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November 5

Sending a new theory around

I have a scientific theory with evidence that if it's true, will be an important finding. The problem is I have no clout, don't know anyone, and have no money. And if I send it to people, nearly all will ignore me. And those few that won't ignore me and think I'm right, might steal my idea and claim it for themselves. So how do I send my theory around while making sure I get credit for it and nobody can claim it was their idea? Eachroomfff (talk) 01:10, 5 November 2011 (UTC)

What field are you talking about? If it's math, physics or anything fairly quantitative, you can try posting your work on the arXiv here: [1]. You will probably get feedback, and definitely receive full credit for your work, regardless of the reception. SemanticMantis (talk) 01:41, 5 November 2011 (UTC)

You have to be sponsored by an established arXiv contributor before you can post preprints there. -- BenRG (talk) 03:54, 5 November 2011 (UTC)

(EC) See Wikipedia:Reference desk/Archives/Humanities/2011 October 29#Where to publish ideas regarding unsolved problems in Humanities and Science?. Note that if you publish your work in well known public websites or similar where the date can't be changed by you, it'll be difficult and risky for others to try to claim credit if their work came after yours, although don't take this as legal advice or something that will stand up if it comes to court. Nil Einne (talk) 01:44, 5 November 2011 (UTC)

In the link to the other thread, it mentioned a getting documents notarized. Is there a way to file things with the government that way so they have some proven copy kept somewhere? Eachroomfff (talk) 02:29, 5 November 2011 (UTC)

Is notarizing documents still relevant? I believe the U.S. just switched from a first-to-invent to a first-to-file patent system - which is prevalent in most other parts of the world as well. (Doh, never mind, it isn't implemented until March 2013) Wnt (talk) 03:15, 5 November 2011 (UTC)

You could register your copyright, or just compute a SHA-1 hash of the document and put it the hash on your Wikipedia user page. However, it's extremely unlikely that anyone with a reputation would try to steal your idea. At most they would ask for co-author credit in exchange for helping prepare the paper for publication. That's assuming the idea has merit, which, I'm sorry to say, is also unlikely. -- BenRG (talk) 03:54, 5 November 2011 (UTC)

Er, no - your Wikipedia user page is an entirely inappropriate place to put 'a new theory', or even a hash of a theory (which isn't actually 100% reliable anyway, as proof of authorship), and could well be removed. This isn't a free web-hosting service. Actually, putting it there would be useless anyway from the point of establishing authorship, since Wikipedia users aren't positively identified. AndyTheGrump (talk) 04:17, 5 November 2011 (UTC)

I meant put the hash there, not the document. It's true that Wikipedia users aren't strongly authenticated, but in a priority dispute, being the only person who can produce a document with the hash in question would be convincing enough, I think. Someone had the document then, you can prove you have it now, and your rivals can't prove they ever had it. (Of course, this means the document you send to others can't be the same as the one you hashed, but even small changes would be enough.) -- BenRG (talk) 16:51, 5 November 2011 (UTC)

Posting the hash would not comply with policy. Wikipedia talk pages are for discussions related to improving the encyclopedia. They are not to be used as personal web pages for purposes unrelated to the project.--Srleffler (talk) 17:43, 7 November 2011 (UTC)

Or just put it on a blog. My blogposting on Newcomb's paradox was cited here on page 12, footnote 2. Count Iblis (talk) 04:29, 5 November 2011 (UTC)

As with BenRG, I don't believe there's any real risk of someone publishing Eachroomfff's work as their own, the reputation damage is simply too severe that anyone would try it even ignoring how people may feel about it ethically. However if this is a concern, putting it on a blog may not really help to allay any such concerns as they often allow the blog owner to edit the post and post date without it being that clear, so don't really establish a publication date. (There may be some internal info that could help, but this seems overly complicated). If the OP can get on something like arXiv, this should sufficiently establish a publication date which will make it even more risky (again I'm not talking from a legal POV) for someone to claim the OP's work as their own. If arXiv isn't an option, look for somewhere or multiple places where you can't change the date and is large enough that it's unlikely you can get people with greater level of control to modify it for you. (So random small forums are a bad idea.) Note that these don't have to be your main form of publication. Another though, whereever you post it, archiving it at Webcitation a few times and submitting the site to the Internet Archive (making sure the site allows robots and isn't blocking the internet archive since the long lead time means it'll take a while before you know if your site was archived) should also help. P.S. A greater risk is that their work won't be convincing enough and someone will publish independent verification with stronger evidence and perhaps a better writeup and be the one people remember. Nil Einne (talk) 16:49, 5 November 2011 (UTC)

I have a similar problem, and one of the best things to do is just to work on it in your spare time, publish on the web somewhere, and try to be as professional as possible about the whole thing. An absolute must read is this website, that tells you what not to do. Scientists are quick to sniff out an amateur, regardless of how careful you are. Remember above all that no one goes into science in order to make someone else famous, so you will have to show them you are intelligent and informed, and above all, responsive to criticism, rather than touchy about it. I am hoping that my theory will at least be useful in giving students an exercise in refuting it - if it is wrong, after all, it can still be used as an undergraduate problem. If it is too hard for an undergraduate to refute, who knows, it might even be worth serious debate. You could try some variant of this approach - at least try to use it first as an exercise for others to engage with intellectually, so their curiosity might be piqued. It's been emotional (talk) 07:05, 5 November 2011 (UTC)

If yo9u wish to patent it you should register patents before publication. Graeme Bartlett (talk) 06:00, 6 November 2011 (UTC)

It looks like the only way to get credited is to cough up $75 and file a provisonal patent and hope they keep records so I don't have to pay something like $400 for a real patent. I actually did design an invention based on my idea, but I don't have the money to make it. Heck, if I had money, I could actually test my theory instead of just parts of it from data others collected. Anyhow, is arxiv.org a good site to share research? It seems that every single tiny subcategory requires endorsements before I can post in it and getting past it is a huge pain and actually very likely for my idea to be stolen while I beg person after person to be endorsed. I'm not arrogant, just distrustful. For sounding professional when I post things there, do I have to write my papers in such a manner that is heavily technical, horribly unpleasant to read, and if shown to the average person, they couldn't make sense of the first sentence? I've worked all my life to write the opposite. I guess it's a college paper kind of thing where you write that way so the professor can't find locations to take points off. So is arxiv.org a good place for work to be seen for review? Eachroomfff (talk) 10:18, 6 November 2011 (UTC)

I can't answer regarding most of those points, and my own theory is not related to an invention, so there's no risk of theft in my case. I'm not sure what the patent situation is, although you should check with a lawyer (or law student since that might be too expensive) about what the risks are there. I can quietly say that by "professional" I only mean in the manner described, responding meaningfully to criticism, such as by asking follow up questions for clarification if your audience is sympathetic (it has helped me to correct errors that would have consumed years of my life). Few people appreciate unclear writing, but academics are a diverse lot, and can easily get seduced by fancy new terminology (it is a sign of laziness, but many of the better writers are well aware of the problem). Some also have the research and analytical skill, but not the flair for writing, and don't even have the slightest clue what it is about - or perhaps they are too pressed for time to be clear. Show them your skill at written expression, but draft relentlessly, even enlisting helpful friends to check you haven't overlooked something that might confuse the reader (it's easily done). Spare no effort, because you will become a better writer through this process. And develop a tough exterior, since it is hard to make it out there, sometimes even for geniuses. If you reflect on everything, you have a fair chance of getting somewhere up the mountain, even if not all the way to the top. It's been emotional (talk) 12:13, 6 November 2011 (UTC)

I'm a bit confused about why you now bring up a patent. If you want to protect some invention, then you probably should file a patent but we can't provide legal advice. If you simply want to get credit for your work, then as several people have said, it is unlikely any reputable scientist is going to claim your work as their own. You can reduce the chance further by making sure you have some evidence for when you first published your work, this doesn't have to be in the form of a patent and in fact this seems an unnecessarily limiting complication (patents are only for inventions and the patent application should concentrate on this only discussion your theory and the evidence for it when it relates to the invention). As I noted, this doesn't guarantee your name is going to be the name most associate with whatever discovery you believe you have made, but filing a patent isn't going to help there. As for writing professionally, helpful advice has already been provided, e.g. IBE and GB. You don't need to use unnecessarily complicated terminology, in fact it's likely to be a negative. However precision and clarity are important, if it sounds like you don't know what you are talking about or you make fundamental errors or inaccurate claims or say wacky things many people will just stop reading. One of the reasons why many papers are 'horribly technical' or difficulty for the average person to understand is because a lot of modern good research is often fairly technical and can be fairly difficult for the average person to understand except in a simplified form. Nil Einne (talk) 14:38, 6 November 2011 (UTC)

I brought in that patent idea, but it was if the idea could earn money. Another alternative is Wikiversity where you can post original contributions. It will time stamp your edits. But don't expect a fair hearing over there as it is a Wiki with people present. Graeme Bartlett (talk) 10:06, 8 November 2011 (UTC)

EMP protection

Is it possible to use a large thyratron to send EMP to ground before it can burn up any other electronics? Or would the gizmo just explode before it can trigger the ground circuit? 67.169.177.176 (talk) 02:00, 5 November 2011 (UTC)

When you design such a circuit you will have to make it withstand several thousand volts of RF, and if you do it wrong you will destroy your source. This is an engineering problem in power electronics and high power RF, how to stop the destruction of the output stages when it is presented with the wrong load. I suspect the answer to your question is yes if the thyratron is making the pulse itself. If the EMP comes from somewhere else then the thyratron may survive, but other more delicate stuff may be ruined. But what is your real question? Graeme Bartlett (talk) 04:21, 5 November 2011 (UTC)

My real question, which I ask for the second time, is whether it is possible to protect high-voltage electrical components from an external, non-nuclear EMP that is transmitted through a power line by using a thyratron to momentarily ground or short-circuit the line when the EMP arrives, giving the main circuit breakers time to open while protecting them from being welded in place by the EMP. 67.169.177.176 (talk) 04:48, 5 November 2011 (UTC)

In the past I have used lightning arrestors for this sort of thing. They have some sort of gas discharge that shorts out during an over voltage. But these were on antenna cable, not power cables. But there are spike and surge protectors for power lines. The thyratron needs to be triggered by a high enough voltage (say a thousand volts) and can dump tens to hundreds of amps. Usually the grid will be in control of initiating the discharge, and this would be a problem for your application as you will not know when to trigger. It will take a fraction of a microsecond to turn on, and this may let in enough of a pulse to destroy your sensitive equipment. You would need some sensor on the power line, plus a delay in the power of say 150 meters of cable, then you could delay the EMP enough to trigger this device in time. Usually it needs a hot cathode and so will consume power all the time. Graeme Bartlett (talk) 05:46, 6 November 2011 (UTC)

OK then, so I take it that your answer means this arrangement is workable in principle (with extra components installed), but won't give complete protection. (In other words, it can keep the main transformers from blowing up, but the telemetry equipment could still get fried.) Thank you very much for the info. 67.169.177.176 (talk) 02:48, 7 November 2011 (UTC)

That is a fair enough summary, If what you are protecting is valuable then spend the money to get a modern MOS protector. And replace it when it has received a spike. And if you are an engineer do not reply on what you get from random people on the internet. Graeme Bartlett (talk) 09:59, 8 November 2011 (UTC)

FYI, this is for a sci-fi detective novel, not for a real-world engineering project. 67.169.177.176 (talk) 05:13, 9 November 2011 (UTC)

charge

what is the meaning of quantization of charge.and what is the meaning of conservation of charge and explain its application with examples and it is also said that mass is quantized what does it mean plz provid the accurate and right information — Preceding unsigned comment added by Bhaskarandpm (talk • contribs) 03:18, 5 November 2011 (UTC)

• Quantization means something comes in discrete units, it means the opposite of "continuous". The smallest unit of a measurement is called the quantum and lots of things are "quantized". Electric charge is quantized; the smallest unit of charge was originally thought to be the "fundamental charge" of electrons and protons (by convention assigned charges of value -1 and +1); but the discovery of quarks indicates that the smallest quantum of charge may be 1/3 of a fundemental charge.
• Conservation of charge refers to a conservation law as it applies to electric charge. What this means is that any interaction or charge must maintain a constant electric charge; if anything gains electric charge there must be something else which loses the same amount of electric charge. You can never have any process which creates (or destroys) electric charge.
• Mass is quantized because mass is energy (see mass-energy equivalence) and energy is quantized; indeed it was one of the first physical quantities to be quantized; quantization of energy is the basis of Planck's law, which is sort of the foundational law behind what became quantum mechanics.

I hope these summaries make sense, and if you want more details, please feel free to read the blue links I have provided. --Jayron32 03:48, 5 November 2011 (UTC)

Why does charge exist? Plasmic Physics (talk) 06:09, 5 November 2011 (UTC)

Why does anything exist? If you are looking for a sense of purpose, I'm not sure science will give that to you. --Jayron32 15:18, 5 November 2011 (UTC)

I think he is asking what is the actual process of creating charge? For example, a moving electron creates a negatively charged electric field. Why? Can an electron move without creating an electric field? Can it move in such a way that it creates a positively charged field? Can it ever stop moving all together? I don't think he is asking for the electron's personal opinion about charged fields. -- kainaw™ 15:40, 5 November 2011 (UTC)

Charge exists outside of motion. Moving electric charges create magnetic fields, but even a stationary charge creates an electric field. Charge was "created" in the Big bang along with a whole lot of other properties of matter; the fact that it is both invariant and conserved in the world today means that it is never created or destroyed; every interaction and change in the universe basically shuffles charge from one location to another, but charge doesn't get "created", it merely transfers. As far as the other implied question, which is why the electron has a negative charge, I'm not sure that's at all answerable on the level you want it to. Charge is merely defined as that property of matter that causes protons and electrons to be attracted and electrons to repel other electtrons. By convention, we call the electron "negative" and the proton "positive", but that's purely arbitrary, the signs could be swapped and have the same meaning. But there is no "why" a particle has a charge. Its a statement of being, not a statement of process. --Jayron32 16:02, 5 November 2011 (UTC)

Davies equation, ionic strength and molality

Is the Davies equation still valid if ionic strength is in the form of molality and not molarity (and isn't ionic strength supposed to be dimensionless)? elle _{vécut heureuse} ^{à jamais} (be free) 17:19, 5 November 2011 (UTC)

I'm not sure about the first question, but the unit of electric charge is the negative charge of the electron. Dualus (talk) 18:54, 6 November 2011 (UTC)

There aren't any Coulombs in the davies equation, so I'm pretty sure this shouldn't be the case....elle _{vécut heureuse} ^{à jamais} (be free) 15:37, 7 November 2011 (UTC)

Simple optics/meteorology question?

When scattered or patchy clouds obscure the sun, it often happens (of course) that sunlight will pour through a gap in the cloud cover. My question is, why does the sunbeam seem to diverge conically? I mean, since the sun is—as we say—at infinity, all of the photons should be traveling more or less parallel, so intuition suggests that the beam ought to be more or less a shaft and not so much conical. What's confounding my intuition? Is it merely atmospheric scattering and a bit of diffraction?—PaulTanenbaum (talk) 16:48, 5 November 2011 (UTC)

The sun may be kind of large, but it's neither a point source nor a plane source. The light rays from the bottom of the sun approach a location on Earth at a different angle from the "top of the sun" (except at the equator at noon). The stars can be assumed to be at infinity, but not the sun. A point source filtered through a lens focused at infinity acts like a plane source... elle _{vécut heureuse} ^{à jamais} (be free) 17:16, 5 November 2011 (UTC)

There's nothing special about the equator at noon... the sun is still a disc. --Tango (talk) 17:45, 5 November 2011 (UTC)

The difference between angle of incidences would be more symmetric though. elle _{vécut heureuse} ^{à jamais} (be free) 17:59, 5 November 2011 (UTC)

Symmetric about the vertical, yes, but why is the vertical significant? --Tango (talk) 18:48, 5 November 2011 (UTC)

Crepuscular rays has some text and references that may help answer this. Textorus (talk) 17:39, 5 November 2011 (UTC)

The beam *is* a shaft of substantially constant cross-section. It appears as a cone due to perspective. The shaft is actually angled towards you, and is nearer to you (and therefore appears wider) the nearer it gets to the ground. It's like looking at a road which disappears into the distance. — Preceding unsigned comment added by Callerman (talk • contribs) 03:41, 6 November 2011 (UTC)

Quantifying splashing; changing the property of the splashing solvent

Suppose I have a concentrated solution of salt water; will it splash more than pure water? The Reynolds number should decrease, but the water is also much denser (and the density seems to increase much faster than the viscosity). Would a greater density increase inertial forces and therefore the Reynolds number, or would the greater viscosity decrease it?

It seems to be there are two types of solutes: a low-concentration solute that increases viscosity greatly but not density (agar?), and increasing density without increasing viscosity (using heavy water?)

