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November 3

motion

In all standard books motion is defined change in position with time and displacment is also defined as change in position and in many closed path the displacement is consider to be zero , so according to the defination of motion change in displacement is zero hence their should be no motion but we say that body has shown motion .. but how plz explain but do not explain with the help of graph? — Preceding unsigned comment added by Bhaskarandpm (talk • contribs) 05:26, 3 November 2011 (UTC)

I have a hard time understanding your question, is this what you meant ?

"If an object moves and then returns to it's original position, wouldn't it's motion be zero since that is displacement over time and no net displacement has occurred ?"

In one sense, the answer is yes, the average speed is zero. That is, if it moves north at 100 kph for an hour, then moves south at 100 kph for another hour, returning to the origin, the average speed is zero ((100+(-100))/2 ). Here it might be more useful to determine the average velocity, which, unlike speed, doesn't have a sign (velocity uses a vector instead to show direction). In this case the average velocity is 100 kph ((100+100)/2).

Similarly, while there is no net displacement, the total displacement would be 200 km. In this case the sum of displacements (ignoring signs) over each leg of the trip gives you the total displacement. For more complex paths (regardless of whether they return to the origin or not), you must use the total arc length of the path, not the distance between the starting and ending points, for total displacement and average velocity calculations.

Note that both the average speed and average velocity have their uses. Let's say you are making a multiple day car trip, and want to know how fast you were going. Assuming that the roads aren't all straight and in the same direction, the two values should differ. One tells you how fast your car was moving, which is useful in avoiding tickets and accidents, and the other tells you how quickly you will be able to reach your destination. StuRat (talk) 06:01, 3 November 2011 (UTC)

Note that StuRat has crossed up "speed" and "velocity"; speed (a scalar) is the signless component (and thus average speed in his example is 100 kph) while velocity (a vector) retains the notion of direction and thus sign. — Lomn 13:08, 3 November 2011 (UTC)

please explain why a graph won't help. And in answer to your question, if I start off in London on Tuesday morning, catch the train to Birmingham, spent the night there, then go back to London to arrive at home in time for supper, I have moved - my displacement over time has changed. The fact that I'm back where I started is merely a side-effect of my motions (relative to London) cancelling each other out. The displacement isn't zero, except in as much as London (which isn't a fixed point in spacetime) is arriving where I am at the same time as I do. AndyTheGrump (talk) 06:07, 3 November 2011 (UTC)

Am I misreading these replies, or is there some confusion between distance and displacement? Average speed is total distance travelled divided by time (no negatives allowed), and can never be zero if you have moved at all. Average velocity is a vector quantity and is net displacement divided by time, and can be zero if you return to the start. Dbfirs 08:41, 3 November 2011 (UTC)

organic chemistry

explain in detail about nucleophiles — Preceding unsigned comment added by Bhaskarandpm (talk • contribs) 06:27, 3 November 2011 (UTC)

Please read Nucleophile. Dualus (talk) 06:31, 3 November 2011 (UTC)

A nucleophile is a particle (usually an ion or molecule, but certain elements like chlorine are nucleophiles in itself) that is attracted by the positive charge of an atomic core (nucleus - usually a carbon core as nucleophiles are primarily of interest in organic chemistry). The attraction results from the fact that the nucleophile always has a free electron pair, which acts as a localized "negative charge" and is thus being attracted by localized positive charges (like that of an atomic core). This free electron pair can form a covalent bond between the nucleophile and the carbon core atom. How much more would you like to know? Phebus333 (talk) 22:34, 3 November 2011 (UTC)

No, that's fairly inaccurate. Nucleophiles are not attracted to the "atomic core". They are attracted to empty or partially empty valence-level orbitals. A nucleophile is basically a lewis base and it is attracted to a lewis acid. The electrons of the HOMO (highest occupied molecular orbital) of the nucleophile will fill into that of the LUMO (lowest unoccupied molecular orbital) of the target carbon atom. The carbon atom can be primed to accept a nucleophile by itself being bonded to an electronegative atom (which will tend to pull electrons away from the carbon, and thus partially "empty out" the LUMO, making it a better electron acceptor). That's what occurs in SN2-type reactions. In SN1-type reactions, there is a carbocation which forms, giving a completely empty LUMO to form a new bond with. --Jayron32 00:29, 4 November 2011 (UTC)

I cannot identify this bird, please help me

Which bird is this?

I saw this bird in Genoa, northern Italy. It was hiding behind a street vase, and was no bigger than a blackbird. Please, let me know what kind of bird is this. Thank you. — Preceding unsigned comment added by 85.18.173.4 (talk) 13:17, 3 November 2011 (UTC)

Could be a water rail, Rallus aquaticus. DuncanHill (talk) 13:39, 3 November 2011 (UTC)

I would agree with what DH says and only add that it might be Rallus aquaticus aquaticus which is a European nominate subspecies. But this is well over the edge of being picky :-). Richard Avery (talk) 14:27, 3 November 2011 (UTC)

DuncanHill and Richard Avery: thank you so much, you are wonderful people — Preceding unsigned comment added by 85.18.173.4 (talk) 14:49, 3 November 2011 (UTC)

Genetic studies of modern Steller's sea lion populations suggest...

"Genetic studies of modern Steller's sea lion populations suggest that this sea mammal likely hauled out on the rocks along Beringia's island-studded south shore. So the migrants may have had their pick not only of terrestrial mammals but also of seafaring ones."

Article is available here, if anyone can access it. A little bit of it can easily be read here. Link to Steller sea lion.

Question: By what means can "Genetic studies of modern Steller's sea lion populations suggest that this sea mammal likely hauled out on the rocks along Beringia's island-studded south shore"? Bus stop (talk) 14:34, 3 November 2011 (UTC)

Having no access to the source, you might want to check the relevant references listed on it instead. However, as with human genetic studies it is possible to use genetic "markers" to trace population divergence among animals. Modern sea lion populations are generally divided into two populations that diverged after the disappearance of the Beringia land bridge, the western population is found in and around the Bering Sea and Asia while the eastern population is found in the western coast of North America. As Beringia does not exist anymore today, you would not be able to find direct evidence of the existence of Steller's sea lions in Beringia, which I guess explains the wording used in that article. However, since Steller's sea lions exist in both Asia and North America with substantial genetic differences, scientists can use genetic evidence to link the two populations together to an ancestral population in the former landmass now beneath the sea. As the linked study says, it may not be the first time the populations have been divided by the rise of sea levels. The two populations separating today is the result of the end of the last ice age and the loss and subsequent population movement to find other rookeries that Beringia once provided.-- Obsidi♠n Soul 15:19, 3 November 2011 (UTC)

