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February 24

What is the effect of alcohol and drugs on non-human animals?

If you were to give a dog or a grizzly bear vodka, or LSD, what would happen?--X sprainpraxisL (talk) 01:01, 24 February 2011 (UTC)

We have an article on the Effect of psychoactive drugs on animals, though it doesn't look like it has much on the specific animal/drug combinations you mention.

Or, here's an article from 2000 in Alcohol Research & Health: Animal Models in Alcohol Research, if that's more the sort of thing you're interested in. WikiDao ☯ 02:08, 24 February 2011 (UTC)

There was a great part in The gods must be crazy I remember from my childhood where some animals got drunk on the fermenting fruit of some African tree. You can find the segment on youtube. Vespine (talk) 07:32, 24 February 2011 (UTC)

I think that was in Animals Are Beautiful People (by the same writer-director). -- BenRG (talk) 09:23, 24 February 2011 (UTC)

From personal experience, if you give a dog a couple of beers, he pretty much gets sleepy. Not especially entertaining. Googlemeister (talk) 14:18, 24 February 2011 (UTC)\

This article [1] is about a serious case of drunk monkey business. 10draftsdeep (talk) 17:49, 24 February 2011 (UTC)

Bees can sometimes get intoxicated when they dine on naturally occuring fermented nectar. The guard bees at the hive act like bouncers, an intoxicated bee is turned away and refused entry into the hive. If that bee is persistent, then it will be treated as hostile, and will be quickly dispatched by the guards. Plasmic Physics (talk) 22:25, 24 February 2011 (UTC)

A cocketiel can get intoxicated from wine, they have a preference of red over white wine. Our cockatiel may lose it's balance and coorination, develop an attention deficit, and puffs up it's feathers, and just becomes generally entertaining. It gets annoyed when we remove access to wine if it hasn't already forgotten about it. Plasmic Physics (talk) 22:25, 24 February 2011 (UTC)

There are videos on YouTube of spiders and cats on LSD, caffeine, cocaine, alcohol, and other drugs. Be aware though, that dosage, set and setting vary the effect. Also see Rat Park. 75.138.198.62 (talk) 20:44, 26 February 2011 (UTC)

Mice exposed to coccaine will prefer the drug over food. Dimethyltryptamine is secreted natually in small amounts by humans and other mammals. ~AH1^(TCU) 20:53, 26 February 2011 (UTC)

Question on collision between hydrogen atoms (momentum / energy question)

Hi all,

I was doing my physics mid term exam today and I came across a question that I couldn't solve. Turns out it's from the textbook. Here it is:

When two hydrogen atoms of mass m combine to form a diatomic hydrogen molecule (H2), the potential energy of the system after they combine is -Δ, where Δ is a positive quantity called the binding energy of the molecule.

(a) Show that in a collision that involves only two hydrogen atoms, it is impossible to form an H2 molecule because momentum and energy cannot be simultaneously be conserved. (Hint: If you can show this to be true in one frame of reference, then it is true in all frames of reference.)

(b) An H2 molecule can be formed in a collision that involves three hydrogen atoms. Suppose that before such a collision, each of the three atoms has speed 1.00 * 10^3 m/s, and they are approaching at 120 degree angles so that at any instant, the atoms lie at the corners of an equilateral triangle. Find the speeds of the H2 molecule and of the single hydrogen atom that remains after the collision. The binding energy of H2 is 7.23*10^-19 J and the mass of the hydrogen atom is 1.67*10^-27 kg

Any help would be appreciated. —Preceding unsigned comment added by 164.67.66.113 (talk) 01:16, 24 February 2011 (UTC)

Consider the simplest possible case for (a), where the final product has no net velocity. To conserve momentum, each atom must approach with the same speed. Now calculate the kinetic energy before and after; and account for the binding energy, and determine if the reaction is possible.

For the second case (b), I think the problem is actually more straightforward, because they give you all initial conditions, and most of the final conditions; (so you don't need to "intuit" anything - just calculate). Nimur (talk) 01:31, 24 February 2011 (UTC)

Is there an assumption that hydrogen can not store excess energy as anything except kinetic energy? Can't it store the binding or collision energy as excited electrons (assuming the energy levels precisely match)? Can't diatomic hydrogen "bounce", i.e. stay bound but oscillate? Or slightly miss each other and rotate at high speed? Ariel. (talk) 05:08, 24 February 2011 (UTC)

That was the implicit assumption; energy is either kinetic or the fixed-value of the "binding energy." The validity of this assumption is at least partially predicated on the "perfect" alignment of inbound particles. (They can't start rotating if they had no rotational momentum in the initial condition). And electron energy might be negligible; you can actually calculate whether the kinetic energy is orders of magnitude larger than the hydrogen ionization potential, 13.6 eV; while the supplied binding energy is about 4 eV; so neglecting energy in the electron-orbitals might be a bit of a tenuous assumption. You can similarly compare order-of-magnitude to determine if diatomic oscillatory motion is "negligible." This is, after all, a hypothetical, simplified treatment. In practice, we should apply a nuclear scattering treatment and solve quantum-mechanical wavefunctions, and represent the collision as a quantum mechanical operation; but from the wording, I suspect that material is outside the scope of the physics class. Nimur (talk) 05:21, 24 February 2011 (UTC)

I suppose I feel the same as Ariel. The fact is, it is possible for H₂ to form in a collision of two hydrogen atoms, with the excess energy being shed somehow (probably as photons, but there are other ways). I guess it's unlikely, but it doesn't violate any conservation laws. Many physicists would describe this as "a collision that involves only two hydrogen atoms". I think there's no worse question you can pose to a student than "show X" where X is not really true. Aside from being misleading, it penalizes the students who understand the material best, since they are more likely to notice the hole in the obvious (intended) proof and waste time searching for a better one. -- BenRG (talk) 10:08, 24 February 2011 (UTC)

True. I agree that this is a drastic oversimplification of the problem. But I am curious if this simplification is a valid "approximation" to the actual chemical kinetics that are experimentally observed. If so, I can understand why the simplified model might have been developed; in a sense, the "assumptions" would be the "reasonable conclusions" that must theoretically follow if the observed experiments found that only 3-atom collisions resulted in hydrogen; but it has a lot of serious drawbacks, and absolutely can't be considered a general case solution to reaction mechanics. This 1960 paper describes dissociation (the reciprocal reaction of formation): The kinetics of dissociation of a diatomic gas - and its opening line is: "One of the most unsatisfactory aspects of the theory of chemical kinetics has been the failure to describe reasonably the simplest of all reactions, the dissociation of a diatomic gas." The paper proceeds to develop a chemical kinetic description that extends the kinetic-energy/momentum conservation to treat the observed data more accurately. Nimur (talk) 20:57, 24 February 2011 (UTC)

Exactly why can't momentum and energy be simultaneously conserved in a collision? Energy is always conserved. Kinetic Energy isn't conserved. And why can't you create H₂? If you send them towards each other at a high enough speed, assuming nuclear fusion does not occur, then they should collide inelastically, and you can calculate the required relative velocity with: ${\frac {1}{2}}\mu v_{(}rel)^{2}=\Delta$ (where μ is the reduced mass of the system). ManishEarth^{Talk • Stalk} 12:30, 24 February 2011 (UTC)

Ah, you've hit the nail on the head! An inelastic collision is defined by the fact that energy and momentum are not both conserved! Only in elastic collisions are both conserved. Of course, energy is always conserved if you do your bookkeeping right, and in the inelastic case the excess energy is "released" as "heat".

To explain that hand-wavy definition, in a two-particle inelastic system, that "heat" is a spring-like binding energy, so with no place else to go, the inelastic collision tries to store this heat in the two hydrogen atoms themselves. But since this energy was precisely sufficient to bind them in the first place, it is sufficient for them to rip apart too. When hydrogen gas burns, an initial spark makes H2→H+H, but then a lot of firey heat is released by the bond-breaking itself. We can't reverse that process and form bonds unless something can take away the excess heat, which is why you need at least one extra "helper" particle (or catalyst to the reaction) to carry it in kinetic energy. I hope this helps you understand how chemistry and physics describe the exact same thing in different terms. SamuelRiv (talk) 21:34, 24 February 2011 (UTC)

Careful: the breaking of bonds absorbs energy. If the freed atoms then form different bonds, they might release even more energy than the breaking absorbed. --Tardis (talk) 22:48, 24 February 2011 (UTC)

That equation seems right but isn't relevant here. $\Delta$ is the energy released by forming the bond. There's no minimum approach velocity because that energy isn't being taken from the kinetic energy. Rather, the molecule can only be formed permanently if whatever initial kinetic energy and some of $\Delta$ can be dispersed during the collision (via photons), so that the resulting system then lacks the energy to separate. In some cases with an off-axis collision, it may be possible to produce a stable, spinning molecule without shedding all of the initial kinetic energy, but I don't know if they occur in practice. --Tardis (talk) 22:48, 24 February 2011 (UTC)

What is this compound?

Resolved

I'm actually doing a course in organic chemistry right now and yet I still can't figure out the name of this. Any help? --✶♏✶ 04:23, 24 February 2011 (UTC)

Looks like 5-hydroxytryptamine, or serotonin. Here's the standard numbering system for tryptamines [2], which is a little confusing to the uninitiated... and needs periodic rechecking by the initiate as well, I'm afraid. Wnt (talk) 04:53, 24 February 2011 (UTC)

Thanks! Thinking of it, that should have been one of my first guesses for "organic compound someone would tattoo on their body". --✶♏✶ 07:09, 24 February 2011 (UTC)

I don't see the appeal. Sounds painful... Wnt (talk) 16:18, 24 February 2011 (UTC)

It's a nice idea, perhaps a reminder of a terrible depression in her life that was overcome with the help of an SSRI. To face one's darkness is to transcend it, hopefully. Of course, it could also mean that she's just really happy and wanted a happy tattoo instead of, say, the oft-used caffeine or ATP or capsacin. SamuelRiv (talk) 21:44, 24 February 2011 (UTC)

Consequences of (admittedly magically) preventing every cell in your body from ever dividing again?

I understand that many parts of the body rely upon rapid cell division to maintain state (at least what we perceive at the macro scale, it's a Ship of Theseus thing). What would happen if you could snap your fingers and prevent every cell in your body from ever dividing again - in effect "freezing" the current state? Cells that die would not be replaced, clearly. I'm curious what would start to breakdown first from a medical perspective. I imagine death would not be long in coming, but I'm unsure as to how one would die? The Masked Booby (talk) 05:13, 24 February 2011 (UTC)

This should be pretty much like radiation poisoning - hematopoiesis (production of red and white blood cells) fails, the intestinal lining no longer regenerates, skin and hair can suffer, etc. I'm not sure offhand why headaches are a symptom of radiation poisoning and I'm not sure if the magical mechanism would replicate them. Wnt (talk) 05:29, 24 February 2011 (UTC)

See also Labile cell and Hayflick limit. Ariel. (talk) 05:35, 24 February 2011 (UTC)

I think your stomach juice would make short work of you. Vespine (talk) 07:26, 24 February 2011 (UTC)

Well, red blood cells have a lifetime of about 100 days, so in a couple of months you would die of anemia if nothing else killed you sooner. Looie496 (talk) 07:31, 24 February 2011 (UTC)

Yes, it's more the immune effects of lethal irradiation that tend to be a problem - though completely disabling gastrointestinal regeneration would probably work the quickest end here, barring extraordinary interventions. I suspect that lethal irradiation is relatively less damaging to the slowest-growing stem cells of the intestine than a magic stop to all cell division would be. Though there's also a certain uncertain ability of hematopoietic stem cells to seed the intestine when need be.^[3] Wnt (talk) 16:17, 24 February 2011 (UTC)

A human being's body experiences about 10,000 trillion cell divisions in a lifetime, see Cell division. The OP's magic snap, if its effect could be focussed, would incapacitate Cancer cells. Cuddlyable3 (talk) 10:35, 24 February 2011 (UTC)

Your digestive system would start digesting itself. I'd give you 2 or 3 hours (at most 5 or 6) to get your affairs in order and say your goodbyes before you bleed out. Roger (talk) 18:48, 24 February 2011 (UTC)

See Biological_timeline_of_radiation_poisoning for the (grisly) details. The "walking ghost" phase in particular gives me chills. —Preceding unsigned comment added by 12.186.80.1 (talk) 21:26, 25 February 2011 (UTC)

See Laron syndrome, telomere and telomerase. ~AH1^(TCU) 20:39, 26 February 2011 (UTC)

Battery rack earthing

Whether battery rack has to connected to the safety earth pit or not? If it has to be connected what is the reason behind this? If not then why it should not? — Preceding unsigned comment added by Magesh1581 (talk • contribs) 12:01, 24 February 2011 (UTC)

You might want to tell us which sort of battery rack you are talking about, but in short, the answer is probably yes. The reason is that earthing the rack prevents harm should an inadvertent connection be made between the rack and the positive terminals of the batteries. Charge will be routed to earth, rather than to the next poor soul who touches the rack. --Tagishsimon (talk) 12:31, 24 February 2011 (UTC)

I think it is much more complicated, it depend on application and regulation. Depending on situation the answer can be yes or no. --Gr8xoz (talk) 23:59, 24 February 2011 (UTC)

The application which we connected the battery is for the UPS system. Batteries are 2volt 1100 ah vrla batteries. My question is if we connect the safety earth to the battery rack when there was any connectivity or short circuit between the positive terminal to the body or the negative terminal to the body or in between any terminal connected to the body, will the circuit close though the body to safety earth? will there be the current flow though the body to earth from positive or negative or inbetween terminal which get connects to the body? If there wasn't any current flow then whether it will affect the human who touches the body of the rack at this condition? — Preceding unsigned comment added by Magesh1581 (talk • contribs) 14:16, 25 February 2011 (UTC)

We cannot really tell you how to connect your battery, since that would be like telling you how to treat medical symptoms or giving legal advice. But we can provide some information and insights. Contact a licensed professional engineer with design questions. Connections must comply with the applicable electrical safety code, and it may well dictate what has to be grounded and how. You ask about current flow in several situations. Try drawing the electrical diagrams and analyzing them, based on the various possible intentional and accidental grounding of positive, negative, and rack. You have not said if your DC system is grounded, and you have not stated the total voltage. I have seen utility 100 volt or higher batteries which are operated in a floating (unearthed) system, with a battery ground detector relay. If somewhere a single positive or negative lead becomes frayed and touches ground, nothing happens except the battery ground alarm sounds, and someone finds and corrects the ground. If the negative lead were intentionally grounded, then a ground anywhere in the system could cause equipment to operate unintentionally, or to fail to operate. As for the battery rack, it would take some work to prevent it from having at least a high resistance earth ground. If a metal rack sits on a concrete floor, or is bolted to a brick or concrete wall to prevent it falling over in an earthquake, then it is grounded to some extent, though perhaps with many ohms or hundreds of ohms of resistance. For it to be ungrounded, insulators would be needed below the feet and it would have to be isolated from the wall by insulating supports. The isolation would need testing on installation and periodically in service, since insulators can crack or grounds can otherwise occur. Then leakage current from the batteries due to acid spills, dirt on the cases, or stray wires would likely cause the rack to be at some undetermined voltage from ground. Depending on the battery voltage, this could present an electrocution hazard or at least a painful shock for anyone standing on the floor who touched the battery rack. Intentional grounding would require a substantial cable or cables permanently connected to the rack in a way that leaking acid will not corrode and make ineffective the ground connection, then connected to an effective ground, such as a system of ground rods driven deep enough to have a low resistance earth connection. The ground cable must be large enough to carry any fault current, as if a battery lead breaks and the battery gets connected to the grounded rack while there is an accidental or intentional ground somewhere. The available fault current from the battery you describe will be very high. Edison (talk) 19:02, 25 February 2011 (UTC)

Electric Field strength at a distance x from an infinite charged sheet

I was solving a problem based on Electric Field, and I noticed, that, in my derived formula for electric field at a distance x from a charged disc of radius R and charge density σ, $E={\frac {x\sigma }{2\epsilon _{0}}}({\frac {1}{x}}-{\frac {1}{\sqrt {R^{2}+x^{2}}}})$
When R tends to infinity, the surface becomes an infinite charged plane, and E is: ${\frac {{}\sigma }{2\epsilon _{0}}}$

Note that it's no longer dependent on x, i.e. the magnitude of the field is the same at all points in space (Except those on the plate)
I rederived the same formula for the infinite case with Gauss' theorem (the surface is a cylinder with its height perpendicular to the plane), and by summing up infinite strings.
My question is, why is E no longer dependant on x? Thanks, ManishEarth^{Talk • Stalk} 13:49, 24 February 2011 (UTC)

I fixed your formula for you. Your answer is correct. The field doesn't depend on x. Just use Gauss' law in a cylinder of length 2x with the charged plane placed symmetrically at the center of the cylinder to get the same result. Dauto (talk) 15:47, 24 February 2011 (UTC)

The reason that it no longer depends on x (distance) is that the farther away you are from the infinite plane the more charge you "see", that extra charge exactly balances the loss of charge force due to distance. Ariel. (talk) 19:20, 24 February 2011 (UTC)

Another way to look at it is that for an infinite sheet the field lines are all parallel to each other and perpendicular to the sheet. The flux density is therefore constant at all points. SpinningSpark 20:26, 24 February 2011 (UTC)

Thanks! I understand it better now! ManishEarth^{Talk • Stalk} 09:27, 25 February 2011 (UTC)

Semen omelet

Unpalatable question, but curiosity is king: Could you make an omelet or a quiche or something out of semen? For the sake of decency, let's say it comes from a free-range bull fed on alfalfa and organic blueberries. Perhaps I'm wrong to suppose that the substance would have the culinary properties of egg. If not, what would it be like when cooked? (Bonus question: Have the Japanese already done this?) LANTZY^TALK 14:05, 24 February 2011 (UTC)

Not a direct answer, but are you aware of Rocky_Mountain_oysters? SemanticMantis (talk) 15:30, 24 February 2011 (UTC)

Doesn't omelet/quiche rely on being made of Egg and don't the female of the species produce the eggs (Ovulation) or am I missing something here? ny156uk (talk) 18:21, 24 February 2011 (UTC)

Well, it's a bizarre question, but you do seem to be missing the point that the OP already knows what omelettes are traditionally made from. The idea of a semen omelette may sounds pretty unpalatable (literally), but I don't see how it's any more horrid than eating a tarantula egg omelette (which I've seen done). I guess the thought (and I don't mean to speak for Lantzy, but this is what I assume to be the case) is that semen, like eggs, contains a lot of protein and therefore might cook in a similar manner. My gut tells me (well, it's telling me not to take part in this thread, but I'm ignoring that) is that it wouldn't coagulate in the same way as even an all-whites omelette. An egg is a discrete object with a structure that gets remade/denatured during cooking while semen is a fluid lacking that kind of cohesiveness; I'm thinking it would turn out grainy or crumbly, but I'll definitely leave it to the OP to do whatever experiments they think would help. Matt Deres (talk) 18:57, 24 February 2011 (UTC)

We have an article on this: Milt. And we also have an article on Roe—hence Row, Row, Row Your Boat. Bus stop (talk) 19:03, 24 February 2011 (UTC)

Being the empirical sort I decided to try it. Fried it was tough, very much like goose eggwhite but with a stringier texture. Considering the time and effort required to obtain the materials, I will not be doing it again.

Focusing camera mounted on biological gel imager

On the top of our gel imaging equipment is a camera, allowing us to capture digital images of fluorescent bands of (usually DNA or RNA). The camera has a ring that we can adjust for zoom. It also has another ring which appears to alter exposure, which I surmise is the aperture. If I adjust the zoom, must I also adjust the aperture for a properly focussed image? Or will the image be equally focussed at all zoom level?