Also does splashing commute? All other conditions constant, will there be more splashing if I drop concentrated salt water into pure water, or pure water into concentrated salt water?

elle vécut heureuse à jamais (be free) 16:54, 5 November 2011 (UTC)

I would expect that you would get smaller droplets if you could reduce the surface tension. Thus, adding detergent should make for a finer spray (but, of course, also produces suds). StuRat (talk) 18:08, 5 November 2011 (UTC)

Hmm...I am curious -- I have heard of non-suds detergents but I never really got the principle. Most phospholipids (the biological kind) wouldn't create visible micelles, right? elle _{vécut heureuse} ^{à jamais} (be free) 18:12, 5 November 2011 (UTC)

Is a splash at the boundary of aerosolization? How many Daltons in the minimum size droplets you want to include in your percent mass loss over time concerning liquid connection to the bulk of the water mass. Dualus (talk) 18:53, 6 November 2011 (UTC)

There's no need to mess with percent mass loss. To measure the splashing, just get a panel of diving judges to score it. – b_jonas 08:55, 7 November 2011 (UTC)

Physiological details of figure skaters' increased tolerance of dizziness

When a figure skater develops or increases the ability to not be as dizzy after some very rapid spinning, is the change a change in the cells in their inner ears that translate the physical spinning into nerve signals, a change in the brain of the processing of nerve signals from the ears, both, or something else? 69.243.220.115 (talk) 20:33, 5 November 2011 (UTC)

It is primarily mental. If you ignore a stimulus (such as the dizzy feeling) long enough, your brain is trained to ignore it. Skaters do get dizzy when they are learning. They slowing get better at simply ignoring it. -- kainaw™ 20:44, 5 November 2011 (UTC)

Kainaw, are you just giving a personal opinion, or is there some other basis for your statement? Our article Motion sickness has a very short section Dizziness due to spinning. The article links to Acclimatization in its "See also" sections, but does not discuss acclimatization within its body. Likewise with our seasickness article, though it does state that some people become "immune through exposure". I've both witness and experienced acclimatization against seasickness, but I do not know how to determine if it is a psychological or a physiological change. -- 49.228.87.218 (talk) 03:27, 7 November 2011 (UTC)

From personal experience in ballroom dancing (a) you are taught some tricks that help minimise the dizziness (b) a good dancer will be dancing long enough to do some anti clockwise turns as well as clockwise in their routine, while you fall over (c) yes I think you do acclimatise a fair bit. FWIW I get somewhat dizzy after 8 spins in succession. Incidentally I have not been seasick while racing ocean going yachts for several years. On the other hand I could make myself seasick pretty quickly, I'm just very careful about what I do and I don't seem as suceptible as most people anyway.Greglocock (talk) 02:30, 8 November 2011 (UTC)

Fiber optic cable damage

Is it true that once a fiber optic cable has been damaged, it can not be repaired? ScienceApe (talk) 23:22, 5 November 2011 (UTC)

I would imagine it could be, but the question is whether that's more economical than replacing it. Since repairing it likely involves some delicate work (I imagine you'd cut it, polish the ends, then use a connector) and still it would never be quite as good as it was, it might often make sense to replace it. Similar logic as with a chipped windshield. StuRat (talk) 23:37, 5 November 2011 (UTC)

Repairing a FO cable is even harder than StuRat says it is -- the optical fibers are made of super-thin filaments of optical glass, so in order to repair any break in the cable, you must (1) cut the cable, (2) polish the ends of each fiber, (3) fuse each fiber together thermally, making sure not to mismatch them and maintaining perfect alignment between the pieces, and (4) grind down the joint between the pieces of each fiber to a perfectly smooth cylindrical section of precisely the same diameter as the rest of the fiber (this is absolutely essential, because any roughness or change in cross-section will allow the light to leak out). Needless to say, the amount of effort involved would be absolutely prohibitive compared to replacing the cable with a new one. 67.169.177.176 (talk) 23:59, 5 November 2011 (UTC)

I can think of a better solution (at least for very long cables which would be too expensive to replace): Instead of matching up the fibers, attach the fibers to a chip on each side, then use the chip to map the fibers from cable A to cable B. I believe they've used a similar fix for severed nerve bundles. StuRat (talk) 00:27, 6 November 2011 (UTC)

The anon above is half-right about the process, but overestimates the difficulty. The fiber needs to be cut and stripped, and then the end is cleaved (not polished). It is not necessary to grind down the diameter after splicing. A good fusion splicer automatically aligns and fuses the fiber ends without distorting them or altering their diameter. Once the fiber is spliced, the joint has to be protected since the fiber's protective coating and jacket have to be removed to splice it. For indoor patchcords and pigtails, a rigid sleeve is slid over the joint and then heated which causes it to shrink, forming a stiff protective cover for the fragile splice. There are also coatings that can be applied as a liquid and then cured to provide a protective covering. I'm not sure what is used to protect cables that require more durability such as outdoor cables or even indoor plenum cable.

The time consuming part is not the actual splice, but the work to strip the fiber and then re-protect it after splicing. Fusion splicers are also not cheap. It may well be cheaper to just replace the cable in many cases.--Srleffler (talk) 18:07, 7 November 2011 (UTC)

Yes it's entirely possible.

Technicians that work for me have been doing FO repairs for at least the 15 years that I've been in the commas infrastructure game.

ALR (talk) 00:04, 6 November 2011 (UTC)

Commas ? StuRat (talk) 00:24, 6 November 2011 (UTC)

You mean commerce, don't you? 67.169.177.176 (talk) 01:08, 6 November 2011 (UTC)

Comms, as in communications. Wide Area Networks using fibre backbones as well as satellite shots, microwave transmissions and in some cases HF radio legs.

Also building and vehicle infrastructure. The main thing for a vehicle is that it can be maintained in the field so fibre repair ki is carried onboard.

ALR (talk) 09:53, 7 November 2011 (UTC)

How about comms as in communications. There are special splicing machines that do the cutting and fusing job so it is not as hard as doing it all by hand. Usually there will be excess fibre coiled in a pit nearby, so that it can be shortened at a splice point without having to insert a piece. This will certainly be done for cables laid underground, and probably between points in a building, as the cost to repull cable will be high. If the damage also damages the conduit, or is at an inaccessible point, eg by crushing it may not be possible to splice it back together and it is an expensive replacement job. Graeme Bartlett (talk) 05:13, 6 November 2011 (UTC)

Hi guys—try to remember that we're the Reference Desk, and we should strive to provide references with our responses. Thermally fusing the cut ends together is called fusion splicing, and we have an article on that. There's also an article covering optical fiber connectors. Remarkably, there's an eHow article on "How to Repair A Cut Underground Fiber-Optic Cable", but you'll need to copy and paste the URL to get past our spam filter (http://www.ehow.com/how_5025648_repair-cut-underground-fiberoptic-cable.html). Here's a short, accessible summary of undersea fiber repair from Slate: How Do You Fix An Undersea Cable? TenOfAllTrades(talk) 15:36, 6 November 2011 (UTC)

November 6

speed reading

If I learn spead reading in my mother language, does it work for any other language, say, English? my language if far from similar to English, but I can read very well in English, but speed reading is different, so is it possible?--81.31.188.59 (talk) 10:32, 6 November 2011 (UTC)

If it's simply a technique that is transferable, then it probably is, and Speed reading is really just a mixture of techniques to draw the key ideas from a text while skimming over unnecessary content. Since it is certainly possible to speed read in English, provided the languages weren't hugely different (say French, Italian, or Spanish for example) then I don't see why it wouldn't be transferable if you had strong reading and comprehension skills in both languages. However if there were big differences in the languages, say an Asian language that didn't use the Latin alphabet, then this may not be the case. --jjron (talk) 10:57, 6 November 2011 (UTC)

I'm not convinced that speed-reading isn't mostly a fraudulent marketing device. 66.108.223.179 (talk) 03:05, 7 November 2011 (UTC)

No it isn't, you can actually practice this by scrambling texts such that they are barely readable. What then happens is that the text becomes easier to read in fast reading mode than in normal slow reading mode. Try it on the following text that I took from a random Wiki article and then I randomly permuted the letters in each word, except the first and last letters, they are kept fixed:

"Qitue often trhee is a tie, in wichh csae a semi-final taerebiekr rnoud is need. For exmpale, if six pyarles fiineshd the plinieamrry rudnos with seven poitns and fefetin fenshiid with six potins, the six who fniehisd wtih sveen ptoins amltcaitolauy acvadne to the fnial cotpiemiton. The fetefin with six pnotis mvoe into the semi-fnail rnuod wehre the top fuor are dniemteerd to fill the reimadner of the setas in the fanils. Tihs is done by aniskg every paelyr the same qeuostin at the same time and gviing ecah player tlwvee socedns to wirte dwon the aswenr. Ecah qetsioun is alutmcaotaily reeptead tcwie. Eronvyee reeavls thier aenwsr at the end of the twvlee sdcones and pyrales are etinelamid on a sgnile-etaoiimniln basis. If, unsig the aovbe explame of four oepn setas in the flanis, three is a qiueotsn wehre eghit pleayrs are lfet in the semi-fnail ronud and there paryles get the qteuoisn rgiht, thsoe terhe ancdave to the filans. The oethr fvie who got the qusioetn worng wlil cunoitne with the sgnlie-eiiaolmtnin purcorede to dneitemre wichh ctemopiotr wlil tkae the last open seat in the falins." Count Iblis (talk) 04:47, 7 November 2011 (UTC)

Intensity of the superposition of two coherent waves

I think I'm missing something here. Say you have two identical, coherent light sources at equal distance from a point $P$, so that the waves from both sources interfere constructively at $P$. Let $I$ be the intensity, and $A$ the amplitude, of the wave from either source as measured at $P$. The amplitude of the superposition of the 2 waves at $P$ is $2A$. Since intensity is proportional to the square of amplitude, so that intensity of the superposition of the waves should be $4I$. But intensity is a power measure; you shouldn't be able to combine power from 2 identical sources and get 4 times as much. Where do I have it wrong? — Preceding unsigned comment added by 173.49.81.140 (talk) 13:03, 6 November 2011 (UTC)

You don't have it wrong. your logic is correct. That's why constructive interference is different than simply adding intensities. Elsewhere in the interference pattern the two sources will interfere destructively and on average over the whole area of influence of the sources, energy is conserved. Energy conservation is done globally, not locally. Dauto (talk) 14:02, 6 November 2011 (UTC)

there are other situations, possibly more intuitive, where similar things happen. For instance, if a mass $m\,$ initially at rest is accelerated by a force $F\,$ for a time $t\,$, its acceleration will be $a={\frac {F}{m}}\,$, the displacement will be $d={\frac {1}{2}}at^{2}={\frac {1}{2}}{\frac {F}{m}}t^{2}\,$, the work will be $W=Fd={\frac {1}{2}}{\frac {F^{2}}{m}}t^{2}\,$ and the power will be $P={\frac {W}{t}}={\frac {1}{2}}{\frac {F^{2}}{m}}t\,$. Now, if a second force identical to the first happens to be acting simultaneously to the first effectively doubling the force, the power quadruples. There is no such a thing a power superposition where the power of two forces acting together is given by the sum of the powers of each one separately. That's just not the way things work. The same thing is true for the superposition of two waves. The powers don't simply add up. The waves interfere and the resulting power can be anywhere between zero and the quadruple of the power of one of the sources (if the waves are identical). Dauto (talk) 16:26, 6 November 2011 (UTC)

Which is more stable, K or K+?

Hey guys, just a senior in high school studying up on chemistry for his finals. There's one small thing bugging me that I just cannot find an answer for.

The statement "K is more stable than K+" : is it true or false? Because if you look at it from enthalpy's point of view, K is more stable than [K+ + e-] because you need to provide it its ionization energy if you want to separate an electron from K. But is the ion itself (just K+, not [K+ + e-]) more unstable than its neutral atom counterpart? Is it even possible to compare its stability without counting the electron? Because the way I see it, the total sum of the enthalpy of K+ and the kinetic energy of the electron is definitely greater that the enthalpy of K, but maybe the enthalpy of the ion itself (without the kinetic energy of the electron) is less than K. Because when you think about it in a simple non-thermodynamic point of view, potassium (or any alkaline metal for that matter) is definitely unstable in its atomic form, and is definitely happier in its ionic form because of the octet rule, so you could say that K+ is more stable than K, right?

Maybe I've got the whole concept of enthalpy wrong, or maybe I'm right, in which case my question above is something worth thinking about. Care to help me out? thanks.Johnnyboi7 (talk) 15:45, 6 November 2011 (UTC)

If you just have an isolated atom, K is more stable than K+. A hunk of pure potassium metal in a vacuum will sit there without the atoms decomposing. But if you have a compound such as KCl, a split into K+ and Cl- is more stable than a split into K and Cl. Looie496 (talk) 16:55, 6 November 2011 (UTC)

To expand on what Looie496 said, and also to answer your question "Is it even possible to compare its stability without counting the electron?", the answer is probably not. In order to consider whether a system is more "stable" with potassium atoms or potassium ions in it, you need to consider what happens to that one electron. If the potential energy of the electron seperated from the atom is lower than the potential energy of the electron joined to the atom, then the seperated state is more stable; if the inverse is true than the joined state is more stable. One can invent any number of possible interactions where the side with the potassium atom is more stable, likewise one could come up with situations where the side with the ion is more stable. There's no single answer. --Jayron32 19:00, 6 November 2011 (UTC)

A common way to compare "stability" is to look at the energy difference between one state and another, under certain conditions. In the gas phase, this energy difference is known as the ionization energy (our article isn't really clear that it applies to gas phase species, but it does). Specifically, it requires about 419 kJ/mol to go from gaseous potassium atoms to gaseous K⁺ and e^- ions. Buddy431 (talk) 19:14, 6 November 2011 (UTC)

I concur — Preceding unsigned comment added by 203.112.82.1 (talk) 19:55, 6 November 2011 (UTC)

Genealogy

how to know my ancestors? who they are a kshatriya or someone else? to which dynasty they belong? — Preceding unsigned comment added by Vichu8331 (talk • contribs) 15:49, 6 November 2011 (UTC)

We have no way of knowing who your ancestors are. Looie496 (talk) 16:49, 6 November 2011 (UTC)

The only way to know who your ancestors were to any specific accuracy is to actually have them documented; that usually means someone wrote down every time someone was born; who their father and mother was, etc. Depending on what culture you live in and at what point in history will determine how easy it is to track down your specific ancestors. See Genealogy for methods on tracking your ancestors. --Jayron32 18:54, 6 November 2011 (UTC)

I added the title "Genealogy" to this question, which was posted without a title. However, perhaps Varna or maybe Caste or Race would have been a more apt title, since I think that's more specifically what the question is about. Kshatriya is a varna, and I'm pretty sure the question about dynasties refers to Lunar Dynasty vs. Solar Dynasty, which are basically racial divisions. So respondents should just respond to the questions per se, and not be influenced by the choice of title. I probably should have added a comment to that effect when I added the title. Red Act (talk) 19:31, 6 November 2011 (UTC)

I think the standard answer is to start with what you know and work backwards, and I think that will apply in this case too. Write down who your parents are, who their parents were, and if you know it, who their parents were. India does keep birth records, but I have only seen a documentary on the Anglo-Indian community's records so I'm not sure of the extent to which the records are kept and how far they go back. --TammyMoet (talk) 19:42, 6 November 2011 (UTC)

That wouldn't be Alastair McGowan's appearance on Who do you think you are? by any chance? That dealt with trying to dig up old records, which were perhaps a little more available than one would imagine. Of course, the producers probably through huge wodges of cash at people to find them. Brammers (talk/c) 09:14, 7 November 2011 (UTC)

Yes it was, hence my caveat of the community. A researcher who knows their subject is worth more than gold, in my experience. --TammyMoet (talk) 10:36, 7 November 2011 (UTC)

The professional historian's association's rate's aren't recent recommendations (2003), but back calculating from equivalent wage earners and adding a consultant's mark up, I'd charge AUD300/hr before GST, you pay my costs (living expenses away from home based off the public servants rates, archival retrieval fees, transport economy air, first rail). The professional association recommends something similar, based off 2003 costs they're asking for a 5x hourly mark-up. The current hourly is around AUD60 (including super) for employee full-time academic historians non-professorial. Fifelfoo (talk) 10:46, 7 November 2011 (UTC)

I double checked the rates; they're 2011 and they're only asking for a 1.5x mark-up for casual consulting. Obviously that's not based on attempting to live off consulting work on a serious basis…and, correspondingly, a contractor would negotiate their professional fee downwards based on a contract with a longer fixed period than hourly engagement. Fifelfoo (talk) 10:50, 7 November 2011 (UTC)

Note: Modern DNA tests can show with some (?) accuracy where a person's ancestors lived and possibly such things as a common ancestor (Genghiz Khan has been the object of studies). DNA also shows a fairly large percentage of people with "Neanderthal ancestry" etc. Collect (talk) 13:39, 7 November 2011 (UTC)

charge

why a charge produce electric field what is the reason for the charge to interact with other charge ? cant charge exist alone — Preceding unsigned comment added by Bhaskarandpm (talk • contribs) 17:28, 6 November 2011 (UTC)

The electromagnetic force is not limited by distance, only weakened. Dualus (talk) 18:50, 6 November 2011 (UTC)

(edit conflict)An electric field is a way to model the effect of electric charges on other electric charges. Because electric charges exert an influence on other electric charges, and that influence is related to the relative positions of those to charges, the "electric field" is merely the model which associates the nature of that interaction with various points in space. Fields are powerful tools in physics because they allow one to predict the outcome of various "thought experiments", such as calculating the effect of one charged particle placed into an environment of other charged particles. Your second question is unanswerable. The "reason" implies that there is some greater purpose. The interaction between two charges is inherent in the definition of what a charge is: Charge is that property of an electron which makes it attracted to a proton and repeled by another electron. It does not have a reason, excepting that it was how the Universe was organized during its creation. It is just a description of charge. You can't assign "reason" to such a quantity. It is just a description of being, not part of a process. --Jayron32 18:51, 6 November 2011 (UTC)

I concur — Preceding unsigned comment added by 203.112.82.1 (talk) 22:32, 6 November 2011 (UTC)

Tempture and heat

In assuming that a body does not reflect all of the radiation that it gets, Does a visble light change the tempture of the objects it hits?77.125.136.181 (talk) —Preceding undated comment added 17:54, 6 November 2011 (UTC).