I checked the Scientific American article but it doesn't really discuss it and doesn't have any references. I searched google scholar for "steller sea lion "beringia"" though and found this and this which are probably what the SA claim is based on. I'll leave it to a population geneticist to explain it though! SmartSE (talk) 17:46, 3 November 2011 (UTC)

I'm afraid I asked a question the answer to which is over my head. I do find this interesting nevertheless. Bus stop (talk) 20:00, 3 November 2011 (UTC)

atom

why octet in most of the cases are one the stable configuration of atom — Preceding unsigned comment added by Bhaskarandpm (talk • contribs) 18:02, 3 November 2011 (UTC)

Definitely answerable by reading our article about the octet rule. DMacks (talk) 18:28, 3 November 2011 (UTC)

I've just read that article, and it doesn't answer the question. It says the 3rd shell can contain up to 18 electrons, so why is having only 8 in it a stable configuration? --Tango (talk) 20:30, 3 November 2011 (UTC)

The key to understanding this lies in understanding how atomic orbitals work. I suggest you read up on that if u really want to understand why, otherwise its much easier just to accept that it is, as this is pretty complicated... Phebus333 (talk) 22:44, 3 November 2011 (UTC)

The 3^rd shell is subdivided into two lots, the lower valence, and the upper valence. The lower valence contains 10 electrons, the upper valence contain 8 electrons. Plasmic Physics (talk) 23:05, 3 November 2011 (UTC)

Now that does not really answer the question for someone who is not familiar with the energetic principles of orbitals anyways, does it, Plasmic?

Can you explain that subdivision? My understanding is that shells are defined by where there are big changes in the energy level of electrons. Is there a larger than normal change in energy level in the middle of the 3rd shell that isn't quite large enough for people to consider it a new shell? --Tango (talk) 00:05, 4 November 2011 (UTC)

This is a pretty complicated subject, as I said. If you study chemistry (as I do) it takes you about 2 months to get the basics you need to understand this. Phebus333 (talk) 23:12, 3 November 2011 (UTC)

No, it takes about a paragraph or two to explain it so someone will understand it; if done properly, so long as the reader has had some exposure to things like electron configuration and atomic orbitals. Here goes:

• In most atoms, the lowest energy atomic orbitals are the "s" and "p" orbitals. While the valence level may also contain " d" and "f" orbitals as well, those orbitals are significantly higher in energy, and thus valence level "d" and "f" orbitals do not carry electrons in the ground state for most atoms. Thus, since most atoms only need to fill their "s" and "p" orbitals to reach a stable configuration, and since there are one s and three p orbitals on any one level, AND since each orbital can take two (spin opposed) electrons; that gives us two electrons in each of four orbitals, which is 8 electrons, thus the octet rule. This rule holds very well for elements which are small (first 3 periods on the periodic table) and in the main group of elements (the "A" groups, or the "tall" columns). The octet rule tends to be easily violated for the transition elements (those in the middle section of the periodic table) and for larger atoms, like those towards the bottom of the main group; especially large nonmetals.

Now, if someone has never heard of atomic orbitals or electron configurations or anything like that, Phebus333 is correct. But insofar as the OP mentions a familiarity with the octet rule, hopefully that will make some sense. --Jayron32 00:20, 4 November 2011 (UTC)

"so long as the reader has had some exposure to things like electron configuration and atomic orbitals" - this is an assumption that I would not have made here ;-)

"those orbitals are significantly higher in energy" that`s someting I would expect the OP not to accept as "god-given" so he would like to have that explained as well, and understanding why that (from a quantum mechanical POV) is would require some serious time explaining as a (German) B.Sc. chemistry student in the 5. semester (me) is definitely not able to answer that question. Phebus333 (talk) 00:58, 4 November 2011 (UTC)

Not really, conceptually you can simply think of it as an electrostatic problem. Electrons lose energy when they are closer to the nucleus (positive and negative charges attract) and Electrons gain energy when they are closer to each other (negative and negative charges repel). The "d" and "f" orbitals pack a LOT of electron density into a relatively small volume; which explains why they tend to be of significantly higher energy. For example, the 4f orbitals are higher in energy than even the 6s orbitals, due to the fact that cramming 14 electrons into the 4the 4th energy level is a difficult proposition. Certainly, this way of modeling the electron distribution glosses over the QM implications, but it is a fairly good heuristic way to think about it, in that it leads the introductory student to the right conclusions regarding the relative energies of the various orbitals and their filling order. The Wikipedia article on this topic, the Aufbau principle, discusses this in some more detail, and one so inclined could follow links from there to more detailed coverage. But just thinking of it in terms of electrostatic interactions between electrons and the nucleus, and among the electrons themselves, gets the broad picture pretty well. --Jayron32 02:48, 4 November 2011 (UTC)

To put it simply (perhaps too simply), s/p/d/f are determined by the angular momentum of the electron around the nucleus, which is closely related to kinetic energy, while the energy levels as I understand it represent, essentially, potential energy. So both numbers represent increases to the total energy of the electron. Wnt (talk) 09:55, 4 November 2011 (UTC)

Instead of electrical current could there ever be a situation where protons or positrons are made to flow as a current?

I know there can be proton and positron beams but is there any positive charge carrier that doesnt travel through a vacuum and flows as current Also do beams of particles meet no resistance in the vacuum so in theory is this a better way to transmit electrical current — Preceding unsigned comment added by 82.38.102.199 (talk) 21:07, 3 November 2011 (UTC)

Naked electrons travel in a vacuum in a thermionic valve. -- Finlay McWalterჷTalk 21:11, 3 November 2011 (UTC)

In a dense, charged plasma, positive ions may flow. If there is a net motion of ions, there may be a DC current. The situation is complicated by the fact that free electrons may counter the motion. Full solutions to plasma require a simultaneous solution of the Maxwell equations and the continuity equations for all species present. Nimur (talk) 21:31, 3 November 2011 (UTC)

The problem with charged beams flowing through vacuum is that all electrons (or positrons) will repell from each other. So you only get very divergence beams. But of course you could try something like the wehnelt cylinder. But then a cable is easier to transport charge.--Svebert (talk) 21:37, 3 November 2011 (UTC)

In a hypothetical "perfect vacuum" there would be no matter at all, so a traveling particle would meet no resistance at all (aside from gravitational effects through stellar bodies and stuff like that). However, such a "perfect vacuum" has never been observed. Even in space there is some amount of matter, its just so few that its density is almost negligible. A traveling particle would at some point collide with some of that matter, causing resistance. But given our current technological abilities, I would think that this resistance would be far less than that of any practical (electric) conductor. Phebus333 (talk) 22:53, 3 November 2011 (UTC)

Regarding the first question; that of positively charged particles flowing to act as a transmitter of electric current. You don't need an exotic high temperature plasma for that. Such things happen just fine in electrolytes; like, for instance, in the salt bridge of a galvanic cell. Cations will carry charge in such situations. --Jayron32 00:08, 4 November 2011 (UTC)