Changing the zoom on a lens is pretty fundamental, and you'll probably have to change the focus by a lot. Changing the exposure (time) or aperture (diaphragm) depends more on how desperate you are to get that faint little band you see to show up on the picture. As a rule, running the gel is enough of an expenditure of time and effort, even money, that you shouldn't hesitate to fiddle with every control on the camera trying to make it better (especially when it's digital!) ... just remember what it was before you started and put it back again so that people don't start murmuring. Wnt (talk) 16:05, 24 February 2011 (UTC)

Knowing what camera would help to give a better answer. Aperture affects the depth of field and the best (and same) f stop should satisfy all images in this application. This leaves only the speed to consider. So in other words: use the recommended f stop and don't fiddle with it!--Aspro (talk) 16:34, 24 February 2011 (UTC)

There are conceivable reasons to fiddle with an f stop - for example, depending on the thickness of your gel and thus the thickness of your bands, or if the surface of the gel is showing up too much for some reason and you want to try to blur that out a bit - but admittedly most of the time this isn't that important to fool with. Wnt (talk) 17:17, 24 February 2011 (UTC)

Note that if you zoom in more, the image will get darker. Some fixes for this are:

1) A brighter light. But too much might cook your sample.

2) A wider lens or lens opening (aperture/f-stop).

3) A longer exposure. Could cause motion blur if the subject moves.

4) Post-processing to brighten the picture. There's a limit to how much can be done this way, though. StuRat (talk) 17:11, 24 February 2011 (UTC)

1) When is flash going to cook a southern blot

2) What's wrong with keeping Aperture#Optimal_aperture

3) Just how fast do you think a southern blot needs to gallop along to cause blur?
--Aspro (talk) 17:28, 24 February 2011 (UTC)

Who says the OP is imaging a southern blot? Might be a regular agarose gel and the DNA might be going to further downstream applications, eg sequencing. In that case I at least wouldn't lengthen the UV-exposure. Albval (talk) 19:35, 24 February 2011 (UTC)

Nobody. Yet... Unless s/he is in the habit imagining places where the sun don't shine, the lens's best performances will be in a very small depth of field - if its a off the self purchase. Of course, the camera/lens system may be specially chosen, but we have not been informed of this yet. So southern blot blah, blah, blah, will it cover most lab camera applications until --or unless-- the OP provides more detail.--Aspro (talk) 22:57, 24 February 2011 (UTC)

Where is KT?

This question is about the iridium rich K-T boundary. Since the chalk of the Chiltern Hills is Cretaceous and the London Clay is Tertiary I am guessing that the K-T boundary lies at the junction of these two beds. Are there any outcrops around North London where the K-T boundary layer is visible? SpinningSpark 18:14, 24 February 2011 (UTC)

The Chalk Group extends up into the Paleocene, so the boundary lies within the upper chalk. According to this the Sarsen stones are derived from Danian age limestone (although our article calls them sandstone - something to check out), so they come from above the boundary, but I can't find anything about an exposure of this boundary in the Chilterns. Mikenorton (talk) 18:42, 24 February 2011 (UTC)

They may be formed in the Danian, but the Sarsens are apparently an example of silcrete, a superficial deposit resulting from weathering [4], so even if you could find the base of this, it wouldn't be a stratigraphic contact. Mikenorton (talk) 18:54, 24 February 2011 (UTC)

Finally, and sadly for your purposes, it seems that all of Britain was above sea level in the Paleocene (the Danian chalks I referred to are found in the North Sea) and there is definitive statement from here that "The earliest Tertiary deposit in Britain is the marine Thanet Sand Formation (Thanetian), a series of slightly glauconitic sands that rest directly on the eroded transgressive surface on Chalk". Sorry, Mikenorton (talk) 19:06, 24 February 2011 (UTC)

On a brighter note, if you fancy a trip to Denmark, you can see the boundary at Stevns Klint, probably the closest to the UK [5], see File:KPg stevns.png. Mikenorton (talk) 19:34, 24 February 2011 (UTC)

Thanks for the information. I was, of course, hoping the answer was going to be "it's at the bottom of your street, just past the pub." Thanks again. SpinningSpark 20:52, 24 February 2011 (UTC)

Uncertainty Principle - Doubt

I have a doubt about Uncertainty Principle. What does it really means ? It means that We cannot measure / know position / speed of anything with acuraccy better than h/4pi due to influence by at least photons in measurements or it means that electron (for example) doesn´t have position and speed precise and in consequence we cannot measure it ? — Preceding unsigned comment added by Futurengineer (talk • contribs) 20:04, 24 February 2011 (UTC)

We have a fairly detailed article with the obvious title "Uncertainty principle". There is some dense math and physics in there, but the very first paragraph or two directly answer your questions in pretty simple language. Idea of position of an electron is confusing because it's not purely a "particle", so you have to account for that as well when measuring it. The third and fourth paragraphs of the article address this idea. DMacks (talk) 20:13, 24 February 2011 (UTC)

Unfortunately, though, there is no simple and agreed answer as to what it really "means". It's connected with the general quantum weirdness, which poses problems for our intuitive realist approach to the physical world. If you read the answers provided in the usual references and feel that they don't really answer the question you were getting at — you're probably right. But I think we have an article on interpretations of quantum mechanics that at least provides a starting point for various ways in which physicists and philosophers approach the problem. --Trovatore (talk) 20:28, 24 February 2011 (UTC)

To put it very simply: it is most like the second proposition of yours than the first. It is not just about the inability to measure it. The measurement issue is a secondary one to the true quantum uncertainty. --Mr.98 (talk) 20:54, 24 February 2011 (UTC)

I believe it started with realizing that both could not be measured (your first interpretation), but over time people came to realize it's not just a measurement issue the values/concept does not actually exist for a particle (your second interpretation). And because of that particles can do some really strange things. Ariel. (talk) 22:00, 24 February 2011 (UTC)

Trovatore and Ariel, that's silly, and you shouldn't equate fairly simple quantum mechanical concepts with philosophy, as QM is no more an epistemological problem than anything in the classical-mechanical realm.

Futurengineer - when things get very small, we can't "see" them like we see everyday objects, simply because we really can only send one photon or electron at a time to look at an object that's of similar size (as opposed to, say, a blade of grass which we observe with literally billions of photons at once. So basically, we only get a "flash" of what the tiny object looks like at a particular time.

Now take an ordinary camera, which also can only take a "flash". If we want to photograph a moving car, we can make that flash exposure extremely quick, giving us a clear imagine of the car, except in the photo the car seems extremely still and lifeless. You could also let the exposure last a little longer, giving the car a "motion blur", but the image is much less sharp (see examples). So in the sharp image, we see very clearly where the object is, but it's still and lifeless, while in the blurry image, we can actually get an impression of the movement of the object, but it's position is blurry and less defined. The mathematics of the Uncertainty Principle article is a very strict, a priori definition of this phenomenon which occurs whenever we can only take "flashes" of an object we want to measure: we either get good position or good velocity, but we can never get both exactly. That's really all there is to it, quantified for the scale of our observation by Planck's constant, which is the only defining QM effect. You don't have to "believe" the principle - you can see it for yourself. SamuelRiv (talk) 22:10, 24 February 2011 (UTC)

I didn't say "epistemological"; it's more ontological. But yes, QM is absolutely more of a philosophical problem than classical mechanics. --Trovatore (talk) 22:38, 24 February 2011 (UTC)

(ec)That doesn't really explain the other uncertainty relationships - like energy and time. It also doesn't explain other effects like how if you constrain a particle in a box (i.e. the location is known) it's momentum becomes fuzzy. It's not just a measurement issue it's fundamental to the nature of reality. Ariel. (talk) 22:40, 24 February 2011 (UTC)

That's an incorrect explanation of the uncertainty principle. The HUP is a consequence of the fact that the momentum representation for a wavefunction is the fourier transform of its position representation (or the same could be said for any pair of conjugate variables). Since it's impossible to arbitrarily localize both a function and its frequency spectrum, you cannot accurately determine the value of two conjugate variables simultaneously. Also, there are quite a few philosophical difficulties with quantum mechanics in general. Truthforitsownsake (talk) 00:18, 25 February 2011 (UTC)

There is no such a thing as philosophical difficulties with quantum mechanics. Some people have philosophical issues with quantum mechanics, true. But that is problem for those people, not for the theory. The theory is completely self consistent and has been tested ad nauseam. That's all that is required from a physical theory. Dauto (talk) 02:42, 25 February 2011 (UTC)

Well, it's not just a problem for those people, as though they're making stuff up. There are genuine difficulties in turning QM's predictions into explanations. Explanation most certainly is part of the function of a theory (see e.g. Nagel on this).

Now, that's completely different from saying that these difficulties refute QM, which is a possible (though not necessary) reading of Truthforitsownsake's contribution. I personally do not make any such claim. I do however think that QM is sufficiently hard to reconcile with our intuitive metaphysics that people have a right to be confused. I think that a lot of times people who ask such questions get answers to different questions, and the person answering should at least acknowledge that it's not precisely an answer to the question that was asked. --Trovatore (talk) 05:19, 25 February 2011 (UTC)

Some philosophical problems are listed here: measurement and quantum theory[6], different interpretations of quantum theory[7][8][9]. Philosophical issues include: what constitutes an observer or a measurement, which entities in quantum mechanics actually exist and which are merely convenient fictions, what is the nature of quantum collapse and how it can exist alongside a smooth wave function, how many universes there are, whether objects exist independent of an observer, and how come there are imaginary numbers in the formulas. The question of whether this matters is itself a philosophical problem: are scientific theories meant to explain the world (in which case the philosophical issues are very relevant), or simply to produce useful outcomes (in which case they are less relevant) - as an analogy, if you had a box that seemed to predict the exact lottery numbers every week, would you want to know how it works, or would you simply accept that it works? --Colapeninsula (talk) 14:35, 25 February 2011 (UTC)

It means that there a movment back and forth to the futher and it afect now /thanks water nosfim . —Preceding unsigned comment added by 84.228.225.214 (talk) 05:42, 25 February 2011 (UTC)

See also quantum zeno effect. ~AH1^(TCU) 20:25, 26 February 2011 (UTC)

Colapeninsula: I will address your philosophical problems in turn: what constitutes an observer is anything that interacts with a particle, be it a photon, another atom, a strong-acting force, etc - the questions of "conscious observer" really aren't valid anymore. Functions vs existence have as much to do with classical mechanics as QM. Quantum collapse and QM in general have multiple equivalent interpretations, as does classical mechanics, but the physics is the same - what constitutes "reality" is a question for all of physics and math and epistemology - QM is nothing special in that sense. How many universes has nothing to do with basic QM (like the uncertainty principle) - it's associated with various cosmologies and particle theories. Whether objects exist independent of a conscious observer again has nothing to do with QM - it becomes a "tree falling in the woods" question, unless you're completely fringe. Imaginary numbers exist in QM theory because they exist in all wave theories as a convenience (though QM has a special complex term in the classical Lagrangian, but this again is a formulation that is nothing special about imaginary numbers). QM doesn't predict lottery numbers - it predicts the probability that a given lottery number will occur. I can do that right now - a pick-three lottery has a 1/1000 chance of giving 1-1-1. The point is that the uncertainty principle is not some kind of mystical magical entity - the ∆x∆y≥hbar form can be derived completely with classical wave theory (though the ∆E∆t form is a bit of trickery) - it exists for any wave that is measured by a forceful interaction. SamuelRiv (talk) 21:26, 26 February 2011 (UTC)

Samuel, you're glossing over some very difficult issues and not even acknowledging that they are issues. Whether a tree falling in the woods with no one to hear it makes a noise, may not be an issue for a logical positivist, but a realist (that is, most of us) considers it a real question that must have an answer. Similarly for the issue of which, if either, slit in the two-slit experiment the electron has really gone through. (The realist would accept the answer, "it's not a particle at all, but a wave, and therefore goes through both slits", but that then appears to be inconsistent with the granular nature of the response of the film.)

The different interpretations try to address these questions in various ways, which have various problems in being reconciled with our intuitive metaphysics sufficiently well to be called "explanations". If you just want to predict pointer coincidences (let's see if we have an article on that!) then QM does fine. But that's not enough for most of us. --Trovatore (talk) 21:55, 26 February 2011 (UTC)

Voice perceiving

Is there any differences between how I hear my own voice and how it's heard by others? Specifically, does my voice sound to others exactly the way it sounds to me? I became a bit suspicious when my mobile phone had echoed my voice differently from what I perceive it. —Preceding unsigned comment added by 89.76.224.253 (talk) 20:31, 24 February 2011 (UTC)

In short, yes, there definitely is a difference. Your own voice vibrates your skull and chest cavity, and you perceive these vibrations as well as the sound waves in the air. When other people hear you speak, they only hear the vibrations you've induced in the air. (WP:OR follows) So most people express some confusion the first time they hear themselves recorded, saying "Do I really sound like that ?!". Also, cell phones are notorious for the artifacts they introduce because of the high levels of compression they use. SemanticMantis (talk) 20:43, 24 February 2011 (UTC)

Definitely. My voice, when recorded, sounds quite a bit higher than it sounds to me. Of course the problem is not the recording, it is the difference of how our own voice sounds. — Preceding unsigned comment added by GaryReggae (talk • contribs) 20:49, 24 February 2011 (UTC)

So my actual voice is that on voice-recording devices? Weird :)) —Preceding unsigned comment added by 89.76.224.253 (talk) 20:50, 24 February 2011 (UTC)

Indeed. To get a fair idea of what you really sound like, it's worth it to get a decent recording in a quiet room with a good microphone (i.e. not cell phone, voice mail, laptop built-ins, etc.). SemanticMantis (talk) 21:09, 24 February 2011 (UTC)

Is this at least a partial explanation as to why some people think that they are great singers when really they are awful? Googlemeister (talk) 19:21, 25 February 2011 (UTC)

Maybe, but when singing alone, people tend also to imagine instruments playing, which makes them sound in reality much amusing. Quest09 (talk) 13:58, 26 February 2011 (UTC)

A classic trick by radio announcers, to hear how their voice sounded to others, was to use a finger to close one ear. The change in resonance approximated the way the voice sounded over the microphone. Gary Owens on Rowan & Martin's Laugh-In did this announcer trick. Edison (talk) 03:29, 26 February 2011 (UTC)

Electric shower temperature fluctuations

I have an electric shower that is frustrating me. I don't know whether the shower unit itself is knackered or if it is caused by outside factors.

I don't know exactly what the setup of the shower is but I am pretty sure it is one of those very common (in the UK at least) wall-mounted devices that go over a bath and heat water as it goes through. I can't see the inlet pipe(s) as it is concealed in the wall but I think these things only have a cold inlet. It works fine when first switched on but after a couple of minutes or so, starts to run cold. The shower has an LED marked with 'Reduce temp' on it and this illuminates when it starts running cold. There is also a very noticable change in the sound it makes - you can hear something (probably a thermostat) go click and then you can hear something turn off (a pump?). After about 30 seconds or so, the light goes out, the motor kicks back in and it gets back up to temperature before starting this whole cycle again.

What is causing it to do this? I have searched the web and looked at the WP page on showers but not been able to shed much light on the subject. Perhaps this type of shower is only used in the UK?

I can understand why there is a function to cut out as this is probably to prevent overheating. However, it should be regulating the temperature so that it doesn't get hot enough to invoke the safety limit. I am not sure that there is anything wrong with the actual shower as I have had this issue with other showers of the same type. But surely in the 21st century it should be possible to produce hot water at a constant temperature.

There are several other things that potentially complicate things. The first is limescale but it is not caused by a colleged shower head as I have unscrewed that and tried it with the hose pointed in the bath. It could potentially be furred up inside but I don't know. The second thing that could be an issue is whether there is a pump in there. I guess if the incoming water rate is inconsistent then it could cause the temperature to reach the limit. That said, I don't think there is a problem with the mains water pressure...it seems pretty good to me. The final point of note is that adjusting the temperature knob on the shower makes no difference to whether this problem occurs. The temperature when it runs is different but it still cuts out on a frequent basis.

So, are there any suggestions for sorting out this annoyance? Should I just get a new shower or is it pointless? Any ideas would be much appreciated! GaryReggae (talk) 20:47, 24 February 2011 (UTC)

These showers have a cut-out thermostat that prevents overheating. It is possible that the thermostat is working correctly but that limescale is causing it to register a higher temperature than was intended by the designers. If the thermostat is faulty then it can be replaced (many years ago I replaced one to give the shower unit years of further use), but this is probably a job for an expert who is both electrician and plumber because there are safety issues involved. If the cause is reduced water pressure as other cold-water taps are turned on then you will be able to see the change in water flow from the shower-head. Dbfirs 21:45, 24 February 2011 (UTC)

limescale would cause a lower reading, not a higher, or more accurately a slower reading, so instead of reacting quickly to temperature changes and cycling at a constant rate it's reacting slowly. Just a guess. Ariel. (talk) 22:03, 24 February 2011 (UTC)

Yes, that's true if the limescale is around the sensor and the heater is on the other side of the limescale. I was thinking of the scale impeding the flow, or the heater being on the same side of the limescale as the sensor. Dbfirs 07:42, 25 February 2011 (UTC)

Try replacing the shower head to see if that has any effect, as they raipdly get blocked. Although you tried the shower with the shower head removed, I think showers are often sensitive to pressure and so the open pipe may have made a difference to its behaviour. 92.28.246.36 (talk) 00:27, 25 February 2011 (UTC)

Pulsar Dyson ring

So my EE friend and I were looking at the pulsar page and when we saw the image of a pulsar's magnetic field his first instinct was to put a wire around it and use it to draw off power. That got me to thinking. Pulsars are relatively small and could fit inside a spaceship or a Dyson sphere or ring relatively easily to be harnessed as a source of massive amounts of energy. Has science fiction explored this idea? -Craig Pemberton 21:29, 24 February 2011 (UTC)

They might be small, but they are astonishingly heavy. If you have the technology to move something that heavy you probably don't need their energy. Plus their gravity is immense because they are so small and yet heavy - it's about as close as you can get to a black hole without being a black hole. But it's a cool idea. Ariel. (talk) 22:22, 24 February 2011 (UTC)

100 Oct LL Aviation fuel in car engines

My question is this: if I were to run 100 Octane LL aviation fuel in an average modern car, which is not supposed to take leaded fuel, would it be bad for the car? I ask this not because I want to run 100LL in my car, but every now and again I find myself having to dispose of aviation fuel, and am looking for environmentally friendly ways to do that (when testing fuel, we aren't supposed to put it back in the airplane). I figure that burning it in an engine is about the best thing to do with it, so why not in the car? Just as a note, 100LL is essentially normal automotive gasoline, except with a higher octane, lead, blue dye, and more stringent quality checks. Falconus^{p t c} 21:53, 24 February 2011 (UTC)

Lead will destroy (foul up) your catalytic converter. The converter will tolerate a small amount, but eventually will stop working, and then you'll fail a tailpipe test. It may also physically clog, but I think it's more an issue of the active components getting coated. You'll probably cause more environmental damage from your bad converter than you will from just burning the extra fuel. Just make sure to have a lot of air when you burn it (i.e. no smoke, small fire) and that's the best thing to do with it. You can also pour the fuel into a plastic soda bottle and just put it in the garbage. It will either be buried, or incinerated and both are fine. As long as it doesn't leak it will do no harm. Fill the bottle only halfway and squeeze out the air, to give it a cushion against being compressed. Write "aviation gasoline 100LL" on the bottle in case some future garbage-miner finds it. Ariel. (talk) 22:09, 24 February 2011 (UTC)

