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I don't like this idea that matter exchanges heat with cooler matter. Matter gives off heat to its surrounding environment. If it's radiant it gives it off equally in all directions. If you want some of it, you have to arrange your physical condition so as to intercept whatever amount you think you need. You can get closer. or in the focus of a parabolic collector. Or get in contact with other matter that has received some of the radiated energy. It's obviously a part of nature's energy dissipation process. And the majority of natures spacial volume is evidently at a temperature of only about 3 degrees kelvin. And so you're used to existing at a temperature of 98.6 degrees Fahrenheit (+296 degrees kelvin), you have to arrange to acquire heat from your environment to reach that goal. But each system of matter delivers heat to its surrounding environment. WFPM ( talk) 22:20, 17 March 2012 (UTC)
The way that systems of matter get rid of excessive heat and energy to the surrounding environment is by the progressive interaction between their constituent particles which results in the smallest particles acquiring an equal amount of the momentum of the larger particles but getting practically all the v squared Kinetic energy. Thus the emitted particles are a matter efficient way to get rid of excess kinetic energy from a physical process. If these particles are intercepted the contained kinetic energy can be either reincorporated into the matter of the receiving substance or else reflected away without adsorption. WFPM ( talk) 02:08, 19 March 2012 (UTC)
To see how efficient and far reaching this system of heat energy dissipation exists, I refer you to an image of the Whirlpool Galaxy, where the individual matter systems (stars) can be seen giving off heat energy at a distance 4 million times as that from the earth to the sun. And the image shows a process that was occurring approximately 30 million years ago.
And to give you the big picture of all this, you can note that our Milky Way galaxy plus the Andromeda galaxy and the Whirlpool galaxy are all located within a cubic volume of space which only accounts for maybe 1 billionth of the estimated size of the universe. WFPM ( talk) 11:51, 19 March 2012 (UTC)
Dear Andrewedwardjudd, your recent edit (21:30, 18 March 2012) to the lead of the present article on heat is a good faith edit but it does not conform to normal Wikipedia requirements for editing.
Your edit was a change in the lead which was not a summary of the article.
Your edit was not supported by any citation of reliable sources. For historical statements such as those in your edit should be supported by concordant secondary and tertiary sources; primary sources by themselves are not enough for the present purposes.
You edit sought to change the direction of thinking of the article, but it did not express your thoughts in terms of classical thermodynamics, while the main drift of the present article is framed in those terms. Your edit therefore is in some ways incoherent with the rest of the article. An edit should not make an article incoherent.
You have some valid things to say, but if you want to say them, you should do so in accord with normal Wikipedia editing requirements. You should read WP:RS, WP:OR, WP:SYN, WP:POV and related Wikipedia policy articles, and thoroughly digest their contents. You seem at present not to have read or understood or followed them. Till now you have ridiculed my comments along these lines, apparently because you have not absorbed Wikipedia editing policy. Ridiculing my comments may be amusing but does not exempt you from the need to follow Wikipedia policy.
The article on heat at present does not discuss enthalpy, and at present the Wikipedia article on enthalpy has considerable room for improvement. Your idea of heat content is closely related to the idea of enthalpy, which is a quantity of classical thermodynamics, and is sometimes called 'heat content'.
Enthalpy is derivable from internal energy by a Legendre transform, which changes the independent variables of a fundamental thermodynamic equation. This would be made clear in a suitable edit.
It may perhaps be that you can properly edit the article making use of the relation between your idea of heat and the classical thermodynamic idea of enthalpy. This should be done in the body of the article and if it is successfully done there, it will be right to summarize it in the lead.
You may wish to write an edit that sort out or clarify the partly dubious term thermal energy. For this purpose you would need to read, summarize, and cite a good range of suitable secondary and tertiary sources.
Your edit uses special historical terms, such as vis viva, in the lead, but they are not adequately defined in the body of the article. The lead should summarize, not introduce new undefined terms.
