you state your knowns and unknowns clearly up-front. Fat Tony doesn't believe that the odds of there being an unfair coin are that small - so he bets tails in perfect accordance with probability theory. The supposed stupid statistician (being a complete idiot evidently) somehow assumes that we're talking about a fair coin. If that is indeed the case then he's completely correct - but if that was not clearly stated up-front then he'd have to be a complete moron to assume it without evidence. While it's all good fun to make the street-wise Fat Tony look smarter than one of those stupid statisticians, I think it's really unlikely that a qualified statistician faced with a real question wouldn't look at the odds and doubt the premise of the question. This makes another of those "just so" stories like the one that says that scientists "proved" that a bee can't possibly fly which turns out to be utterly without foundation. SteveBaker (talk) 13:43, 8 February 2010 (UTC)

You just have to think about how people react to things like not finding WMDs in Iraq. Did they think, ah we've tested the hypothesis and now we have to decrease our original estimate of the probabilities? Not a bit of it, he must be more evil than we originally thought and has cunningly hidden then so he is more dangerous was how many people dealt with it. And that was a simple case compared to the dreadful miscarriages of justice that have happened from a practically universal failure to handle probabilities right in courts. Dmcq (talk) 23:56, 7 February 2010 (UTC)

keeping roses in tip top shape

It's Singles Awareness Day again but I'm planning to change that by giving someone 12 red roses :) Anyways, so how does one make the roses survive for at least a day? I plan to buy the flowers on Feb 14 but I can only see the girl on Feb 15.--121.97.236.134 (talk) 10:56, 7 February 2010 (UTC)

Buy ones that are not quite open. The main thing is to keep them cool and in the shade, and in water of course. As long as they are fresh they should last at least a week anyway. Good luck!--Shantavira|^{feed me} 11:14, 7 February 2010 (UTC)

Some more tips here[10]. How much science is involved I don't know. Alansplodge (talk) 15:00, 7 February 2010 (UTC)

Just curious: could you perhaps buy them on the 15th? You might well save money and not have to worry about keeping them fresh as long. Nyttend (talk) 20:25, 7 February 2010 (UTC)

Indeed. Prices on roses might drop significantly on the 15th. Dismas|^(talk) 06:47, 8 February 2010 (UTC)

radioactivity

Do radioactive things really glow green in the dark? --Nick —Preceding unsigned comment added by 76.230.229.140 (talk) 16:37, 7 February 2010 (UTC)

Glow, yes. Radium glows blue Click HERE Don't know what radioactive material (if any) glows green though--220.101.28.25 (talk) 17:16, 7 February 2010 (UTC)

You can also get other (non-radioactice) materials to glow by bombarding them with radiation. Some of these do glow green, but it's not the radioactive substance itself that's glowing. See Radioluminescence. Buddy431 (talk) 17:23, 7 February 2010 (UTC)

(edit conflict)The actual colour can be changed, but this is not the 'natural' colour directly produced from radioactive decay see Tritium illumination. "The electrons emitted by the radioactive decay of the tritium cause phosphor to glow", from Tritium. --220.101.28.25 (talk) 17:33, 7 February 2010 (UTC)

the whole 'glowing green' thing is actually a comic book invention based on the effect of phosphorescence - common phosphorescents have a green hue, and react to radiation. they were, in fact, important to the discovery of radiation, and people may have confused them as a product of radiation rather than an indicator of radiation. --Ludwigs2 18:04, 7 February 2010 (UTC)

....so Springfield is safe then.--Shantavira|^{feed me} 18:14, 7 February 2010 (UTC)

With Bart around and Homer in the Reactor? No one else has said it so I will, standard Kryptonite glows green! :-) —220.101.28.25 (talk) 04:32, 8 February 2010 (UTC)

See: "Phosphor#Radioactive_light_sources" About green light from radioactive paint on dials of watches.
  --Seren-dipper (talk) 18:59, 7 February 2010 (UTC)

Some radioactive things can glow orange or red (because they are hot!), some glow blue in water (for more complex physical reasons). I don't think anything glows green on its own, without a phosphor, though. --Mr.98 (talk) 20:28, 7 February 2010 (UTC)

Don't forget about neon lights, which are not radioactive, and aurora (astronomy)e which can glow green. ~AH1^(TCU) 21:07, 7 February 2010 (UTC)

The tradition of "glow green in the dark" radioactivity presumably derives from the radioactive luminous paint mentioned in the article to which Seren-dipper refers above: ("The formula used on watch dials between 1913 and 1950 was a mix of radium-228 and radium-226 with a scintillator made of zinc sulfide and silver (ZnS:Ag).") I recall playing with this paint about fifty years ago. I wonder how much radiation I absorbed! Dbfirs 22:17, 7 February 2010 (UTC)