Also the blue dye is designed to stain your car's fuel system. If the police/tax men find a dyed engine, you can get prosecuted for fuel-tax evasion. What the smallest amount of dye that is detectable, and how long it lasts is a different matter. CS Miller (talk) 22:19, 24 February 2011 (UTC)

[EC] Do you have a source for that? I most certainly pay fuel taxes for 100LL, and I would be surprised if they would try to dye an aircraft engine. That's just one more variable. I have always been told that the blue dye is solely to distinguish it from MoGas, JetFuel, other Octane AvGases (which are died Green, Red, etc), etc. Falconus^{p t c} 22:28, 24 February 2011 (UTC)

Ah, I might have been mistaken. From our fuel dye article, some of the dyed fuels are dyed because they are low-rated duty, but for AvGas, as you said, it is to clearly indicate which grade of AvGas the fuel is. CS Miller (talk) 22:56, 24 February 2011 (UTC)

I'm not so sure about trashing fuel. I mean, if you ordered something like that to be shipped to you in the U.S., you know how it would come, in some fancy packaging with placards and whatnot. I doubt it would be ORM-D. I mean, if you trash it, some hydraulic ram or bulldozer is probably going to break open the container and spray fuel all over, and then, at best, you're likely to have some kind of trouble trying to find its way back to you. If you're going to do something faintly illegal with it, at least you could pour it all down a mine shaft and blow it up for fun. Wnt (talk) 22:53, 24 February 2011 (UTC)

How about using the fuel in a model aircraft? Nimur (talk) 22:25, 24 February 2011 (UTC)

I think it should be left at a collection site for harmful/dangerous waste. I do not know how it is handled in your state. The next best thing to do is probably to burn it in free air or in an engine without a catalytic converter. I would certainly not throw it in the thrash, especially not if the waste goes to a landfill, a plastic bottle will break sooner or later. --Gr8xoz (talk) 23:27, 24 February 2011 (UTC)

Actually soda bottles are quite strong - they are not easy to break, even on purpose. An ordinary garbage compressor will do nothing to them, especially if you only fill them halfway and squeeze out all the air. I think I will do an experiment involving a 5lb sledge hammer and an empty soda bottle. Ariel. (talk) 07:55, 25 February 2011 (UTC)

Most of them will probably not break immediately but I do not think a bottle will withstand the pressure if pressed between something hard and sharp and these [10] wheels on a 50 ton machine. I think most plastic bottles will begin to leak after some decades of exposure to gasoline. It will certainly leak some time in the future, in thousands or million years. It is highly irresponsible to recommend someone to throw toxic waste in the household garbage. There are also a very big difference between an empty bottle and an closed half filed bottle with uncompressable fluid.--Gr8xoz (talk) 13:31, 25 February 2011 (UTC)

While you may own a car with a catalytic converter and use an electric or push-powered lawnmower, perhaps you have a friend who owns a vintage automobile or uses gas powered lawnmower. -- 119.31.126.66 (talk) 11:38, 25 February 2011 (UTC)

Many modern gas powered lawnmowers have a catalytic converter.--Gr8xoz (talk) 13:31, 25 February 2011 (UTC)

Your local fire department will be happy to advise you on how to store and dispose of flammable liquids. Also, google for your local Hazardous Waste Disposal Centre and your local Recycling Centre might take it as well. In most civilized countries today it is illegal to dump it along with other trash. --Aspro (talk) 13:51, 25 February 2011 (UTC)

Wouldn't AvGas deplastisize a plastic soda bottle anyway? Googlemeister (talk) 14:17, 25 February 2011 (UTC)

Is there any value in rethinking the fuel testing protocols -- for example, having a stock of clean sterile and inexpensive containers for holding your fuel samples -- such that you could afterward put the fuel back into the airplane?? Solves the problem by making it not a problem in the first place... DaHorsesMouth (talk) 23:41, 25 February 2011 (UTC)

The thinking is to get all of the potential water and contaminants out that were in the bottom of the fuel tank, whether visible or not. It would defeat the purpose to return them to the fuel tank. Thanks for all the responses guys! Falconus^{p t c} 02:41, 28 February 2011 (UTC)

The fate of Voyager 1

According to its article, it will run out of power in 2025, but what happens after that when it's a powerless block of metal floating through space? Assuming it doesn't slam into a star, what will happen to it in the long run? Will it be gradually eroded by the interstellar medium, or burnt away by radiation, or will it slowly evaporate, or will it fall into the centre of the galaxy, or will something else happen to it? Or, indeed, will it stay around long enough to experience a cosmological fate like the big rip/big crunch? Smurrayinchester 22:42, 24 February 2011 (UTC)

You might find this discussion from last October interesting. Nobody really knows what happens to technologically-formed metallic objects over billion-year timescales. Micrometeorite impacts, exposure to extreme cold, vacuum, and high-energy cosmic rays and energetic particles will eventually degrade the lattice-structure of any metals. The objects are too small to self-gravitate into a hydrostatic equilibrium spherical ball (the material strength is orders of magnitude larger than the self-gravitation). In a sense, interstellar space is a pretty darned good clean-room - it's cold, empty, and very little is happening; but there are the occasional sand-granule, large asteroid, or mega-electron-volt energetic hydrogen nucleus slamming into the object. Accumulated across billions of years, those impacts with the spacecraft might stress-fracture or deform the material macroscopically. If the spacecraft is subject to tidal or gravitational forces, it may be sheared or drawn into a collision with a massive object. Nimur (talk) 23:15, 24 February 2011 (UTC)

There is no reason to assume it will be eroded by the interstellar medium, or burnt away by radiation, evaporate, or fall into the centre of the galaxy. Interstellar space will treat it exactly the same way that space treats meteorites. Ever since the planets and galaxies formed, meteorites that strayed too close to a planet or moon were drawn into it and destroyed on impact. Meteorites that were drawn too close to a sun or something else with an atmosphere were burnt up entering that atmosphere. The remainder of the meteorites are still out there, wandering around. It is reasonable to assume Voyager 1 will do the same. Dolphin (t) 02:41, 25 February 2011 (UTC)

On its current course, how long untill it enter's another solar system with sufficient solar radiation to recharge its solar panels? Should it still be able to relay interpretable imagery? Plasmic Physics (talk) 03:03, 25 February 2011 (UTC)

It doesn't have solar panels, it has an RTG. The article says it will be 40,000 years before it even comes close to another star (1.6 light years, which isn't very close). But even if it did start transmitting, it would no longer be pointed in the direction of earth. Ariel. (talk) 03:21, 25 February 2011 (UTC)

See the links which I provided at Wikipedia talk:WikiProject Environment#The (outer) Space Environment (permanent link here).

—Wavelength (talk) 16:18, 25 February 2011 (UTC)

Sorry, I must be confused with another probe. Plasmic Physics (talk) 21:58, 25 February 2011 (UTC)

It could possibly enter into a parabolic orbit when it crosses the outer limit of another star's sphere of influence (astrodynamics). ~AH1^(TCU) 20:22, 26 February 2011 (UTC)

Pioneer Anomaly

Hi. I was browsing the usually laughable Conservapedia website when I came across this quote regarding the Pioneer spacecraft anomaly by a Dr D Russell Humphreys: "The only non-standard assumption I used was that the matter of the cosmos is limited in extent, with a fair amount of empty space beyond the matter—an assumption supported by the Bible. With those relatively modest beginnings, I was able to explain the Pioneer anomaly — it’s due to a change in the ‘fabric’ of space. In fact, this anomaly could be the first local manifestation we have observed of the expansion of the cosmos, and the first evidence that expansion is occurring in the present, not just the past. The assumption I used violently contradicts the foundational assumption of the big bang, which says the universe has no centre and no edge. In that model, the fabric of space would not change. Consequently, the big bang model has been unable to explain the anomalous Pioneer acceleration"

I don't really understand what this guy is trying to say, and less whether it has any connection with real science. Can anyone enlighten me? —Preceding unsigned comment added by 81.129.125.167 (talk) 22:48, 24 February 2011 (UTC)

Frankly I don't really see how this would explain the Pioneer anomaly (which may not have anything to do with the fundamental laws of physics — it's likely something quite banal). It's unclear to me why this "fabric" of space (what, exactly, does he mean by that?) being "changed" (changed how?) would affect only the Pioneer satellites and not, say, all of the planets that are further out from said satellites. Anyway, whatever the merits of this guys theory, it would have to be put into actual astronomical terms before it could be really evaluated. The above description of it is insufficient to make sense of what he's proposing. --Mr.98 (talk) 22:59, 24 February 2011 (UTC)

Wikipedia has an article on Russell Humphreys, though it doesn't say much about his cosmology. It does say that his cosmology predicts that the Earth has a (proper) age of ~6000 years, which is contradicted by a huge body of evidence, so it's pretty much a non-starter. I might glance through his book if I find it online for free, but in my experience (some of it firsthand!) it's common for people with new theories of everything to imagine that they've explained some unexplained phenomenon on the most amazingly flimsy evidence. I doubt that he has done a single calculation of the magnitude of the supposed "change in the fabric". For what it's worth, the shell theorem applies in general relativity, meaning that the Pioneer anomaly can't be explained by adding or removing distant matter (unless, perhaps, it's done in a non-isotropic way). -- BenRG (talk) 01:53, 25 February 2011 (UTC)

Natural gas

How much of it is burned every day? --T H F S W (T · C · E) 23:17, 24 February 2011 (UTC)

According to BP (boo, hiss), 2940.4 trillion cubic meters was consumed in 2009, which gives an average of just over 8 trillion per day. Clarityfiend (talk) 04:45, 25 February 2011 (UTC)

Just for clarity, is that at STP or is that in some conditions? With numbers that large, and when dealing with a gas, it makes a big difference as to what conditions it is being counted under? If it is at non-standard conditions, the volume numbers would be less meaningful than, say, mass numbers might be. --Jayron32 05:19, 25 February 2011 (UTC)

Based on this I don't think that number is accurate. You mean billion (10^9), not trillion (10^12). And Natural gas#Energy content.2C statistics and pricing has info on what the unit means. Ariel. (talk) 05:49, 25 February 2011 (UTC)

Yes billion is what the source says Nil Einne (talk) 17:33, 25 February 2011 (UTC)

D'oh. Clarityfiend (talk) 20:52, 25 February 2011 (UTC)

World production in 2008 was 3.127 trillion cu m[11] so I don't think consumption was nearly 1000 times that. --Colapeninsula (talk) 15:12, 25 February 2011 (UTC)

infra red radiation

how does infra red radiation make something warmer — Preceding unsigned comment added by Lufc88 (talk • contribs) 23:30, 24 February 2011 (UTC)

Most molecules, if not all, absorbs infra red better than wavelengths of EMR. The energy bound within the radiation is converted to kinetic energy of the molecules. Since temperature is a measure of the mean thermal kinetic energy of a system, the temperature is also raised.

Infrared is prefered due to the very nature of molecular bonds. Plasmic Physics (talk) 23:43, 24 February 2011 (UTC)

Thanks — Preceding unsigned comment added by Lufc88 (talk • contribs) 23:53, 24 February 2011 (UTC)

February 25

Shine-Dalgarno sequence

How is this pronounced? "Shine" as in the word "shine"? Nadando (talk) 00:02, 25 February 2011 (UTC)

The Wikipedia article on John Shine, for whom the sequence is part named, gives no pronunciation guide, which weakly suggests that it is indeed not out of the ordinary for someone of apparently Anglo-Saxon heritage, as can be seen here. 87.81.230.195 (talk) 01:18, 25 February 2011 (UTC)

Greenhouse effect from producing methane

If you plant trees, you are extracting CO2 from the atmosphere. What would happen, in terms of greenhouse effect, if you produce methane with this biomass from the trees and release it into the atmosphere? I know that burning the methane would bring you back to the CO2, but this is a hypothetical question. Quest09 (talk) 01:51, 25 February 2011 (UTC)

Methane is also a green house gas. And it is pound for pound much stronger than CO2. Dauto (talk) 03:31, 25 February 2011 (UTC)

(ec)Methane has a much stronger greenhouse effect than co2, but it doesn't last long. It reacts with oxygen and essentially burns. See Global warming potential. Ariel. (talk) 03:34, 25 February 2011 (UTC)

Yes, I know, but since you are also removing a green house gas from the atmosphere, even if it's to produce other, the question remains, is the balance positive, or negative - in terms of greenhouse effect? Quest09 (talk) 12:17, 25 February 2011 (UTC)

Because methane decays faster than carbon dioxide, you need to specify a timescale. Global warming potential is the time-dependent factor used to compare different gases. It is calculated by mass. One mole of CO₂, molar mass 44g, would presumably be converted to one mole of CH₄ (methane), molar mass 16g. So one mole of methane has 0.36 the mass and over 20 years around 72*0.36=26 times the global warming potential. Over 500 years one mole of methane has around 7.6*0.36=2.76. So even over 500 years, converting the CO2 to methane would be worse. Unless my sums are wrong, which is fairly likely! --Colapeninsula (talk) 15:31, 25 February 2011 (UTC)

It doesn't matter, because methane decays to carbon dioxide. You'll have a certain period with a much more potent greenhouse gas, and then you'll get back the original greenhouse gas that you were trying to avoid. Releasing methane is always worse than releasing an equivilent amount of CO₂. Buddy431 (talk) 17:53, 25 February 2011 (UTC)

Methane does not decay to carbon dioxide. It reacts with hydroxyl radicals and forms CO2 and water. 212.169.176.233 (talk) 22:21, 25 February 2011 (UTC)

I'm just using the terminology that user:Colapeninsula. Maybe "react" or "degrade" is a better term in this case, but it's really just semantics. The point is, methane (a greenhouse gas) doesn't last long in the atmosphere, but in being destroyed, it produces another, less potent but longer lived greenhouse gas, carbon dioxide. In fact, that gas is the same gas that would have been produced if the tree had been burned, and is produced in the same quantities, assuming that carbon is not converted into other compounds. Buddy431 (talk) 01:06, 26 February 2011 (UTC)

Methane capture technology is useful for electricity generation. Anoxic decay (better links available?) of plant matter (for example submersed in water) produces methane, as do methane clathrates. ~AH1^(TCU) 19:55, 26 February 2011 (UTC)

Rest mass

Okay, so suppose two electrons initially at rest begin to repel each other. They will evidently speed up, but the total momentum will remain zero. The total mass will remain zero as well, so that energy is conserved. That means that each electron's mass will remain constant. But $m={\frac {m_{0}}{\sqrt {1-v^{2}}}}$. So does that mean the electron's rest mass decreases? 74.15.137.130 (talk) 06:29, 25 February 2011 (UTC)

Why would the total mass of the system be zero? The electron has a non-zero rest mass, see Electron#Fundamental_properties. --Jayron32 06:37, 25 February 2011 (UTC)

Erm, I meant remains constant, sorry! 74.15.137.130 (talk) 07:15, 25 February 2011 (UTC)

Let me answer the question I think you are asking. In the initial state both electrons have potential energy - and the potential energy shows up as mass. Once they repel each other the potential energy gets converted to kinetic energy, which also has mass. So it's not enough to just calculate the mass due to velocity, you also need to include the mass due to potential energy. (Which BTW is almost impossible to do in practice - if someone on the other side of the planet turns on an electromagnet my magnet here suddenly has more potential energy since it could in theory be drawn toward that electromagnet, this is also true of a magnet on the other side of the universe, so in practice it's impossible to include all sources of potential energy.) Ariel. (talk) 07:18, 25 February 2011 (UTC)

Wanting to be able to work out the potential energy without considering all possible long-distance interactions is one good reason that we set the 0 of potential energy at infinity: then if that electromagnet turns on, your magnet merely has the possibility of negative potential energy. (Potential potential energy, I guess.) Its current potential energy doesn't change. Another reason to set that 0 is that it lets us (at least approximately) localize the potential energy within the mass of the object. (It's approximate because the EM/gravitational fields have some of that energy; see my further reply below.) If electrons were defined to have, say, 1 eV of potential energy even at infinite separation, we'd have to count up all the electrons in the universe and subtract that many eV from the measured mass of the electron to find its "true" mass without all of those interactions. --Tardis (talk) 15:53, 25 February 2011 (UTC)

Momentum staying zero doesn't imply that mass is constant. In this case, the momentum vectors are opposite and equal in magnitude, so the mass of the two particles is the same at any point in time (assuming velocities same--which you get from symmetry) but it can decrease or increase. So the mass of the electron decreases, but the rest mass is a constant, like the speed of light in a vacuum. Similarly, you can pass light through water, and its speed decreases, but that doesn't affect the speed of light in a vacuum. ManishEarth^{Talk • Stalk} 09:37, 25 February 2011 (UTC)

This is one of the many questions where "mass" merely causes confusion. Just say energy, and then throw in $c^{-2}$ if you don't like the units. I don't know what definition of mass you're using when you say it decreases: maybe some sort of "apparent rest mass" derived by removing the kinetic energy and supposing the rest to be rest mass. But in this case that's just the true rest mass plus the electrostatic potential energy, so we can just say that the latter is decreasing and be done with it. If we simplistically assume that the electrons do not radiate, then by simple symmetry the total energy (aka relativistic mass) of the electrons must remain constant because the total over both is conserved and each must always bear half of it. Yet another way of looking at it is that the electrons have their rest masses and the electric field in their vicinity has additional energy (mass/whatever). If you work out the energy of that field (which requires some care around infinities), you'll find that it drops as the charges separate, such that the process may be described as the electrons absorbing some of the energy from the electric field and manifesting it as kinetic energy. --Tardis (talk) 15:53, 25 February 2011 (UTC)

Hmmm, what's sort of odd about that is that when, say, an electron raises or drops a few levels in a nucleus, the light that mediates this is quantized and can be expressed as a particle. But how is the energy stored in the electric field quantized and described? (It has to be photons, but it seems hard to figure out where they are, how many there are, what frequency, and above all what prevents them from escaping) Wnt (talk) 04:01, 27 February 2011 (UTC)

medicine gaity-400

details about medicine gaity-400 —Preceding unsigned comment added by 220.225.96.217 (talk) 07:33, 25 February 2011 (UTC)

Gaity is a brand name for Gatifloxacin, 400 is the dosage in mg. See the linked article on it for more info - in particular note that it is considered unsafe and has been taken off the market, but still seems to be available in China and India. Unfortunately the article neglects to say what it's used for but it seems to be an antibiotic. Also, I've created a redirect for Gaity. Ariel. (talk) 07:51, 25 February 2011 (UTC)

pvc

is Vinyl Flooring pvc or another plastic — Preceding unsigned comment added by Wdk789 (talk • contribs) 09:01, 25 February 2011 (UTC)

Yes, PVC, but with Plasticizers to make it flexible (unlike white PVC water pipes which don't have any). Ariel. (talk) 09:19, 25 February 2011 (UTC)

Surge Protection

Hi, how much surge protection in power adaptor of consumer electronic devices like a TV or STB should be enough? Thanks? Dearkundan (talk) 10:06, 25 February 2011 (UTC)

It depends entirely on the stability of your AC power. I currently live in a residential area of California, and we "never" have power spikes - the electric current out of our wall plugs is pristine. So I consider surge-protection redundant, (in a sense because I'm trusting my power company). But I've lived elsewhere on other power grids, and also on a home electric generator; in those times, I would pay a lot more attention to the surge protector and/or invest in a uninterruptable power supply for important/expensive electronics. Surge protector explains some of the parameters to worry about - clamping voltage, total surge energy dissipation capacity. Larger total-energy capacity will mean that you can sustain multiple, repeated surges, or one very large surge, but let's be honest - if lightning strikes your transformer or distribution box, no surge-protector has the capacity to absorb and dissipate that level of energy. It's been my experience that a UPS is the best way to keep nasty power lines (particularly, if the power is coming from a generator) from zapping my equipment, but UPSes are much more expensive. Nimur (talk) 16:16, 25 February 2011 (UTC)

how to find hot and cold temp

calculate hot and cold temprature after 25 orbit .assume a 100kg sherical spacecraft is in an equatorial orbit.How is calculation different for a spacecraft in a 90 degree polar orbit 124.124.247.141 (talk) 11:19, 25 February 2011 (UTC)