This is of course true, but I believe the OP had the concept of long distance conduction in mind, and salt bridges are pretty impractical in that context. Phebus333 (talk) 00:36, 4 November 2011 (UTC)

Positive ions (as well as electrons) flow between the electrodes in a thyratron. (Of course, few people have even heard this word in this solid-state-electronic day and age.) 67.169.177.176 (talk) 06:13, 4 November 2011 (UTC)

No one seems to have mentioned yet that one could presumably set up a current whose charge carriers are positrons, in a wire made of anti-copper. --Trovatore (talk) 00:44, 4 November 2011 (UTC)

The protons in a neutron star are believed to flow without resistance, providing the highest temperature superconductor known to natural philosophy. [1]

Proton conductor. --Heron (talk) 17:51, 4 November 2011 (UTC)

Thanks for your answers guys so could somebody explain more about this thyratron? Do positive ions flow in high temperature plasma? Is there a situation where there is negative and positive charge carrying current? — Preceding unsigned comment added by 82.38.102.199 (talk) 22:13, 4 November 2011 (UTC)

A thyratron is an ancient type of electronic device that was used in times immemorial to convert high-voltage, low-frequency AC current to DC, as well as to switch such currents on and off. It was a big, sealed glass or metal tube with three electrodes (cathode, anode and control electrode), kind of like the vacuum tubes found in ancient radios, but usually a lot bigger and filled with an inert gas instead of a vacuum. So when you applied a voltage across the tube and then energized the control electrode, this created both free electrons and positive ions in the gas, which then carried the current across the gap. (Which answers your other questions: yes, in a plasma, both positive and negative particles carry the current.) This was very convenient for high currents, because having positive charge carry some of the current really cut down on the resistance losses; the drawback, however, was that this device couldn't be used with high-frequency current, because it took too long for the positive ions to travel from the anode to the cathode. The thyratron is not used much anymore -- it was replaced by the thyristor and the triac, which don't have this limitation (not to mention that they're so much smaller and lighter, and don't burn out); the only place you might still see one is at your local electric substation. 67.169.177.176 (talk) 01:32, 5 November 2011 (UTC)

Somehow I find "ancient" rather grotesque when applied to things that were common in my childhood. --ColinFine (talk) 17:03, 7 November 2011 (UTC)

Thank you for all your answers it is interesting that letting positive ions do some of the work resistance losses are cut

November 4

regulator genes

what is the role/significance of regulator genes in embryo development?" — Preceding unsigned comment added by 68.229.53.198 (talk) 01:10, 4 November 2011 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. --Jayron32 02:37, 4 November 2011 (UTC)

These are generally called regulatory genes - there are some classic well-studied systems, like the role of Hox genes in Drosophila embryo development, which should give you a good idea. Wnt (talk) 09:44, 4 November 2011 (UTC)

message to director of wikipedia

i choosed this place to clear all my doubts but these people themselfs are very confused even they dont know the differnce between a vector and saclar quantity and insteD OF giving me the accurate answers they all temselfs are fighting so then how would i decide who's answ i have to except plz solve this problem otherwise their is no use of having such sections thank ubhaskar 03:05, 4 November 2011 (UTC) — Preceding unsigned comment added by Bhaskarandpm (talk • contribs)

There is no director of Wikipedia. I will do my best to answer, but I'm just a random person like you (Wikipedia is nothing except random people.)

A scalar quantity is a number. A vector quantity is a number with a direction. Speed is a scalar, velocity is a vector. That means that speed is represented just by a number. If I say I am going 100 km/hr in an airplane, I am expressing a speed. If I say I am going 100 km/hr due north, I am expressing a velocity. --Jayron32 03:10, 4 November 2011 (UTC)

(edit conflict) And seeing that your complaint about the intelligence of the Reference Desk regulars is terribly spelled and riddled with horrific grammar.... →Στc. 03:12, 4 November 2011 (UTC)

There is almost nothing in the world that has a 100% consensus; even the fact that the earth is round and revolves around the sun is not accepted by absolutely everyone, with no exception. This means, like with any information in life: which answer you accept is ultimately up to you. You have to take some responsibility for what knowledge you trust, the only way to do that at all reliably is employ a little critical thinking, consider the reliability of the source, seek impartial corroboration and interdependently verify anything you aren't sure about. Vespine (talk) 04:14, 4 November 2011 (UTC)

sorry for writing harsh languagebhaskar 04:53, 4 November 2011 (UTC) — Preceding unsigned comment added by Bhaskarandpm (talk • contribs)

And note that whether "speed" or "velocity" is the signed quantity really is irrelevant to the answer. The important part is that you can either add them up with the signs, and get zero average, or add them up without the signs, and a get a non-zero average. And, as explained to you, both approaches have their uses. Don't get all hung up on semantics (the names of things). StuRat (talk) 05:29, 4 November 2011 (UTC)

I assume that you've read our articles on speed and velocity (to which we should have linked in our previous replies). I would regard "signed speed" as one-dimensional velocity, but the treatment does depend on the context, so we need to know how you are using the words if we are to provide better answers. In particular, the words "speed" and "average" are used in different ways by different people, and instantaneous speed is not the same as "average speed". Dbfirs 09:30, 4 November 2011 (UTC)

The term "velocity" is often used in baseball to describe the "speed" of a pitch. However, there is an implied vector, i.e. from the pitcher's hand to at least the general direction of home plate. ←Baseball Bugs ^{What's up, Doc?} carrots→ 10:05, 4 November 2011 (UTC)

I would propose the following approach: For lots of users who contribute here you can find information relating to their education on their user pages. If there are contradictory statements about a subject, you can check these out to get an idea who is more likely to be right. For example, when asking a question about physics, someone who has a master in physics is (generally) more likely to give you the correct answer than an undergrad student majoring in chemistry. Phebus333 (talk) 23:31, 4 November 2011 (UTC)

is methyl salisilate reacting with tollen's reagent

tollens reagent + methyl salysilate = — Preceding unsigned comment added by 175.157.79.54 (talk) 13:23, 4 November 2011 (UTC)

Tollen's reagent gives a positive result (silver precipitate) when in the presence of aldehydes and α-hydroxy-ketones. It will give a negative result for carboxylic acids and basic, unsubstituted ketones. So, to answer your question, you need to look at the structure of Methyl salicylate and decide if there is an aldehyde or an α-hydroxy-ketone. Otherwise, you're going to have to do your own homework. --Jayron32 14:21, 4 November 2011 (UTC)

S.I.M card

how does a subscriber identity module work on a network? — Preceding unsigned comment added by Intr199 (talk • contribs) 14:05, 4 November 2011 (UTC)

You might find the article Subscriber Identity Module interesting. --Jayron32 14:15, 4 November 2011 (UTC)

attic insulation

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?