Yes. See Absorption (electromagnetic radiation). --Jayron32 18:44, 6 November 2011 (UTC)

Of course it does. Light is electromagnetic radiation, and thus contains energy. If a certain amount of light is absorbed, the corresponding energy has to go somewhere (see conservation of energy). If your absorbing object is not capable of systematically transforming this energy into another form (like a photodiode or a chloroplast) it will be transformed into heat energy.

For the average human this is hard to notice as we usually do not get to deal with sufficient quantities of light that only contains visible wavelengths to make this effect measurable by human senses. Phebus333 (talk) 03:23, 7 November 2011 (UTC)

For any warm-blooded animal, the core body temperature isn't likely to vary much, although the skin, hair or fur facing a bright light may get warmer. Thermoregulation will work to keep the core body temperature more or less constant. In a human, that includes shivering, putting on warmer clothes, eating and drinking warm things, etc., when cold, and sweating, taking off clothes, eating and drinking cold things, etc., when hot.

Of course, we also regulate our temperature by moving into and out of the light, as do cats, who are famous for sleeping in a spot of sunlight on the floor, and moving to follow it. StuRat (talk) 16:17, 7 November 2011 (UTC)

Indeed, sunlight is not all visible, but most of its energy is in the visible frequency range. Glass is not, usually, transparent in infrared, and fairly opaque to UV, so if you use a lens to start a fire, that mostly depends on visible light. --Stephan Schulz (talk) 10:59, 8 November 2011 (UTC)

A mirror and an image projector

When an image projector projects on a wall you usually see a picture. But when a projector projects on a mirror the mirror reflects the image, So what is the regularity of which the projector works in? Exx8 (talk) —Preceding undated comment added 17:59, 6 November 2011 (UTC).

your question is unclear. You stated to unrelated facts of optics (1. Screens allows us to see real images and 2. mirrors reflect light) and then you ask for a regularity? What do you have in mind? Dauto (talk) 19:03, 6 November 2011 (UTC)

I think you are asking about how overhead projectors work, but I'm not sure. Quest09 (talk) 20:49, 6 November 2011 (UTC)

If you shine a projector ONTO a mirror, I don't think you'll see the image in the mirror, you'll see the reflection of the projector shining AT YOU. The image will be projected onto you and your surroundings. Vespine (talk) 01:55, 7 November 2011 (UTC)

That is correct. The image from a projector is so bright that your eyes cannot discern an image when seeing the light reflecting from a mirror. But, there is a slightly related way to see a reflected image. To avoid glare, projector booths in movie theaters have tilted windows that the projects shine through. The tilted glass reflects some of the light - but not a lot of it. Because only a small percent of it is reflected, you can see the movie image on the glass. -- kainaw™ 14:04, 7 November 2011 (UTC)

Is that an application of a Brewster angle window that is not mentioned in that article? DMacks (talk) 15:19, 7 November 2011 (UTC)

No, the idea of the (slightly) tilted projection room window isn't to pass light of a particular polarization, it's to prevent multiple reflections between the window and the optics in the projector. (Oftentimes there are two panes of glass between the projection room and the theater to improve sound isolation; these two panes will be set at slightly different angles to suppress distracting reflections between these layers of glass as well.) The goal isn't to prevent all reflections so much as to try to keep the reflections that do occur from ending up anywhere annoying. TenOfAllTrades(talk) 15:47, 7 November 2011 (UTC)

What kind of effect?

If you give some innocuous pill to someone with an illness which heals alone within x days, you'll obtain some success. How do you call this effect? Quest09 (talk) 20:25, 6 November 2011 (UTC)

placebo effect. --Jayron32 20:29, 6 November 2011 (UTC)

yes, but isn't the placebo effect isn't always related to the expectations of the patient? I was thinking about a coincidence effect which is not a placebo effect. Note that here we are treating a condition which will heal alone, and not improving some treatment at all. I suppose there is a name for this fallacy. Quest09 (talk) 20:46, 6 November 2011 (UTC)

Not sure which way round you mean in "placebo effect isn't always related to the expectations of the patient" – the placebo effect is always related to the expectations of the patient. Returning to teh rest of the question as I understand it (it's not clear), I think what you mean is they were going to get better anyway, they take a sugar pill and they then attribute the success to the pill. It's an extension of the correlation does not imply causation fallacy. Grandiose (me, talk, contribs) 20:55, 6 November 2011 (UTC)

Yes, I was asking "isn't the place effect always related to the expectations of the patient?" What I wanted is something like correlation does not imply causation fallacy, thanks. Quest09 (talk) 21:07, 6 November 2011 (UTC)

It's also the expectation of the physician, and other researchers. If the doc knows you've been given some experimental new wonder-drug he may examine you with a different mind-set than if he knows you haven't received any treatment. The doctor's attitude may even 'rub off' on the patient. (This is why the placebo effect can occur even in veterinary drug trials. ) APL (talk) 21:12, 6 November 2011 (UTC)

I'd call it Post hoc fallacy, it's similar to the above but the pill comes before the cure so I think it fits better. Vespine (talk) 22:09, 6 November 2011 (UTC)

There's an important distinction there that you'll want to be careful of. The placebo effect is only the difference between the group that receives no treatment and the group that gets a sugar pill: the psychologically-driven physiological benefit of a biochemically-irrelevant therapy. Consider patients with the common cold in a clinical trial comparing sugar pill to no treatment, using survival as the measured outcome. (I admit that it would be difficult to secure funding for such a trial.) In the control group, 100% of patients survive, and in the placebo (sugar pill) group, 100% of patients survive. In that case, there was no relevant placebo effect on survival, because we got the same outcome in both groups.

If one of the patients in the sugar pill group nevertheless concluded that he had been saved from a horrible death by the placebo pill, it would be an example (per Vespine) of the post hoc fallacy, which in turn is either a subcase of or a related error to (depending on one's definitions) the correlation/causation fallacy noted by Grandiose. TenOfAllTrades(talk) 22:59, 6 November 2011 (UTC)

It's an example of regression to the mean. Such a disease/condition is called self-limiting. --Colapeninsula (talk) 12:42, 7 November 2011 (UTC)

Regression to the mean has nothing whatsoever to do with recovery from a self-limiting illness. Regression to the mean is a statistical artifact not reflective of the underlying properties of the system being examined. The recovery from illness (a fever declining to normal temperature, for example) is a genuine phenomenon that is being measured accurately. TenOfAllTrades(talk) 14:48, 7 November 2011 (UTC)

While I agree it's not really the answer the OP is after, I'm not sure I'd say it has "nothing" to do with it. I have read regression towards the mean used to explain why people can be fooled into thinking some treatment they are taking has an effect even if it does not, specifically with regard to chronic illness like arthritis, rather then self limiting illness like a cold. Taking the arthritis example, pain is generally experienced in cycles of good and bad periods, so you'll take the medicine when the pain is at its "worst" and regression towards the mean typically results in the pain eventually lessening and this is ascribed to whatever treatment was taken. Vespine (talk) 23:21, 7 November 2011 (UTC)

Likelihoods and conditional probabilities, in the context of sensitivity and specificity.

I would appreciate some help in getting the concepts of likelihood and conditional probability straight. I'm posting here and not on the maths desk, because the question relates to fairly elementary staticstics applied to science, and because I think I'll have a greater chance of understanding the answers here. I shall begin with presenting what I think I know about the matter first, and then point out what appears to me to be inconsistant usage.

Here's my understanding of a likelihood: A likelihood is the probability of obtaining the data that actually resulted from an experiment, given that some hypothetical statistical model were true. The concept is often used when the parameters of the model can be varied, creating a likelihood function that dependes on the parameters, which can be used for obtaining maxiumum likelihood estimates of the parameters. Thus, a likelihood is a special case of a conditional probability, which matches the pattern "probability of observed data given hypothetical model".

Here's my understanding of sensitivity: It is the conditional probability that a person will test positively, given that he has the condition that is tested for. I would not call this a likelihood, since it does not match the pattern "probability of observed data given hypothetical model".

Here is my understanding of specificity: Specificity is the conditional probability that a person will test negatively, given that he does not have the condition that is tested for. Again, I would not call this a likelihood, since it does not match the pattern "probability of observed data given hypothetical model".

After this long introduction, here is my question. Why do we use the term likelihood rato about the ratio between sensitivity and (1 - specificity) in diagnostic testing? I've argued above that sensitivity and specificity should not be called likelihoods.

• Are my definitions above too restrictive or otherwise wrong?
• Is the nomenclature itself sloppy?
• Or is there some other explanation?

Thanks in advance, --NorwegianBlue ^talk 22:14, 6 November 2011 (UTC)

I'm not at all qualified but until someone else turns up... It sounds to me like the word likelihood is being used with several slightly different meanings. The common meaning of "how likely an event is" can be used to describe sensitivity (what's the likelihood of a true positive) and specificity (what's the likelihood of a true negative), but it also has specific meaning, as you point out, in terms such as "likelihood ratios" (what's the likelihood someone who tested positive really is positive). Those two are obviously closely related. Our article on Sensitivity and specificity doesn't actually use the word "likelihood" to describe those terms, or even the word "likely", so it's possible that for strict usage those words are avoided to avoid ambiguity.. It does use the word "unlikely" however, so I don't think it's "incorrect". Vespine (talk) 01:01, 7 November 2011 (UTC)

Per our article Likelihood ratios in diagnostic testing, where D+ means you have the disease and D- means you don't:

${\mbox{sensitivity}}=P({T+}|D+)$

${\mbox{specificity}}=P({T-}|D-)$

so

${\mbox{1-specificity}}=P({T+}|D-)$

giving a ratio

${\tfrac {\mbox{sensitivity}}{\mbox{1-specificity}}}={\tfrac {P({T+}|D+)}{P({T+}|D-)}}$

This is referred to as the (positive) likelihood ratio, because in statistics, $\scriptstyle {P({T+}|D+)}$ is known as the likelihood of a positive condition (D+) given a positive test result (T+). Similarly $\scriptstyle {P({T+}|D-)}$ is known as the likelihood of the negative condition (D-) given a positive test result (T+)

$\scriptstyle {LR+=P({T+}|D+)/P({T+}|D-)}$ is therefore known as the statistical likelihood ratio given a positive test result.

The likelihood ratio is useful, because it can be used to express a very neat form of Bayes's rule expressed using the odds for D+:

Posterior odds = Prior odds × Likelihood ratio

Or, expanding that out a bit,

${\tfrac {P({D+}|T+)}{P({D-}|T+)}}={\tfrac {P({D+}|I)}{P({D-}|I)}}\times {\tfrac {P({T+}|D+)}{P({T+}|D-)}}$

The prior odds ratio is the odds of having the disease based just on its prevalence in the relevant population, before any test is made. The likelihood ratio gives the factor that this is multiplied by to give the final odds ratio that takes into account both the background prevalence and the results of the test. Jheald (talk) 17:13, 7 November 2011 (UTC)

I should probably add some of the above into our Likelihood ratios in diagnostic testing article. Jheald (talk) 17:27, 7 November 2011 (UTC)

Thanks! But why is the word "likelihood" used for the conditional probability P(T+|D+)? The term likelihood is usually reserved for the probability of existing data (events that already have occured), given some model. See the definition at Mathworld - The concept differs from that of a probability in that a probability refers to the occurrence of future events, while a likelihood refers to past events with known outcomes. I don't see how P(T+|D+) fits that definition, and would have been happier with "Probability ratio". --NorwegianBlue ^talk 21:25, 7 November 2011 (UTC)

Then I would repeat what I said and say that the definition in mathworld is a very specific and narrow "statistical" use of the word. Other common definitions I can find, don't seem to have this temporal stipulation. For example, out of those sources valid uses of the word are "what is the likelihood it will rain today?" and "what is the likelihood a candidate will be elected?" Vespine (talk) 23:12, 7 November 2011 (UTC)

OK. Let me try to answer this with a very rough-and-ready potted history, though my answer may not be entirely NPOV. (You might get some alternate views from the Statistics wikiproject, or if you asked at Reference desk/Maths).

The "classical" view of probability of the 19th century, largely taking its cue from the works of Laplace, used Bayes' theorem to evaluate questions of so-called "inverse probability", ie

$P(\theta |D)\propto P(D|\theta )P(\theta |I)$

where θ is some unknown quantity of interest, which we are trying to infer on the basis of D that is some data which has been observed.

One question such a formulation leads to is how to assign the prior distribution P(θ|I). Laplace's recommendation, in the absence of any other information, was to assign to each possible case an equal possible chance -- i.e. a flat prior, $\scriptstyle {P(\theta |I)\propto {const}}$.

However as the 19th century wore on, this recipe came increasingly under pressure, due in part to the highlighting of things like Bertrand's paradox -- a flat prior for P(θ|I) implies a non-flat prior for any nonlinear function f of θ. But what was the justification for giving θ instead of f(θ) the flat prior?

This led to people like John Venn proposing the frequency interpretation of probability -- essentially denying there could be any meaning to probability apart from in the case of the ratios of outcomes of long-run series of repeated trials. In particular, the very idea of probabilities of parameters like θ was rejected, because how could you talk about something that had an actual real fixed value in terms of probability?

But this left the question of how to do inference problems -- a gap that was filled by R.A. Fisher in 1922, who suggested ignoring the P(θ|I) term entirely, and just considering the forward probability P(D|θ), as a function of θ. This could be well defined, and co-incided with the most-used results from the classical theory. In the limit of an infinite amount of data would end up sharply peaked at the true unknown value of θ. If the data was not quite infinite, it should still be quite a strong indication of the true value of θ. Now this couldn't be called a "probability", since on the frequency interpretation things like θ couldn't have a probability, so instead he called the function a "likelihood".

Thus it seemed this new more rigorous, more sophisticated interpretation (in truth: a real mind-fuck) had banished the problems of the classical interpretation, while putting on a new rigorous basis its most important results. Thus was born so-called "orthodox statistics", and with the rise of university statistics departments by the 1940s its dominance had become pretty much total, part of the package if you wanted to be a member of the club. A few held out, such as the geophysicist Harold Jeffreys or the economist Keynes, but these were very much onlookers from well outside the tent.

However nothing remains the same for long, and by the late 1940s and 1950s the frequentist orthodoxy had started to be challenged by a small number of discontents who became known as Bayesians, who wanted to see inference done "right" -- i.e. in a way compatible with Bayes' Theorem. Their influence has steadily grown, particularly on the machine learning side, helped by the very close links between Bayes' Theorem and information theory, and by growing computer power and new algorithms in the 1990s which made it possible to realistically estimate full Bayesian posterior probability distributions for really very complicated models. Bayesian methods have also come very much to the fore in fields like medical statistics, where prior probabilities (such as in the form of background disease prevalences) simply have to be taken into account. Nevertheless, most standard university statistics books and courses still tend in the first instance to be primarily focussed around frequentist ways of thinking and the frequentist approach. Jheald (talk) 02:01, 8 November 2011 (UTC)

two different meanings, same term, as the article says at the top -not to be confused with.... can't be more longwinded, my ipad sucks for editing wikipedia It's been emotional (talk) 01:56, 8 November 2011 (UTC)

Thanks everyone! Special thanks to User:Jheald, for your thorough replies to my questions. --NorwegianBlue ^talk 08:07, 9 November 2011 (UTC)

November 7

Explaining those who claim to communicate with God

How best to explain those who claim to communicate with a god? Delusional? Charlatans? Brain not working properly? I'm not referring to people who simply pray, but to those who might say "God told me to..." or "I received a message from the Lord..." etc. These people are far fewer in number, but still quite common... The Masked Booby (talk) 01:15, 7 November 2011 (UTC)

You mean, how differenciate between true and false communication events? Plasmic Physics (talk) 01:24, 7 November 2011 (UTC)

Well, they can't all be true. So why don't you stick to those claiming to communicate with what you believe is a false god? HiLo48 (talk) 01:28, 7 November 2011 (UTC)

Don't you mean "those falsely claiming to communicate with what you believe is god?" Plasmic Physics (talk) 01:34, 7 November 2011 (UTC)

No, but that would be an interesting category too. HiLo48 (talk) 01:39, 7 November 2011 (UTC)

I suggested it, because he never agrued for or against the falsity of God. Plasmic Physics (talk) 01:43, 7 November 2011 (UTC)

I concur — Preceding unsigned comment added by 203.112.82.1 (talk) 01:54, 7 November 2011 (UTC)

The question leaves many holes before it can be answered, because it can be interpretted in many ways:

First, one has to establish if the question presuposes the existance of God or not. If the question assumes God exists, it changes the nature of the meaning of the question than if the question assumes God does not exist. Secondly, one has to establish the mindset of the voice-hearing person in light of the first point. So you have all of the following permutations:

• If God does not exist, then the voice-hearer can either be delusional or outright lying.
• If God does exist, then those options exist, but a third option, that they actually hear God, also exists.