Sorry, the Reference Desk will not answer your homework for you. The clues you need will probably be in your textbook or in your notes from class. Matt Deres (talk) 11:38, 25 February 2011 (UTC)

EM wave and magnetic field

Can a em wave and a magnetic field create a stream of electrons. Like the opposite of a cavity magnetron like when a magnetic field and a stream of electrons creates a em wave —Preceding unsigned comment added by 82.38.96.241 (talk) 11:50, 25 February 2011 (UTC)

Yes. Like most physics, Maxwell's equations are invariant under T-symmetry. 213.49.110.245 (talk) 18:41, 25 February 2011 (UTC)

Is there a example of it happening naturally or artificially. —Preceding unsigned comment added by 82.38.96.241 (talk) 19:19, 25 February 2011 (UTC)

Electron precipitation might count. A radio-signal from Earth (usually man-made, but sometimes caused by lightning), sends an electromagnetic wave or disturbance into the Earth's magnetosphere. The electromagnetic wave interacts with the steady-state magnetic field and the magnetically-confined plasma at high altitudes; and sometimes, electrons "squirt out" and rain down to low altitudes. It's a very complex process, though. Various ground experiments, atmospheric remote-sensing experiments, and satellites have investigated this phenomenon: here's a sensationalized (but scientifically accurate) account of killer electrons from space. Nimur (talk) 19:43, 25 February 2011 (UTC)

Sorry to bother you again but what does 'gyroresonate' mean in this context 'Some of the VLF waves from these transmitters will leak through the ionosphere, couple into the magnetosphere, and gyroresonate with trapped particles leading to particle precipitation.' — Preceding unsigned comment added by Lufc88 (talk • contribs) 19:58, 25 February 2011 (UTC)

The term "gyro-resonance" is a short-name for electron cyclotron resonance. This gyro-resonance describes the most simple type of electron motion in a magnetic field. The electron cyclotron resonance article describes it in more detail, but very briefly, it means that an electron (or other charged particle) flies in a circular or helix-shaped orbit around the magnetic field-lines. This is due to the Lorentz force, which describes how a charge moving through a magnetic field experiences a force perpendicular to the direction it is traveling - causing a circular-shaped orbit. In Earth's magnetic field, the magnetic field lines are non-uniform, because of the shape of the Earth's magnetic field. Also, the exact value of the magnetic field strength varies at any specific location, due to complicated interactions with radio waves and plasma. As a result, the path that each electron "flies" can be very strangely-shaped. Due to gyro-resonance, electrons spiral around in "circles", and due to field-parallel motion, these "circles" get stretched into "coil-shapes" (a helix). The size of those spirals ranges from a few meters, to more than a kilometer in radius. As the electrons also move parallel to the field-lines they follow a curved path along the Earth's dipole field, so they also bounce back and forth between the north- and south- polar regions of the earth, tracing out thousands of kilometers of motion. If, during any of these motions, the electron ever reaches a "very low" altitude (say, about a hundred miles above the ground), it's very likely it will "knock" into a gas molecule in our atmosphere. This causes the electron to lose energy, and so it can no longer sustain its magnetic-field interaction, and falls to earth (usually "zapping" a gas molecule in the ionosphere and creating new electromagnetic waves).

I should say - when a radio wave is in gyro-resonance, it means that the radio wave is at the same frequency as the electron's circular orbit frequency. This is a bit like a matched impedance - it means that energy can flow from the radio signal into the electron. Nimur (talk) 21:18, 25 February 2011 (UTC)

Thanks — Preceding unsigned comment added by Lufc88 (talk • contribs) 21:28, 25 February 2011 (UTC)

Malaria - could I be infected with malaria and not know about it?

I wanted to donate blood today, but I was sent away to take a test for malaria instead. I lived in India 15 years ago and according to Polish law I have to be tested for malaria before I am allowed to donate blood. Does this regulation make any sense? I assume I would have found out a long time ago if I had been infected with malria so this test will be just a waste of my time and the taxpayers money. Mieciu K (talk) 15:46, 25 February 2011 (UTC)

Makes some sense AFAIK Plasmodium vivax is capable of surfacing after quite long dormancy periods (many years) although the one I had Plasmodium falciparum is not. --BozMo talk 15:56, 25 February 2011 (UTC)

(e/c)P. vivax and such don't go away until you get cured. Chances are you would have noticed, but it's theoretically possible. It's worth noting that blood donation controls are a little on the paranoid side, mostly because people have this irrational fear of diseases from blood transfusion that leads them to refuse transfusions that might save their lives. SDY (talk) 15:57, 25 February 2011 (UTC)

Given that there have been notable instances of diseases transferred by contaminated blood products, a little healthy paranoia is probably warranted: Contaminated haemophilia blood products, HIV-tainted blood scandal (Japan), [12]. Recently, there's been some scare about people getting donated blood from people who later developed vCJD. It's unclear how well (if at all) CJD is transmitted through blood, but most blood officials are erring on the side of caution (rightly so, in my opinion). The BBC article I linked to above details the case of what's believed to be the first vCJD transmittion through contaminated blood (though symptoms never showed themselves, and the man died of other causes). Buddy431 (talk) 17:50, 25 February 2011 (UTC)

Here in Spain, you can donate your blood no matter what, but you also get asked lot of question, including in which countries you have been. It gets tested only after the donation. I don't know if this is a better system, but it seems evident that you need to test for possible hidden risks. 212.169.184.39 (talk) 16:29, 25 February 2011 (UTC)

Well, the blood can only be tested after the donation, can't it? Here in the US, one interesting feature of blood donation is that there's a big box that you can check on one of the forms telling them: "Destroy my blood after I leave". I think the reason for the box is in case a donor hears all the questions ("Have you had homosexual sex in the last X years"; "have you ever traded drugs or money for sex"), and answers "Um, no, certainly not" out of embarrassment or shame, then the donor may be insecure enough to actually go through with the entire donation so the questioner won't detect the donor has done these things. And then make sure not to endanger others. (Yes, some of these questions are becoming a bit controversial.) Comet Tuttle (talk) 18:31, 25 February 2011 (UTC)

No. There's a difference of about 400 ml between a donation and a simply extraction. For testing your blood, they only need a little. Homosexuals are still considered a risk group, although the most logical question would be: how many partners/with or without condom/anal or not. But, I suppose that's too personal for most donors. Anyway, I doubt that blood contaminated with HIV gets through the system. 212.169.176.233 (talk) 22:14, 25 February 2011 (UTC)

Well, to give an idea of the absurdity of it, the U.S. and many other countries ban blood donations from any man who has had sex with a man since 1977. Several countries making reforms to this policy have reduced this period to one year.[13] Such policies, no matter what they turn out to be, are probably a combination of public relations and defensiveness against liability suits, representing largely the relative political power and social status of each group affected, with only a small element of medicine involved. Wnt (talk) 01:55, 26 February 2011 (UTC)

You should read this explanation of why exactly the UK excludes men who have sex with men as donors, which the Terrence Higgins Trust currently supports. It is based on the body of evidence, although the current review of recent evidence may lead to changes. Blood contaminated with HIV can indeed get through the system, even though every donation is tested for it, especially if the donor is only recently infected: this is why they go to such lengths to discourage donations from people who might be infected, and include information on how to get tested for HIV if you think you might be infected (rather than treating blood donation as a test). 86.166.42.200 (talk) 13:59, 26 February 2011 (UTC)

The word I have been looking for is Asymptomatic carrier "a person or other organism that has contracted an infectious disease, but who displays no symptoms." Are there any human asymptic carriers of malaria? I have already donated 4 or 5 times in Poland always stating in the questionare that I lived in India for over 6 months but until today nobody took notice of this. Mieciu K (talk) 16:50, 25 February 2011 (UTC)

Vivax malaria isn't nearly as dangerous as falciparum, which causes almost all of the malaria-related deaths, and the symptoms of malaria aren't very specific and could theoretically be mistaken for some other illness if mild enough or if misdiagnosed. Here in the states, a blood donor is considered "at risk" for one year after travel to a malaria risk area and is not allowed to donate, with the exception of Korea (longer deferral due to some unusual strains in that area). No testing is ever done. Honestly, malaria, especially non-falciparum, is not a big deal for a well-equipped medical system (compared to, say, other transfusion-transmitted infections), as there are several fairly cheap and reliable cures available, so even if someone "got through" it's easy to fix. The tragedy of malaria is that "cheap" cures, like a $4 course of an ACT or the even cheaper synthetic quinine derivatives, are too expensive for many of the people affected. Presumably they use the testing instead of forcing donors to wait after traveling, which means you get more donations if your donor pool is mostly people who travel (most notable in the US with the Armed Forces Blood Program). SDY (talk) 20:47, 25 February 2011 (UTC)

Note that is you carry one sickle-cell anemia gene, you may have a partial resistance to malaria, but still be a carrier. This gene is more common among blacks. See Sickle-cell disease#Genetics. StuRat (talk) 22:50, 25 February 2011 (UTC)

As detailed in the Plasmodium article, the hypnozoite stage can lie dormant for many years, but is less common in the falciparum form. Wnt (talk) 03:20, 26 February 2011 (UTC)

In 2004 after about 25 years of blood donation in the UK my blood was declined in Spain because I had lived in the UK during the 90s. I was told that I was at risk of carrying bovine spongiform encephalitis prions (the incorrectly named mad-cow disease) At that time Spain was free of that disease. Richard Avery (talk) 08:21, 26 February 2011 (UTC)

water survival

Assuming that you did not drown, die of thirst, or be eaten by sharks, how long could a person survive in the ocean if the water is 85 degF? Googlemeister (talk) 16:03, 25 February 2011 (UTC)

There may be some links leading to a specific answer to that at Hypothermia#Water. WikiDao ☯ 17:56, 25 February 2011 (UTC)

Not at 85F. If you had water to drink and a buoyancy jacket I would imagine starvation would be the next barrier at that temp. --BozMo talk 17:59, 25 February 2011 (UTC)

According to this chart, that is correct. :) WikiDao ☯ 18:12, 25 February 2011 (UTC)

A question related to this was discussed last year. To recap, the longest authenticated record of survival in open water is 5 1/2 days, by a shipwrecked Japanese sailor in World War II. Looie496 (talk) 18:37, 25 February 2011 (UTC)

I would think that overheating could be a problem during the day. If the water is 85°F, how hot is the air ? And add to that sunlight in the day. If overheating wasn't an issue, then sunburn might be. This could eventually lead to ruptures in the skin and then infections. StuRat (talk) 22:41, 25 February 2011 (UTC)

Sunburn would be a problem. Overheating would impossible in those conditions.

I think overheating might be possible. Specifically, if the air temperature is well over body temperature, humidity is 100%, and if the Sun is shining brightly, and if the people have short, dark hair and maybe dark skin, then their brains might overheat. They could continually dunk their heads underwater to cool off, but might not do so if they fall asleep during the day or if their flotation device prevents this. Splashing water on themselves might help, but as their energy gets lower, from lack of food, they may stop doing this. StuRat (talk) 21:07, 27 February 2011 (UTC)

Excessive jellyfish and any exposure to marine pollution (depending on location) may be another concern. ~AH1^(TCU) 19:06, 26 February 2011 (UTC)

Round and round the cell pellet goes.... how fast do you spin yours?

Is 1000 g not a rather large force to subject cells to in culture? Will it cause many cells to burst? Sigma Aldrich (at a course I went to) and Invitrogen (here) suggest 100-200 g, yet the place where I work routinely uses 1000 g. I'm planning on investigating the effects by counting cells before and after centrifugation, to see if many have "disappeared". In fact, I think I'll go and do it right now. --Seans Potato Business 19:07, 25 February 2011 (UTC)

Didn't seem to make a difference. *shrug* ----Seans Potato Business 19:59, 25 February 2011 (UTC)

Because the cells are inside water (fluid) they don't really experience the full effects of that force. Cells and water have nearly the same density, so while they feel a downward force, so does the water, which counteracts it. The only thing left is the small difference in density from water. Ariel. (talk) 20:02, 25 February 2011 (UTC)

Carbon dating

On Wikipedia today, I came across a claim that carbon dating once showed that two volcanoes from Hawaii that erupted in 1800/1801 erupted millions/billions of years ago (and that presumably, carbon dating is discredited). A quick websearch showed that this claim was repeated on various young-earth creationist websites. This had me wondering - what is the actual scientific explanation for this phenomenon, as I'm not as willing to dismiss carbon dating out of hand? Kansan (talk) 20:34, 25 February 2011 (UTC)

Carbon dating doesn't work for millions or billions of years anyway. But assuming you mean tens of thousands then if the sample is in water it can mess with the results, making the sample appear to be older than it really is. I've read that if your sample is, or ever was, in water, you can not use carbon dating on it. And unfortunately people are not always careful about this. Ariel. (talk) 20:41, 25 February 2011 (UTC)

How do you carbon-date a volcano, anyway? Doesn't that process require once-living material? APL (talk) 21:07, 25 February 2011 (UTC)

I'm pretty sure all you need is some trapped atmospheric CO2. Although I'm not sure you could get that with volcanic rock, since the gases are from the volcano, not the atmosphere. Ariel. (talk) 21:10, 25 February 2011 (UTC)

See uranium-lead dating and my comment below. Nimur (talk) 21:30, 25 February 2011 (UTC)

Carbon dating measures the carbon in things that use to be made out of plants or use to eat plants. It's used to measure the age of fabrics in archeological sites, frozen mammoths, mummies, etcetera. It is not used on things that are made out of rock, like dinosaur fossils or volcanic rocks, because they never breathed in any carbon isotopes.

Maybe they are dating plants that lived and died on the slopes of the volcano? Ariel. (talk) 21:12, 25 February 2011 (UTC)

Except nobody would do that since they already knew when the volcano erupted - and presumably with a much better margin of error than they'd get with even calibrated carbon-dating. Matt Deres (talk) 21:21, 25 February 2011 (UTC)

That may be a perfect reason to do it: To calibrate the tests. Ariel. (talk) 02:33, 27 February 2011 (UTC)

Comment - it's very common to see the term "carbon dating" used incorrectly. Radiocarbon dating measures the ratio of Carbon-14 to Carbon-12, and is "scientifically useful" only over a few thousands of years. Many other types of radioactive dating exist - our top-level article is radiometric dating. In all cases, the idea is to compare ratios of isotopes measured in a sample against those of a control-group. The assumption is always that the relative abundance or ratio of an isotope depends on the condition the object was in - so if it were buried underground, its expected isotope mix is different than if it were exposed to air (for example). Pop-science publications rarely get the subtleties correct - and often just say "carbon dating" when they really mean some other scientific radiometric assay. Nimur (talk) 21:25, 25 February 2011 (UTC)

It's also common for creationists to use a straw man argument, that by finding one discrepancy in a field, they then claim that the entire field of science is thus discredited. For example, one misidentified fossil is used to "prove" that all fossil evidence is bunk. This is, of course, total nonsense, as a complete T-Rex skeleton is definitely not a deformed elephant, or whatever else they claim. Now, I have no idea if anybody mis-dated a volcano by that long, but, if so, it certainly doesn't invalidate the method, just that particular measurement. StuRat (talk) 22:36, 25 February 2011 (UTC)

Thank you very much for the excellent answers. Kansan (talk) 21:42, 25 February 2011 (UTC)

In my view it is a blunder to try to explain what is wrong with a claim without having a clear and specific statement of the claim in the first place. Could you give a pointer to where on Wikipedia you saw the claim you are talking about? Looie496 (talk) 03:37, 26 February 2011 (UTC)

Fortunately, it isn't in mainspace. It was on Talk:Behemoth, but was removed as a rant unrelated to the page. See here: [14] Kansan (talk) 21:41, 26 February 2011 (UTC)

These two deal with the problem.

• doi:10.1016/0012-821X(69)90160-5
• doi:10.1007/BF02597188

And these are creationists trying to interpret the 40 year old measurments :

• 200 Year Old Lava Dated 2.96 Billion Years Old?
• How do you date a volcano?
• The Cause of Anomalous Potassium-Argon

--Stone (talk) 11:30, 26 February 2011 (UTC)

You might want to check Mark Isaak's Index to Creationist Claims, in particular this page that debunks the claims. [15] and [16] are about similar claims, but the first page has links to where I assume the claim mentioned byt the OP comes from.Sjö (talk) 11:42, 1 March 2011 (UTC)

Singular Value Decomposition and prediction

I'm working on a project where I have an existing dataset where each record contains some textual data and a metric relating to that data. My plan had been to represent this as a matrix where columns were records and rows were 'terms' (n-grams) - so that each element was the frequency of that term in that record.

I'd then hoped that I could augment this with the metric as an additional row, and use the incremental SVD to determine a relationship between the terms and this metric such that, when given an new (i.e. not in the training dataset) incomplete record where I have only the textual data (which I can represent as a vector of frequencies of terms), I could attempt to predict the metric for that record.

However, whilst I'm more-or-less okay with the SVD in principle, I'm unsure of its use for prediction (so my question here is 'how do I do this?'). Looking at various papers, particularly on product/movie recommendation, it looks like I'd have to add the incomplete record to my matrix and then compute the SVD, then... do something. However, this seems like it would be incredibly slow to work. 131.111.255.9 (talk) 22:08, 25 February 2011 (UTC)

All SVD does is decompose the input vector into a different set of coordinates (an output vector), with the intent that most elements in the output vector are close to zero. The SVD algorithm will produce a matrix that transforms between input- and output- coordinate spaces. The output vector is now in a new coordinate-space, whose unit-vectors are usually pretty abstract (they don't necessarily correspond to any observable property of the input-space).

If your input vector represents word frequency, what exactly are you trying to predict? Nimur (talk) 22:19, 25 February 2011 (UTC)

Yes, please tell us what data you have and what you are trying to predict, then we can recommend an extrapolation or interpolation method. StuRat (talk) 22:29, 25 February 2011 (UTC)

I'm trying to predict the metric. The text field explains an idea, and the metric is a retrospective numerical assessment of the quality of that idea. So, given a dataset of ideas and their qualities, can I discover some relationship between some aspect of the text and the potential quality of the idea it represents. Sorry for the vagueness, I'm not sure precisely what I can disclose. We've tried a few methods so far, and the SVD was recommended to us as an avenue to pursue. 131.111.255.9 (talk) 23:01, 25 February 2011 (UTC)

Singular Value Decomposition can be used to reduce the number of dimensions of the problem se [17] so other methods can be used on the reduced problem but I do not know how it can be applied directly. I think a naive implementation would just reduce to a least square algorithm. You need a Supervised learning algorithm such as Support vector machines. I think the software Weka (machine learning) can be useful to you.--Gr8xoz (talk) 14:30, 26 February 2011 (UTC)

If you can't disclose the actual data, could you come up with a similar example, so we can tell what kind of data you are working with ? StuRat (talk) 21:01, 27 February 2011 (UTC)

February 26

Entropy Quote

Resolved

 – Smallman12q (talk) 04:00, 26 February 2011 (UTC)

Entropy currently has the following unreferenced quote:

Any method involving the notion of entropy, the very existence of which depends on the second law of thermodynamics, will doubtless seem to many far-fetched, and may repel beginners as obscure and difficult of comprehension.