Perhaps your interest is more directly historical than physical. If so, your edits should be based on secondary and tertiary sources which are explicitly historical. Ancillary citations of primary sources would then be fitting, in order to back up and exemplify the historical conclusions of the secondary and tertiary sources that are cited as the main reliable sources. For example, you may find statements that support your views in the book by Truesdell on the early history of thermodynamics; Truesdell is an example of a secondary or tertiary historical source. Partington is also often useful. It will be best if you find several more concordant explicitly historical secondary and tertiary sources. Your own reading of primary sources does not by itself constitute reliable sourcing as defined by Wikipedia policy. Chjoaygame ( talk) 23:56, 18 March 2012 (UTC)
Andrewedwardjudd ( talk) 05:46, 19 March 2012 (UTC)andrewedwardjudd
What is this 'explanation' [ [2]] doing in the article? Is this the return of ' Caloric'. "A potentially confusing term is thermal energy, loosely defined as the energy of a body that increases with its temperature. Thermal energy, even when not in transit or motion, is sometimes referred to as heat or heat content"? 'Loosely' defined is it? What is this editor trying to say?
Reif ( Fundamentals of Statistical and Thermal Physics ) has been cited, so? On page 269 Reif has:- 1/2mv2 = 3/2KBT.
Read further if you wish but it is quite clear from this that Reif is a fully signed up believer in classical kinetic theory where heat, measured by temperature, is directly related to the energy of moving particles by the Boltzmann constant (KB). -- Damorbel ( talk) 16:19, 19 March 2012 (UTC)
Diatomic gas | CV, m (J/(mol·K)) | CV, m / R |
---|---|---|
H2 | 20.18 | 2.427 |
CO | 20.2 | 2.43 |
N2 | 19.9 | 2.39 |
Cl2 | 24.1 | 3.06 |
Br2 (vapour) | 28.2 | 3.39 |
Damorbel, having failed to read the article on heat capacity, actually believes it is a constant for any given material, and not a function of temperature, so that thermal energy is linearly dependent on temperature. Well, it isn't. And 1 gram of any matter at 1000 K will have a hugely larger thermal capacity than 1000 grams of the same matter at 1 K, where the heat capacity will be reduced to almost nothing. See Einstein solid and Debye model. S B H arris 07:56, 21 March 2012 (UTC)
You know, you could read the article on temperature. Temperature is very simply a measure of the mean kinetic energy per particle in a system in thermal equilibrium. The two would be measured with the same scale if it weren't for the fact that they (temperature and energy units) were developed historically independently. So now, because of that, we now need a scaling factor between kinetic energy (in joules) and temperature (in kelvins), which are related linearly. That simple scaling factor, which is not a law of nature but just a sacling factor between historical scales, is the Bolzmann constant gives you kinetic energy per particle per kelvin, and the gas constant for kinetic energy per mole per kelvin. That's all they are, and we're done.
Much of the rest of this is obfuscation by Dramorbel, who hasn't "got" the idea that neither heat nor thermal energy are (necessarily) kinetic energy. His equation (3/2)kT = kinetic E, gives how much kinetic energy there is in an object with a temperature, but it doesn't say that this is where all the thermal energy is. It's not all kinetic. Thermal energy is a different sort of energy, of which kinetic energy of atoms may only be a part, depending on the number of degrees of freedom for thermal partition in the system. In a monatomic ideal gas, heat is all kinetic energy, but that's one of the few systems for which that is true. In systems where atoms are bound to each other with chemical bond, or there is electronic exitation, or electrons themselves participate as particles, a lot of heat is other types of energy, often potential. Thus, there is no linear translation from temperature to thermal energy, as there is between temperature and mean kinetic energy. The ratio of the thermal energy (or heat input) to temperature is heat capacity, which is a nonlinear complicated business, although the heat capacities of most substances in practice fall into a fairly narrow range per particle (no more than a factor of 2 differece per particle), at least at higher temperatures (ie, well over the Einstein or Debye temps for that substance, if it is a solid, and another corresponding substance specific reduced temperature if it is a polyatomic gas).
The other problem with this article is that heat has many colloquial uses (one of which is temperature) and many historical uses in physics (on of which we now call thermal energy content). But that hsould simply be pointed out in the lede (as it now actually is, though not optimally), and the historical changes in usage (like how Lord Kelvin used the word "heat") can be left for the history section. When scientists say the word "meter" today, they don't mean what they did in 1890 or 1990. But we leave most of that for the historical section on that subject. S B H arris 17:32, 21 March 2012 (UTC)
As described so clearly by Planck in the reference I provided on the main article page, classically a thermometer measured degree of heat, or the ability of heat to flow from one object to another of a lower temperature. But the thermometer gives no measure of the amount of heat that can flow, nor does it measure degree of heat accurately between the arbitarily inscribed marks between the two reference temperatures that produce the scale of the thermometer.