If the God aspect bothers you, you can subtitute something else in there. For example, a person may claim to have talked to their friend Bill on the phone. Now, the same scenarios could exist: Bill may not exist at all; and the person who claimed that fact could be lying or could be delusional. Bill may exist, which means that the person who claimed to talk to him on the phone may have actually done so, but that doesn't eliminate the possibilities that they are either lying or delusional. --Jayron32 02:00, 7 November 2011 (UTC)

203.112.82.1: It's nice to know that you are very agreable, but if you are intermittently adding "I concur" to section in the reference desk just so sound intellectual without adding any scientific value to the arguement then it starts to look strange. Just because someone has crazy hair and a German accent doesn't mean that he's a genious like Einstein was. Plasmic Physics (talk) 02:06, 7 November 2011 (UTC)

"To be a genius is to be misunderstood", but the converse is not necessarily true. --Jayron32 02:09, 7 November 2011 (UTC)

See here. Count Iblis (talk) 02:18, 7 November 2011 (UTC)

This [YouTube 0:40] PSA states that "If you talk to God, you are religious, but if God talks to you, you are sick. Schizophrenia is treatable." Our Schizophrenia article does discuss auditory hallucinations, but does not discuss religiosity in any depth. Note that some who claim to hear God may, when further question, not describe auditory hallucination but instead describe an "inner voice" which they attribute to God, suggesting mere delusion. Religious hallucination and Religious delusion are both redlinks and Voice of God discusses something else entirely. Don't we have an article on this? -- 49.228.87.218 (talk) 02:47, 7 November 2011 (UTC)

That's is an insulting statement, to say that all instances are false. I've witnessed someone experience a "He told me to..." event, and they are most definitely not schizophrenic or deluded. Plasmic Physics (talk) 04:05, 7 November 2011 (UTC)

It's not an actual PSA, just one guy's homemade video. And of course many religious believers who are quite sane by all objective measurements have had occasional moments when they felt that God was communicating with them in some manner - sometimes not such much in hearable words but by a definite sensation or impression made upon the mind. For most such folks, it's a rare and often unexpected thing, and accomplishes some good purpose. Even non-believers sometimes experience something unusual or uncanny that seems to be unexplainable in ordinary terms. Just about everyone I've ever known has had some sort of "supernatural" experiences along the line, at wide intervals. Yet from there to fanatical believers who talk as if God is chatting with them like a talk-show host every day of the week, is a big leap. And then down to certifiable types who are truly delusional and have to be hospitalized is another leap. It's important to distinguish among the three kinds. Textorus (talk) 04:56, 7 November 2011 (UTC)

Oops. I apologize for misrepresenting that video if it is not an actual PSA. I thought that it had the look of the real thing (aside from the "Acid Atheist" splash at the start and the English subtitles, which I assumed had been added on). -- 49.228.87.218 (talk) 06:59, 7 November 2011 (UTC)

It appears I have misjudged many of the participants of this desk. I assumed that by posting this question to the Science desk the assumption that there are no gods would be implicit and obvious. That's why this isn't on the Humanities desk... With one eyebrow firmly raised, The Masked Booby (talk) 05:00, 7 November 2011 (UTC)

There is no religious test one way or the other required to participate on these desks. If you want to hear answers only from firm atheists, it would be more helpful to specify that in your question so that no one else wastes your time. But then, if you have already predetermined that there cannot possibly be any communication whatsoever from a god or gods, then obviously any such claim must either be self-delusion or the result of a fraud by a third party, and you've answered your own question before you asked - so what else could anyone tell you? Textorus (talk) 05:19, 7 November 2011 (UTC)

They could tell me whether it is more likely conscious (fraud) or involuntary/subconscious (mental disorder), which, you will note if you read carefully, I make clear in the original question. There is plenty to answer, thank you. The Masked Booby (talk) 05:32, 7 November 2011 (UTC)

Well, then, let me suggest that my reply above is relevant to your question. You seem to be assuming that "all members of group X" - i.e., people who claim that God has spoken to them - are, in the absence of fraud, crazy. But this is a logical fallacy; as I pointed out, there are at least three different kinds of people who might make such a claim, in one sense or another, so to get the intelligent answer you seek requires more nuance in your question. There are many varieties of religious experience - and on that note, I wonder if you have ever read psychologist William James's famous work, The Varieties of Religious Experience? I have a feeling that you would find it very interesting. Textorus (talk) 07:12, 7 November 2011 (UTC)

Science has not disproved the existence of God, so the appropriate attitude should not be to take sides. As for how people get messages from God, it's generally a matter of interpretation. To use some classic examples, many people might have a dream of seven lean heads of grain and seven fat heads of grain and assume that it was simply a dream, or if not, then call it prediction or even precognition but not assume that it was a divine communication. Many people seeing a wheel within a wheel in the sky would call it a flying saucer, blame pranksters or aliens. We are all surrounded by unfathomable amounts of information we don't understand - birdsongs, the patterns of raindrops falling from the sky, the minute-to-minute fluctuations of the stock market, the numeric sequence of the digits of pi. People try to read information or meaning or intelligence into these things because it's there - somewhere - but doing so is a difficult task. Is a divine communication part of that meaning? Hard to say... even harder still to define what a "yes" or a "no" would mean. Wnt (talk) 05:24, 7 November 2011 (UTC)

There is nothing to disprove. Science does not disprove. Burden of proof etc etc but you're well off the topic. The Masked Booby (talk) 05:32, 7 November 2011 (UTC)

Alright, to be more precise, science has not proposed any experiment capable of determining the existence or nonexistence of an omnipotent entity, as such an entity is capable of altering, avoiding etc. any detection mechanism. Wnt (talk) 15:59, 7 November 2011 (UTC)

Mmm, I'm not sure that's quite true, that "science does not disprove." Have scientists not very effectively disproved the existence of Luminiferous aether, phlogiston, spontaneous generation, and the Ptolemaic system, among many other things? Textorus (talk) 07:31, 7 November 2011 (UTC)

Some people use the phrase "God told me to ..." very broadly or metaphorically. It often doesn't literally mean that they heard the voice of God commanding them to do something. Sometimes it means that they thought of a new, but risky, path they wanted to take in life, prayed for wisdom and guidance for a while, and afterwards still thought it was a good idea. APL (talk) 05:44, 7 November 2011 (UTC)

Wnt: the person whom I witnessed, acted as intercessor. The person received a vision, and described it to the assembly, giving them a chance to identify themselves as the intended recipent. This was followed by a clear and unambiguous message. I was infact the intended recipent. Plasmic Physics (talk) 05:50, 7 November 2011 (UTC)

Our articles Revelation and Direct revelation do not discuss psychology, but Religious experience does include the section Scientific studies on religious experience. You may also be interested in our Speaking in tongues#Scientific explanations and its subsections "Neuroscience", "Mental illness", "Hypnosis", "Learned behavior". -- 49.228.87.218 (talk) 08:40, 7 November 2011 (UTC)

From a purely materialist point of view, there seem to be quite a lot of plausible explanations because the number of phenomena you are discussing are quite varied. There isn't just one "talking to God" phenomena. In some cases you have people who are hearing audible or visual hallucinations (which can have a lot of causes), in some cases people are just being imagining that God would like whatever they happen to like (I suspect many of the politician's "God told me to run for office" falls into this category), in some cases you're getting some kind of psychological wishful thinking along the lines of a Ouiji board (I can make false conversations in my head with someone unpredictable results, but I have no doubt they're just some sort of runoff from background processes), and in some cases you're probably getting outright charlatans. Distinguishing between mental illness and the other categories is probably not too hard (the God of the mentally ill often does not lead one to do things that are beneficial to one's self, while all of the other Gods more or less do), but distinguishing between the other categories is probably not possible externally at this point (perhaps brain imagining technology will be able to do this someday, though).

Personally I do not think that from a scientific point of view there is much reason to entertain the possibility of a real communication. The simpler explanation is that humans have complicated psychologies and complicated neuroscientific makeups. We see this every day, we see this clinically, we can test it, categorize it, analyze it. Having a multitude of contradictory communications from actual or false deities with only a few, specific, often quite mundane instances being valid, seems like the rather extraordinary position. Were I a religious man (I am not, plainly) I would not dispute this fact — I would agree, heartily, that being actually spoken to by God was a tremendous assumption, and a remarkable show of faith, and so forth. --Mr.98 (talk) 16:00, 7 November 2011 (UTC)

People who claim that god talks to them are probably mentally ill, but because of political correctness, and the fact that there are a lot of people who are theists, their illness is often ignored or worse, believed. Science doesn't deal with god because it can't be falsified. See not even wrong. Science does not deal with disproving claims that have no evidence supporting them. It's sad that otherwise intelligent people believe in something that is clearly irrational and baseless, only supporting their belief on "faith" which just means believing in it without evidence. The fact of the matter is, even intelligent people are negatively influenced by precognitive biases based on how they were raised, the culture they grew up in, etc. They are, after all, only human and suffer from the same psychological defects that all humans suffer from. Users like Plasmic Physics, who is otherwise intelligent and knows about science, doesn't employ his own skepticism and knowledge of how science works, to his own religious beliefs because he is biased towards it. ScienceApe (talk) 20:27, 7 November 2011 (UTC)

To elaborate on this a bit more, if I claimed I was communicating with the ghost of Napoleon, that claim would carry the same merit as claiming I was communicating with god. They both have exactly the same amount of evidence supporting them, which is none. The only difference is, the vast majority of people do not believe Napoleon exists as a ghost, while many people believe in god, so while no one would take issue with believing someone who believes they are genuinely communicates with the ghost of Napoleon is mentally ill, they would not believe the person who communicates with god to be mentally ill because of their own biased, irrational beliefs agree with the individual who claims they are communicating with god. ScienceApe (talk) 20:35, 7 November 2011 (UTC)

I forget if this has been mentioned before, but hallucination is not rare and not just suffered by a small minority of delusional people. We all hallucinate at night (dreaming), which explains cases where people claimed to have communicated with god at night. During the day, occasional auditory hallucinations are commonplace. Even those who suffer frequent auditory hallucinations don't have a widely recognized mental disease--see Hearing Voices Movement. --140.180.16.167 (talk) 20:54, 7 November 2011 (UTC)

It sounds more like you are trying to make their hallucinations more acceptable. Basically an apologetic for theists. You're going as far as trying to suggest that hearing things that aren't there is not mental illness. It is. This is the problem with theism being so widespread. You begin to rationalize their behavior so that it's more acceptable as opposed to if it were applied to anything else (like hearing Napoleon talk to you), it would not be. Hallucinating and dreaming are also not the same, hallucinating is done in the conscious, awake state. ScienceApe (talk) 23:39, 7 November 2011 (UTC)

Where did I rationalize the behavior, or suggest that hearing voices from God is different from hearing voices from Napoleon? I'm an atheist, and just like all scientists (theist or not), I'm not saying that hallucinations have a factual basis. However, it is in fact true that most people experience at least one auditory hallucination some time in their lives. It's also true that many people who hear voices aren't diagnosed with a mental disease. Those are facts, not opinions. The opinion I expressed was that the high frequency of hallucinations might explain the frequency of claimed religious communication--after all, if everyone's hallucinating, at least some will be hallucinating about god. --140.180.16.167 (talk) 02:57, 8 November 2011 (UTC)

It doesn't matter if you're an atheist or not, you live in a society where theism is acceptable, so you would still apologize for them. If those are facts, then you need evidence to back then up, because I'm not buying your claims without them. ScienceApe (talk) 04:32, 8 November 2011 (UTC)

Well, in reference to my case, it sound statistically unlikely that the person whom I witnessed had hallucinations or other symptoms of a neurological disorder, based on the specificity of the information content delivered in the vision and message. Plasmic Physics (talk) 01:44, 8 November 2011 (UTC)

But that assumes that hallucinations have low specificity in terms of the information content delivered. What evidence do you have of that? Dreams are often very specific to the person's life, and they happen when brain activity is very low, unlike hallucinations during the day. --140.180.16.167 (talk) 03:01, 8 November 2011 (UTC)

No, you're miunderstanding. The quality of the information used to identify the intended recipent was very specific, the constraints excluded 99% of the sample population. Plasmic Physics (talk) 04:10, 8 November 2011 (UTC)

I don't even know why you believe in god in the first place plasmic. There's no evidence that it exists, and your friend telling you that he talks to god is not evidence either. ScienceApe (talk) 04:32, 8 November 2011 (UTC)

Are you sure you weren't the victim of a fraudster? As the case of psychics (who I presume given your religious beliefs you accept are usually fraudsters) show, it's fairly easy for people to pretend to know details of someone's life by a variety of cold reading techniques, even more so if the target wishes to believe. Even if the person wasn't being intentionally deceptive, have you considered the possibility that because they genuinely believed they'd received a message from god, they unintentionally and without realising did a similar things to what fraudsters do when they decided you were the one who the 'message' was intended for. Nil Einne (talk) 14:36, 8 November 2011 (UTC)

Yes, I'm sure the person was not a fraudster, they had no prior knowledge about me. Infact they did not know who the message was for untill afterwards. Plasmic Physics (talk) 06:10, 9 November 2011 (UTC)

I don't think that is related to the question, and please don't disrespect me by calling Him an it. I respect your decision to be an atheist. Plasmic Physics (talk) 05:15, 8 November 2011 (UTC)

Actually it is related to the question, because you are presuming that it exists, and it doesn't. Therefore the answer you gave actually presumed you can have genuine conversation with this fictional entity. And it is an it because unless it produces spermatozoa, and has the biological function of fertilizing the opposite sex of its species, it's not a male. I don't respect your decision to be a theist, because you should know better, and your warped belief in a god perverts the genuine quest for knowledge in science. I also couldn't care less about respecting christianity when they teach their followers that people who don't accept jesus christ as their lord and savior DESERVE to be tortured for an eternity in hell. Any religion that teaches that doesn't deserve any respect. You're letting your preconceived biases interfere with rationale thinking. ScienceApe (talk) 14:05, 8 November 2011 (UTC)

Highlighting your own god brings me back to a point I made near the start. Surely a devout Christian must wonder about non-Christians who believe in other gods. You can't all be right. If those others say they hear from their god, the OP's question applies there. How can that be explained? HiLo48 (talk) 07:29, 8 November 2011 (UTC)

Easily, being a devout Christian myself, we see communications by other gods as strategic subversions by Satan who masquerades as those gods. Plasmic Physics (talk) 10:40, 8 November 2011 (UTC)

Whereas, since Christianity is not a small, monolithic sect but a very big tent covering many divergent points of view, it must also be said that other Christians, equally devout, do not "succumb too easily to the temptation to exclusiveness and dogmatic claims to a monopoly of the truth of our particular faith," but "in humility and joyfulness acknowledge that the supernatural and divine reality we all worship in some form or other transcends all our particular categories of thought and imagining." --Archbishop Desmond Tutu, God Is Not a Christian: And Other Provocations, 2011. Textorus (talk) 12:05, 8 November 2011 (UTC)

Or maybe your god doesn't exist, and christians made that up to coerce people into being christian and demonizing other religious beliefs at the same time? That would be the real answer. ScienceApe (talk) 14:10, 8 November 2011 (UTC)

It's also illogical to demonize all Christians as ignorant, intolerant oafs. Some are, to be sure, but many millions are not so smug and self-righteous as you assume. The same applies to many other religious people around the world. As well as to atheists. Textorus (talk) 15:32, 8 November 2011 (UTC)

I didn't say they were all ignorant, intolerant oafs, you're arguing a strawman. I said believing in god is illogical. I said their religion teaches that people who don't accept jesus as their lord and savior deserve to be tortured for an eternity in hell. I don't respect religions that teach that. Saying atheists can be smug or self-righteous, is about as meaningful as saying that people who don't believe in Santa Claus can be smug or self-righteous. Atheism isn't an ideology, it's a single stance on a single issue. ScienceApe (talk) 18:48, 8 November 2011 (UTC)

Where in scripture does it say that anyone will be tortured for eternity in hell? That belief is unchristian. Plasmic Physics (talk) 20:41, 8 November 2011 (UTC)

After debating with christians and theists for so long, I've found that citing verses from the bible is a useless exercise. The bible could say snow is white, and then a christian would interpret it as saying it's black. That's the other problem with chrisitianity. You have a bible that apparently doesn't mean what it says, it means whatever you want it to mean. But in debating all of these christians, the one thing they always say is that unless I accept jesus as my lord and savior, I am destined to be tortured for an eternity in hell. Apparently this all powerful and all knowing god is quite conceited and immature. ScienceApe (talk) 04:41, 9 November 2011 (UTC)

Well, they have it wrong then. Torture is mentioned nowhere, neither is hell a place where someone is sent, hell is an event. Plasmic Physics (talk) 06:10, 9 November 2011 (UTC)

What does it say in simple english? Plasmic Physics (talk) 12:18, 8 November 2011 (UTC)

Why don't you read the entire excerpt and decide for yourself? I just wanted to make the point that your reply to HiLo does not represent the views of all devout Christians everywhere. Textorus (talk) 12:49, 8 November 2011 (UTC)

That depends by what you mean by devout. Now that I've read that excerpt, I can tell you that it is heretical, as in it speaks against scripture. Plasmic Physics (talk) 20:41, 8 November 2011 (UTC)

For me, "devout" means to actively persue humility, rightouness, and truth. A truly devout person would make certain that what they are told is in complete agreement with scripture, otherwise there is room for error. Inspired by Acts 17:10-12. Plasmic Physics (talk) 23:50, 8 November 2011 (UTC)

This suggests to me that the communication is pure idea, not sound or direct sensory experience. ~AH1 ^(discuss!) 03:25, 9 November 2011 (UTC)

How do you reckon? Plasmic Physics (talk) 04:10, 9 November 2011 (UTC)

Historical choice of "positive" and "negative" charge in the one-fluid theory of electricity

Was the choice of the type of charge to be call "positive" entirely arbitrary?