Dbfirs, this information |HERE about the paint may help. (Hopefully to allay any fears!) Has anyone accused you of glowing? --220.101.28.25 (talk) 07:26, 8 February 2010 (UTC)

Another Avatar question - helicopters

I finally had to time to check out Avatar. I am wondering about the helicopters (or whatever the flying machines are).Could such a design really fly? They are similar to the machines in the Terminator movies except that they had thrusters rather than rotors. I assume that the machines from Terminator could likely fly as depicted as evidenced by the Harrier Jump Jet. —Preceding unsigned comment added by 99.250.117.26 (talk) 20:19, 7 February 2010 (UTC)

It's supposed to be a low-gravity planet, so a flying machine could have smaller rotors/propellers/whatever than would be needed on Earth. This design from the movie looks a lot like the real-life V-22 Osprey, except for the armament and the use of ducted fans, and it looks to me as if it would indeed be practical.

Now, airborne mountains, on the other hand... --Anonymous, 20:30 UTC, February 7, 2010.

Pandora is supposed to be an Earth-like moon, not a planet. ~AH1^(TCU) 21:05, 7 February 2010 (UTC)

Right you are, but that makes no difference to anything I was talking about. --Anon, 06:26 UTC, February 8, 2010.

That design unlike the Osprey appears to have stacked contra-rotating propellers. Any idea why? Cuddlyable3 (talk) 13:02, 8 February 2010 (UTC)

The Osprey has a single engine - so (a) it is guaranteed that the two rotors turn at the exact same speed and (b) if the engine craps out, you're in a rather heavy glider. A better design might have two engines - but then you'd have to match their RPM's exactly in order to avoid torque-steer and in the event that one engine died, you'd spun around too violently to keep flying without shutting down the other engine too. With contra-rotating propellors, there is no torque steer and you could even use throttle control to bank the aircraft without needing a cyclic pitch control for the rotors...and even with one engine out, you might maybe have enough lift to carry on flying....Either that or it just looked cool to the movie's art director. SteveBaker (talk) 13:26, 8 February 2010 (UTC)

A single pair of contra-rotating propellers must turn on an axis that passes through the center of gravity of a helicopter otherwise torque-steer is inevitable. Cuddlyable3 (talk) 14:54, 8 February 2010 (UTC)

Even in our gravity, something like that could be made to fly if you had a sufficiently large source of power and sufficiently strong materials from which to build the rotors. We're also not told about the density of the atmosphere on that planet and that also makes a big difference. Worse still, this planet has rocks that float in the air, anchored to the ground only by the plant life. There are hints that this is due to the mysterious material called "unobtainium" - which is the reasons humans came there to do mining operations in the first place. If unobtainium has this mysterious antigravity effect - then perhaps that is what lightens these craft to the point where they can fly with improbably tiny rotors and thrusters. The problem is - this is science fiction - and whatever the author says works is what works - regardless of currently known science. Just relax and enjoy the movie. SteveBaker (talk) 13:21, 8 February 2010 (UTC)

James Cameron, from this PopSci interview: "What can cause a mountain to float? Well, if it was made out of an almost-pure room-temperature superconductor material, and it was in a powerful magnetic field, it would self-levitate. This has actually been demonstrated on a very small scale with very strong magnetic fields. Then my scientists said, 'You’ll need magnetic fields that are so powerful that they would rip the hemoglobin out of your blood.' So I said, 'Well, we’re not showing that, so we may just have to diverge a little bit from what’s possible in the physical universe to tell our story.'" —Akrabbim^talk 13:39, 8 February 2010 (UTC)

February 8

Kangaroos

Are there any documented evidence of kangaroos using their pouches to hold things like spare change or receipts when they are not carting around their young? (98.20.170.216 (talk) 07:02, 8 February 2010 (UTC))

No. -- kainaw™ 07:09, 8 February 2010 (UTC)

light (2)

if light does not slow down as it travels through space and the red shift means everything is moving away from us. does that mean that if the process was in put in reverse everything would end up here. would it also mean the big bang started here? —Preceding unsigned comment added by 82.22.255.246 (talk) 10:15, 8 February 2010 (UTC)

No. Everything stared in one point, now everything is expanding. Imagine a ball of dough with seeds in it, now imagine it is expanding in all directions, from any seed it looks like all the others are moving away. Vespine (talk) 11:54, 8 February 2010 (UTC)

OTOH we can't say the big bang didn't start here. Cuddlyable3 (talk) 12:53, 8 February 2010 (UTC)