— Willard Gibbs, Graphical Methods in the Thermodynamics of Fluids (1873)

Unfortunately, it doesn't seem like their is a digitized version of the 1873 Graphical Methods in the Thermodynamics of Fluids. Can anyone confirm this quote with a reliable source?Smallman12q (talk) 02:30, 26 February 2011 (UTC)

The same quote appears in the collection of his scientific papers vol 1 (Relevant area of Graphical Methods.. is on page 11) available on archive.org here (record overview here). Nanonic (talk) 02:52, 26 February 2011 (UTC)

Thanks!Smallman12q (talk) 04:00, 26 February 2011 (UTC)

"Graphical Methods in the Thermodynamics of Fluids (1873)" looks like a reference to me. Just because there isn't a link to an online version doesn't make it unreferenced... --Tango (talk) 23:42, 26 February 2011 (UTC)

Sucking the wind

Once upon a time, the waters of the earth were thought to be infinite, and we poured all manner of crap into them because we did not know that the crap didn't just get diluted to oblivion, and eventually caused damage.

Are we on a similar path today with wind energy?

A few windmills here and there certainly don't have a noticeable impact on anything. But, if a few hundred of them become a few thousand or a few tens of thousands, will converting the energy of the wind to motion and thence to electrical power "slow down" the wind enough to have an impact on something else? What if the wind, like the water, is not an infinite resource, for us to use up as much as we can?

Seems inconceivable -- but we once thought that of the oceans, too. DaHorsesMouth (talk) 04:26, 26 February 2011 (UTC)

It's not inconceivable at all. Large objects, such as mountains, do have a profound impact on weather and climate, see Rain shadow and we are well aware how man-made structures affect weather and climate (see Urban heat island, which notes that one side benefit of these manmade hot spots is how they decrease the likelyhood of tornadoes; which is why it is rare that tornadoes will hit major cities). It is not inconcievable at all that large-scale windfarms could alter weather and climate patterns in many ways; indeed I don't think anyone is claiming that they wouldn't. The question over their usage isn't that they are zero-impact; literally NO power source is to be zero-impact; its that the negatives of windfarming, while very real, are also very much smaller than the negatives of burning fossil fuels. I don't think anyone claims that the technology is harmless, just less harmful than what we are doing now. Environmental effects of wind power would be a good place to look at some of the real concerns with windfarming. --Jayron32 04:46, 26 February 2011 (UTC)

The impact of wind power on climate has been studied in [18]. They found that over 100 years the magnitude of the impact is one fifth of that of current power production. Wind power gives a direct effect on the climate while CO2 will accumulate and the effect will increase with time. They also showed that the impact will partly be the opposite of that from C02. Wind power slows down the heat transport from the equator towards the poles while the polar regions (not sure about definition.) will be most effected by CO2 warming. They calculated simulated wind power usage at the same scale as the current total energy usage, 15 TW.(All fuels, renewable power, nuclear and so on, excluding the the solar energy used by plants in farming and so on.). This [19]article suggests that the oceanic heat transport could also be sensitive to differences in wind patterns.

It is interesting to compare the scale of the different energy flows:

• Total solar power: 3.8*10^26 W
• Solar power hitting the earth: 174 000 TW (1 TW=1*10^12 W)
• Total wind power :1000-4000 TW (conflicting estimates, better figures probably known)
• Total photosynthesis 75-2250 TW (Depends on if you count energy used by the plant it self and other issues with the definitions.) (approx. 25% of the photosynthesis are used or directly affected by humans.[20])
• Geothermal power from radioactive decay and cooling of the inner parts of the earth: 44 TW
• Total human power consumption: 15 TW (In technological systems, not solar energy or non fuel biomass in e.g. agriculture, forest.)
• Total tidal power: 3.75 TW
• Total wave power: 1-10 TW
• Total human electricity production: 2 TW (uses about 5 TW primary energy.)
• Total human wind power production in year 2009: 0.04 TW

If human power consumption continues to increase with 3% a year or 20 times in a century (Approximately the increase year 1900 to 2000) it is obvious that wind power is not unlimited but it can make a significant contribution to power usage at today's level. With 3% yearly increase in power consumption not even the total solar power on earth is enough year 2350.

--Gr8xoz (talk) 12:44, 26 February 2011 (UTC)

Depending on the scale of wind production, large-scale wind farms could potentially slow local/global wind speeds by a measurable amount according to numerical modelling studies. See the following articles from LiveScience: Nov 2004 Nov 2008 Oct 2010. ~AH1^(TCU) 18:40, 26 February 2011 (UTC)

Availability of the generic Adderall XR

"In 2009, Barr and Shire reached a settlement agreement permitting Barr to offer a generic form of the drug beginning April 1, 2009."[8] I just read the above quote in Wikipedia. Last month I was told by three pharmacies in my home town that the company is no longer going to make the generic capsule. I have ADHD and the capsule was working well for me. The price was right too. Does anyone else make a generic capsule? The brand is too expensive for me even with the help of insurance. Thank you. —Preceding unsigned comment added by 24.197.183.193 (talk) 06:00, 26 February 2011 (UTC)

Barr is owned in a roundabout way by Teva who still have generic Adderall listed as a product on their website. Global Pharma still have generic Adderall XR listed on their website. The best people to contact for confirmation of continued availability would be those companies. Nanonic (talk) 06:27, 26 February 2011 (UTC)

Humbucking pickups and 60Hz hum

I have an electric guitar with humbucker pickups, which are designed to cancel out 60 Hz hum. I am thinking about getting a guitar with P-90 pickups, with are not humbucking. I have a lot of compact fluorescent in the house and I am worried about picking up hum (from them and any other sources). Will these cause hum on the guitar? Will any compact florescent bulb in the house cause hum, or only ones on the same circuit breaker? Bubba73 ^{You talkin' to me?} 06:39, 26 February 2011 (UTC)

Compact fluorescents put out electromagnetic interference, but mostly in radio frequencies interfering with radio reception. Your main problem with guitar pickups will be magnetic fields. You should keep any power cords away from the pickup leads or guitar. Electric motors will have a much bigger effect than lights. SO keep these away too. If cords have to cross, do this at right angles. Keep the cords short. Do not create earth loops. Graeme Bartlett (talk) 22:28, 26 February 2011 (UTC)

Then I'll probably be OK. No motors except when the A/C or an appliance is running, and they aren't close. Not too many power cords running around. Thank you. Bubba73 ^{You talkin' to me?} 00:31, 27 February 2011 (UTC)

Modern florescent lights use electronic ballasts (both CFLs and tubes), but old ones used magnetic ballasts - those will probably interfere. One way to tell is simply to listen - the old ones hummed a little. A second way to test is wave your hand under the light. With modern fixtures your hands will simply "smear" out, with old one you will see a sort of strobe effect and you'll see images of your hand in various positions. (The old ones flashed at 60hz, modern ones at many thousands of hz.) Ariel. (talk) 01:29, 27 February 2011 (UTC)

Thanks. Some of the CFLs are up to 7 or 8 years old. Sometimes they start making a sound when they are going bad. There are a few long tube florescents in the kitchen that make noise - they may be the old type, but they are not on most of the time. (BTW, I ordered a guitar with non-humbucking pickups tonight.) Bubba73 ^{You talkin' to me?} 05:19, 27 February 2011 (UTC)

What's the problem with non-native species?

Why are conservationist groups so concerned about the introduction of non-native species to new environments? It's not like it's a new phenomenon (species have been migrating around the planet for hundreds of millions of years, e.g. the Great American Exchange) and it actually seems quite unnatural to try and prevent non-native species from taking hold on new territories. I know new species may be detrimental to the survival of native ones, but that's what natural selection is all about, no? Who are we to get in its way? --Leptictidium (mt) 10:50, 26 February 2011 (UTC)

The funny answer would be: Than have fun with the tigers in your suburb and the crocodiles in the public pool. Frogs do not migrate from Africa to Australia and rats were unable to cross over to New Zealand so why should humans help them. Humans are simply stupid to know what they are doing and at the end they do harm to their environment that it become less providable to live there.--Stone (talk) 11:11, 26 February 2011 (UTC)

"but that's what natural selection is all about, no? Who are we to get in its way?" -> http://en.wikipedia.org/wiki/Naturalistic_fallacy#Other_uses 213.49.110.245 (talk) 11:53, 26 February 2011 (UTC)

Rabbits in Australia. Vimescarrot (talk) 12:23, 26 February 2011 (UTC)

In the Sahal the sourthern part of the sahara desert people use non native herds of cattle and goat which unlike camels strip the grass right down to there roots this leaves the ground bare and the soil gets blown away and eventually it causes desertification which is land turning into desert this is a real damaging effect on the enviroment. Also non native goats and wildboar have been extremely damaging to the enviroment and wildlife populations. —Preceding unsigned comment added by 109.77.244.8 (talk) 12:34, 26 February 2011 (UTC)

Humans can speed-up the introduction of new species many times the natural rate. The human activity in an area is adapted to the historical environment there, it can be costly to adapt to handle the consequences of new weeds, or other spices. Evolution is most efficient when there are many weakly connected habitats and high biological diversity. If all habitat with the same conditions get the same ecosystem then it is mush more sensitive to changes, say fore instance that a new pest develops. --Gr8xoz (talk) 13:16, 26 February 2011 (UTC)

See non-native species and invasive species for more examples of the damage they can cause.--Shantavira|^{feed me} 13:37, 26 February 2011 (UTC)

However, non-native species do not always cause damage. They may simply take over from an equivalent native species. Concern about this (such as concern over the loss of the red squirrel to the grey squirrel and its associated pox) seems to me to be conservatism rather than conservation (unless, perhaps, conservation is its sub-category). See damage for a discussion of the different meanings that the word takes on when used within different value systems - oh wait, that doesn't work (it's just a disambig page). Well, imagine it did. 213.122.25.248 (talk) 14:39, 26 February 2011 (UTC)

The main problem is that invasive species tend to fill an occupied ecological niche and outcompete the original species in a way that alters the proportions of predators and prey. The introduced species often creates a rapid directional selection in the other species within that ecosystem and those species cannot evolve quickly enough to adjust to this new state. Notable examples of invasive species include the emerald ash borer, dandelion (especially New Zealand), large blooms of Nomura's jellyfish (not strictly invasive but oceanic changes are encouraging blooms), purple loosestrife, the common reed, and the historical Y. pestis. ~AH1^(TCU) 18:31, 26 February 2011 (UTC)

While the mechanism is true it is not necessarily clear that it is a problem. It can be a problem if it affects human activity in a negative way or if for some other reason the old ecosystem is valued higher than the new one.--Gr8xoz (talk) 23:29, 26 February 2011 (UTC)

Another problem with invasive species is that they may hybridize with native forms. This is important with things like killer bees, coy-dogs and mosquitoes transmitting West Nile virus. Hybrids have a larger gene pool to draw upon, and can evolve rapidly, e.g. hybrid speciation. Though measures of environmental damage usually focus on the loss of species, I would suggest that the evolution of new species could also be a major environmental challenge. Wnt (talk) 00:53, 28 February 2011 (UTC)

Did we just call speciesation and rapid evolution an environmental challenge? What else is the biosphere supposed to do? Mac Davis (talk) 14:19, 28 February 2011 (UTC)

It would be an environmental challenge for us. Clearly the biosphere is free to do as it "wishes" - even extinction represents a natural reaction to circumstances - but when such change is imposed on a rapid timescale by human action, it doesn't seem all that natural or benign. Wnt (talk) 16:35, 28 February 2011 (UTC)

Scientific American did a short interview in the Feb '11 issue with Mark A. Davis, who argues that invasive species aren't all that bad, in general. Certain examples, such as the brown tree snake in Guam, aside, the introduction of exotic species to new locations isn't necessarily a negative thing, he says. The interviewer summarizes by saying "the field needs less emotion and more science." The interview leaves me with about 100 questions, though, because it's very short and superficial. Davis does have a new book out called Invasion Biology, which might be more informative. -IceCreamAntisocial (talk) 18:10, 28 February 2011 (UTC)

Converting % and ppm to g/kw-hr

I am working on a project, to determine the level emissions from generators. The values from the Gen. sets using an exhaust gas analyzer are in % and ppm, which has to be compared to international standards,which are in g/kw-hr. what is therefore the conversion rate. For example,CO and CO2 are in percentage (%), while HC and NOx are in parts per million (PPM).I will be most gratefull to be assisted in converting to g/kw-hr. Sample:

                                                CO=6.62%;4.71%;3.67% etc
                                                CO2=5.63%;7.27%;7.84% etc
                                                HC=136ppm;145ppm;152ppm
                                                NOx=40ppm;60ppm;68ppm

Thank you in anticipation

—Preceding unsigned comment added by 41.78.80.94 (talk) 12:40, 26 February 2011 (UTC)

You need to know the mass of the exhaust gas produced then generating 1 kWh. If you know the amount of fuel and fuel type used to produce 1 kWh then that could be used to get a rough estimate. --Gr8xoz (talk) 12:56, 26 February 2011 (UTC)

Victoria waterlily

Why do these have a high raised lip? I presume it isn't for buoyancy, since they seem to stay afloat even when pushed partly underwater (they have some sort of air pockets, don't they?) ... and if it was for buoyancy, what would happen when it rains? Besides, there is a cleft at one point on the circumference (to let rainwater out?), which would be a poor design for a boat. 213.122.25.248 (talk) 14:46, 26 February 2011 (UTC)

I think you answer your own question. The lip aids in buoyancy, but the cleft prevents filling with rainwater. SemanticMantis (talk) 16:48, 26 February 2011 (UTC)

I guess. I suppose the lip helps a bit, despite the unlikeliness of a human designing a boat with a big hole in the side. It's an odd-looking evolutionary compromise. I'm not even sure it makes logical sense. If, when there is some water inside, the pad is buoyant enough for the water to run out the gap, wouldn't this still be the case with no lip? I can only think its purpose is to prevent sudden flooding, like in the case of being jumped on by one of those giant Amazonian otters ... but the article says the leaves are very fragile, so the leaf would be punctured by the otter's feet anyway. Maybe the point is to protect against being splashed by animals? 81.131.21.81 (talk) 16:57, 26 February 2011 (UTC)

Ok, here's a few other things to consider.

• The leaf doesn't need to be a boat; it doesn't 'want' or need to have much Draft_(hull).
• Under no load, the 97% rim is quite effective at keeping out all kinds minor slosh/ ripples of water, regardless of the source. This is good for the plant in terms of gas exchange and photosynthesis.
• If the leaf submerges for any reason, it can more easily drain and resurface due to the gap compared to a full rim.
• The 97% rim allows allows the leaf to stay afloat under small dry loads, such as frogs, insects, and detritus.
• A full rim would not be much advantage over 97% rim in most circumstances, and is worse in a the case of submersion.
• There may be genetic limits to the leaf#morphology, wherein a full rim is more difficult to achieve than it's worth. Most traits do indeed strike some sort of balance or trade off, i.e. as described with respect to shade tolerance here [21].

In short, I conclude that the 97% rim is a benefit due it its effects on buoyancy. Also, the cleft is not a big problem, and in fact provides additional benefits. I don't think a trait this distinct is ecologically neutral. Indeed if there are any suggestions for benefits aside from buoyancy issues, I'd be interested to hear them :) SemanticMantis (talk) 17:56, 26 February 2011 (UTC)

Oh OK, that's very good, particularly the part about needing to stay dry, rather than avoiding a risk of sinking. Thank you. 81.131.21.81 (talk) 17:59, 26 February 2011 (UTC)

It's an interesting question. On the other hand, if the lip is so great, we might wonder why it's not more common among water lilies... SemanticMantis (talk) 18:37, 26 February 2011 (UTC)

I did wonder that. It might be a thing which is only needed at large scales for some reason (*waves hands*). It might be that the non-Victoria waterlilies have better water-repelling surfaces (this is achieved by tiny hairs, or some amazing quantum effect and/or goretex). It might be (this is my bet) that there is much more detritus (particularly falling twigs, or falling branches which could cause splashes) in the Amazon than in your typical pond elsewhere in the world. 81.131.21.81 (talk) 18:53, 26 February 2011 (UTC)

I think you're on to something with scale. Those leaves are huge. For species with smaller leaves, surface tension plays a relatively larger role in keeping the leaf afloat, so the rim isn't as useful. A small needle can float on surface tension, but a large nail can not. SemanticMantis (talk) 20:06, 26 February 2011 (UTC)

This picture of Victoria amazonica would argue against that. Ariel. (talk) 02:28, 27 February 2011 (UTC)

While we are speculating wildly, what about preventing the leaves from overlapping? That seems like a simpler explanation; overlapping would have a big impact on photosynthesis, obviously. -- Scray (talk) 02:02, 27 February 2011 (UTC)

Sure, preventing leaf overlap is probably another slight benefit. SemanticMantis (talk) 17:07, 27 February 2011 (UTC)

Electrons circular orbit frequency

Can a electrons circular orbit frequency be changed or altered — Preceding unsigned comment added by Lufc88 (talk • contribs) 18:08, 26 February 2011 (UTC)

Do you really expect anybody to know what you are talking about without a little more context?? Dauto (talk) 19:57, 26 February 2011 (UTC)

It is asked in the context of my question above called EM wave and magnetic fields — Preceding unsigned comment added by Lufc88 (talk • contribs) 20:37, 26 February 2011 (UTC)

Do you mean Electron cyclotron resonance? If you do, as you can see by yourself in the linked article, the frequency depends on the magnetic field. Dauto (talk) 00:57, 27 February 2011 (UTC)

Thanks sorry about that i did not see that bit — Preceding unsigned comment added by Lufc88 (talk • contribs) 12:44, 27 February 2011 (UTC)

Ruhmkorff lamps

"Finally we had all the necessary chemicals for the Ruhmkorff lamps."[22] -- Jules Verne. Journey to the Centre of the Earth

How do you make a Ruhmkorff lamp? I saw the foreign languge links in Heinrich Daniel Ruhmkorff, but I'm looking for some simple step by step procedure. And what chemicals are used? Thanks. -- Uzma Gamal (talk) 20:09, 26 February 2011 (UTC)

As the article states, you need a Geissler tube and a source of electricity. Apparently they were powered either by a battery or a portable generator (which maybe fed the battery?). DMacks (talk) 20:27, 26 February 2011 (UTC)

The Google link didn't work for me, but from s:Journey_into_the_Interior_of_the_Earth/Chapter_XI:

"Ruhmkorff's apparatus consists of a Bunsen pile worked with bichromate of potash, which makes no smell; an induction coil carries the electricity generated by the pile into communication with a lantern of peculiar construction; in this lantern there is a spiral glass tube from which the air has been excluded, and in which remains only a residuum of carbonic acid gas or of nitrogen. When the apparatus is put in action this gas becomes luminous, producing a white steady light. The pile and coil are placed in a leathern bag which the traveller carries over his shoulders; the lantern outside of the bag throws sufficient light into deep darkness; it enables one to venture without fear of explosions into the midst of the most inflammable gases, and is not extinguished even in the deepest waters. M. Ruhmkorff is a learned and most ingenious man of science; his great discovery is his induction coil, which produces a powerful stream of electricity. He obtained in 1864 the quinquennial prize of 50,000 franc reserved by the French government for the most ingenious application of electricity."