If it isn't too deep, start at the opening and brush it aside as you move toward the leak, so you can find and walk on the ceiling joists. (You'd better be in good health and agile. Wear a dust mask.) When the problem is solved, brush it back. Alternatively, call a contractor (or two) out to give you an estimate. The roofer might tell you the whole roof needs to be replaced, in which case there won't be much need to enter the attic. Jc3s5h (talk) 15:55, 7 November 2011 (UTC)

Theoretical maximum possible temperature

Hi. The minimum possible temperature of anything is absolute zero (particles stop moving). Is there a theoretical maximum possible temperature, beyond which the particles cannot move faster or further (e.g. they would exceed light speed or something)? What is that temperature? 86.182.222.189 (talk) 15:31, 4 November 2011 (UTC)

This isn't your actual question, but just by the way, particles actually do not stop moving at absolute zero. See zero-point energy. --Trovatore (talk) 06:47, 5 November 2011 (UTC)

Strangely enough, the answer is that there is a maximum possible temperature, and it is absolute zero. This is because negative absolute temperatures are possible, but they are actually hotter than infinity -- a system at a negative temperature will lose energy to a system at any positive temperature.

Even if you only consider positive temperatures, there is no upper limit. This is because temperature is defined in thermodynamics as the slope of a certain curve, and it is possible for the curve to be vertical in some systems. A vertical curve means a temperature of infinity. Looie496 (talk) 16:02, 4 November 2011 (UTC)

This is a popular question at the Ref Desk. I would be remiss if I were to fail to mention our article on absolute hot. TenOfAllTrades(talk) 16:21, 4 November 2011 (UTC)

And, every time this question comes up, I point out that the word "temperature" refers to many different, but related, properties, depending on the context. In physics, we often define temperature as "the average kinetic energy per particle." But we don't always define temperature this way. Using the kinetic energy definition, negative temperature makes no sense (particles would have an imaginary velocity? - or negative mass? - or non-classical kinetic energy? ... All these are possibilities; but in fact the answer is much simpler). Instead, in those contexts where physicists consider negative temperature, they are referring to the entropy definition of temperature, explained here. This is not an easy or intuitive version of temperature; most people outside of the field of thermodynamics do not use this definition; so try not to jump to conclusions about the meaning of "negative" temperature until you really really understand the theoretical constructs that are being used in that scenario. For starters, read our article on temperature. To mitigate the risk of sounding like a broken record, I'm going to eschew a recommendation of my favorite book on thermal physics; instead, let's go with... Kittel's thermodynamics textbook - because... after you read it, you'll see that engineers never use negative temperature. They ... just ... don't... make ... any ... sense - at least, not when you are actually measuring an actual temperature of an actual object. Only theoretical thermodynamicists use the more esoteric definitions that permit such strange phenomena as negative absolute temperature. Even better: take a thermal physics class in a physics department; and then take a thermals class in a mechanical engineering department, and draw your own conclusions! Nimur (talk) 17:10, 4 November 2011 (UTC)

No. In physics, temperature is never defined as "average kinetic energy per particle", except in a context where all you have are single particles flying around, with no rotational or vibrational modes (or at least where those are negligible). Basically the kinetic-energy version of temperature is just simply wrong, period. In some contexts it works, but conceptually it's in error. --Trovatore (talk) 06:28, 5 November 2011 (UTC)

I also seriously question the claim that engineers never use negative temperature. Engineers work on lasers, for example, and the population inversion in a lasing medium is expressible in terms of negative temperature. Never having done engineering on lasers myself, I can't say whether those engineers actually do use the terminology, but they certainly reasonably could. --Trovatore (talk) 06:46, 5 November 2011 (UTC)

The speed of light doesn't result in a maximum temperature because temperature is actually dependant on kinetic energy, not speed (if you use the kinetic energy definition rather than the weird entropy definition that Nimur talks about above). At very high temperatures, I believe you do need to use a relativistic formula for relating temperature and speed, but you can get as hot as you like by just getting closer and closer to the speed of light (since kinetic energy approaches infinity as speed approaches the speed of light). --Tango (talk) 18:04, 4 November 2011 (UTC)

Indeed. You can always increase the amount of kinetic energy of a particle (thus increasing temperature). The closer you get to the speed of light, the less increase in velocity will result from the increasing kinetic energy. But as the common/practical definition of temperature does relate to the particle`s kinetic energy and not its speed, this means you can always increase the temperature, there is no maximum. Phebus333 (talk) 23:01, 4 November 2011 (UTC)

Look, you can't define temperature in terms of kinetic energy, period. It's just wrong. It doesn't work even approximately, in even the second-simplest case (diatomic molecules). If you have one container with helium in it (monatomic) and another with air (diatomic), and they have the same kinetic energy per particle (whether you take particle to mean atom, or whether you take it to mean molecule), they will be at different temperatures, by a very substantial margin. (I think which one is hotter depends on whether you're taking the particles to be atoms or molecules). --Trovatore (talk) 19:55, 5 November 2011 (UTC)

What if you include rotational and vibrational modes in the definition of kinetic energy? Translation is not the sole form of motion, and I don't think the "average kinetic energy" definition presupposes that it is. After all, if you say that you cannot define temperature in terms of energy, you're going to have to go through all of the physics and chemistry and theromdynamics textbooks in the world and redact the sections on the Equipartition theorem. I'm not sure that you, as a sole person, have the power to declare such a long-standing principle invalid... --Jayron32 01:10, 6 November 2011 (UTC)

You have to take the kinetic energy to be only that of the center of mass motion. Then the statement is valid, unless the temperature is so extremely low that the translational motion is frozen in the quantum mechanical ground state (long before you reach this point, the gas will have become a solid). Count Iblis (talk) 02:17, 6 November 2011 (UTC)

Then, I guess I am trying to understand Trovatore's bold statement: If temperature is unrelated to energy and to motion, then what is the entire point of the equipartition theorem? The opening sentence of the article says "In classical statistical mechanics, the equipartition theorem is a general formula that relates the temperature of a system with its average energies." Trovatore's statement seems in direct contradiction of this. Now, I fully understand that in extreme conditions, quantum effects start to take over (and I also understand that quantum mechanical effects should always be valid, but the classical model of the equipartition theorem should hold for the general definition of temperature under most conditions, at least to a workable approximation). But Trovatore seems to imply that the equipartition theorem can't be applied ever; that's not right, is it?!? --Jayron32 02:27, 6 November 2011 (UTC)

I certainly never said the equipartition theorem can't be applied! My point is that the equipartition theorem is a very different thing from "average kinetic energy per particle". If you average the energy over particles, rather than over modes, you get something that's just completely wrong. --Trovatore (talk) 04:51, 6 November 2011 (UTC)

Yes, but you are free to define the kinetic energy to be the kinetic energy in only the center of mass motion. The energy in the other modes is then defined as potential energy, despite being kinetic in nature. This is the convention in some books. They would actually not consider the average energy per mode, because the equipartition theorem is typically not valid for the vibrational modes at room temperature.