Electric charge#History briefly describes how early natural philosophers witnessed the triboelectric effect in which, when two types of material were rubbed, one (such as glass) built up a certain type of charge which we now call "positive" (but was called "vitreous electricity" during the time of the two-fluid theory of electricity), and the other built up another type of charge which we now call "negative" (but was then called "resinous electricity"). Benjamin Franklin and William Watson independently proposed that the two types of electricity were actually a surplus or deficiency of a single electrical fluid -- a positive or negative pressure. Clearly they chose "vitreous electricity" as that fluid, but the articles do not indicate why. Was the choice purely arbitrary on their part (and if so, did they state this) or was there some reason to suspect that the one true fluid was vitreous and not resinous? -- 49.228.87.218 (talk) 01:47, 7 November 2011 (UTC)

I'm pretty sure they assigned the "+" charge to the "fluid"; thus more of it would be more + and less of it would then be -. I'm not sure they "chose" the vitreous fluid specifically to make positive; I think Franklin and Watson concieved of a single electric fluid which there was either too much of or too little of. This coincidentally gives the same "sign" as that of the vitreous fluid, but that's a coincidence, and wasn't part of Franklin and Watson's thinking here. --Jayron32 01:52, 7 November 2011 (UTC)

When rubbed with fur, glass tends to lose electrons, and become vitreously electric (positively charged), amber tends to gain electrons and become resinously electric (negatively charged). Plasmic Physics (talk) 01:56, 7 November 2011 (UTC)

Yes, but that does not change the fact that there are two theories being explained above, and the first does not necessarily influence the second. There is a "two fluid" theory: Whichever of the two fluids that was in excess determines the charge of the substance. There is a "one fluid" theory: an excess or deficit of that fluid determines the charge. The + and - convention was created by people who adhered to the "one fluid" theory, which is why + merely means an "excess" of that fluid. The convention got carried through to the modern theory, which is how the modern particles (electrons and protons) got assigned their charges. --Jayron32 02:06, 7 November 2011 (UTC)

But Franklin and Watson were certainly aware of the behavior of both glass and amber, and for some reason they chose the charge that built up on glass as the positive one. If this choice was in fact arbitrary, weren't they intelligent enough to recognized that fact and honest enough to state it? If it was not entirely arbitrary, did they write of why they made the choice they did? For instance, perhaps the charge they were able to build up on glass was significantly stronger than what they could build up on amber. -- 49.228.87.218 (talk) 02:31, 7 November 2011 (UTC)

Might be enlightening to this discussion to go read what Franklin himself had to say about the terminiology in his Experiments and Observations on Electricity, pub. 1769. From the second letter in that book, on page 8, dated 1747: "Hence have arisen some new terms among us: we say, B is electrised positively; A negatively. Or rather, B is electrised plus; A, minus. . . ." That's as far as I got, and I'm not a scientist, but he refers to the two charges many more times in subsequent passages of the book. Textorus (talk) 03:48, 7 November 2011 (UTC)

You're awesome! That is exactly the sort of reference I was seeking. I'll write back after I've read through it all. (It might be a while.) -- 49.228.87.218 (talk) 04:18, 7 November 2011 (UTC)

Glad I could help. Textorus (talk) 04:37, 7 November 2011 (UTC)

I don't know what Franklin wrote about it, but I do know that the choice was indeed completely arbitrary. Dauto (talk) 15:37, 7 November 2011 (UTC)

The end result ends up being arbitrary, but that doesn't mean that Franklin's rationale at the time he came up with the convention was arbitrary to him. He may have believed his choices made sense specifically, even if they don't today. --Jayron32 15:40, 7 November 2011 (UTC)

That is possible, of course, but I imagine he would have been smart enough to realize it was an arbitrary choice, even if he didn't specifically state that somewhere in his writings. Dauto (talk) 16:08, 7 November 2011 (UTC)

Not completely arbitrary. Negative charges move more easily in certain situations than positive ones, even concerning the triboelectric effect. It's a common school experiment I think, though I forget the exact setup. I think it involves the ground.... but I can't remember what exactly is done to distinguish the two. elle _{vécut heureuse} ^{à jamais} (be free) 16:20, 7 November 2011 (UTC)

Also, negative lightning is different from positive lightning, which one would imagine Franklin had a bit of experience with. "An average bolt of positive lightning carries an electric current of about 300 kA — about 10 times that of negative lightning." (From lightning.) elle _{vécut heureuse} ^{à jamais} (be free) 16:26, 7 November 2011 (UTC)

Though past the heyday of alchemy, it might possibly have had a few things to contribute. (Didn't they pioneer a primitive form of electroplating?) And there was the heyday of animal magnetism too. Maybe positive charges were regarded as "positive" for the health. And wouldn't people have noticed at some point that sparks for really large potential differences (where you could actually watch it happen) that it always flowed from negative to positive? Maybe "positive" attracted sparks. You have things like Van de Graaff generators after all. (From the article: "The fundamental idea for the friction machine as high-voltage supply, using electrostatic influence to charge rotating disk or belt can be traced back to the 17th century or even before.") At some point, people would have noticed that direction really did matter. elle _{vécut heureuse} ^{à jamais} (be free) 16:39, 7 November 2011 (UTC)

Finally, from electrostatic generator may provide your answer: In 1785, N. Rouland constructed a silk belted machine which rubbed two grounded hare fur covered tubes. Edward Nairne developed an electrostatic generator for medical purposes in 1787 which had the ability to generate either positive or negative electricity, the first named being collected from the prime conductor carrying the collecting points and the second from another prime conductor carrying the friction pad. elle _{vécut heureuse} ^{à jamais} (be free) 16:46, 7 November 2011 (UTC)

Yes, as you have pointed out there are many ways to tell the positive and negative charges apart. But none of that makes the choice of which one is positive and which one is negative less arbitrary. Dauto (talk) 18:26, 7 November 2011 (UTC)

I think you're reading the arbitrariness too ahistorically. Under our modern understanding of charge, calling them one or the other is indeed arbitrary.

As Jayron points out earlier, Franklin (in some contexts, anyway) saw electrical charge as a subtle fluid, and considered that the building up of the fluid made something positive, and being deficient of it made one negative. So for him it wouldn't have been an arbitrary labeling of the charge — it would have been a measure if one had an abundance of the fluid (and thus were in the positive side of a balance) or in the detriment of it (and thus a negative). In his case they aren't arbitrary labelings, but metaphors for understanding the mechanism behind them (probably from the domain of accounting or commerce — something like a balance of the charge).

Of course, we now know considerably more about charge and can say with confidence it doesn't quite work that way, but that's a very different theoretical regime than Franklin was using. He was a smart guy, but he was not thinking about it in the same way we were. For him they aren't arbitrary terms. (A similar issue is found in considering the title of a biological cell — you could call them whatever, but Hooke gave them that name for non-arbitrary reasons.) --Mr.98 (talk) 21:00, 7 November 2011 (UTC)

He must have known that there was no way to tell which one was positive and which one was negative irregardless of his understanding (or lack of it) so he arbitrarily chose one to be positive. He was smart enough to know that that choice was arbitrary. Dauto (talk) 21:07, 7 November 2011 (UTC)

But there were many subtle differences between the behaviour of positive and negative charges. Lightning would be a very good example. elle _{vécut heureuse} ^{à jamais} (be free) 23:44, 7 November 2011 (UTC)

Yes, there are subtle differences, but the choice of names - which one to call positive and which to call negative - is completely arbitrary and could vary well have gone the other way. It's arbitrary now and it was arbitrary at Franklin's time. The question is: did Franklin know that? Dauto (talk) 05:25, 8 November 2011 (UTC)

The clairvoyancy on display in this thread is truly breathtaking. All these folks who can't be bothered to quote what Franklin or anyone else actually had to say about the matter - but who are utterly, utterly certain they can read the old boy's mind when he's been mouldering in his grave for over 200 years . . . wow, that's quite a feat. Textorus (talk) 11:42, 8 November 2011 (UTC)

You must have misread the thread. Try again. Dauto (talk) 16:01, 8 November 2011 (UTC)

My reading skills are very good; the article is paved with "I think," "I believe," "I imagine." As well as a raft of assertions backed by no citations to reliable sources. It doesn't take a Ph.D. in physics to see that. In any case, the question is about the choice of a word, and who and why - not the physical properties the word describes. Textorus (talk) 17:49, 8 November 2011 (UTC)

You must have missed the disclaimer at the beginning of the side discussion, and I quote "I don't know what Franklin wrote about it". I never caimed I knew what Franklin said or knew. I'm just pointing out that from physical principles the choice cannot have been anything other than arbitrary. Dauto (talk) 18:16, 8 November 2011 (UTC)

OP here (finally logged in). Respectfully Dauto, I believe that you are wrong. Yes, by today's understanding of electricity the choice of positive and negative is entirely arbitrary, but Franklin and Watson's single fluid theory is not the same as our modern understanding (which in some ways should be considered a mix of the two preceding theories). It was not a matter of Franklin naming one type of charge negative and the other positive. His theory posited a single type of charge, and he did attempt to determine the direction of motion of that charge in various triboelectric experiments and he came to the wrong conclusion, deciding -- based on evidence -- that the charge which built up on a piece of glass was due to a surplus of charge carriers ("electric fire" or "electric fluid") and thus called it positive. (We now know that the charge is due to a deficit of electrons -- the moving charge carriers.)

In Franklin's model, all matter was permeated with very fine pores (too fine to absorb air or water) which attracted electric fluid much as a sponge "will naturally attract and absorb" water. A material in its "natural state" contained exactly enough electric fluid to fill these pores and exhibited no "electric atmosphere". Any additional electric fluid added must then build up on the surface and create an "electric atmosphere". Conversely, removing electric fluid left the internal pores empty, and their natural affinity for the electric fluid created an electric atmosphere of the opposite polarity.

In his early letters he seems to take for granted that the triboelectric charge which builds up on glass was due to an excess of electric fluid. In February 1752 [Letter VII / p 99 / PDF p 128], Ebenezer Kinnersley wrote to Franklin, describing an experiment using both sulphur and glass spheres which built up opposite charges, stating that it was unclear which direction the "electric fire" was running in each, and offering to lend a sulphur sphere to Franklin in hopes that he could "discover some method of determining which it is that charges positively". On March 2 [Letter IX / p 102 / PDF p 131], Franklin acknowledged receipt of the brimstone sphere, and said that, while he had not yet gotten the experiment working, he doubted Kinnersley's results, suspecting "that the different attractions and repulsions you observed, proceeded rather from the greater or smaller quantities of the fire you obtained from different bodies, than from its being of a different kind, or having a different direction." Two weeks later [Letter X / p 103 / PDF p 132], Franklin wrote that he was "agreeably surprised" to have successfully replicated Kinnersley's work, and put forward the belief that it is "the glass globe that charges positively, and the sulphur negatively" primarily because the charge which built up on the glass was stronger than that which built up on the sulpher, stating that "bodies of a certain bigness cannot so easily part with a quantity of electrical fluid they have and hold attracted within their substance, as they can receive an additional quantity upon their surface by way of atmosphere. Therefore so much cannot be drawn out of the conductor, as can be thrown on it." But he does add that "these are hasty thoughts". He is still not entirely convinced a year and a half later when he wrote to Peter Collinson [LETTER XII / September 1753 / p 113 / PDF p 142] asking that he "recommend it to the curious in this branch of natural philosophy, to repeat with care and accurate observation, the experiments I have reported in this and former papers relating to positive and negative electricity, with such other relative ones as shall occur to them, that it may be certainly known whether the electricity communicated by a glass globe, be really positive."

That is as far as I've gotten, even just skimming. Between the long s, ct ligatures, and inconsistent scanning quality, the manuscript (thanks again, Textorus) is a slow read, and the ePub has a fair number of OCR errors. There is more to this story (including an apparent disagreement with Watson about the direction of charge flow) and I'll report here again after perusing the work. I close with this Franklin gem [p62 PDF p 91].

Nor is it of much importance to us, to know the manner in which nature executes her laws; 'tfs enough if we know the laws themselves. 'Tis of real use to know that china left in the air unsupported will fall and break; but how it comes to fall, and why it breaks, are matters of speculation. 'Tis a pleasure indeed to know them, but we can preserve our china without it.

-- ToE^T 00:27, 9 November 2011 (UTC)

That is a very good description, thank you. I've briefly skimmed the book some further. Letters are not in the strict chronological order. There is some discussion on the nature of electricity in the lightning, other properties of electricity, a few letters discussing relationship between electricity and electromagnetism. There are long sections which are not concerned with electricity at all - in one, Franklin and his correspondents go at length about things like demographics of American colonies, water spouts, whirlwinds, and effects of mountain ranges on climate. Starting page 284, we have 35 pages describing a novel fireplace design of Franklin's invention, including instructions to the prospective bricklayer such as ".. if this air-passage be so situated as that mice may enter it, and nestle in the hollow, a little grate of wire will keep them out."

Things get back on the subject of electricity around page 390 with some letters dated 1761-62. I don't see him questioning the identification of positive/negative charge. But, on page 407, there is an interesting discussion that shows how little he really understood electricity even at that time. His correspondent proposes that similar electric charges repel and opposite electric charges attract. Franklin counters that there is no evidence for attraction between opposite charges, and proposes instead that "the electric fluid is attracted strongly by all other matter that we know of, while the parts of that fluid mutually repel each other"! Then the book drifts away from the subject of electricity again, and any subsequent references to electricity are only made with regard to the lightning.

It seems to me that he never got around to rechecking that subject - and, even if he did, his equipment was too crude to make correct conclusions. (In his case, the correct conclusion would be that he is physically incapable of determining which charge is positive and which one is negative, because they are symmetrical for all practical purposes. It took until 1890's to determine the sign of the elementary charge carrier.) He started with his original assumption that rubbing the glass imparts a positive charge onto the glass. There is a statement on page 6 regarding experiments "demonstrating" "afflux and efflux" of electrical charge onto and off the electrical sphere - he found some years later later that those experiments demonstrated no such thing, but, by then, the choice was made. Then in 1752-53 he may have tried to reconsider the choice, but results were not decisive enough to redefine positive negative and vice versa.--Itinerant1 (talk) 01:58, 9 November 2011 (UTC)

Vin de Borgia

What substance(s) were the Borgias known/believed to use to poison their rivals? 67.169.177.176 (talk) 02:56, 7 November 2011 (UTC)

Arsenic, according to the second paragraph of the House of Borgia article. Red Act (talk) 03:22, 7 November 2011 (UTC)

Interesting... Was there an antidote for it at that time? 67.169.177.176 (talk) 01:50, 8 November 2011 (UTC)

I don't believe there is an antidote even now that would save you from a single dose of such strength that it could kill an adult human. Most treatments for arsenic poisoning take more time than a person who had ingested such a dose has left. However, according to the article on it, " Dimercaprol and dimercaptosuccinic acid are chelating agents which sequester the arsenic away from blood proteins and are used in treating acute arsenic poisoning. " Doesn't sound like something they would have had 500 years ago. Beeblebrox (talk) 05:40, 8 November 2011 (UTC)

What about concentrated garlic extract? That stuff contains lots of thiols and other sulfur compounds that also can chelate the arsenic right out of the victim's body (although not as effectively as BAL, to be sure). 67.169.177.176 (talk) 05:53, 8 November 2011 (UTC)

I wouldn't attempt that at home if I were you. Textorus (talk) 12:54, 8 November 2011 (UTC)

Neither would I. 67.169.177.176 (talk) 05:24, 9 November 2011 (UTC)

cotton balls

our cotton balls for facial use washed in a factory to remove the pesticide? — Preceding unsigned comment added by 92.48.194.147 (talk) 15:25, 7 November 2011 (UTC)

Yes, they are washed for sterility, which is very intensive and should remove most if not all pesticide residue. 67.6.136.218 (talk) 17:18, 7 November 2011 (UTC)

calculating the entropy of dissociation for an ideal gas

The entropy of expansion for a gas is +nR(ln V2/V1). What is the entropy of dissociation for an diatomic ideal gas for the reaction XX <----> X-X? (We could also add this to our articles on dissociation)?