The same page says "all the articles needed to supply Ruhmkorpff's apparatus", but doesn't specify what they were. (it lists "a row of phials containing dextrine, alcoholic ether, liquid acetate of lead, vinegar, and ammonia drugs which afforded me no comfort" just before that, but I think these are actually intended for human use???) I have to assume that the unspecified ingredients are the material needed to supply the Bunsen pile. Wnt (talk) 21:05, 26 February 2011 (UTC)

Looking over it, I still can't be sure - probably you'd need zinc anodes, sulfuric acid, and the potassium dichromate mentioned; with the sulfuric acid being used to convert that to chromic acid in the Bunsen pile. Such a pile wouldn't emit NO₂ - I'm not sure what sort of chromium salt would come out of it, but I think it would avoid the noxious fumes, hence the "makes no smell" in the text. Note however that hexavalent chromium has quite a bad reputation nowadays. Wnt (talk) 22:06, 26 February 2011 (UTC)

The Ruhmkorff coils would be called "induction coils" in publications from the early 20th century onward. Such a device has a primary coil fed at a low voltage, such as 6 volts, which coil acts as an electromagnet to attract the armature of an interrupter switch, which on being attracted breaks the current for a bit. A spring then recloses the primary circuit. This is the same as how a DC doorbell or buzzer works. Wound around the same magnetic core of a bundle of steel wires is a secondary coil with hundreds of times more turns which produces impulses of several thousand volts every time the primary circuit makes and breaks. The device is a transformer fed by pulsating DC. This is how primitive spark wireless telegraphy got its high voltage in the early Marconi days. The Geissler lamp is like a fluorescent lamp, but without the white phosphorescent coating which generates the nice white light. A basic Geissler coil would have been a dimmer light with less of a broad spectrum than a fluorescent light. Such a coil is rather a current hog, and a substantial and thus very heavy battery would have been needed to run it for extended periods. Short battery life and low light output are arguments against the basic system Verne described. So an induction coil, or a Model T spark coil, would be the "Ruhmkorff" device, and an evacuated tube like a neon sign would be the light emitting element. The battery described would be a complex 19th century wet cell, but as a demo you might use a modern rechargeable battery of the voltage the coil primary is designed for, such as 6 volts. A fluorescent tube, even a "dead" one, will glow brightly when connected to one output terminal of the induction coil. Note: painful and possible dangerous shocks from the high voltage generated are very likely., even from the primary circuit. I found it helpful to ground the primary circuit, a difficult task if the device is carried around. Further caution: High voltage can produce xrays from the light tube connected to the high voltage, so don't try this at home. A battery powered fluorescent lamp would be a modern and safe analog of the Vern lamp. Edison (talk) 02:36, 27 February 2011 (UTC)

Though to be fair, we have altogether lost the artistry of the Geissler tubes depicted in the article, especially as one considers the light such intricate baubles would shed in caves of fantastic minerals in the unknown depths of the Earth. I do concede, however, that whatever Verne said, such a high voltage circuit seems quite likely to involve sparks that would set off firedamp, especially if it truly used a buzzer mechanism. (though would it possible, in concept, for a well-crafted Bunsen pile to reach the needed voltage simply by using thousands of cells cleverly linked to be filled from common reservoirs?) Wnt (talk) 03:04, 27 February 2011 (UTC)

Verne did not suggest that a battery of 2000 cells, like Humphrey Davy's Great Battery of the Royal Institution, circa 1808 was carried on someone's back. Much easier to carry a primary battery which could produce 6 volts at several amps for several hours, and an induction coil with an interrupter to produce 4 kilovolts or so to make the Geissler tube glow. He might also have imagined an incandescent lamp powered by the battery, since one passage in the book says the battery was connected to the "filament" of the lamp. All he needed was an 1860's carbon filament in vacuum lamp, with a late 1870's vacuum pump. Then they would simply have had flashlights. Edison (talk) 06:18, 27 February 2011 (UTC)

You're right on this one. I was only speculating at a way to try to avoid the sparks, but among other problems you point out such a massive pile would not use the induction coil Verne specified. (Alternatively, maybe there's a way to encapsulate the entire relay/transformer mechanism to prevent contact with the air ...?) Wnt (talk) 16:33, 28 February 2011 (UTC)

Tricky physics problem

Dear Wikipedians:

I am working on the following tricky physics problem:

a 0.234 kg shoe is dropped onto a vertically oriented spring with a spring constant of 104 N/m. The shoe becomes attached to the spring upon contact and the spring is compressed 0.117 m before coming momentarily to rest. What work is performed by the weight of the shoe while the spring is being compressed?

My first approach is the gravitational approach:

W = mgh = 0.234×9.8×0.117 ≈ 0.268J

My second approach is the spring approach:

W = ½kx² = ½×104×0.117² ≈ 0.712J

I would tend to the 0.268J answer, but the computer system is rejecting both of my answers as wrong! I have only one more try left and I am desperate to see where I went wrong.

Your help is much appreciated.

174.88.35.131 (talk) 21:02, 26 February 2011 (UTC)

The gravitational approach doesn't consider any kinetic energy the shoe had upon hitting the spring. Not sure about the spring method, looks OK to me. Grandiose (me, talk, contribs) 22:18, 26 February 2011 (UTC)

The question is a little odd. I can't quite work out what it wants. Since your two answers don't work, the only other thing I can think of is to take the difference between the two. That is, calculate the work done by the resultant force on the shoe. That's not how I would have interpretted the question, but you've already tried my other ideas. --Tango (talk) 23:55, 26 February 2011 (UTC)

How many significant digits your answer is required to have? The data of the problem has three significant digits, and given that the average value of earth's surface gravitational acceleration is actually 9.81m/s^2, I'm getting W = 0.269J. If that turns out to be the correct answer to this problem I would say that this computer program is too picky. Dauto (talk) 00:08, 27 February 2011 (UTC)

It sounds like the shoe free-falls, then continues to drop as it compresses the spring. Both these things must add up to account for the force that the spring absorbs when compressed. Hmmm, on second thought, that should simply be the .712 figure, since all the force of the shoe goes into the spring (with typical frictionless assumptions and one-dimensionality it could rebound endlessly). But the question doesn't ask about the force of the shoe, only the work done by the weight of the shoe. That's just (F=mg=2.2955) x distance = (0.117 m) = 0.269 after all. Hmmm... Wnt (talk) 03:07, 27 February 2011 (UTC)

Is there a documented possible link between gender identity to sexual orientation?

Ya know, in a superficial way it seems that indeed there is, i myself don't agree and i think that even if there is, it ain't that robust...

but, what does the research shows to us?, is there a link?, and if there is, how significant it is by this stage of the research?

thanks and blessings,

Beni —Preceding unsigned comment added by 109.66.8.242 (talk) 22:56, 26 February 2011 (UTC)

I think it is rather well established that most persons that identifies them self as male primarily are sexually attracted to women and vice versa. I think almost every one agree that this is true in at least 80% of the cases, is it this correlation you want documented or did I misinterpret the question?--Gr8xoz (talk) 23:09, 26 February 2011 (UTC)

The question only makes sense if you ask: if my gender identity doesn't match my biological gender, which sexual orientation do I have? Normally that of the biological gender you wish to have... —Preceding unsigned comment added by 212.169.187.124 (talk) 00:08, 27 February 2011 (UTC)

Yes, normally but not always. Dauto (talk) 00:58, 27 February 2011 (UTC)

My guess is that the intended question is something more like this: If all you know about someone is that they are cisgender, what (if any) information does that give us about the statistical likelihood that they are also heterosexual? And I don't know the answer. --Allen (talk) 08:14, 27 February 2011 (UTC)

What does it mean to say that this transgender person is heterosexual? Is that according to his biological or intended gender?Quest09 (talk) 00:11, 28 February 2011 (UTC)

Presumably the term "transgender heterotsexual" would apply to person born with male sex characteristics, living as female gender identified, who is attracted to the male gender. Just a terminology note: Biological traits determine sex, but gender is a socio-cultural construct."Intended gender" would probably be considered a loaded term to some. The OP's entry needs clarification if s/he wants more help. SemanticMantis (talk) 00:39, 28 February 2011 (UTC)

February 27

Why is blood iron test taken from finger?

When one donates blood, at least in the UK, they first test your blood to make sure you're not anaemic. To do this, they prick your finger and deposit a couple of drops of blood in cylinders of fluid - if a drop sinks, you have enough blood iron and you're okay to donate. Out of curiosity alone, this leads me to a couple of questions:

1. Can someone point me to a description of the actual mechanism of this test (the sinking blood bit) - what's in the cylinders, etc. Wikipedia's article about blood iron/haemoglobin tests seem to all be about fancier lab tests not this rough-and-ready one.
2. Why must they take blood from a finger (as Penfield's homunculus shows, one of the most nerve-ending-rich places in the body)? I asked the technician if they could take it from elsewhere, and he said they had to use the finger, but didn't know why.

Thanks. 91.125.171.235 (talk) 00:42, 27 February 2011 (UTC)

Re: 2; This is a fairly rough test for your Haemoglobin (Hb) level; sadly neither the WP article on Haemoglobin or blood test covers it in any detail, but fingerprick does mention that it's "typically quicker and less distressing than venipuncture".

The Hb level in blood from your fingertip won't be significantly different from that from anywhere else. The "technician" probably had no idea.

Probably the real answer is "fingertips are easy to get at without removing any clothing". Though fingertips are sensitive you'll hopefully have found that by the time you've given your blood donation, had your cup of tea and removed the sticking plaster from your fingertip the sharp prick of the sample is but a distant memory.

I've an appointment to give my 38^th unit next month - I'll be sure to ask about the above (particularly 1 above as I've always wondered too). If I get an answer I'll put it on my userpage. Tonywalton ^Talk 01:10, 27 February 2011 (UTC)

The blue solution is copper(II) sulfate (see this section), and here PMID 2646909 is a reliable source referring to the screening procedure. That paper is more than 20 years old, and I presume that since then the cutoff (i.e. the specific gravity of the solution used for the screening) has been adjusted to improve the test's performance. Entries here and here describe the procedure in more detail. -- Scray (talk) 01:34, 27 February 2011 (UTC)

Interesting that the specific reagent is available for sale here . -- Scray (talk) 01:37, 27 February 2011 (UTC)

(ec) I'd thought it looked like CuSO₄, however the system in the UK is that the blood drop goes into a blue (sulphate)- looking tube for males but a green (looks more like copper carbonate) tube for females. I'll be sure to read the refs above tomorrow (it's 1:44AM here, and I need some sleep!) Tonywalton ^Talk 01:47, 27 February 2011 (UTC)

It could just be that they add dye so people don't mix them up and they are the same thing just in different concentrations because the acceptable iron level is different for males and females (is it? If it isn't, that would invalidate my theory! I know women often have lower iron levels due to menstruation, but I can't see how that would make the safe level different). I've never seen this green liquid you describe, but then I've never donated blood as a woman! Are you sure they use different ones? --Tango (talk) 02:14, 27 February 2011 (UTC)

More recent, showing the cost-effectiveness of CuSO₄ screening: PMID 20808648 -- Scray (talk) 01:39, 27 February 2011 (UTC)

Additional detail on the performance and characteristics of the test here. -- Scray (talk) 01:42, 27 February 2011 (UTC)

Regarding site: this PMID 11274589 suggests that use of earstick (rather than fingerstick) tends to under-estimate anemia. -- Scray (talk) 01:46, 27 February 2011 (UTC)

Further, this page discusses "microcollection" (about 80% of the way down the page) and the issue of pain receptors in fingertips, stating that despite this problem it's preferred. -- Scray (talk) 01:50, 27 February 2011 (UTC)

Its easier to get a small drop of blood of the size used for this hematocrit test that can be dropped into the tube of solution from the fingertip with a stick from a micro lancet than if, say the forearm were stuck, but it should be possible to use alternate sites as is now done for diabetic blood sugar testing. Maybe they just like to keep using this early 20th century technology because it is cheap compared to some new meter and test strips which could measure iron in smaller droplets. But If the pain of the fingerstick is too much to bear, then the pain of the blood donation would be worse. Edison (talk) 14:23, 27 February 2011 (UTC)

Measuring iron concentration from a small volume of blood might be feasible, but it will not accurately assess degree of anemia. There are multiple carriers of iron in the blood other than hemoglobin. The question is not iron level - it's hemoglobin level. Iron deficiency is only the most common of many causes of anemia, and they don't want to take blood from any anemic volunteer. -- Scray (talk) 00:58, 28 February 2011 (UTC)

Destroy secret papers

I think I've been watching too many spy movies and so I've got this weird question in my head; here goes. Suppose I have a stack of (secret) papers in my super-secret attaché case that is airtight with a perfect vacuum inside and with the temperature of the contents maintained at -5 C. What would be a good chemical reaction (with reactants contained in some mechanism in the case) that could be used, if the case falls into enemy hands, to destroy all the contents of the case beyond possible recovery as quickly as possible, and that could be triggered by a button, remotely, or by an internal timer (or all three)? Assume this reaction might be needed at an arbitrarily long time into the future. 72.128.95.0 (talk) 03:48, 27 February 2011 (UTC)

I have a few ideas:

• Chloroform is pretty good at lifting ink off paper, as I found out when I accidently erased a paragraph in my laboratory manual.
• Concentrated sulfuric acid carbonise paper, it turns paper into a handful of carbon dust. (not that I'd encourage using your hands, for fear of acid burns). With enough paper, it may catch on fire, as the reaction can get very hot.

Plasmic Physics (talk) 05:51, 27 February 2011 (UTC)

Well you could try concentrated perchloric acid, but with these sort of destructive acids, you will not be allowed to carry it on board a plane. Graeme Bartlett (talk) 10:15, 27 February 2011 (UTC)

I believe codebooks carried by the navy in WW2 were designed to be destroyed by dumping them in a bucket of salt water. Dmcq (talk) 13:14, 27 February 2011 (UTC)

If all the documents were on flash paper (the nitrocellulose kind), you could possibly set them alight with an electrical spark, although it would probably best if the case wasn't under vaccuum (needs oxygen to burn completely). Alternatively, you could spray the papers with a mist of pyrophoric liquid, which would ignite upon contact with oxygen (although the enemy could just open the case in a nitrogen filled glove box, if they knew about your countermeasures). -- 174.31.194.183 (talk) 18:40, 27 February 2011 (UTC)

It seems to me that destroying papers is trivial, but doing so without any outward sign (like a flaming/exploding attache case) is more of a challenge. Using magnetic media instead of paper provides for a possibility of wiping them with a strong magnetic field, without any outward sign, if a Faraday cage is constructed inside the case, to keep the field from escaping (does the Faraday Cage work to keep a field inside, instead of outside ?). StuRat (talk) 20:55, 27 February 2011 (UTC)

There is a scene in Cryptonomicon, I vague recall, where various Wikileaks-style hackers had rigged up their office so that any media passing through the door would be subjected to a strong magnetic field, so that if they were ever raided, the police would find themselves with completely scrambled hard disks. --Mr.98 (talk) 17:45, 28 February 2011 (UTC)

Have something that releases pure oxygen into the case, and make a spark. In pure oxygen, things burn very rapidly (for example the tragic example of the Apollo capsule interior that caught fire in pure oxygen). The oxygen could come from a small cylinder or a chemical reaction. To prevent the burnt remains of the papers being read, then you could have something such as large loose nuts and bolts in the case that would pulverise the ashes when you shook it. Or perhaps you could have "plastic" paper that would melt as well as burn. 92.24.189.108 (talk) 00:35, 28 February 2011 (UTC)

Ability to understand accents

I've always had a problem (more than most people) hearing what people are saying in a noisy environment(nightclub/factory/party). Tonight I was out with some friends and a bunch of their friends who were from various locations around the UK (so they had a variety of accents). Even in the quiet pubs I was constantly having to ask them to repeat what they'd said even though they could understand each other. Is there a term to describe why some people can't understand accents and is it connected to the ability to filter out background noise? --BlackberryPicking (talk) 04:03, 27 February 2011 (UTC)

Any fault in binaural hearing (such as a very slight blockage in one ear) will increase the difficulties in picking out individual voices from a noisy background. It is also possible that a slight under-development or slight damage to the Primary auditory cortex will have the same effect. I don't think that this causes specific difficulties with comprehension of unfamiliar accents, but it will increase the problems that we all have in converting sounds into words that we recognise, especially when the sounds don't follow the pattern we expect. (I have difficulties with the Glasgow accent, and I live less than a hundred miles away.) The more one hears of an accent, the easier it becomes to decipher the words, so perhaps it was just the noisy environment combined with unfamiliar accents, but you might wish to undergo a simple hearing test to rule out the possibility that one ear is less sensitive than the other (we can't give medical advice here). Dbfirs 10:08, 27 February 2011 (UTC)

I don't have a source for you, but in my work as an Audiologist, I often hear these two complaints together from people with even very mild high frequency hearing losses. Some people seem to have these problems with normal hearing thresholds on audiogram; no-one really fully understands why, though it is thought there may be some neurological/cortical involvement Si1965 (talk) 11:54, 27 February 2011 (UTC)

I think there is a natural difference. I've never really had much trouble understanding any English accents, as opposed to many of my friends, who sometimes have trouble understanding my accent. On the flip side, while I can understand people's accents, I often can't recognise them. Chipmunkdavis (talk) 12:15, 27 February 2011 (UTC)

In addition to the other causes listed, the McGurk Effect may come into play here. That is, you may be better able to understand somebody if you watch their mouth as they speak. If you are in a dark nightclub with flashing lights, it may be more difficult to get any visual cues. I've noticed this effect on TV news. When I watch the reporter speak, I understand what they say, but when I turn away, I often misunderstand what they say.

Also, context also plays a part in speech recognition. If somebody says "My favorite fruits are apples, orangutans, and bananas", you will likely hear "oranges". Those with accents may also use different words, or use the same words differently, and this could throw you off. For example, when somebody says they are going to "eat tea" or "wash their hands in the toilet", this doesn't make sense to Americans, so they might hear it differently. StuRat (talk) 20:41, 27 February 2011 (UTC)

Regarding the role of context: I'm not sure you'd hear oranges. You'd guess oranges. I have a friend who is very prone to malapropisms, such as saying "pacific" instead of "specific" and "bi-curiously" instead of "vicariously". These don't escape my attention at all, quite the reverse, they tend to distract me from whatever he's trying to say. 81.131.30.247 (talk) 00:45, 28 February 2011 (UTC)

The same thing applies to reading. The first time I read that, I got oranges. Googlemeister (talk) 14:30, 28 February 2011 (UTC)

Good point. StuRat (talk) 22:35, 28 February 2011 (UTC)

Wow, over 20 years in Audiology and I've never heard of the McGurk Effect. Thanks! Si1965 (talk) 23:31, 27 February 2011 (UTC)

You're welcome. I hope it helps with your job. StuRat (talk) 22:34, 28 February 2011 (UTC)

I can only offer anecdotal evidence: I share your inability to understand people over background noise, but I am quite good at understanding accents. I think the main thing that affects how well you understand an accent is how familiar you are with it. I am quite well-travelled, so I'm used to a wide variety of accents. That probably helps me. --Tango (talk) 00:57, 28 February 2011 (UTC)

I think that a lot of it has to do with traveling and being exposed to many different accents or ways of speaking a language. Mac Davis (talk) 14:16, 28 February 2011 (UTC)

(OP here) Thanks for all the responses, as always they are an education! I'd thought there might be a term to describe it but maybe it's too non-specific a problem. I kinda assumed it was probably a 'processing' problem rather than a physical problem (mainly because I'm 36 and have had the background noise problem since I was in my teens, maybe younger). Understanding accents wasn't really a problem until this night out so I think I will book a hearing test as well. --BlackberryPicking (talk) 18:45, 28 February 2011 (UTC)

Flavored condoms and infections

This page claims that flavored condoms can cause yeast infections if used during vaginal sex. Is there a source for this info? I'm a development worker in HIV prevention in the Philippines; if anyone can help me find an authoritative source linking flavored condoms to vaginal yeast infections, I'd appreciate it. You can email me at <email redacted>. Cheers, Casey.