Defining kinetic and potential energy in this way is not as crazy as one may think. You would not have any problems with the kinetic energy of an atom of mass m at velocity v being exactly 1/2 m v^2, despite the fact that the electrons have some finite kinetic energy in the ground state configuration of the atom. This energy is considered to be potential energy. If you consider two atoms at rest at some distance r and consider how the electrostatic interaction between the electrons and nuclei of the two atoms shifts the ground state energy, you obtain the van der Waals energy. We then define this to be "potential energy", despite it having a kinetic component in terms of the electron motion. Count Iblis (talk) 15:36, 6 November 2011 (UTC)

I'm not sure I follow that in detail, but it sounds like special pleading and fancy bookkeeping to me. Better to understand the real (statistical mechanics) definition than to try to preserve the notion that it's just kinetic energy, if you don't watch the kinetic energy in my right hand.

On another note, if the vibrational mode is not active, then why is the specific heat for a diatomic ideal gas 5/2 R? I thought it was 1/2 R for each component of motion of the molecule, 1/2 R for rotation, and 1/2 R for vibration? Is it a full R for rotation, and if so why? --Trovatore (talk) 18:59, 6 November 2011 (UTC)

It's not my favorite definition either, but some books and lecture notes define it in this way when discussing classical statistical mechanics. They then prefer to not define temperature in terms of entropy to sidestep the fact that it is infinite in classical physics. Defining ensemble averages is possible without regularizing the infinity of the number of states witin a finite volume of phase space, and you can therefore write down a formal expression for the average kinetic energy without much problems.

In case of a diatomic molecule, the single degree of freedom for vibration yields a heat capacity of R, because there are two quadractic terms in the Hamiltonian, p^2/(2m) and 1/2 m omega^2 r^2, bith yield 1/2 R by the equipartition theorem. The total of 6 degrees of freedom (3 for each atom), decomposes as 3 for translation of center of mass, 2 for rotation (there are two axes of rotation orthogonal to the bond, the axis parallel to the bond doesn't count as that would amount to a spin degree of freedom for the atoms which we didn't consider), and one for vibration.

Then in the high temperature limit, you end up with 7/2 R, which looks to be wrong, because you would expect that it should become the same as for two independent atoms so 3 R. What is going on here is that the 7/2 R can be written as 3 R + 1/2 R, where the 1/2 R is due to the potential energy term of 1/2 m omega^2 r^2. Obvously, this is only (approximately) valid as long as you have a bound state. There is also a binding energy that doesn't contribute to the heat capacity, so the average potential energy is actually of the form 1/2 k T - e as long as the harmonic approximation for the potential holds. But clearly at large enough temperatures, the average of the potential energy will become zero, and you then get the heat capacity of 3 R . Count Iblis (talk) 21:05, 6 November 2011 (UTC)

OK, so what do these texts do in a crystal lattice, where surely you can't ignore the vibrational modes for the crystal as a whole? Are those "potential energy" as well, and how do you tell? --Trovatore (talk) 21:14, 6 November 2011 (UTC)

An old lecture note I have, discusses that after introducing quantum statistical mechanics. It simply states the definitions of the micro-canonical, canonical and grand canomical ensembles for quantum systems and then that automatically defines the temperature, which is then different from the earlier given definition for a classical system. It's not how I would set up things, but this is what the Prof. did for an advanced course. It allowed him to go through the things we already knew from earlier courses rapidly but still in a self-contained way. Count Iblis (talk) 21:33, 6 November 2011 (UTC)

Interesting, thanks. So is it fair to say that the pre-quantum formulation just didn't really have a definition for temperature in crystal lattices, except "would be in equilibrium with an ideal gas at that temperature"? Or did they do some other special bookkeeping to make it fit? --Trovatore (talk) 23:10, 6 November 2011 (UTC)

The pre-quantum definition based on (kinetic) energy is still available, but it will give the wrong result when applied directly to the crystal. See the Dulong–Petit law. Count Iblis (talk) 00:51, 7 November 2011 (UTC)

The temperatures don't have to be extreme for quantum effects to be important: eg it's not until about 1000 K that a CO₂ principal bending mode starts to "unfreeze", and that temperature is not untypical for gas-molecule vibration modes. But it is fair to say that temperature will be proportional to the average energy in degrees of freedom for which equipartion applies. Jheald (talk) 02:35, 6 November 2011 (UTC)

A monoatomic gas has a kinetic energy of E=3/2nkT. A diatomic gas has E=5/2nkT (kinetic + rotational energy). Therefore, temperature is NOT the average kinetic energy per particle, E/n; it's not even proportional to E/n because the "proportionality factor" would depend on how many degrees of freedom were available to the particles. This is all assuming an ideal gas. If we take internal energy into consideration, energy would not have such a simple relationship with temperature. Also, temperature is meaningful even in situations where there's no kinetic energy at all. If you have a system of particles with a magnetic moment, for example, and the system is under a magnetic field, you can define 1/T = dS/dE and find a perfectly meaningful temperature (which might be negative, because E has an upper bound), even though the particles could be completely stationary. --140.180.36.161 (talk) 02:44, 6 November 2011 (UTC)

Can anyone expand on why absolute hot should give an ultimate nothing-smaller-than-this minimum for dS/dE ? (Neglecting set-ups like nuclear spins etc, that can achieve negative temperatures, but aren't in equipartition with the other modes of their systems.) I can see from micro black hole why this (or perhaps just a fraction more) might be the highest temperature a black hole could reach. But why should the set-up that minimises dS/dE necessarily be a black hole? The absolute hot article doesn't seem to address this. Jheald (talk) 02:04, 6 November 2011 (UTC)

I find it surprising that no-one has as of yet mentioned the Planck temperature... Whoop whoop pull up ^{Bitching Betty | Averted crashes} 21:43, 7 November 2011 (UTC)

Elephants, Cape Buffaloes and hominids

Hi, could the high intelligence of elephants and cape buffaloes be a result of coevolution with hominids? Thanks.--Richard Peterson24.7.28.186 (talk) 17:59, 4 November 2011 (UTC)

Does their intelligence actually help them evade/defend against hominids? Their size is rather helpful, but I don't think their intelligence is particularly. --Tango (talk) 18:04, 4 November 2011 (UTC)

Unlikely. Being large and quite capable mammals, they are not prey animals of early presentient hominids; and being herbivores, they would have no reason whatsoever to interact with hominids. This is not the case with later hominins which did hunt big game, but it's highly unlikely they had any significant impacts to the vast populations of the two groups. And even long before that, AFAIK the brain sizes of the ancestors of both animals were already increasing even before the rise of human predation (hominins capable of hunting big game only arose a couple of million years ago or so). In the case of elephants, it's more a case of convergence rather than coevolution believed to have partially been caused by the necessity for fine motor control of their trunks (cf. human hands and bipedalism). Being social animals (both live in large herds with complex social dynamics) may also have something to do with it.