To measure the amount of heat transferred by a tested object at say 100C, you need to transfer an amount of heat to a reference object of 0C, for example water is reference object, where you have a reference temperatures of 100C and 0C for state changes in water and reference heat content of water, and observe the temperature rise. You can then have a calibration table of known power transfers to the reference water to know how much energy was transferred to the water to create the observed temperature change. You then know how much heat energy was transferred from the object under test and then construct tables of relative sensible heat contents for certain temperatures.
So you have two different things.
1. is a measure of hotness or degree of heat by temperature
2. Is a measure of amount of hotness or amount of heat which involves using temperature.
So if you say that temperature is a measurement of heat you are not being clear what you mean
Similarly if you say that temperature is not a measure of hotness or degree of heat you are really mangling our language, to the point that nobody can understand what you are talking about unless they realise you have decided to use the word heat only for what we call amount of heat.
For example when we look at the picture of the Sun in the main article and it begins 'Heat generated by the sun' we are not looking at the amount of heat. We are looking at the degree of heat and we know that is incredibly hot. If you want to be picky the caption should be 'thermal energy generated by the sun, that is being transferred away from the sun as heat'?
Otherwise, maybe somebody who is very strict can help me with my understanding on why heat is being used in the first word of that description? Andrewedwardjudd ( talk) 07:00, 20 March 2012 (UTC)andrewedwardjudd
Andrewedwardjudd ( talk) 07:00, 20 March 2012 (UTC)andrewedwardjudd
' Greenhouse effect' has difficulty with heat and thermal effects in general, frequently GHE editors do not engage in discussion, some have been banned for abuse of contributions from other editors. -- Damorbel ( talk) 17:03, 22 March 2012 (UTC)
The term "thermal energy" is not a standard term strictly defined by standard texts that I am familiar with. I think some homework needs to be done on this term so that this term should be well sourced from reliable sources, or that it should be made explicitly clear in the article that it is not to be found in reliable sources, or that the term should be removed from the article. Chjoaygame ( talk) 03:48, 24 March 2012 (UTC)
Work and the technical definition of
heat share something in common in that they are process quantities. Most people tend to think of heat as a kind of energy, as opposed to a kind of work. So how about this distinction then: Let's have the articles
Heat (work) and
Heat (energy). Anyone in favor say Aye! or Support.
siNkarma86—Expert Sectioneer of Wikipedia
86 = 19+9+14 + karma = 19+9+14 +
talk
04:01, 24 March 2012 (UTC)
Heat (energy) suggests that there is some other kind of heat that is NOT energy, which is also wrong. S B H arris 17:55, 24 March 2012 (UTC)
Splitting this page up, without consensus to do so is unacceptable. Please don't do it again; it has been undone, wasting people's time William M. Connolley ( talk) 19:55, 24 March 2012 (UTC)
Well, we do in fact have two articles on work. One is work (physics) which is synonymous with force x distance = mechanical work. It probably includes (as a subset) electrical work, even though when you charge a battery that's hardly mechanical work. The action of electrical fields on charges, however, gives a "force" and one actually does move such a charge through a distance when charging a battery, so this is very similar. Other types of work with forces other change mechanical/contact forces (like gravitational work when a book falls off a table inside a closed room) can be treated similarly.
The other article is work (thermodynamics) which defines this term as any energy change to a system that isn't a thermal/heat change. So this "work" includes chemical potentials in systems, which are not mechanical work, but are something like changing a dead battery for a fresh one in a system, rather than charging the dead one from a battery charger (which of course does electrical work on it). Whether changing a battery is using a "mechanical and/or quasi-mechanical external device with a number small enough to count on your fingers and toes" depends on your perspective. A fresh battery is ONE thing, to be sure, bui it consists of many mols of fresh/different atoms all in a different state, so in that sense, you've done a lot of switching. The fact that in a battery you can do this all at the "same time" instead of by means of a zillion different mechanical "strikes" of hot atoms (heat transfer) is related to the fact that changing a battery, like charging a battery, doesn't change entropy (much), and need not change it at all.
The problem with "radiation" (let us just examine electromagnetic radiation) is that you can add it thermally or not. Clearly, if you irradiate a cold system with radiant heat at some blackbody temperature (like the Sun does for Earth) you are adding "heat." But if you irradiate the body with a monochromatic laser beam, you are not. (To be sure, such energy can be converted to heat immediately, but unlike the other heat, it need not be, and could be stored (in theory) a photon at a time to increase some chemical potential and never appear as thermal energy at all). So, light energy delivered by laser has no entropy and no temperature. What kind of work is it?