I do not have a good source for you, but I work in HIV prevention in America and India. I have heard that flavored condoms can cause this problem but I have also seen condoms which specifically state that they are made for intercourse. On disreputable sites found by searching Google it seems that many people say that yeast infections can be caused by flavoring or chemicals in the condoms.

I recommend that you consult with a doctor in your area as condoms manufactured in different parts of the world may be made to different specifications. Also, I just sent a note about this post to your email address. Blue Rasberry (talk) 05:39, 27 February 2011 (UTC)

And is Blue Raspberry one of the flavors ? :-) StuRat (talk) 20:31, 27 February 2011 (UTC)

I suspect that the mechanism of infection is that flavored condoms are first used for oral sex, where they pick up yeast, then are used in vaginal intercourse, where they deposit the yeast. Much like Q-tips are supposedly "not for use in the ears", despite being on the end of a long stick so they fit inside ears, the same skepticism should be aimed at flavored condoms "not meant for oral sex". StuRat (talk) 20:31, 27 February 2011 (UTC)

polycarbonate

how can i tell the difference between polycarbonate, acrylic, and abs plastic ? — Preceding unsigned comment added by Wdk789 (talk • contribs) 09:43, 27 February 2011 (UTC)

Is destructive testing allowed? (i.e. break a piece off and run tests on it) Ariel. (talk) 10:37, 27 February 2011 (UTC)

no --Wdk789 (talk) 11:25, 27 February 2011 (UTC)

I don't know but I suspect it's quite difficult from visual inspection alone. Can you find some hints in our articles on polycarbonate, acrylic, and ABS plastic?--Shantavira|^{feed me} 16:37, 27 February 2011 (UTC)

The three plastics have different densities. ABS is 1.04, Acrylic 1.18, Polycarbonate 1.20. They also have different hardness levels and tensile modulus - if you have other plastics to compare it to you should be able to tell just from the feel. A pretty definitive test is their refractive index. You can try various colors of light and compare. (That's how they do it in recycling facilities BTW.) Ariel. (talk) 18:30, 27 February 2011 (UTC)

what do u mean by " refractive index You can try various colors of light and compare." — Preceding unsigned comment added by Wdk789 (talk • contribs) 03:52, 28 February 2011 (UTC)

Do you know what a refractive index is? It's a measure of how much light bends when it passes through a material. Different materials bend light by different amounts, and by comparing you can distinguish them. You can google for some methods of how to measure this. Additionally different plastics absorb different frequencies of light that is passed through it. See Spectrometer and spectroscopic analysis. Ariel. (talk) 04:13, 28 February 2011 (UTC)

how can i pass light thru if its a thick plastic and if its not clear? — Preceding unsigned comment added by Wdk789 (talk • contribs) 08:23, 28 February 2011 (UTC)

You'll need a sensitive spectrometer, but you can probably check the light that reflects from it. You've reached the limit of what I know on the subject though. Research how recycling stations do it - they have this exact same problem when dealing with mixed plastics. Ariel. (talk) 08:35, 28 February 2011 (UTC)

u mean how shiny it is? — Preceding unsigned comment added by Wdk789 (talk • contribs) 13:10, 28 February 2011 (UTC)

Weak interaction: figures

I'm attempting to improve the referencing and clarity of the weak interaction page. The commonly quoted range is ~10^-18m; carrier mean lifetime ~3x10^-25s and W-boson mass ~80 GeV (80.4 GeV/c2). I'd like authoritative sources for these numbers if you know of them, and also which ones are calculated from which ones. The first two appear to be related by the maximum velocity of c (although not quite), but I don't know which one is actually measured. I did once see an equation linking mass to mean life for virtual particles, but I can't remember it and it doesn't seem to be on an obvious page here. If this does exist, then the same question applies. Thanks! Grandiose (me, talk, contribs) 14:07, 27 February 2011 (UTC)

The authoritative source for anything related to particle physics is the PDG page. Go to that page, click on "Summary Tables" and then click on "gauge and Higgs bosons". There you will find information about the W and Z masses MW = 80.399 ± 0.023 GeV, MZ = 91.1876 ± 0.0021 GeV. You will also find their full widths ΓW = 2.085 ± 0.042 GeV and ΓZ = 2.4952 ± 0.0023 GeV. The widths are related to the carries lifetimes through the formula Γ = ħ/τ as you can see on the page Resonance (particle physics) which unfortunately for you is still only a stub. Finally, as you pointed out, the range of the interaction is roughly given by multiplying the particle's lifetime by the speed of light. Dauto (talk) 15:51, 27 February 2011 (UTC)

Thanks, does one find the width first and use it to calculate the lifetime, or vice versa? Grandiose (me, talk, contribs) 16:48, 27 February 2011 (UTC)

Either thing can in principle be measured but in practice the width is often easier to measure. Dauto (talk) 16:57, 27 February 2011 (UTC)

Actually, rethinking what I said above I realized that the distance obtained through the formula I gave : d=cħ/Γ is the average distance traveled by carrier particles after they are produced in collisions. In a interaction virtual particles carry the interaction and the average distance traveled by those is given by d=cħ/M which is about two orders of magnitude shorter for the weak interaction. See for instance the first paragraph of Yukawa potential. Dauto (talk) 16:49, 27 February 2011 (UTC)

Sorry. There is still a mistake above. I forgot a time dilation factor in the expression for the average distance traveled by carrier particles after they are produced in collisions. Dauto (talk) 03:44, 28 February 2011 (UTC)

Thanks. I have most of the key factual information now reasonably referenced. I was attempting to get some grasp of the strength of the weak interaction force, but have suddenly realised I have no idea of what a force means in this context [a mechanism]. (I should point out I'm in above my head and thus treading carefully.) Possibly the force preventing decay? In any case here has a couple of useful comparisons, but do we have anything more detailed/a better source? Some sort of formula or graph, for instance? I might be missing some facet or other, so do bear with me! Grandiose (me, talk, contribs) 18:02, 27 February 2011 (UTC)

In a fundamental level the strength of an interaction is given by the coupling constant. I'm busy now so I won't be able to give you a better explanation. I will try to post again later today. Dauto (talk) 19:04, 27 February 2011 (UTC)

cloud formation

I watched a video about global warming they say that cosmic rays forming with water droplets is what creates clouds and they say when the sun is more active fewer particle get through to make clouds so this is why it is colder. Is this true do cosmic rays create clouds — Preceding unsigned comment added by Lufc88 (talk • contribs) 14:34, 27 February 2011 (UTC)

The main cause of cloud formation is Cloud condensation nuclei, but it is true that a more active sun could alter the stage and altitude at which clouds form (see Solar variation). The exact process and the interpretation of the observed correlations has not been agreed on, but the effect is probably small compared with other causes of cloud formation. Did you mean more particles from a more active sun? Dbfirs 17:26, 27 February 2011 (UTC)

No, it isn't. That's a load of bull, that's what that is. Dauto (talk) 17:12, 27 February 2011 (UTC)

Then please change our articles and add appropriate references (though I agree that the effect is disputed and probably small). Dbfirs 17:27, 27 February 2011 (UTC)

What articles? Dauto (talk) 03:18, 28 February 2011 (UTC)

Well they do only suggest a possible effect. I've just re-read the OP's post about what the video claims, and I agree with you that cosmic rays are not "what creates clouds", so I'm with you on the bull call there. Dbfirs 10:08, 28 February 2011 (UTC)

no it said when the sun is more active fewer rays get through so there are less clouds so things warm up quicker. But my intial question was so cosmic rays form with water to make clouds and if so how? — Preceding unsigned comment added by Lufc88 (talk • contribs) 17:32, 27 February 2011 (UTC)

One possible process is that increased solar activity interacts with the earth's magnetic field to deflect more of the galactic cosmic rays that are the main cause of ionisation in the atmosphere. Whether this ionisation affects cloud condensation nuclei to any significant extent is not currently known. Dbfirs 18:07, 27 February 2011 (UTC)

You're very quick to say that Dauto. Henrik Svensmark is the primary researcher of cosmic rays' effect on atmospheric nucleation. It's new research, and it could turn out well--we don't know yet. Mac Davis (talk) 14:11, 28 February 2011 (UTC)

I'll eat my hat if that turns out to be an important factor. Dauto (talk) 15:17, 28 February 2011 (UTC)

Is there any special reason you're driven to make this pledge, or is it just a hunch? 213.122.11.147 (talk) 22:25, 28 February 2011 (UTC)

mass & motion of earth

Is there any effect on the mass and motion of the earth from taking mass from the earth (mostly satellites and space probes that never come back to earth)? and also, the fact that more and more of the earth's mass (airplanes ships cars trains) moves around where before (1000 years ago) it was all stationary in the earths crust? How much does meteorites counter this effect? —Preceding unsigned comment added by 98.221.254.154 (talk) 16:22, 27 February 2011 (UTC)

The mass will change but by a very small amount. It could be offset by meteorites hitting the earth or add to the loss in mass we get as the atmosphere drifts off (slowly) into space. The force of gravity between ourselves and the moon (and the sun etc) is directly proportional to our (and their) mass, but you need to look at the mass of the earth and see where the decimal point is, compared with satellites that might be of the order of 1000 kg. (See Wikipedia for facts on mass) Victuallers (talk) 16:37, 27 February 2011 (UTC)

Our article on Micrometeoroids suggests that the mass of the earth might be increasing by around ten million kg per year from the inflow of Cosmic dust alone, so a few satellites are not going to make a measurable difference. Moving vehicles that don't go beyond the atmosphere will have an effect that normally cancels out to zero ( though if the whole human population with all their transportation converged on one island, there would be be a measurable effect on mass distribution and the orbit of the moon would change). The eruption of a large volcano can change the length of the day by a very tiny but measurable amount, so having many aeroplanes high in the sky, and many satellites in orbit might also slow the rotation very slightly (because angular momentum is conserved), but the effect will be very small because the earth "weighs" nearly six million million million million kg. Dbfirs 17:54, 27 February 2011 (UTC)

The entire Earth's crust (which is the only part we can have any impact on) makes up less than 1% of the mass of the Earth. There is no way anything we do could have a noticeable effect on the Earth's mass. The total mass of everything launched into space is perhaps a few tens of thousands of tonnes (that's a guess, but it's probably about right - it's more if you include fuel, but that's mostly burnt early in the launch, so the resulting CO2 and water probably remains part of the Earth). The total mass of the Earth is 6 thousand billion billion tonnes. As you can see, our impact is minimal. --Tango (talk) 01:09, 28 February 2011 (UTC)

While humans are not able to significantly change the mass of the earth, we are able to shift its distribution a bit, thus changing its moment of inertia. This NASA article mentions that filling the Three Gorges Dam reservoir (which can hold 40 cubic kilometers of water, at a maximum of 175 metres above sea level) could increase the length of a day by 0.06 microseconds. In comparison, the 2004 Indian Ocean earthquake was calculated to effect a 2.68 microsecond decrease in the length of the day. To what precision are astronomers able to measure our rate of rotation? Sidereal day#Exact duration and its variation would suggest that such measurements are made to the fraction of a nanosecond. -- ToE^T 02:37, 28 February 2011 (UTC)

Bond angle of water

At Water (data page), I read this:

Bond angle 104.4776° (equilibrium)

Not being ignorant of geometry, I put that into the cosine function on a calculator and got −0.250001484. So arccos(−1/4) ≈ 104.477512186 and that got rounded. If it's not exactly arccos(−1/4) then the three consecutive 0s are an odd coincidence, and Occam's razor favors such a simple thing. So I edited it to say this:

Bond angle 104.4776° = arccos(−1/4) (equilibrium)

I find various web pages explaining why the bond angle is not 109.47°, which is the arccosine of −1/3, and is what would result from a certain kind of tetrahedral symmetry. Instead of just explaining physical reasons why it should be smaller than arccos(−1/3) ≈ 109.47°, shouldn't it also explain why it's the angle whose cosine is such a simple fraction?

Can someone here explain that? Michael Hardy (talk) 17:13, 27 February 2011 (UTC)

A google search for "cosine of the bond angle of water" gets 0 hits! Michael Hardy (talk) 17:19, 27 February 2011 (UTC)

that's just a funny coincidence. You should revert your edit. Dauto (talk) 17:57, 27 February 2011 (UTC)

If it's a "funny coincidence", then why does it agree to seven decimal places? Getting the same decimal digit seven times in a row happens once in 10 million trials if it's "just a coincidence". Michael Hardy (talk) 18:03, 27 February 2011 (UTC)

....and how do they actually measure it so accurately that they get seven digits? Could it be that they concluded it's arccos(−1/4) and then computed that to seven places, rather than actually doing a physical measurement that's so phenomenally accurate? Michael Hardy (talk) 18:05, 27 February 2011 (UTC)

Think what you will. It is a coincidence. Besides, the second page you linked has the figure 104.45 degrees. Dauto (talk) 18:07, 27 February 2011 (UTC)

The page Properties of water also has the figure 104.45 degrees. Dauto (talk) 18:08, 27 February 2011 (UTC)

(ec)The lack of Google results probably means that the correspondence to the arccos might be a coincidence. The reason why arccos(-1/3) is the bond angle of, say, methane, is because of the tetrahedral symmetry of the molecule. Water doesn't have that symmetry, or any other symmetry which would constrain the bond angle. You have a plane of reflection that splits it down the middle, you have another in the plane of the three atoms, and you have a 2-fold axis splitting the angle in the plane of the three atoms. There is absolutely no geometric reason why the angle would be exactly arccos(−1/4). Indeed, anyone rounding arccos(−1/4) ≈ 104.477512186 to 104.4776° is off (you would round it down to 5, not up to 6). 104.47759732 (which also rounds to 104.4776) is not equal to arccos(−1/4), no matter how hard you squint at it. I would *not* put the correspondence in there unless you were able to cite a reference for it (no original research and all that). Frankly, there is a heck of a lot of precision in that angle measure, and I am slightly uncomfortable with the absence of a citation mentioning how it was derived (from experimental measurements - how precise were they? From quantum chemical calculations - what level of theory? From geometric considerations - what was actually calculated?). Looking at the history [23], it looks like the reference was for (Hoy 1979), which was then removed [24] with the edit summary of "fix references". I'm not sure what paper was meant by (Hoy 1979) (no further specification was given), but the edit summary mentions the CCCDBD, which currently lists the experimental equilibrium bond angle as 104.48 [25]. -- 174.31.194.183 (talk) 18:25, 27 February 2011 (UTC)

The figure we give would appear to come from this paper, assuming this is the Hoy (1979) that was meant in the edit [26]:

A. R. Hoy and P. R. Bunker, A precise solution of the rotation bending Schrödinger equation for a triatomic molecule with application to the water molecule, Journal of Molecular Spectroscopy 74(1), 1--8. (January 1979). doi:10.1016/0022-2852(79)90019-5

The abstract gives a figure of 104.48, and says it was the result of least-squares fitting a model with 7 parameters (one of which was the equilibrium bond angle) to 375 spectroscopically observed vibration mode energies.

I don't have access to the full paper, so I can't confirm whether or not it contains the 4 d.p. number inside. You're right to be suspicious that this is so close to such a round number as arccos(−1/4), and it's not impossible that there might be some hidden symmetry underlying this (cf the virial theorem etc). It's also possible that somebody has said "Ooh, that looks close to arccos(−1/4)", and simply made up the extra figures. But there doesn't seem to be any immediately obvious reason to expect it.

We give the bond angle for ammonia as 107.8°, which would be about arccos(-0.306); but that doesn't seem to reflect any numerology -- unless there's something you can see there too? Jheald (talk) 18:41, 27 February 2011 (UTC)

I do have access to the full paper: the value given is indeed 104.4776(19) degrees. Buddy431 (talk) 21:07, 27 February 2011 (UTC)

This is clearly a coincidence. Look at for instance the angle of the Hydrogen sulfide molecule which has a structure very similar to water. Dauto (talk) 18:45, 27 February 2011 (UTC)

FWIW, ab initio calculation (as of 2005) gives 104.50°; the discrepancy between that and the observed value is said to be accountable for, by various factors not included in the basic calculation. [27] Jheald (talk) 19:13, 27 February 2011 (UTC)

It may also be worth noting that the current value for the bond length is 95.777 pm, not 95.84 -- this should be updated. I'd change the [:File:H2O 2D labelled.svg SVG] but someone's changed all the text elements to drawing paths, so somebody else can have the fun of working out what the fonts and sizes are meant to be.

It's a bit alarming that (1) we were showing out-dated information; and (2) that when somebody updated it, they only updated one data-element not the other; that they may have added spurious digits; and that we didn't spot any of this till Mike got suspicious of the numerology. Jheald (talk) 19:45, 27 February 2011 (UTC)

The quoted value is indeed the one given in the paper (they didn't add spurious digits), though there's a not insignificant amount of uncertainty in the final two digits. Wikipedia, and indeed any reference source, will always have out of date information. There's not much we can do about that (although I am suspicious of the article cited, seeing that it's over 30 years old). Buddy431 (talk) 21:07, 27 February 2011 (UTC)

Someone has now changed it to say 104.48 degrees, citing the paper by Hoy. That's more credible since it's not so many decimal places. When I put 104.48 into a calculator and hit the cosine key I get −0.250042041528. It still seems suspiciously close to −1/4, since it has two 0s immediately after −0.25. Michael Hardy (talk) 22:13, 27 February 2011 (UTC)

It is just a coincidence. Dauto (talk) 03:27, 28 February 2011 (UTC)

Decay products (further questions)

Further to my question above, I have a couple of questions about the data given in this document. As I read it something like 10% of W- bosons should decay into e- and electron antineutrinos. However, explanations of beta minus decay always gives this outcome – is there a reason why? I'm also a little bemused by the numbers given. The first four (all leptons) given are ~10%, hadrons are listed at 67% and 67+40>100. My reading of the numbers below this suggests they don't total to 67% either. Can you assist? Grandiose (me, talk, contribs) 20:17, 27 February 2011 (UTC)

β⁻ decay can't produce heavy particles because there isn't enough energy available (the nuclear energy only decreases slightly), but that energy is available in spades when a "free" W boson decays. There are three leptonic decay modes (eν, μν and τν) and those together with the hadronic modes add to 100% within the margin of error. The "ℓν" decay on the first line must come from a different measurement or calculation that didn't distinguish the lepton generations. Likewise, the lines below "hadrons" are limited by the experimental data that happens to be available. It's a bit confusing because this summary document doesn't cite its sources. -- BenRG (talk) 20:58, 27 February 2011 (UTC)

Thanks, that's that pretty much cleared up. Grandiose (me, talk, contribs) 21:01, 27 February 2011 (UTC)

Circuit of Unique Equivalent Resistance

Hello. Is it possible to design a circuit that has a unique equivalent resistance regardless of the order in which resistors are connected? Thanks in advance. --Mayfare (talk) 23:17, 27 February 2011 (UTC)

Please clarify. Surely you are asking for something harder than the fact that the equivalent resistance of a string of series resistors is independent of the order in which they are connected. Similarly the sum of a series of numbers does not depend on their order (commutative property). Edison (talk) 23:47, 27 February 2011 (UTC)

February 28

Spaying and neutering of feral animals

I know that there are groups in America who trap feral animals (cats mostly, but sometimes dogs) and have them spayed/neutered and then return them to their ranges. I just had my cat spayed and she must wear bandages and a funnel for about 10 days, as per the vet's orders. How does this work for feral cats? Do they stay at the vet for a week or so, or are they turned loose early with some sort of slowly-degrading bandage? The Masked Booby (talk) 00:58, 28 February 2011 (UTC)