However, the reverse (human intelligence developing further from the necessity of having to hunt big game) is a different matter. -- Obsidi♠n Soul 18:45, 4 November 2011 (UTC)

I disagree. Hominids having been hunting large game long enough to have had some impact on them. In many cases this impact is extinction (such as with mammoths). For the survivors, an instinct to avoid humans seems common (even though such a slow-moving animal walking on only two legs and lacking fangs or claws doesn't look dangerous), but perhaps a general increase in intelligence has occurred, as well. StuRat (talk) 21:14, 4 November 2011 (UTC)

Part of the reason that made me wonder about it and ask the question wass i read wounded cape buffalos ambush hunters. That's pretty smart. But I can't see wounded buffalos ambushing lions or hyenas. But a human with spear or bow and arrow, yes.Thanks again.24.7.28.186 (talk) 22:20, 4 November 2011 (UTC)

I think wounded animals will attack any pursuer, even lions. They aren't likely to win, but considering the alternative is certain death, there's very little to lose in the attempt. StuRat (talk) 22:51, 4 November 2011 (UTC)

Yes but i don't think a wounded buffalo is greatly quicker, if at all, than lions or hyenas, so i don't think it could temporarily escape, hide and ambush a lion-it either fights the lions off, or succumbs. But it's likely it could outrun a human over short distances and hide and wait for its pursuers.-Rich Peterson24.7.28.186 (talk) 01:22, 5 November 2011 (UTC)

Evolution is not magic. In long-lived iteroparous megafauna like elephants, 10,000 years is not enough to develop the intelligence they possess now, nor does it explain the development of intelligence in other animal groups as well (and it exists in varying degrees in many different groups). Remember that the last glacial period lasted around ~100,000 years (it repeats in cycles) with animals that have already evolved during the current ice age, the Quaternary glaciation (which started around ~3 million years ago and is still ongoing though global warming may put an end to it permanently). These animals have developed their adaptations long before humans became a significant threat. Mammoths and modern elephants themselves, have existed in more or less the same form we now know today since the Zanclean age of the Pliocene (4.8 million years ago), when the only hominins around were Ardipithecus and Australopithecus who both largely ate plants and fruits, stood only around 3 to 4 feet, did not even have the technology for spears, and definitely did not eat large animals (even the possibility that they may have eaten small animals is sketchy at best). The increasing encephalization quotient evolutionary trend of proboscideans in the meantime, has been ongoing since Moeritherium, which existed since the Priabonian of the Eocene epoch (around 37 million years ago), long before Hominidae arose.

While the most recent (and still ongoing) Holocene extinction event might be anthropogenic to a very large degree in recent times, most of the mass extinctions of megafauna happened right after the end of the last glacial age. It helps if you realize that the entire human population 10,000 years ago hovered at a mere 15 million. Too small to significantly affect populations to the degree it does now, it is far more likely to be caused by the abrupt change in climate. In woolly mammoths and other animals adapted to much colder conditions, the very sudden change in temperatures would have decimated them, forcing them to migrate further and further north until they ran out of land and grazing areas. Humans may have played a part in wiping out the last survivors, but it's more a coup de grâce than anything. The current flight response animals now have at the sight of humans is a mere adaptation, given enough time it might develop into something more permanent, but as it stands it wasn't and still is not enough to save them.-- Obsidi♠n Soul 22:57, 4 November 2011 (UTC)

Note that an extinction occurring at the end of the last ice age does not preclude humans from being the agent, since this event allowed humans to spread into vast new areas (like the Americas and Siberia) and come into contact with those animals, which presumably had no defenses against humans. StuRat (talk) 23:05, 4 November 2011 (UTC)

No. You seem to be confusing encephalization quotient with animal behavior. The former is hardwired and happens because of evolution. The latter is an adaptation, a precursor to evolution but is typically simply a short-term response to new threats using preexisting traits - in this case, the animals already possessed the required EQ to learn to avoid humans (as mentioned they possessed this long before human hunters). In addition to elephants and cape buffalos, bison, musk oxen, gaurs etc. have the same responses to threat even when the attacker is not human. They developed this responses against predators in general, not humans specifically. Lions (and in earlier ages - sabre-toothed cats, dire wolves, leopards, hyenas, and similar large predators) already played a large part in the development of defensive behaviors and morphology of herd animals today, including the fact that they are forced to stay in groups for protection itself (which then lead to increased intelligence and in some cases altruism). And yes, it's coevolution, specifically an evolutionary arms race. To put it simply, before human hunters, they were not stupid peaceful grazers that simply toppled over as soon as something tried to kill them; who, at the sight of humans, suddenly decided to grow a larger braincase to counteract human ingenuity. Evolution does not happen like that. Compare dodos, moas, steller's sea cows, etc. which did not have natural predators. When they first encountered humans, did they suddenly become intelligent? No. They were wiped out.

And as I said, humans did hunt a lot of species to extinction and may have caused the extinction of a lot of megafauna, but in most cases, they were species already suffering decline from the end of the last glacial age. And But we are not responsible for why elephants have high EQ's or why cape buffalos have a highly developed all-for-one defense system.-- Obsidi♠n Soul 23:46, 4 November 2011 (UTC)

Your indentation and placement confuses me, as this does not appear to be a response to my last post. StuRat (talk) 02:23, 5 November 2011 (UTC)

It is. All of my replies are in the context of the original question of the OP. Correct me if I'm wrong, but you seem to be saying that elephant and cape buffalo intelligence were caused by human hunters?-- Obsidi♠n Soul 04:42, 5 November 2011 (UTC)

You placed your reply directly after, and indented from, my post saying "extinction occurring at the end of the last ice age does not preclude humans from being the agent". If you were responding to an earlier post of mine you should place your reply there. StuRat (talk) 16:41, 5 November 2011 (UTC)

Moot point. You are saying that human hunting pressures caused the extinction of the last glacial age megafauna and thus by extension the development of intelligence among proboscideans. Both are what I replied against. Regardless of what you may have wrote, it is what you implied. I do not seem to have guessed wrong judging by your reply below.-- Obsidi♠n Soul 21:11, 6 November 2011 (UTC)

Additionally, humans migrated out of Africa long before the end of the last glacial period and were already in contact with these animals long before the mass extinction event 10,000 years ago. See Human migration.-- Obsidi♠n Soul 00:11, 5 November 2011 (UTC)