Phase changes and dissociations have a molar entropy value, but it seems to me that from stat mech molar entropy for a dissociation would not be constant....or would it? elle _{vécut heureuse} ^{à jamais} (be free) 15:35, 7 November 2011 (UTC)

If we have N molecules of X_2 in a volume of V, then the entropy increase if they all dissociate is:

$\Delta S=Nk\left[{\frac {3}{2}}-{\frac {7}{2}}\log(2)+{\frac {1}{2}}\log \left({\frac {m^{3}kT}{2\pi h^{2}I^{2}n^{2}}}\right)\right]$

where n = N/V is the number density of X_2, I is the moment of intertia of the X_2 molecule, and m is the mass of a single X atom. This is assuming that vibrational modes are not excited (as is usually the case around room temperature). Count Iblis (talk) 18:15, 7 November 2011 (UTC)

Hmm, I meant to examine iodine, actually, whose vibrational transition temperature occurs at 307K. But thanks! How would I examine molar change in entropy, say, if there were only partial dissociation? I basically was thinking of a value in J/(mol*K). elle _{vécut heureuse} ^{à jamais} (be free) 23:46, 7 November 2011 (UTC)

added insulation

my previous question was archived so I'm posting again

I had extra cellulose insulation blowing into my attic Several years ago. I think I have a roof leak. How am I supposed to go into the attic or have a contractor go into the attic to find the leak, without them stepping on the insulation compressing it and how are they supposed to see the studs to walk on. — Preceding unsigned comment added by 92.48.194.153 (talk) 15:18, 4 November 2011 (UTC) Contact a reputable contractor who does this sort of work all the time, and comes with a stellar reputation and good recommendations. Not to be blunt, but someone who does this sort of thing all the time should be able to deal with your situation, through experience and knowledge. In other words, while you may not be able to see how to get around the problem, I would trust someone who deals with the problem all the time to know what they are doing. --Jayron32 16:51, 4 November 2011 (UTC) I doubt if the contractor would care if they compress the insulation. As for finding the studs, he'd start at the opening to the attic, and feel around for them, then follow the ones he finds. Eventually he would be able to predict where the rest were. If he was going to spend any amount of time up there, he would likely put down some walkways over the insulation and across the studs. Yes, this would compress the insulation more, but he wouldn't care about that. StuRat (talk) 21:19, 4 November 2011 (UTC) Waterlogged insulation is unlikely to be very effective anyway, so I would deal with the more pressing issue (the leak) first. --Colapeninsula (talk) 12:02, 7 November 2011 (UTC)

okay is there anyway I can go up in the attic and look around without compressing the insulation? — Preceding unsigned comment added by 92.48.194.178 (talk) 15:48, 7 November 2011 (UTC)

Heh, I saw a plumber use an endoscope recently. Of course, if you call a plumber for a roof leak people might say you're nuts. ;) Wnt (talk) 16:03, 7 November 2011 (UTC)

Probably not without compressing it somewhat, no. But, if you are careful to always step in the same few spots, then you can minimize the compression. But really, even if you went up there and intentionally compressed all the insulation you could, I bet your energy bill would only go up maybe 1%, which is silly to worry about compared with how much water damage could cost you. Just don't worry about it. Or, if you wish, have some more insulation blown in after the leak has been fixed. StuRat (talk) 16:09, 7 November 2011 (UTC)

A thin stick or a stiff wire will let you probe enough to find the framing without un-fluffing the insulation. In principle, the framing should be regular, either 16" or 24" apart. If the roof is of truss construction, the framing will be obvious, as the trusses will emerge from the insulation. If it's blown in, you can still fluff it as you retreat. Acroterion (talk) 20:08, 7 November 2011 (UTC)

Note that there are various kinds of cellulose insulation. In most cases the adverse effects from stepping on it a few times would be minimal. If you are planning to go in ther yourself I strongly recommend that you wear a dust mask or respirator, that stuff is not something you want to be breathing in, and any disturbance at all will stir it into the air, especially in such an enclosed space. Beeblebrox (talk) 05:23, 8 November 2011 (UTC)

I had a house with an attic which had cellulose blown in over the joists, which were out of sight below the surface of the insulation. I found it easy enough to walk along a joist, shuffling along with the feet on the joist, and displacing rather than stepping down on the fluff. It pretty well fell back into place behind the feet. There is a very real risk of missing the joist and stepping or falling through the ceiling, more so if one is lifting the feet up and stomping down rather than following the joist with the feet. Edison (talk) 15:21, 8 November 2011 (UTC)

Turning our sun into a black hole

Lets say we turn out sun into a black hole. Would our planet orbit around it without any significant changes? How would the temperature change? I understand that the black hole would emit electromagnetic radiation due to Hawking Radiation, but I don't know how that compares to how much it emits right now, would a black hole emit more? 165.230.177.154 (talk) 17:07, 7 November 2011 (UTC)

No, much less. It would cool quickly with only the stored heat of the planet's core keeping surface temperatures barely above about 150 Kelvin. The planet would freeze solid and lifeless. 67.6.136.218 (talk) 17:16, 7 November 2011 (UTC)

The black hole (and its Hawking radiation) itself would be rather colder than the 3 Kelvin of the cosmic microwave background radiation.

In rough terms a black hole has to be lighter than the planet Mercury (or the moon) for its temperature to be higher than the microwave background. Jheald (talk) 17:52, 7 November 2011 (UTC)

And there would be no change to the planet's orbit (Assuming that the unknown process that created the BH did dot significantly disturbed the orbit). Dauto (talk) 18:17, 7 November 2011 (UTC)

You can calculate the temperature of a black body (such as a black hole) by its Blackbody radiation. A blackhole emits very little Blackbody radiation -- as someone pointed out, Hawking radiation is weaker than CMB. elle _{vécut heureuse} ^{à jamais} (be free) 23:49, 7 November 2011 (UTC)

Is the bowsprit considered a mast?

To settle an argument with a sailing relative (I have no experience with sailing): apparently in France, the beaupré, or bowsprit, is considered a mast, so a three-masted ship is actually a two-mast ship with a bowsprit. He also argued this is internationally recognized. I honestly believe this is not the case. As can be seen at the French article for USS Constitution ([2]), the ship is categorized as a Trois-mâts. So what's the truth? Reflectionsinglass (talk) 19:43, 7 November 2011 (UTC)

This is purely a semantic argument? Then the proper course of action is to determine who is the authoritative source for sailing definitions. If, as your friend contends, there is an "international recognition" for some definition, somebody (or some agency) must actually have the authority to provide canonical definitions of terms, by decree. Which agency is that? Where does it publish its glossary of terms? If this question can't be answered, it's fair to settle the argument as "no standard definition exists," and various individuals may choose whichever definition they like. Nimur (talk) 19:53, 7 November 2011 (UTC)

It can be quite difficult to prove something does not exist, such as some existing but almost universally ignored "international recognition" on how to define and count ships' masts, as one can always argue that there might exist evidence one has not yet found. For what little my personal experience is worth: over some 50 years of reading English-language fiction and non-fiction, some of which has been about multiple-masted sailing vessels, I have only ever encountered "mast-counts" that exclude the bowsprit, and never encountered one that includes it. My guess is that an old salt is exerting traction on a landlubber's lower limb here. {The poster formerly known as 87.81.230.915} 90.197.66.220 (talk) 20:56, 7 November 2011 (UTC)

Google translate and french wiki page for "Trois-mâts" seem to be on your side. It says three masts vertical. Vespine (talk) 22:16, 7 November 2011 (UTC)

I concur with tpfka8829 and wish to add that bowsprits, as with masts and booms, are spars, but I have never heard of a vessel categorized by spar count. -- ToE^T 01:17, 8 November 2011 (UTC)

A quick look at Google Books produces some backup - Chapman Great Sailing Ships of the World By Otmar Schäuffelen shows a "3-masted staysail schooner" that has three masts AND a bowsprit. Alansplodge (talk) 10:06, 8 November 2011 (UTC)

Also, our Sail-plan article says "The standard terminology assumes three masts, from front to back, the fore-mast, main-mast and mizzen-mast. On ships with fewer than three masts, the tallest is the main-mast. Ships with more masts number them." Alansplodge (talk) 12:56, 8 November 2011 (UTC)

Destroying the Vatican

Is the Vatican protected against rocket-propelled grenade attack? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:47, 7 November 2011 (UTC)

No, it would not be difficult for a group of people to sneak into the Vatican and launch a attack with heavy weapons. The recent attack by a group of militants in Kabul shows that you can't defend a city against such an attack.

You may also read about the military and police in the Vatican. Do you have a science reference question? Nimur (talk) 22:11, 7 November 2011 (UTC)

Can something really be protected against RPG fire? At some point, they will destroy the target. 88.9.210.187 (talk) 01:21, 8 November 2011 (UTC)

Two words for you: Reactive armor. 67.169.177.176 (talk) 01:52, 8 November 2011 (UTC)

A simple steel grill is effective against shaped charge weapons - it explodes the charge before it makes contact with anything substantial. This Ulster observation post is protected in this way, and this; but it wouldn't do much for the aesthetics of the architecture. Alansplodge (talk) 09:14, 8 November 2011 (UTC)

I don't know much about the subject but I'm not sure how that would work in the case 88 mentioned. Yes it may protect against the first few? (it seems one or two would be enough to me if you fire at the same location but this isn't something I know much about) charges but you're going to destroy the grid soon enough and then I don't see what's stopping you getting to the main structure. In other words, as 88 said, just keep attacking and you'll destroy it eventually. The grid may be effective if your concern is someone launching one or a few charges and then either running away or being killed. Nil Einne (talk) 10:23, 8 November 2011 (UTC)

Would that work to protect the Vatican? Our article suggests many current implementations are vunerable to being hit in the exact same location several times. As our article suggests, this likely to be difficult if you're hitting a moving tank which is likely to shoot back, unless your weapon fires 2 charges in rapid succeession, but if you're launching an attack against a stationary structure which doesn't shoot back I presume it's far less difficult. Nil Einne (talk) 10:28, 8 November 2011 (UTC)

Maybe after the first couple of rounds, someone might notice and do something about it. They're bloody noisy[3] and the Italian Carabinieri are famously armed to the teeth[4]. Anyhow, a 2.5kg warhead is not going to "destroy the Vatican" although it would do a lot of damage to a single room and its occupants. Alansplodge (talk) 11:19, 8 November 2011 (UTC)

I don't think anyone questioned that someone will notice, the question raised by 88 was more whether they'd be able to destroy the target (which I presume would be a specific structure, not necessarily a building but potentially just a statue or whatever, rather then the Vatican in the entirety) with enough firepower. The question of how plausible it would be for someone to sneak in and if they do, how long they will be able to continue their attack before they are killed or at least have to engage defenders is a distinct issue, relevant to considering what sort of defences you should build and how effective those defences may be, but not so relevant to the issue raised by 88 particularly if what you're suggesting will only defend against 10-20 RPGs (in other words, if we aren't talking about completely unrealistic possibilities like someone shooting the structure non stop for a few hours). (Although it's worth remembering as Nimur has pointed out, the recent Kabul attacks have highlighted the fact if someone does manage to bring in a fair amount of heavy weaponary, flushing them out isn't that simple even if you have ample firepower and training.) Nil Einne (talk) 14:12, 8 November 2011 (UTC)

I did not make that comment. The comment above mine was made by Count Iblis, who wishes to remain anonymous. The risk of misattribution was exactly why I fixed his unsigned comment in the first place. Nimur (talk) 16:51, 8 November 2011 (UTC)

These various armour types are designed to withstand a number of hits from a specified device; seven hits from a 7.62mm round in the same place, four hits from an RPG etc. To an extent that depends on the firer being able to hit the same place multiple times to breach the vehicle. An RPG isn't all that accurate.

There is also,l in the case of vehicles, a balance between armour defence and movement. A lighter armour may take fewer hits but the vehicle can get through or round obstructions more easily than a more heavily armoured vehicle. A V-shaped hull to defend against under-vehicle IEDs is of limited use against an IED constructed to fire into the side of the vehicle. A roller mounted out in front is fine against a pressure plate initiation immediately above the charge but of no use of it's a command wire or the charge is 8 feet ahead of the switch.

There is always a balance given the diversity of threats.

ALR (talk) 13:50, 8 November 2011 (UTC)

Er I don't get the relevance to vehicles here. Aren't we talking about whether reactive armour would provide much of a defence against a sustained attack by RPG fire on structures? This is what I thought we were discussing since 88 questioned whether it was realistic to protect the Vatican against sustained RPG attack and 67 suggested reactive armour was the answer. Nil Einne (talk) 14:16, 8 November 2011 (UTC)

RPGs are designed as anti-vehicle weapons and countermeasures are normally designed for vehicles; including stand-off armour, reactive armour, structural design etc. Essentially it's all context dependent.

ALR (talk) 14:31, 8 November 2011 (UTC)

The Vatican is protected by the Armor of God. Mitch Ames (talk)-

From a security planning perspective I'd turn that around and say what effect would a potential attacker want to have on the Vatican?

An RPG would be a "demonstration of vulnerability" attack, a media embarrassment as much as anything else. The volume of damage something like that could do is pretty limited as they're not all that accurate and don't pack a significant punch.

If one wanted to do some significant structural damage then a car-bomb would probably deliver more result, although I don't know anything about the geography so it may not be possible to get a car/ small van close enough to something structurally significant.

The debate about specific protection hinges around some of these issues, is it financially or architecturally viable to build in either adequate protection against a device? Given the age of the building you're then talking about either external blast netting or structural reinforcement. Since there is nothing visible, and no evidence of significant public works to reinforce then I'd suggest not. There are other defences that might be in play, including stand off distance controls and similar, but that probably needs local knowledge and a security planners eye to determine.

ALR (talk) 13:50, 8 November 2011 (UTC)

Agreed. Alansplodge (talk) 13:55, 8 November 2011 (UTC)

Schlick-Tweedie principle

This is a technique for balancing triple expansion steam engines. What is the principle?Okaha (talk) 22:23, 7 November 2011 (UTC)

In the Yarrow-Schlick-Tweedy system, the cranks of a four-crank engine are placed at angles such that a polygon with sides corresponding to the corresponding inertia forces will close.[5] On Wikipedia, the system is mentioned but not really explained in much detail at Steam engine#Multiple expansion engines and Compound engine#Marine applications. Red Act (talk) 00:07, 8 November 2011 (UTC)

I concur — Preceding unsigned comment added by 203.112.82.129 (talk) 01:54, 8 November 2011 (UTC)

FWIW we were taught this method of balancing engines at uni. It results in good first order balance if the crankshaft is short, but as the crank gets longer a rotating first order couple may prove troublesome. For a high speed engine you'll still need a proper dynamic balance as well. Greglocock (talk) 02:49, 8 November 2011 (UTC)

molar heat capacity of a black hole

Are we to assume that the molar heat capacity of a black hole (a property independent of mass though not density) is near-infinite? Say a supermassive black hole is strong enough to pull a very hot star into its sink. Where does all that heat energy go, if the black hole still remains at a few millionths of a degree Kelvin? elle _{vécut heureuse} ^{à jamais} (be free) 23:52, 7 November 2011 (UTC)

On an order of magnitude level, what would the molar heat capacity (per mol of some particle) be? Does the black hole just spin faster and faster? If the black hole is treated as a single particle... then wouldn't its heat capacity be some order of 5k/2 -- a very small number? (Or 7k/2, or corresponding as many modes as a black hole allows.) How does statistical mechanics work in black holes? elle _{vécut heureuse} ^{à jamais} (be free) 23:58, 7 November 2011 (UTC)

Note that the heat capacity of a black hole is negative -- as you add energy to a black hole it gets colder. (As in fact is the heat capacity for many other gravitating objects, such as stars -- see the references at Heat capacity#Negative heat capacity (stars) for some discussion about whether this is physically acceptable and/or what it means).

Statistical mechanics is still pretty tentative for black holes. On the one hand, the Hawking entropy formula that comes out of various semiclassical approximations seems to be pretty solid. This directly relates the entropy of the BH to its area, and from there you can get a formula for entropy as a function of the BH radius or BH mass. In principle this may very well be an entropy to which S = k log W can be applied, to get a density of microstates; but until there is a solid theory of quantum gravity, it is far from clear what those microstates actually are. Some calculations have been done based on some string theory models however, which apparently were thought to make some sort of sense.

Probably not appropriate to talk about a "molar" heat capacity, though, when a black hole is not made out of molecules. Jheald (talk) 00:17, 8 November 2011 (UTC)

The Earth is self-gravitating yes? Does it have a negative heat capacity too? (Ignoring its atmosphere.) elle _{vécut heureuse} ^{à jamais} (be free) 00:26, 8 November 2011 (UTC)

No, the Earth, unlike the sun has positive heat capacity. Dauto (talk) 05:18, 8 November 2011 (UTC)

But - and that's cool - An object in orbit around the Earth will accelerate when a braking force is applied and will brake when an accelerating force is applied. For instance, if you were in the shuttle and were trying to catch up to and dock with the space station that happened to be right ahead of you, you would fire the forward pointing jets (stepping on the brakes so to speak) and that would accelerate you forward. Dauto (talk) 05:37, 8 November 2011 (UTC)

Wait, what? --Jayron32 05:44, 8 November 2011 (UTC)

Yep. It's a consequence of the virial theorem by which you can see that if you provide negative work, the gravitational potential energy drops twice as much forcing the kinetic energy to increase. Dauto (talk) 06:02, 8 November 2011 (UTC)

That makes no sense. If I'm floating in orbit around earth next to another object, and I push on that object, it doesn't accelerate towards me! Can you explain how your scenario is different from that? --Jayron32 06:08, 8 November 2011 (UTC)

In other words, by removing energy, you go into a lower orbit effectively starting a Low Yo-Yo maneuver. Dauto (talk) 06:15, 8 November 2011 (UTC)

(EC) I think the procedure used to catch up with a spacecraft orbiting in front of you is generally more complicated than simply firing a single reverse thrust. But the basic idea is that firing a reverse thrust will lower the spacecraft's orbit, and lower orbits are faster than higher orbits, so to catch up to something in front of you, the first firing at least would counter-intuitively be a reverse thrust. See the second-to-last paragraph of Orbital mechanics#Rules of thumb. Red Act (talk) 06:20, 8 November 2011 (UTC)

See also that page that has a quote by Buzz Aldrin. Dauto (talk) 06:26, 8 November 2011 (UTC)

OK, thanks all. That sort of maneuvering is more complicated than Dauto made it sound. It makes sense when explained in the context of what ALL the steps in the manuever were, rather than simply "putting on the brakes makes you go faster". What is actually happening appears to be conservation of angular momentum which makes perfect sense; turning tighter orbit around the Earth will result in moving faster to maintain a constant angular momentum. When you decelerate, you reduce your kinetic energy, which means you drop into a tighter orbit around the earth, which makes you catch up faster to your target. When you are directly under your target, you then accelerate towards it, to move "out" from the earth into the higher orbit. Did I get all of that correct? --Jayron32 06:32, 8 November 2011 (UTC)