Technically, that's true - but without clarification, it's misleading. Vespone's cookie dough analogy is a frequently given one. The one I prefer is the balloon analogy: If you draw a bunch of dots on a deflated balloon and then inflate it - as the balloon grows, so the dots move further apart - but from the vantage point of any given dot, it looks like all the other dots are moving away from it. Now, if the balloon started out as an infinitely small speck and slowly grew to become the size of our universe - that would be a good analogy for the big bang. So - the question of where the big bang started from is analogous to asking which of the dots on the balloon was closest to where the balloon started to inflate from - and the answer (because the balloon started out as an infinitely small speck) is "all of them". All of the dots on the balloon - (and all of the points in our universe) started out at the same place because before space itself started to expand, there only was one place. SteveBaker (talk) 13:11, 8 February 2010 (UTC)

Misleading analogy. Real space is 3-D but a balloon has only a curved 2-D surface. At any time when individual dots are distinguishable, one of them is closest to where the balloon started to inflate. Balloons make their big bang after inflation and not before it. A baker should save dough and not insist on blow jobs.Cuddlyable3 (talk) 14:44, 8 February 2010 (UTC)

light (3)

if there were two observers in two different spaceships observing the same distant star. but with one going towards it while the other came away from it. would one observer see the light with a red shift while the observer see a blue shift at the same time from the same star —Preceding unsigned comment added by 82.22.255.246 (talk) 12:17, 8 February 2010 (UTC)

Yes. Going towards: blue. Going away: red. --Tagishsimon (talk) 12:31, 8 February 2010 (UTC)

Scar removal?

I know that this may sound like an oxymoron, but I was wondering if it may be possible to remove scars now, if not, somewhere down the future. I am not looking for medical advice, and certainly hope that this won't be considered medical advice, but I saw the wikipedia article on scars and in the treatment section it said something to the extent of, that according to the authority at aad.org, there is no scar that can be completely removed.

I was just wondering how credible that statement is, and if it will ever be possible to remove a scar?

Also, I was just looking into gene therapy as well, and was wondering why the skin can't produce normal skin after injury and has to form scar tissue instead of regular dermis?

Thanks. —Preceding unsigned comment added by 139.62.223.27 (talk) 12:51, 8 February 2010 (UTC)

Using an array of cosmetic techniques, it is possible to reduce the appearance of many scars, though it is virtually impossible to eliminate them completely. Dermabrasion or microdermabrasion can be used to 'flatten out' raised scar tissue. An assortment of laser techniques can be used to reduce or even out pigmentation in the scar tissue compared to the surrounding area, and may also be used to thin out blood vessels to reduce redness. Chemical peels can be used to alter (and, ideally, improve) skin texture. In more severe cases, surgical excision of the scar tissue may be required; grafts of new skin can be generated through tissue expansion. Carefully controlled conditions and the use of anti-inflammatory drugs can help to minimize the appearance of the new post-surgical scars. Google is your friend here — look for 'scar removal' and the like. TenOfAllTrades(talk) 14:37, 8 February 2010 (UTC)

An extract of onion is marketed for scar improvement but has apparently failed multiple clinical trials. Rmhermen (talk) 15:00, 8 February 2010 (UTC)

"beanie" or "paint" taste of soy flour

I have now experienced the taste difference between genetically modified soy (Now brand) and organic soy powder (Arrowhead brand) and I can tell you that I now know why GM has so much support among diners and cooks alike. However, many people still have reserves of Arrowhead they do not want to throw out so what is the conventional method of deflavoring soybean powder/flour to hide the "beany" taste? 71.100.0.210 (talk) 14:04, 8 February 2010 (UTC)

GM soy is altered to make it more resistant to herbicides, not to change its taste. The "L-Star" hybrid soybean was bred normally in Japan and has no lipoxygenase which gives the beans a "beany" flavor. However this is not GM soy, just normal field breeding. Rmhermen (talk) 14:55, 8 February 2010 (UTC)

If this question becomes another anti-GM rant, I will remove such posts on sight Nil Einne (talk) 14:57, 8 February 2010 (UTC)

Black Malenic stools

Hi everyone, I would like to ask why are black malenic stools foul smelling as well? Is the foul smell due to the blood (due to some oxidation process?)?

Thanks a million! —Preceding unsigned comment added by 116.15.191.61 (talk) 15:06, 8 February 2010 (UTC)

Sport: Baseball Pitcher vs Cricket Bowler

I thought that a baseball pitcher was faster than a cricket bowler simply because a pitcher basically throws the ball while in cricket a bowler releases the ball without bending his arm when it passes his shoulder hence the term bowler and apart from it being a rule, but...

a) A pitcher pitches/throws the ball from a stationary position not forgetting that most people would instinctively throw a handheld object if they want to generate a lot of power and speed from it while...

b) A bowler bowls the ball after he has had a running start not forgetting that he also jumps in the air (almost like a catapulting movement) just before releasing the ball and thus creating momentum (from the running start) for himself which can create equal or more power.

...but I still don't know who is or can be the fastest.

--41.193.16.234 (talk) 15:32, 8 February 2010 (UTC) Thanks, NirocFX