It depends on which extinctions you're talking about. In the case of smilodons, they didn't have any contact with humans until the end of the ice age, and this contact seems likely to have caused their extinction. See smilodon#Extinction. Other species, like most mammoth species, had some contact with humans before that, but not over their entire range, which would have significantly increased the pressure on them. (There were actually small populations which escaped contact with humans then, and thus survived until much later, such as the dwarf woolly mammoth of Wrangel Island.) StuRat (talk) 02:23, 5 November 2011 (UTC)

Please read my original post:

a) I freely admitted that humans caused the extinction of survivors of the end of the glacial period (not the ice age, we are still in the middle of an ice age), thus preventing their recovery as they did in previous interglacials.

b) The massive rapid decline of megafauna species within a brief period right after abrupt changes in the climate tells you one thing: humans played the part of the executioner rather than the exterminator you seem to be suggesting. These species were already in decline, humans merely tipped them over the edge of extinction. Please read the linked articles: Holocene extinction and the Holocene extinction event.

c) This, of course, does not apply to later Holocene extinctions (the so-called "asynchronous" extinctions which happened long before or after the beginning of the current interglacial) which are decidedly almost purely anthropogenic.

d) Furthermore, I do not see how this would apply to the OP's question. Homo species which hunted big game appeared relatively late, when elephants and cape buffalos and their characteristic social structures already existed. Earlier hominids were not big game hunters and existed in even fewer numbers than the modern humans which arose later.

There are numerous scholarly works tackling this. All of them carefully differentiate the Pleistocene-Holocene border mass extinction event/decline (climate-caused) with later elimination of "survivor" pockets (human-caused). See [2], [3], [4], [5], [6], [7], etc. -- Obsidi♠n Soul 04:42, 5 November 2011 (UTC)

b) I don't get your distinction between "exterminator" and "executioner". Without humans, they would have likely survived the climate change, as they had in the past. With humans, they died out. I call that a human-caused extinction. Perhaps you meant to say that they might have survived contact with humans, had the climate not also warmed at the same time. I'm not sure that they would have.

d) You seem to be relying on the fossil record to tell us when animal intelligence developed. Thus, you must base your conclusions on brain size (technically skull cavity size) and social structure alone. Neither of these is a reliable way to determine intelligence. Thus, it's entirely possible that their intelligence increased after they came under hunting pressure from humans. Do we know this for sure ? No, but neither can we dismiss the idea. When you consider the radical changes ancient humans caused in the evolution of wolves into dogs (even before intentional breeding), it's not unreasonable to suppose that we've had some effect on every species we interact with. StuRat (talk) 16:49, 5 November 2011 (UTC)

re: b - there is a great deal of difference between the two. Some of those species were already doomed, with or without human intervention. They would survive as relict populations (exactly the kind of populations as the dwarf mammoths you mentioned) in refugia (specifically, glacial refugia), where they may still struggle to exist until such a time as favorable conditions return. Even then, these populations are inherently very very fragile. Any additional stresses can doom the entire line, in this case it was human hunting. But you can not blame humans for their disappearance, they merely dealt the final blow, they did not kill nor did they have the capacity to kill the vast numbers of the animals that once existed. Nevertheless, the rapid disappearance and the already very decimated populations remaining leave little room for adaptations to be developed and there certainly is no time for them to evolve. Remember, these are megafauna, like humans they are long-lived and reproduce slowly. Concentrated hunting on small populations will almost certainly leave them little time to produce young, much less evolve.

re: d - Occam's razor. And yes, what other evidence would you have then? Even the development of human intelligence is gauged by hominid fossil skulls. We might as well be arguing about intelligent design here if you choose the more unlikelier scenario over a likely one. The greater size of the skull cavity overwhelmingly implies a greater brain size and exceptional intelligence. Given how their [proboscideans] descendants share the same trait, it is the far more likely hypothesis than to imagine an animal which somehow had a large skull cavity with no evolutionary advantage. Intelligence is a very desirable evolutionary outcome, it should not be surprising that multiple animals have acquired it with or without human assistance. It is bordering on anthropocentric arrogance in fact to suggest that there would be no other way for them to acquire such intelligence without human intervention. Other natural predators are perfectly capable of inducing far greater evolutionary pressure than humans, in far more specialized ways than human hunting.

Wolves as well, already possessed the same (if not greater) intelligence as dogs - the reason why they were so easy to domesticate into human "packs" in the first place. And this was the result of their preexisting social system rather than human breeding. Wild wolves are most assuredly not "dumber" than domestic dogs. Furthermore, the evolutionary stresses of predation is far different than the evolutionary stresses of artificial selection. Yes we had quite a dramatic effect on other species on this planet as out populations ballooned, but no, we had no hand in a trait so basal as proboscidean intelligence. You might as well start arguing that cetaceans developed their intelligence because of recent human hunting. They share about the same lifespans and the same high intelligence as terrestrial megafauna, also reproduce slowly, and were also decimated and some driven extinction by whaling and fishing activities within relatively the same timespan as the Pleistocene megafauna extinctions. I think you would agree that that idea is preposterous. -- Obsidi♠n Soul 21:11, 6 November 2011 (UTC)

Thanks everyone. I've learned quite a bit.--Rich Peterson24.7.28.186 (talk) 15:14, 5 November 2011 (UTC)

Do cooked carrots have more calories than raw carrots? Why?

I've heard that cooked carrots have more calories than raw carrots. Cooked carrots taste sweeter, so I suspect that some of the indigestible starch in the raw carrots gets broken down to digestible, tasty, calorie-endowing sugars during the cooking process.

Do carrots have more calories? If so, why?

Thank you. — Preceding unsigned comment added by 137.131.48.128 (talk) 19:10, 4 November 2011 (UTC)

This comes from an observation in many diet plans where raw carrots are 0 "points" towards a diet and cooked carrots are 1 or 2 "points". This has nothing to do with an increase in calories in the cooked carrots. It has to do with portion size. Raw carrots are served in smaller portions than cooked carrots. Similarly, a raw potato will have few points because it is just one potato. Fries will have a lot of points because a single serving of fries tends to be two or three potatoes. -- kainaw™ 19:14, 4 November 2011 (UTC)

Comparing raw/cooked carrots to raw/fried potatoes is probably not valid in this context. Fries tend to be fried in fat or oil - which I suspect (although I am not a nutritionist) is where the calories come from. Mitch Ames (talk)

No, it appears that the opposite is true. I looked at two sources: Handbook of the Nutritional Contents of Foods, an old book containing data from 1963, and the fully modern database in Nutribase 9. The data between those two sources were roughly consistent. Depending on the source, a 100g serving of raw carrots is 41 or 42 cal, and a 100g serving of boiled and drained carrots is 31 or 35 cal. Raw carrots have more calories than boiled and drained carrots. Red Act (talk) 19:35, 4 November 2011 (UTC)