No, not correct. There is no angular momentum conservation here since the applied force causes a torque. Really, what happens is that you speed up because you go into a lower orbit when you brake. that's at the heart of the sun's negative heat capacity as well. Dauto (talk) 06:44, 8 November 2011 (UTC)

You go into a lower orbit when you break because you reduce your kinetic energy; this is the same reason that an electron drops into a lower energy level when it emits a photon, but on a classical rather than quantum level; do I at least have THAT part correct? (ignoring the angular momentum issue). --Jayron32 06:50, 8 November 2011 (UTC)

The lower orbit has higher kinetic energy. Dauto (talk) 06:58, 8 November 2011 (UTC)

Then why does "hitting the brakes" lower your orbit? I would think that lowering the orbit would require you to shed energy somehow, like an electron sheds energy in the form of photons. Can you perhaps explain how hitting the brakes causes you to gain energy? --Jayron32 07:16, 8 November 2011 (UTC)

You shed twice as much gravitational potential energy than the increase in kinetic energy (because of the virial theorem) for a net loss of energy. Dauto (talk) 07:23, 8 November 2011 (UTC)

My math sucks, but is that the 2<T> = n<Vtot> bit, where n = -1 since the Earth and the orbiting bodies are gravitationally bound? What you are saying is that equation means that increasing the T value causes the Vtot value to decrease by twice as much, due to the n = -1 for a gravitationally bound system. Did I get that correct? --Jayron32 07:29, 8 November 2011 (UTC)

Yes, that's it. So when you brake you lose energy, but even as you're losing energy you are also gaining kinetic energy because the loss in potential energy more than make up for the gain in kinetic energy, so you in fact speed up. Cool isn't it? That's also what happens to the particles in a cloud that eventually form a star. They lose energy by radiation and that forces them to gain kinetic energy warming the cloud up, hence the negative heat capacity. Dauto (talk) 07:37, 8 November 2011 (UTC)

Can I just point out for clarity that the word you want is "brake" (apply a stopping force), not "break" ([cause to] come apart). Also (less critically) "losing/lose", not "loosing/loose". AndrewWTaylor (talk) 17:32, 8 November 2011 (UTC)

Sorry about that. I fixed the mistakes. Dauto (talk) 18:09, 8 November 2011 (UTC)

(undent) Black holes violate most properties of physics, excluding gravity and possibly electromagnetism. That means values like temperature may not apply inside the event horizon, and in fact may travel out from the white hole on the other side. Some of the energy is excreted via bi-polar jets. ~AH1 ^(discuss!) 03:22, 9 November 2011 (UTC)

What's a mole of black holes? According to the no-hair theorem, the only thing I can think of is that a black hole is a single particle, so you mean 6x10^23 of them? --Trovatore (talk) 03:24, 9 November 2011 (UTC)

November 8

Neurons v computer chips

Hi, The binary funtion has two states, on and off. How many states does the neuron have particularly the human one?

If you don't understand the question, the computer runs on wires which can be on or off, two states. The neuron works on chemicals and has more than simply on or off? ~ R.T.G 11:35, 8 November 2011 (UTC)

Neuron#All-or-none principle implies that there are only two states, firing or not, although the frequency may vary. (However I am not a medical person - I just had a quick look at the article.) Mitch Ames (talk) 12:08, 8 November 2011 (UTC)

But a neuron can't remain in a "firing" state, unlike a binary electrical signal, which can stay in either the "0" state or the "1" state indefinitely. A neuron also acts asynchronously, which is different from the synchronous circuitry within a clock-driven CPU. So the information content of a neuron's firings is roughly comparable to the information content of the timing of the leading edges of pulses in an asynchronous binary electrical signal. Red Act (talk) 14:48, 8 November 2011 (UTC)

Artificial neural networks, by the way, don't in general model a "neural" signal with an asynchronous one-binary-digit signal as mentioned above, but rather usually as a continuous-valued (actually multiple binary digit) signal, that's conceptually updated in discrete steps, synchronously with the other "neurons" (although the "neurons" are actually updated sequentially, unless perhaps if the ANN is being run on a highly parallel CPU). The idea is that the continuous-valued signal is analogous to the frequency with which a biological neuron fires. Red Act (talk) 15:27, 8 November 2011 (UTC)

Neurons are not binary. The internal state of a neuron can be extremely complicated. The mechanism by which neurons send signals to each other is simpler, though: most neurons signal using action potentials, and to a first approximation all action potentials have the same size and shape -- the only thing that distinguishes them is the time at which they occur. Thus the signals coming from a neuron can be thought of as a train of identical pulses, each of which can occur at an arbitrary time. (This is the common situation, but some types of neurons work differently.) Looie496 (talk) 16:01, 8 November 2011 (UTC)

You may be interested in quantum computing, which uses qubits instead of traditional 0s and 1s. ~AH1 ^(discuss!) 03:18, 9 November 2011 (UTC)

Or why not go to old circuits instead of future ones. In the past (before common computers) analog and digital circuits were often mixed together. The result was "digital" logic that used continuous analog voltage values. So, a "bit" could be anything from -5 to +5 volts. If you wanted an analog value, you just read it. If you needed a binary value, you use a transistor to fire off a positive value when the bit contained a value above a predetermined level. I know that is being very vague, but it is a lot more complicated than such a trivial example. -- kainaw™ 03:27, 9 November 2011 (UTC)

Oxidation & Reduction

3 Cu + 8 HNO3 → 3 Cu(NO3)2 + 2 NO + 4 H2O

(3 Cu + 8 H+ + 2NO3 → 3 Cu2+ + 2 NO + 4 H2O)

In the reaction above, how many moles of HNO3 would be needed to oxidize 3 moles of Cu? If it had asked "how many moles of "NO3-"?", I am certain that the answer would be 2 moles. But if it asks "how many moles of "HNO3"?" would the answer be 8 or 2?Johnnyboi7 (talk) 14:43, 8 November 2011 (UTC)

The answer would be 8. Since it takes 8 H+ ions to complete the process, you would need all 8 of "HNO3", even though you only need 2 of the NO3-. Look at it this way: Lets say nuts and bolts are packaged together in pairs, one nut and one bolt per package. Lets say you need 8 bolts and only 2 nuts to complete a project. You still need to open 8 packages, even if you only need 2 of the nuts. How you phrase the question matters. If you say "How many nuts do I need to complete 3 projects" then you need 6 nuts. If you say "How many packages do I need to open to complete the project", you need to open 24 packages, because even though you only need 6 nuts, you still have to open 24 boxes to get all 24 of the bolts. Same story here: If the question asks "How much HNO3 is needed to make 3 moles of Cu2+" then you need 8 moles of HNO3. If the question asks "How much NO3- do I need to make 3 moles of Cu2+", then you need 2 moles of NO3-. --Jayron32 18:50, 8 November 2011 (UTC)

3(Cu → Cu²⁺ + 2e^-)

2(NHO₃ + 3H⁺ + 3e^- → NO + 2H₂O)

3Cu + 2NHO₃ + 6H⁺ → 3Cu²⁺ + 2NO + 4H₂O

Here, two acid molecules are oxidising and six are acidifying, thus eight are neccesary to complete the reaction. Plasmic Physics (talk) 21:05, 8 November 2011 (UTC)

Signal Format Specification of Very Early Television Sets

From History_of_television#Television_sets,

"The first commercially made electronic television sets with cathode ray tubes were manufactured by Telefunken in Germany in 1934, followed by other makers in France (1936), Britain (1936), and America (1938). The cheapest of the pre-World War II factory-made American sets, a 1938 image-only model with a 3-inch (8 cm) screen, cost US$125, the equivalent of US$1,863 in 2007. The most expensive model with a 12-inch (30 cm) screen was $445 ($6,633)."

What was the signal format of the 1938 image-only models sold in America in 1938? Presumably, if they were going for US$125 in 1938, which the article says is $1,863 in 2007 dollars, somebody must have been making broadcast content that consumers wanted to see in that format. Is a link to that format specification to be had here in 2011? The format specification is all I want. 20.137.18.53 (talk) 14:54, 8 November 2011 (UTC)

We have an article on television systems before 1940 that details the many various standards that existed in the early era, and it appears that RCA's 441-line television system was the chief predecessor to NTSC. — Lomn 15:12, 8 November 2011 (UTC)

In case anyone wants to use the references:

Grandiose (me, talk, contribs) 16:49, 8 November 2011 (UTC)

Properties of brass

what are the properties of brss?

Have you read our article on brass? — Lomn 15:57, 8 November 2011 (UTC) note: added title

Is the universe hologram-like?

How credible is the idea championed by Brain Greene? [6] Thanks. 65.88.88.75 (talk) 16:17, 8 November 2011 (UTC)

It's a real possibility that cannot be discounted off hand. So, yes it is credible. We don't know yet whether it's true or not. Dauto (talk) 16:32, 8 November 2011 (UTC)

By the way, I think the holographic principle was first proposed by Gerard 't Hooft and Leonard Susskind. Dauto (talk) 16:37, 8 November 2011 (UTC)

But, the holographic principle is just a special case of Green's theorem, which is some 2 or 3 centuries old. Green's theorem (or, more generally, Stokes' theorem) states that, for certain properties, it is mathematically equivalent to express as a volumetric vector field or as a surface potential. With sufficient extension, Green's theorem applies to arbitrary dimensional spaces and fields. For example, Gauss's law states that if we know the electric field at every point on a surface, we know the net charge inside the volume. By extension, if we can parameterize several vector-fields on a surface, we can compute the equivalent volumetric contents for anything that is physically related to those vector fields.

At present, we do not know a physical law that relates "everything interesting" to "some vector field," so even if the principle is theoretically valid, we aren't able to use it to effectively describe the arbitrary contents of a gaussian pillbox. (We do have several such laws, though: we can relate charge to electric field; we can relate mass to gravitational potential; we can relate mass flux to many properties, and so on). Nimur (talk) 17:07, 8 November 2011 (UTC)

That's not what the holographic principle is about. The holographic principle comes about because the maximum amount of information that can fit within a given region of space is proportional to the surface area of the region - not it's volume. So if you put two identical volumes side by side, the maximum information they can hold doesn't double. How does one explain that? Dauto (talk) 17:14, 8 November 2011 (UTC)

The way I read holographic principle, it "states that the description of a volume of space can be thought of as encoded on a boundary to the region." I don't pretend to know every possible mathematical consequence of that statement. However, as I mentioned above, we don't know if we can construct a valid description of any arbitrary volume and encode it on to the surface of that volume. At present, we only know how to do that for certain special cases, like the very simple case of stationary electric charge. I wouldn't be surprised if we run in to some logical conundrums if we try to extend this mathematical tool ad infinitum to try and describe every physical property: for example, consider magnetic fields. Their closed path integrals are pathological forgive the pun - they depend on the path you choose. Physical consequence? We can't even construct a coherent description of a "volume" of magnetic "charge" within the mathematical framework we use. (No magnetic monopole). We cannot use a surface-integral, nor a path-integral, to deduce a complete description of a magnetic field. It is a physical impossibility.

When our math and our physical observations clash, one or the other must be modified. So, if your assertion is correct, and placing two volumes side by side doesn't double some property, I see two ways to resolve this: (1) either the property is doubled, and you are mistaken; or (2) you are correct, the property does not double, but we can not conclude any physical conservation law for that property. Nimur (talk) 17:25, 8 November 2011 (UTC)

Or, put more succinctly: for all the handwaveyness of Brian Greene's pop-science books, he is essentially making one simple mathematical assertion: the Grand Unified Theory is specified by a curl-less field. That is a testable hypothesis, but it is not a fact. Nimur (talk) 17:36, 8 November 2011 (UTC)

You're looking at it the wrong way. Green's theorem is NOT one instance of the holographic principle because it says nothing about the maximum information content. Electrostatics isn't even a quantized theory so there is no limit to information content within Green's theorem. The maximum information content is infinite here, but that's irrelevant because as I pointed out it's not a quantized theory. The hlographic principle comes up when one tries to put Quantum mechanics and General relativity together and finds the surprising fact that the maximum information content of a region is proportional to the regions surface area. Dauto (talk) 17:59, 8 November 2011 (UTC)

Would this refute conventional scientific materialism, or simply suggest that our universe is a parallel universe to something inside the multiverse? ~AH1 ^(discuss!) 03:16, 9 November 2011 (UTC)

crazy cure for both AIDS and blood cancer

I've a doubt.In AIDS patients the white blood cells eventually died and causing low immunity.In leukemia patients white blood cells generate excessively.What if a guy has both diseases.The excessive white blood cells due to cancer is destructed of AIDS and an equilibrium forms.guy will be saved..please reply ?--nijil (talk) 17:19, 8 November 2011 (UTC)

Certainly not. You're taking a too simplistic view of those disease/cancer; see the articles leukemia and AIDS for a range of points. Grandiose (me, talk, contribs) 18:24, 8 November 2011 (UTC)

Your question is built on two ideas that don't connect well. In leukemia, the cancer cells don't function well (in part because they are immature), so they don't help fight infection; also, leukemia is generally a cancer of granulocytes and monocytes, which don't play the principal role in fighting viral infections. In lymphoma (a cancer of lymphocytes, the cells that fight viral infections and that are also the cells that HIV infects) the cancer cells are a clone - they have (at most) one specificity. If they functioned at all, it is vanishingly unlikely that they would be specific for an epitope of HIV, and even if they had such a specificity, the virus would almost certainly mutate to avoid them - as demonstrated when some clever people tried something like this to treat HIV - with disastrous results: PMID 7585062. -- Scray (talk) 19:28, 8 November 2011 (UTC)

While the above two responses explain why, in general, HIV infection would not be an appropriate or effective therapy to treat leukemia, it might be worth mentioning bone marrow transplantation as a potential cure for HIV infection. CCR5 is a protein that is naturally expressed on the surface of T cells, and its presence seems to be required for HIV to enter those cells. There is a known mutation, CCR5-Δ32, which confers resistance to HIV infection in people who carry it. People with two copies of the mutant CCR5 gene appear to be immune to (most strains of) HIV; about 1% of northern Europeans have this trait. In principle, one could use radiation and chemotherapy to wipe out a patient's original bone marrow (thus eliminating the supply of T cells that HIV can infect) and replace their marrow with HIV-resistant bone marrow from a donor with two copies of CCR5-Δ32.

Just such an approach was tested in Germany in 2007: Hematopoietic stem cell transplantation#Experimental HIV treatment. An HIV-positive patient with had developed leukemia (who therefore required a bone marrow transplant to cure that condition anyway) was matched to a bone marrow donor who carried the appropriate CCR5 mutations. Remarkably, the patient appears to be fully cured—of both diseases. That said, this solution won't work as a universal cure for AIDS. Finding a matching marrow donor who also carries the appropriate CCR5 mutation is difficult (and may be impossible for the majority of recipients). Bone marrow transplantation is a painful, risky procedure that will kill at least 10% of recipients, and is prone to other unpleasant complications. Consequently, this approach is only likely to be tried with patients who require a bone marrow transplant to cure another condition. TenOfAllTrades(talk) 01:38, 9 November 2011 (UTC)

The Vinca alkaloids are currently being used to treat leukemia. ~AH1 ^(discuss!) 03:12, 9 November 2011 (UTC)

source of elwha river pre dam chinook salmon numbers

What is the source of the estimates of the Elwha River's pre dam Chinook Salmon numbers? 400,000 Chinook is used as a factual number with no source for that number.The Elwha River has a gradient of over 80 feet per mile;which means to me that much of the river was impassable to salmon.Further this estimate is equal to or greater than the known runs of major,very much larger salmon streams. — Preceding unsigned comment added by 75.106.235.161 (talk) 18:19, 8 November 2011 (UTC)

The relevant article is Elwha River. Try Google Scholar. ~AH1 ^(discuss!) 03:10, 9 November 2011 (UTC)

aliens?

what would most likely happen if humans found alien life? Also, what is the slowest speed electricity will travel? Heck froze over (talk) 19:45, 8 November 2011 (UTC)

Depends on what type of alien life, and where we found it. Non-intelligent life (likely microbes) found in our solar system (on Mars, Europa, Enceladus, or other places) would be rigorously studied, its chemical make-up ascertained, its characteristics catalogued in extreme detail. For intelligent life, it would likely be lightyears away, so we'd need to devise a way to communicate with such beings, knowing that it would take years (possibly lifetimes) before we received any reply. --Goodbye Galaxy (talk) 20:07, 8 November 2011 (UTC)

a) Kill it, eat it, or otherwise find some way to profit from it.

b) Static electricity doesn't move at all.-- Obsidi♠n Soul 20:17, 8 November 2011 (UTC)

I think that he's talking about non-zero electrical current - if the electrons are moving from one point in a conductor to another point, how slow can they move to that point. Plasmic Physics (talk) 20:44, 8 November 2011 (UTC)

The electrical charge technically doesn't move much. It is merely passed along (in the usual form of electric "currency" - electrons, which good conductors like metals have in abundance). The apparent speed is the net total movement of the charge as the electrons are bounced along, but the individual electrons move only tiny distances (drift velocity). Like billiards or dominoes, atom 1 gets an extra electron, but atom 2 steals one from atom 1, atom 3 steals another one from atom 2, etc. In alternating currents, the atoms merely grab each other's electrons back and forth even. So the slowest electricity can go is technically the slowest net velocity electrons can achieve with their movements. What would seem like random movement of electrons to us for example may result in a net velocity that can only be apparent if you observe it for billions of years. Hence static electricity is a fair enough answer! :D ...I think... Physics make my nose bleed! The important question here is, would you eat aliens?! I have one for a low low price of $4.99! Order now and you can get a small vial containing 0.1 μg of prime quality moonrock for free!!! Perfect for alchemical experiments, picnics at the beach, love potions, good for your liver, and for curing those exotic diseases doctors don't even have names for! -- Obsidi♠n Soul 23:15, 8 November 2011 (UTC)

If my memory serves me right, physical electrons in a conductor move exceedingly slowly (order of mm/s). But the electric current is transmitted by the electormagnetic field and that moves at the speed of light.