I think they're just kept for a couple of weeks in a cage. This site looks like it has all the answer but you have to go through a free registration process requiring an email address to access it. Vespine (talk) 01:17, 28 February 2011 (UTC)

where do aliens come from

where do aliens come from ? — Preceding unsigned comment added by Joshuad95 (talk • contribs) 04:06, 28 February 2011 (UTC)

Presumably the same place humans come from. But no one has even seen an alien, so it's hard to know. Ariel. (talk) 04:16, 28 February 2011 (UTC)

We have articles on these kinds of aliens, these aliens and even a list of aliens. Vespine (talk) 04:58, 28 February 2011 (UTC)

"Alien" is a word derived from the Latin words aliēnus (“belonging to someone else, exotic, foreign”) and alius (“other”). Basically, an "alien" is a word for someone or something from elsewhere. Hence the terms "illegal alien", "resident alien", and even "alienation" are literal usages of the term "alien", and are in no way metaphorical. So the answer to the question "where do aliens come from" is simply "somewhere (anywhere) else". -- 174.31.194.183 (talk) 05:01, 28 February 2011 (UTC)

If you mean extraterrestrial life, the general assumption seems to be that it would need an environment similar to that of Earth, which would mean a small, terrestrial planet/asteroid or a moon of a larger, Jovian planet. Planets like Venus, which at first seem inhospitable to life, due to extreme temperatures and pressures, may support life in a manner similar to that found at undersea volcanic vents on Earth. But, alien life could also be "totally alien", perhaps evolving in deep space or as magnetic currents inside stars. We don't know anything about such life, though, so it would be difficult to judge whether it's possible and what it requires, making it impossible to pick probable locations. StuRat (talk) 22:27, 28 February 2011 (UTC)

Pureed Food

Do vegetables and fruit lose their vitamins and nutrients if they are pureed? And if they don't if you added the puree into food like spaghetti or meatballs and then cooked the meatballs, would that cause the vegetables or fruit to lose their vitamins and nutrients, would it still be just as healthy as if you ate the veggies steamed or the fruit raw? —Preceding unsigned comment added by 70.141.255.136 (talk) 06:07, 28 February 2011 (UTC)

Vitamins and nutrients aren't destroyed by macroscopic mechanical stress. You can crush a cucumber with a hammer, steamoll a pumpkin, the vitamins and nutrients will stay intact. They are however destroyed or ruined by chemical attack, thermal damage, or excessive air pressure. Plasmic Physics (talk) 06:57, 28 February 2011 (UTC)

It may be a bit more complicated than that - vitamins and the like are stored inside cells where they are protected to some degree. Pureeing them breaks the cell wall exposing them to further damage. But in general I think it's not something to worry about. Ariel. (talk) 07:00, 28 February 2011 (UTC)

Yes, and breaking those cell walls makes it easier for our body to absorb the vitamins. No point in protecting the vitamines so that they can be flushed down the toilet. Dauto (talk) 15:12, 28 February 2011 (UTC)

Some of the water-soluable vitamins, such as Vitamin C, may dissolve into the cooking water. But if you use the cooking water when making the sauce etc, then that is not a problem. 92.15.3.182 (talk) 11:11, 28 February 2011 (UTC)

UV-A, UV-B, UV-C of metal halide lamp

Hello,

I wanted to ask here how dangerous the UV radiation of a 150w metal halide lamp can be, compared to the sun( i have the numbers of the lamp they are:

• UV-A:6.1
• UV-B:0.003
• UV-C:0.006. microwatt/cm2/500 lux

I cannot find the numbers for the suns radiation on earths surface (average, temperate climate)
TY
DST — Preceding unsigned comment added by DSTiamat (talk • contribs) 09:59, 28 February 2011 (UTC)

Sorry, I couldn't find anything. And if you get no other replies it means no one else found anything either. Ariel. (talk) 23:23, 28 February 2011 (UTC)

Birds and eyelashes

Random question, but something I was thinking about. How common is it for birds to have eyelashes? --95.148.106.158 (talk) 10:34, 28 February 2011 (UTC)

Birds do not have eyelashes. Some have bristles, which are feathers that lack barbs, around the eyes which appear to be similar to eyelashes. That feature is primarily only in insect-eating birds. -- kainaw™ 13:34, 28 February 2011 (UTC)

And do they serve to keep insects out of the eyes ? StuRat (talk) 22:13, 28 February 2011 (UTC)

view full size - not easy to see, but they're there

Budgerigars have eyelashes. The one in the pic doesn't have particularly prominent/thick lashes, but that's the only pic I could find on here with sufficient resolution to show them at all. I think (IIRC) that Cockatiels do too. --Kurt Shaped Box (talk) 22:57, 28 February 2011 (UTC)

They're also mentioned in our articles on the Hornbill and some of the Vulture species. Our Eyelash article mentions that they are barbless feathers as Kainaw describes, rather than true hairs as in mammals, but I don't think that that excludes them from being defined as eyelashes. 87.81.230.195 (talk) 23:39, 28 February 2011 (UTC)

So, having a look at another couple of parrot species...

• 
  African Grey Parrot appears to have (very fine) 'eyelashes'
• 
  as does this Umbrella Cockatoo
• 
  Whereas this macaw seems to have a ring of 'nodules' (dunno) that may serve a similar purpose

--Kurt Shaped Box (talk) 23:53, 28 February 2011 (UTC)

The close up of that macaw is going to give me nightmares! lol.. Vespine (talk) 02:00, 1 March 2011 (UTC)

Can holograms work in broad daylight?

Does it need to be very dark for them to be clearly visible? ScienceApe (talk) 13:26, 28 February 2011 (UTC)

It depends on what you mean by hologram. Ones that are generated by lasers must be brighter than the surrounding light. However, white-light holograms (seen commonly on credit cards) work best in daylight. -- kainaw™ 13:30, 28 February 2011 (UTC)

Yeah I was talking about the holograms that are suspended in midair, presumably generated by lasers. ScienceApe (talk) 14:19, 28 February 2011 (UTC)

Such holograms does not exist. A hologram can show objects in front of or behind its surface but only in the direction of the hologram as seen from the viewer. --Gr8xoz (talk) 17:33, 28 February 2011 (UTC)

I have seen laser-generated holograms that you could walk around 360 degrees. They are expensive. The one I was was being licensed by a popular magician for his stage show - which should give a general idea of the cost. -- kainaw™ 17:35, 28 February 2011 (UTC)

That seems interesting, do you have any idea of where to get more information. Are you sure it was a hologram? not every 3D projection is a hologram. Was there any transparent materials between you and the background? --Gr8xoz (talk) 18:50, 28 February 2011 (UTC)

I have never been able to find the manufacturer online. I was paid through a company named "Magic Stage", which I also cannot find online. I did computer programming - which was the easy part. The setup required a lot of lasers on little pivots. The best I could tell, the lasers do not produce noticeable light until the beams cross. I programmed vector lines in 3D space, which the lasers "drew" in the air - oscillating quickly to keep it visible. The program I wrote just drew a little red apple with a green leaf on top. The demonstrator had a transmitter on his wrist that relayed the position to another computer so as he moved his hand around the apple moved with it - looking like he was holding it. That's about all I remember - and it was a good 20 years ago. I'm sure that the technology is much better now. -- kainaw™ 19:11, 28 February 2011 (UTC)

Was it something like this? http://www.aist.go.jp/aist_e/latest_research/2006/20060210/20060210.html 83.134.177.173 (talk) 19:53, 28 February 2011 (UTC)

Yes. It was just like that with two exceptions. First, I never heard anyone mention plasma. Maybe the plasma in your example makes it much easier to see in normal lighting. Second, the one I saw used three colors (red, green, blue) to produce nearly real-color images. Now that I think of it - I may be mis-remembering the existence of blue since the only example I saw used red and green. I've always meant to get two laser pointers to see if they make a dot of light when you cross the beams, but just never think to try it when I actually have two laser pointers on hand. If it works, then there's no "plasma" involved - just a disruption of the laser beam. -- kainaw™ 19:58, 28 February 2011 (UTC)

That isn't a hologram BTW. Ariel. (talk) 20:31, 28 February 2011 (UTC)

I think the plasma involved is just air made very hot by pointing multiple lasers at it, rather than the plasma of neon that's used in a plasma globe - if that was what you were thinking. 81.131.17.66 (talk) 20:59, 28 February 2011 (UTC)

The air would not get hot! If the laser was strong enough to do that it would burn holes in the walls. Ariel. (talk) 23:15, 28 February 2011 (UTC)

The lasers are focussed, with the focal points in mid-air, and there it gets hot. After that point, the beam diverges. Icek (talk) 23:51, 28 February 2011 (UTC)

That sounds like an incredible amount of effort to go to, just to make an apple appear or disappear; something any magician could do with a regular apple. Maybe there's important information missing from the descriptions above. Light is not cohesive, the main "problem" with holograms is you can see THROUGH them. That might work if it is kept in front of a black curtain with the audience only to your front, but in other situations it would fail. Lasers also definitely do NOT make a visible "point" of light where beams intersect in air, they need something to reflect off, (the little balls of plasma are definitely not "rgb"). I'm not calling anyone a liar, but I smell something very fishy, IMHO something doesn't add up. Vespine (talk) 00:23, 1 March 2011 (UTC)

I made an apple disappear today for lunch and I'm not even a magician. Dauto (talk) 02:12, 1 March 2011 (UTC)

MOND or MOG theory

If MOND or Scalar–tensor–vector gravity turns out to be correct, will any changes need to occur to other physical laws apart from gravity? Would it ever have any effect on everyday life? Thanks 92.29.122.72 (talk) 15:33, 28 February 2011 (UTC)

No, and No. Dauto (talk) 16:07, 28 February 2011 (UTC)

The second one seems to be answered in the article anyway:

On the scale of the solar system, the theory predicts no deviation[7] from the results of Newton and Einstein. This is also true for star clusters containing no more than a maximum of a few million solar masses.

Nil Einne (talk) 17:29, 28 February 2011 (UTC)

Just to answer the last question; when scientists tweak existing laws, it doesn't actually change the nature of the universe. The universe keeps doing what it always has, so there's no change to what happens to you. What changes is our understanding of how the universe works. Just because Copernicus figured out that the earth moves around the sun doesn't mean that it hadn't been doing that before he figured that out! Its the same deal here; if our understanding of gravity changes, it doesn't mean that it hadn't been doing the same thing even before we changed the laws... --Jayron32 17:43, 28 February 2011 (UTC)

No, really? I am not a three year old, thanks. 92.24.179.104 (talk) 22:18, 28 February 2011 (UTC)

Modified Gravity Makes Galaxies Brighter Count Iblis (talk) 22:41, 28 February 2011 (UTC)

Snake venom myokymia

I saw on a TV program that some type of snake can cause this. Which is it ? Also, could this venom be used (in low dosages, of course), to exercise the muscles of patients who are either comatose or immobile, to prevent muscular atrophy ? StuRat (talk) 19:35, 28 February 2011 (UTC)

Timber rattlesnake?[28] DMacks (talk) 20:46, 28 February 2011 (UTC)

Christchurch volcano

Following the recent quake there, a noticeable increase in the temperature of water in the harbor has been measured, leading to speculation that the earthquake may have either triggered, or been triggered by, an increase in volcanic activity in the area. So, then, which volcano(es) are involved and do we have article(s) on them ? StuRat (talk) 19:38, 28 February 2011 (UTC)

New Zealand has a lot of volcanoes. It's right on the Ring of Fire, and Volcanism of New Zealand lists quite a number. The map shows that most of them are on the North Island, not the South. But List of volcanoes in New Zealand has 4 candidates on the South Island. And of those, the first two are exactly in the right spot: Akaroa and Lyttelton Harbour. However those are very old, so it may also be a new unnamed volcano. Ariel. (talk) 20:56, 28 February 2011 (UTC)

Right, so which one is the likely candidate ? Also, do we have any articles on those volcanoes ? (The links you provided aren't to volcano articles.) StuRat (talk) 21:11, 28 February 2011 (UTC)

If it's an existing one, then most likely is Lyttelton Harbour I guess. But I think more likely is that it's a new opening that may or may not eventually become an underwater volcano. And I know those aren't links to volcano articles, but that's what was there. We don't seem to have anything else, probably because those volcanoes are so old. Ariel. (talk) 23:19, 28 February 2011 (UTC)

As the volcanoes are there a result of the subduction zone, it may just mean that the earth moment has provided new crevasses for sea water to peculate down to the hot rock in the zone (and then rise again). So I think it might be less to do with volcanism more to do with popular fear-mongering. In a few months/years time, the sea temperature may return to its former levels. Crack in the overburden around the volcano aren't going to afford easier passage for magma to rise. If it wants to rise - it will regardless of the overburden and the upage will have been noticed before now. Also, the quake was in the wrong place and over the subduction area --Aspro (talk) 21:21, 28 February 2011 (UTC)

Chromosome numbers and speciation

We have articles about how an individual can have a different number of chromosomes than its parents, but how does this change occur to an entire species? When the first proto-human was born with 46 chromosomes instead of the 48 of chimps and gorillas, how did that individual produce viable offspring with its 48-chromosomed mates? If it happened gradually over many generations, why don’t we see species with fractions of a chromosome as part of their speciation? —Arctic Gnome (talk • contribs) 19:46, 28 February 2011 (UTC)

It seems that this individual must have reproduced with "normal" individuals matching one of his chromosomes to two of the "normal" ones. What is a fraction of a chromosome anyways? Dauto (talk) 19:54, 28 February 2011 (UTC)

Chromosomes do sometimes break: [29]. StuRat (talk) 02:02, 1 March 2011 (UTC)

When the number of chromosomes changes, it is usually because either one chromosome has split in two or two chromosomes have merged into one. As long as all the genes are still arranged in the same way, with just an extra split/join, then reproduction is still possible (although fertility would probably be greatly reduced). Women with Down syndrome can (with difficulty) reproduce, for example, despite having an duplicate chromosome. --Tango (talk) 20:03, 28 February 2011 (UTC)

There are people right now who carry abnormal chromosomes yet are phenotypically normal and reproduce -- albeit with a higher chance of having an offspring with severe birth defects. See Robertsonian translocation and balanced translocation. There are some rather complicated models of how primate chromosomes evolved - see [30] and [31]. --- Medical geneticist (talk) 20:11, 28 February 2011 (UTC)

Not an 'answer' but you might find Chromosome 2 interesting. I think the questions you are asking are one area which isn't fully understood yet. why don't we see fractions of a population with different numbers of chromosomes is a very interesting question... Different number of chromosomes occurs above the level of species. All Hominidae have 24 pairs of chromosomes, so it's possible to see many "speciation" events before you see any "chromosome count altering" events making them relatively rare, we struggled to find "speciation events" in action so it might be even harder to find the chromosome events. Also, if you think about scenarios where such an event might take place, they might take place relatively "fast", so it might make such events very hard to "catch in the act" so to speak. Vespine (talk) 23:23, 28 February 2011 (UTC)

Toxorhynchites?

I was discussing mosquitoes with another entomology student, and he mentioned a blood-feeding Toxorhynchites species in Panama. I was quite certain that all Toxorhynchites species were nectar-feeding only and not one species was hematophagous. He mentioned that the mosquito was metallic, and thus he inferred it was a Toxorhynchites species. Can anyone find information on what mosquito species he may be referring to?130.127.130.191 (talk) 20:55, 28 February 2011 (UTC)

Relativity and nuclear bombs

Did Einstein's theory of relativity have anything to do with discovering how to build and explode nuclear bombs? Could the later have been done without the former? 92.24.179.104 (talk) 22:25, 28 February 2011 (UTC)

There have been previous Ref Desk threads about this. Certainly the role of special relativity (and "E=mc²") in nuclear physics is grossly oversold, and I think that the Manhattan Project could have succeeded without any understanding of special relativity, but that doesn't mean that special relativity wasn't helpful to them. -- BenRG (talk) 22:51, 28 February 2011 (UTC)

(EC)No, not directly. Off course relativity is one of the pillars of 20th century physics so it is a fundamental part of the science of physics as a whole including nuclear physics. Dauto (talk) 23:00, 28 February 2011 (UTC)

Einstein's other, "more important contribution", led to our understanding of modern atomic theory, and probably had more direct impact on the line of research that eventually led to nuclear fission. General relativity has more direct application to astronomy and gravity than it does to atomic or nuclear physics. Lawrence, Fermi, and Oppenheimer all made theoretical contributions that had far more direct impact on the discovery of nuclear fission than any work by Einstein. And even these contributors were primarily theoretical. Most physicists concede that experimental radioisotope research predated modern nuclear theory; but I don't think anyone could have discovered the energetic applications of fissioning radioisotopes without the development of theoretical nuclear physics. Nimur (talk) 00:09, 1 March 2011 (UTC)

Einstein's main contribution to the bomb was writing a letter to Franklin Roosevelt. Edison (talk) 01:47, 1 March 2011 (UTC)

March 1

Modified Newtonian dynamics

I've read 3/4 of the article and still don't understand what the theory/idea is, other than it seeks to explain the Galaxy rotation curve. My question: Can someone explain MOND simply? Albacore (talk) 01:04, 1 March 2011 (UTC)

It's a modification of Newton's theory of gravity in which the usual gravitational force law, G M m / r² = m a, is replaced by G M m / r² = m a μ(a/a_o), where a_o is a new constant and μ is tanh or another function with a similar shape. Does that help? -- BenRG (talk) 01:41, 1 March 2011 (UTC)

How do oral ansthestics with benzocaine work?

Yes I have read the articles but I still dont understand how they work.Accdude92 (talk) 01:18, 1 March 2011 (UTC)

There's a brief explanation at Benzocaine#Mechanism_of_action. Basically Benzocaine blocks the sodium ion channels that, when opened, propogate a signal down the nerves. Since the sodium channel stops working, no signals can get sent down the nerve. --Jayron32 01:34, 1 March 2011 (UTC)

Then what makes the numbing fealing? If it cant transmit a signal, the why dont you feal nothing at all?Accdude92 (talk) 01:36, 1 March 2011 (UTC)

It only blocks certain nerves, those which reach the surface of the skin and sense pain there. You also have nerves whose endings stop some distance under the skin; these nerves sense pressure but not touch. The "numb" sensation you feel when you use benzocaine comes from the fact that you've deadened the surface nerves, but not the deep nerves. Other "caines" like novocaine operate in the same manner; however they are usually injected subcutaneously, thus you tend to lose ALL sensation from the deadened region. With a topical anesthetic, however, you are only deadening the surface nerves. --Jayron32 01:58, 1 March 2011 (UTC)

ear piercing

Is there ever a time when its impossible for an ear piercing to heal?Accdude92 (talk) 02:04, 1 March 2011 (UTC)

Check out wound healing, it should work as with any wound. Constantly traumatizing the site can at least slow the process, also infection probably would do the trick.But frankly cases of non-healing wounds, I've heard about are rather discusting 84.52.32.149 (talk) 02:56, 1 March 2011 (UTC)

The secret magic of color intensity?

I am taking an arts related course in university as an elective, it is meant for people studying audiovisual media. The teacher has been trying to make a point that something happens, if you put two colors of similar intensity together, but she can't explain what and when I tried to make her clerify this she said that I would see. What I see is that any two colors look difrent when put together, but frankly the particular combinations she sugests look dull. Also she seems to have discovered this effect on her own (she's a painter), so I can't find anything on this. What I want is someone to explain what effect this could posibly have 84.52.32.149 (talk) 02:45, 1 March 2011 (UTC)