Which makes sense... heating up food burns calories. To get it to have more calories, you have to add something to it, like a pound of melted butter. -- kainaw™ 19:39, 4 November 2011 (UTC)

No, it has nothing to do with heating the food to "burn up calories". That's bullshit. The reason cooked (specifically boiled and drained carrots) has more calories per gram is that in cooking they absorb water, which adds weight to the carrots but adds no calories, bringing the calories/gram values down. --Jayron32 21:10, 4 November 2011 (UTC)

According to http://caloriecount.about.com, cooked carrots have 27 calories in 78 grams, while raw carrots have 8 calories in 28 grams. That's 0.346 cal/gram for cooked and 0.286 cal/gram for raw carrots. So, cooking the carrots seems to impart 21% more calories per gram. If carrots lose 17.5% of their weight via loss of water during the cooking process, that could account for the 21% more cal/g. — Preceding unsigned comment added by 137.131.48.128 (talk) 19:40, 4 November 2011 (UTC)

This is more complicated than simply "burn it and see how much energy you get." Cooked food is (in general) more readily absorbed, so the question comes down to how much dietary energy you're getting out of it. Olestra has an almost identical energy content as other fats if you're getting a calorie count by burning, but because of the chemistry none of that energy is absorbed into the body. Celery has plenty of calories by heat, but it doesn't get absorbed by the body during digestion. There's also the glycemic index question, where more rapidly absorbed food is considered problematic for a diet, and raw vegetables are rather an extreme on that scale. SDY (talk) 19:42, 4 November 2011 (UTC)

That's if you search http://caloriecount.about.com for "carrot", and select "Carrots – Whole, Raw." But if you select just "Carrots"or "Carrot", it lists 52 calories in a 128 g serving, or .41 cal/g, consistent with both of the sources I gave. I think the important word that explains the difference might be the word "Whole". If "Whole" includes the tops (greens) of the carrots, that would add mass, without adding as many calories per gram as what the root has. Red Act (talk) 20:37, 4 November 2011 (UTC)

I concur with some thoughts expressed above:

1) Cooking should not increase calorie content. It may convert starches to sugars, but they both have the same number of calories per gram, so that doesn't matter.

2) This, of course, assume the carrots are cooked in water alone and serve naked. If you use oil in the cooking process or put a glaze on them, then calories will be increased. Of course, a dip with the raw carrots will also increase calories there.

3) Note that you may eat a lot more carrots, if cooked. Raw carrots, especially large ones, take some effort to eat. Your jaw may soon tire of the effort.

4) Note that it may take more energy to digest raw carrots, too, and that figures in to how many calories you get from them (although not into how many they contain). StuRat (talk) 21:07, 4 November 2011 (UTC)

We evolved smaller intestines because we started to eat cooked food. Trying to get enough calories from raw natural foods is almost impossible. In a BBC documentary they showed an experiment where people were given only raw foods to eat, the same sort of diet they give Chimps in a Zoo. Within a few days, everyone was feeling very hungry despite having a full stomach all the time and not long after that people were getting diarrhea. Count Iblis (talk) 21:54, 4 November 2011 (UTC)

I would think the results would depend entirely on which raw foods they ate. I could see those results with raw potatoes, but eating raw tomatoes, berries, citrus, nuts, eggs, milk, etc. should be fine, provided you don't get a disease from an infectious agent in them. StuRat (talk) 22:48, 4 November 2011 (UTC)

The unit of energy is obviously causing some problems here. A carrot cooked or uncooked provides the same calorific 'heat' value when desiccated and 'burnt' in oxygen (which is how the caloric value is determined in the lab). However, when considering carrots from a dietary point of view, then cooked carrots have a higher “net energy value” for some of the reasons already posted. Put a mouse/human/etc. in a sealed box and measure the CO2 and other metabolic rates and one can consider that in terms of Calories (or Joules) also. However this is not quite the same type of energy conversion. When one counts calories for dietary control, one is using (by now) a very old nutritional concept – which is lacking in some practicality in this application. For instance, people eating way above the correct (?) calorific in take may still feel hunger because they are not getting the right nutrition. Dietary advice thrives on pseudo-sciences and commercial gobbledygook and and over simplifications, so whether the above mentioned adjustment to suggest the higher “net energy value” is right, or even how it is derived at I don't know. Yet in essence, it is useful to know that raw carrots have a less “net energy value” than cooked. Maybe the OP will find this article suitably elucidating, as it cover some of the comments already put: [8].For human evolution, guts and cooking there is this: [9]--Aspro (talk) 23:18, 4 November 2011 (UTC)

Reflection and smoothness

Hi, I would like to ask you a question about physics. If I have an object that it's smooth to the scale of the particle, and it is not black, will there always be reflection? I mean in assuming that there is no Refraction. Exx8 (talk) —Preceding undated comment added 22:29, 4 November 2011 (UTC).

Yes, I believe so, as long as it's not 100% transparent (and nothing is). However, the reflected rays may well be scattered, so it won't reflect like a mirror. StuRat (talk) 22:44, 4 November 2011 (UTC)

If the object's surface is smooth, why would the rays scatter? Dauto (talk) 02:00, 5 November 2011 (UTC)

It can only be so smooth, and some light will pass through many layers of molecules and reflect off atoms further down. StuRat (talk) 02:06, 5 November 2011 (UTC)

See Diffuse reflection#Mechanism. Much of diffuse reflection is not due to surface roughness, but rather due to scattering below the surface. As stated in the article "A piece of highly polished white marble remains white; no amount of polishing will turn it into a mirror."--Srleffler (talk) 17:37, 7 November 2011 (UTC)

Even a perfectly transparent substance still can reflect light rays as long as the objects refractive index is different from the refractive index of air. Dauto (talk) 02:03, 5 November 2011 (UTC)

The OP said we should assume there is no refraction, which I take to mean it has the same refractive index as air (or whatever medium surrounds the object). StuRat (talk) 02:08, 5 November 2011 (UTC)

I doubt that is what he meant. If the refractive index is the same as the surrounding medium there is no reflection at the surface. All the light is transmitted or absorbed.--Srleffler (talk) 17:37, 7 November 2011 (UTC)

The major challenge is that the particles themselves are not absolutely 'smooth'. Rayleigh scattering occurs even in 'pure' materials, due to minor inhomogeneities at the molecular and atomic scales. To be clear, this is a scattering event (with a random component) rather than a specular reflection; the scattered photons won't all bounce in the same place or the same direction. TenOfAllTrades(talk) 15:50, 6 November 2011 (UTC)

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: [10]. 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)

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)

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)

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)

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)

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

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

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)

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)

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)

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)

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)

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)

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)

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 ([11]), the ship is categorized as a Trois-mâts. So what's the truth? Reflectionsinglass (talk) 19:43, 7 November 2011 (UTC)