A back of the envelope calculation: one Ampere current going through a copper wire with 1 mm^2 cross section would send 1.6*10^19 electrons per second through any cross section. If copper has one conductivity electron per atom, 1.6*10^19 electrons are contained in 0.00077 grams of copper, which is 0.087 mm^3, so the average speed of the electrons is 0.087 mm/s. --Itinerant1 (talk) 21:35, 8 November 2011 (UTC)

(think there should have been an EC)The answer to 2 is more complicated then it seemed to me at 1st, i'm not sure I can answer it.. The typical answer is that electricity travels at the speed of light, even if the charge carriers (typically electrons) are not going that fast. But to answer how SLOW it can go,.. A lightning strike for example propagates a LOT slower then the speed of light, about 140,000 mph (light is 670 million mph) but I think that's more to do with Velocity of propagation then with the speed of electricity, that complicates things a bit. Once a lightning bolt actually hits the ground, then the discharge actually happens at the speed of light.. So I'm not sure what the answer is, it seems like strictly electicity travels at the speed of light, but then what is a lightning bolt if not "electricity" travelling at 3000 times slower then light? Vespine (talk) 21:49, 8 November 2011 (UTC)

If we find intelligent aliens, creationists still won't change their views. HiLo48 (talk) 21:52, 8 November 2011 (UTC)

You won't know unless you find some. Plasmic Physics (talk) 22:58, 8 November 2011 (UTC)

Yep, that's what's fun about hypotheticals. We're all allowed to speculate. HiLo48 (talk) 23:10, 8 November 2011 (UTC)

For example, if those highly-intelligent, highly-advanced E.T.'s believed in a supreme being (a god, or whatever), that would probably baffle the Richard Dawkinses of the world. ←Baseball Bugs ^{What's up, Doc?} carrots→ 02:25, 9 November 2011 (UTC)

Astrobiology is the current theoretical study of aliens. ~AH1 ^(discuss!) 03:02, 9 November 2011 (UTC)

Expanding universe and conservation of energy.

A photon travels through extragalactic space. The universe expands, and the photon is redshifted. Where does that energy go? Goodbye Galaxy (talk) 20:00, 8 November 2011 (UTC)

Nowhere. Expanding universe is a prediction of general relativity. In general relativity, energy is not globally conserved. --Itinerant1 (talk) 20:03, 8 November 2011 (UTC)

Similarly, a train in motion has kinetic energy, but if you are inside of the train it seems to you to be at rest. Where does that energy go? Dauto (talk) 20:08, 8 November 2011 (UTC)

So the photon wouldn't redshift locally? Only relatively? Goodbye Galaxy (talk) 20:38, 8 November 2011 (UTC)

If the photon is kept in one place by reflecting it back a forth between to mirrors and the mirrors are kept at constant distance from each other than there will be no red-shift. Dauto (talk) 20:44, 8 November 2011 (UTC)

@Itinerant1: Not exactly. From my understanding, it depends on what kind of universe we live in as to whether or not General Relativity allows for universal conservation of energy. That is, under some closed geometries, the universe is considered a finite system, and may allow for conservation of energy to hold universally. If the universe has an open geometry, then conservation of energy may only hold in closed systems within the universe, but not across the entire universe. At least, that's my understanding of what it says at Conservation_of_energy#Relativity and Shape of the Universe. --Jayron32 21:05, 8 November 2011 (UTC)

Why would an expanding universe cause light to redshift? ScienceApe (talk) 20:10, 8 November 2011 (UTC)

Woops, nvm. I realized the answer. ScienceApe (talk) 20:11, 8 November 2011 (UTC)

Perhaps the "energy" goes into either quantum energy or the metric expansion of space, neither of which are non-infinite in an open universe. ~AH1 ^(discuss!) 02:56, 9 November 2011 (UTC)

STEM shortage: education or raw ability?

To what extent does the shortage of scientists, technology professionals and engineers in the US result from a lack of access to education, and to what extent is it a shortage of raw ability (including the ability to retrain in adulthood)? What initiatives, if any, are underway to address the latter? NeonMerlin 21:59, 8 November 2011 (UTC)

There is no shortage of scientists in the US. There are tens of thousands of scientists willing to work non-tenure-track jobs for meager pay well into their 30's. They are called post-docs. I'd call that glut rather than shortage. Engineers are a different story. --Itinerant1 (talk) 22:10, 8 November 2011 (UTC)

There is a shortage of Engineers at the salary rate at which Capital would like to purchase their labour. I'd suggest to Engineers and prospective Engineers that maintaining the labour supply of Engineering at the current level works in their interest. Other professions where the labour supply was successfully expanded have been proletarianised. Fifelfoo (talk) 22:12, 8 November 2011 (UTC)

The OP postulates "a lack of access to education" or "a shortage of raw ability" as the two possible explanations for a perceived shortage of professionals. Another explanation is cultural. An old saying is that you can lead a horse to water but cannot make it drink. I'm a high school teacher and I see hundreds of kids every year not achieving to their potential simply because they don't care. Life is comfortable. They cannot be bothered putting in the effort to gain high level qualifications. Obviously that doesn't apply to all students, but to a sadly increasing percentage in western society. <Here endeth the lecture> HiLo48 (talk) 23:00, 8 November 2011 (UTC)

There are elements of class consciousness in the despair of students. When your workplace expectations are conditioned by the double hurdle of a proletarian and a menial work experience, it is difficult to imagine the freedoms at work and in income that engineers currently possess—that which is unimaginable but possible is not worth pursuing, especially when there are imaginable but improbable alternatives like the lottery or celebrity. My experience comparing a working class university with, frankly, bourgeois and managerial intake universities, is that working class students have smaller horizons of expectation, and go for safe professions with low incomes that they've seen directly modelled and repeatedly noted in culture; and, that they're aware from immediate experience are attainable and achievable. Nursing, Teaching, Accounting, Business or Arts to become a menial drone, IT rather than SEng CompEng or CompSci. Fifelfoo (talk) 01:22, 9 November 2011 (UTC)

There was an article on this in the New York Times just the other day. Education seems like an important juncture point — but not because of "lack of access," but because lots of people decide pretty quickly, once they are in college, to do something else. There is a lot that can be said about education other than "lack of access" — it can also be, "lack of preparation" or "unreasonable expectations" or things along those lines. Personally I suspect that the systematic de-skilling of primary and secondary school educators (thanks in no part to the terrible chase for standardized test scores, which leads to idiotic, standardized teaching) is partially responsible for this here. The college age students you are seeing now grew up under the terrible consequences of the No Child Left Behind Act, which has been systematically making public education a far more miserable and pointless affair than it has ever been previously (and it was always a bit pointless and miserable). But this is just conjecture on my part, to be sure. --Mr.98 (talk) 01:23, 9 November 2011 (UTC)

You may also be interested in Pygmalion effect and dyscalculia. ~AH1 ^(discuss!) 02:49, 9 November 2011 (UTC)

The engineering shortage is a smoke screen. But the sallary has to be higher than a commodity sallary and the workplace has to treat its employees right to induce an interest in students. Electron9 (talk) 03:42, 9 November 2011 (UTC)

This isn't true for a vast number of professions inculcated at Universities. Veterinarian incomes have crashed in Australia as the field has been feminised and veterinarians reduced from small capitalists to employees on salary. A similar process is happening with non-consulting doctors. A number of professions, (K-12, Nursing, Accountancy, HR) are at or below the average for employee remuneration, and are well below trade certified or diplomate trade salary incomes. Some merely skilled or unskilled occupations earn in advance of these professions. So it is untrue to say that a profession's salary needs to be above the average to induce an interest in students. Correspondingly, Nurses, Doctors, Social workers, Teachers and a whole host of professions are treated like shit in workplaces without any measure of workers' control and where management prerogative is absolute, and they still provide excellent service and inspire student interest. Fifelfoo (talk) 03:57, 9 November 2011 (UTC)

I want to reinforce the statement that there is no engineering shortage. There are many engineers in the United States who can't get jobs as engineers for many reasons. U.S. companies refuse to hire "old" engineers (by old, I mean more than 30 years old). Then, when they do hire an American engineer, he or she will ask for something ridiculous like $15/hr. The engineers from India and China will do the same job for $8/hr and put in 1.5 hours for every 1 hour paid. Basically, U.S. companies are creating the illusion of an engineering shortage so they can profit from government-sanctioned slave labor. -- kainaw™ 04:07, 9 November 2011 (UTC)

• In the US they like seasoned engineers getting $45 per hour to retire and make way for young engineers making far less. I question degreed engineers in India working for $8 per hour, let alone the 5.33 per hour if they work 1.5 hours for every book hour. Edison (talk) 04:28, 9 November 2011 (UTC)

I've never met an engineer who makes anywhere near $45/hr. $30/hr is around $60k/year. In government, commercial, and university places I've worked, managers will make over $60k/year, but not the engineers. Many engineers get an MBA and become managers - but they are no longer engineers. As for low-paid foreigners, I work with a guy from China who makes less than half what I make and puts in more hours. Why? He is on a work visa. He has a masters degree (and nearly finished his PhD). He actually took a pay cut to come to the U.S. and work. There are many more waiting to follow. When I leave, they will surely replace me with two more Chinese engineers. -- kainaw™ 04:34, 9 November 2011 (UTC)

HI! It's nice to meet you. Edison (talk) 06:05, 9 November 2011 (UTC)

Making suet for birds at home...

As winter has arrived where I live, I would like to try making some suet. It seems simple enough. However, I have two questions:

1. Will pork fat do or must I use beef fat? Where I live the former is abundant and the latter hideously expensive.

2. Does it really need to be strained 2+ times through cheesecloth? What is being strained out during this step?

If anyone has any general tips on making suet for backyard birds, I'd also like to hear them. Thank you! The Masked Booby (talk) 22:18, 8 November 2011 (UTC)

I don't know anything about suet, the article seems to say specifically that you need beef fat, but, if you want to use pork fat, you could make Salo instead, and birds like that too. --Itinerant1 (talk) 22:26, 8 November 2011 (UTC)

The difference is that beef abdominal fat, if pure enough, will harden almost to the consistency of wax, and doesn't easily melt. Pork fat is soft and greasy even when it is cold. Nutritionally they are pretty much equivalent, but the texture is very different. Looie496 (talk) 22:46, 8 November 2011 (UTC)

Salo is hard enough that you need to cut it with a knife. As far as I understand, fat only becomes soft if it is rendered and purified. In its raw form, as salo or suet, it is quite firm because it is kept together by cell walls, and you need the temperature above 100 C to break them. But you are correct that purified pork fat is softer and its melting point is at least 10 C lower than the melting point of beef fat. --Itinerant1 (talk) 23:11, 8 November 2011 (UTC)

Maybe you missed it, the suet article actually says in the bird feed section Bird feed is commonly used in the form of cakes of suet, which can be made with other solid fats, such as lard. and the reference given has the instructions of how to make it with lard. Vespine (talk) 01:10, 9 November 2011 (UTC)

November 9

Why can't you watch 3D movies on a regular television?

What makes the illusion of 3d impossible on a normal screen? Quest09 (talk) 01:32, 9 November 2011 (UTC)

You can watch 3D movies on a normal screen if you have the right tools. Going old school, you can get some of those red/blue glasses and watch a movie done in red/blue 3D. No problem. Though it never caught on, there was a flicker glasses add-on for any VCR or DVD player that used NTSC (the PAL version simply wasn't very usable). Every other frame of the NTSC signal would black-out one side of the glasses. So, the television shows the left-eye image then the right-eye image, back and forth. The glasses flicker left-right-left in sync with the signal going to the television. Again, this is on a regular television. Some televisions on sale right now use that type of 3D signal. It has problems. The image is dimmer since only half the picture is shown to each eye (solution, auto-increase brightness in 3D display mode). There is noticeable flicker in bright white horizontal lines. Fancier sets have a "flicker fixer" mod that bleeds some of the bright horizontal lines to the surrounding image to limit the flicker. -- kainaw™ 01:43, 9 November 2011 (UTC)

See also 3D film and Stereoscopy. There are many different techniques and some of them work on a normal TV. PrimeHunter (talk) 01:51, 9 November 2011 (UTC)

If you watch motion such as a pendulum swinging back and forth on a B&W TV, and have a dark filter such as a sunglass lens over one eye, there will be a powerful illusion of motion in 3D, caused by the delay of perception of the darker image. See Pulfrich effect. It is amazing! It has been used on lots of TV shows to create a 3D effect. Edison (talk) 06:04, 9 November 2011 (UTC)

The problem with glasses-less 3D is that you need to have a very narrow viewing angle over which the effect will "work". You can send a normal TV signal which can encode a 3D image which will look to be in 3D, but only for someone sitting directly in front of the screen, and only if they are at the correct distance; people viewing from another angle or distance will see garbage. You do this by presupposing the viewing angle and distance and then encode the 3D image specifically for that angle and distance, viola: natural 3D on a 2D TV screen. This is called Autostereoscopy, and our article covers a few known methods of making it work. However, because of the impracticality of this, it only works in limited cases; this is basically how the Nintendo 3DS works; because of the small screen and the fact that everyone uses it roughly the same way (you hold it in your hands, at comfortable arm length, and centered in front of your field of vision). This means that just about everyone will be viewing the device within the tolerances that autostereoscopy needs. With a standard livingroom TV set, however, there's just too many variables to make a working 3DS-style three-dimensional TV screen. --Jayron32 06:19, 9 November 2011 (UTC)

Cylindrical tube elastic deformation?

Suppose a cylindrical tube with a wall thickness of t, external diameter d, with a length of L exposed to a force of F at the middle (L/2) is made of a metal X. How does one calculate how much the material will move by the elastic deformation? I looked at the elastic module article, but didn't get it ;) Electron9 (talk) 03:26, 9 November 2011 (UTC)

This looks like a hard problem to solve analytically. The shape of the contact area between the tube and the external force matter a lot. (Consider force F applied by the blades of a bolt cutter, vs. the same force applied by a vise.) To the lowest order and in the limit of thick walls (t~d/2), the compression deformation would be on the order of (F/lE) where l is the length of the contact patch and E is Young's modulus of the material of the pipe. For more precise results, you may need to find a good book on solid mechanics.--Itinerant1 (talk) 03:54, 9 November 2011 (UTC)

No good book available at the current location. The picture above is just for illustration of pipe, the cutter is just clutter. The pipe in question would be attached in the ends and the load is a human hand grabbing the middle (worst case). I'm curious to know if it would bend enough to feel unstable. Hopefully it won't be permanently deformed (another calculation). Electron9 (talk) 04:16, 9 November 2011 (UTC)

OK, then that's a very different problem, it is called "beam deflection", there are multiple online calculators that can do calculations for you, but right now I can't find the one that matches your needs precisely (most will do calculations for a beam that is attached at one end, or for a solid beam on two supports). Google "hollow tube beam deflection calculator". --Itinerant1 (talk) 04:53, 9 November 2011 (UTC)

Red Arrows Accident 8 Nov 2011

What was the probable cause of the unfortunate accident for the Red Arrows team with an ejector seat at RAF Scampton recently? It seems that the pilot ejected on the ground but the aircraft did not suffer an emergency such as an engine explosion, when the pilot would have deliberately ejected. So it looks like accidental ejection with the canopy in place, which killed the pilot.Pensioner.bsc (talk) 04:01, 9 November 2011 (UTC)

I'm inclined to agree with the sentiments expressed in this BBC News article, by Gp Capt Simon Blake, from RAF Scampton: "It would be inappropriate to speculate on the cause of the incident until that inquiry is complete. The investigation will determine the facts." Nimur (talk) 04:16, 9 November 2011 (UTC)

Isn't the ejector seat designed to punch through the canopy? 67.169.177.176 (talk) 05:26, 9 November 2011 (UTC)

I don't believe so, the canopy usually jettisons using explosive bolts before the seat ejects.. (EDIT)In fact, Ejection_seat#Egress_systems seems to confirm this. Vespine (talk) 05:30, 9 November 2011 (UTC)

2005 YU₅₅

How much time did the asteroid 2005 YU₅₅ spend at a distance from Earth that is less than the distance to the moon? (I'm crudely guessing about six or seven hours.) Michael Hardy (talk) 04:23, 9 November 2011 (UTC)

Well, our article 2005 YU55 has a nice animation. Using some screenshots, I've ascertained the asteroid crossed the moon's orbit at close to Nov 8.8 and 9.2, (I'm assuming that number is the date) which makes 0.4 of a day or about 9.5 hours, that's pretty rough but I'd be confident within +/- one hour. Vespine (talk) 04:47, 9 November 2011 (UTC)

How come NASA has radar images but no optical images? There should be scads of telescopes larger than the minimum 6 inch objective said to be needed to see the thing. Why can't large telescopes such a Hubble or ground based telescopes move fast enough to image the asteroid? Radar traditionally just provided a dot showing the range and bearing to a target, not the somewhat fuzzy images of the 6 frame movie of the asteroid. It's passage was a disappointment in terms of the imagery, so far. Edison (talk) 05:58, 9 November 2011 (UTC)

Issues with dog's eye

Veterinary Question removed. Sorry. APL (talk) 07:17, 9 November 2011 (UTC)