Much the same thing happens with molecular/atomic impacts. You can warm a system by bathing it in a gas at some temperature, and that guarantees heat transfer. But if, instead, you project molecules at it, each one of which are at exactly the same velocity, now you're not transfering entropy unless some process that makes it happens. You could in theory (even without a Maxwell Demon) catch all those atoms, or charge them, and use their monochromatic kinetic energy to raise the potential of the system in a way that didn't increase its entropy. Put these zillions of atoms into lumps, and it's like firing bullets at the system. By the time you get to one "bullet" (or one piston) it's clear you now are doing mechanical work on it. So where does the "fingers and toes" number come in, inasmuch you can divide your mechanical impacts into as many subunits as you like, just as in the case of the (one) fresh battery composed of many, many new chemically altered atoms? Again, the fact that you CAN do this has to do with the low phase-space content of your addition. That's what allows you to collect it into a "fingers and toes" number like with ONE battery or ONE bullet or ONE piston (or ONE set of photons all in the same state, as in a laser beam). But you don't HAVE to do it. With heat, you do have to do it; the fact that you can't collect the hot particles in the same way, or transfer their kinetic energy in the same way, is intrinsically connected with the higher entropy of the (kinetic) energy that they carry. S B H arris 18:13, 27 March 2012 (UTC)
The English language does not require an article (such as 'the' or 'a') by automatic default. An article is not needed here, and it is idiomatic not to use it in this case. Chjoaygame ( talk) 10:56, 24 March 2012 (UTC)
Thank you for your comments. I think that nature and art agree here. The sentence in question is "Quantity of heat transferred can be estimated by ..." The word 'the' would point to an instance already defined, which does not exist for this sentence. The word 'a' would be permissible, because this sentence might be regarded as creating an instance, but, I think unhappily, it would seem to demand a further 'a' for the "direct measurement" and perhaps for the "heat" and perhaps a "some" for the "calculations". Better with no article, I feel. Chjoaygame ( talk) 20:31, 24 March 2012 (UTC)
I have undone the redirect by Kmarinas86 of 19:41, 24 March 2012. That redirect was not nearly adequately justified and might be considered as some kind of misbehaviour. A redirect like that would need plenty of notice and consensus. Chjoaygame ( talk) 19:58, 24 March 2012 (UTC)
http://en.wikipedia.org/?title=Heat&diff=483739254&oldid=483738800
I was told to see the talk page about this one, but I see nothing here about it yet.
siNkarma86—Expert Sectioneer of Wikipedia
86 = 19+9+14 + karma = 19+9+14 +
talk
20:50, 24 March 2012 (UTC)
I don't think the edit that read "Estimates of the transfer of heat can be conducted ..." is better. The added word "conducted" serves only a grammatical function, not a substantial one; likewise for the added word "methods". And the removed word "quantity" gave direct continuity with the preceding sentence. And the subject of the sentence was made to be "transfer of heat" instead of "quantity of heat transferred", which is not an improvement, because the key idea here is "quantity". Chjoaygame ( talk) 20:54, 24 March 2012 (UTC)
There is a new edit of the lead of the article on heat. The new edit is concerned with the possible meanings of the word heat and how they should appear in the article. There arise concerns about the present-day and about classical physical principles, and about historical readings.
The newly edited words are
The words which the new edit has replaced are
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The questions at issue are whether this new edit should stand as it is in the lead, and whether its content or similar content should be entered somewhere in the body of the article, from which a summary entry might be put into the lead, and what sourcing is needed. Chjoaygame ( talk) 07:18, 19 March 2012 (UTC)
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Rethink I decline to comment on the preferable form of the definitions etc and their relative equivalence or superiority. I do however object to the discussion of the history or any other details that do not directly assist in the immediate understanding of what the core subject matter of the article is intended to cover. You could say what heat is, as the first paragraph does, and you might add brief statements of what heat is not (with suitable links to terminology). You might for example say briefly in what way heat is not not temperature or internal energy etc, but that is that. All the other stuff, if you do not think that it is good to confine the discussion to respective related sections, can go into an introductory overview section. Most of the current lede belongs in such an overview section if it is to be retained at all. Keep the lede short enough and specific enough to satisfy anyone who elects not to read the article after having read the lede, and informative enough to keep anyone reading, who has any functional interest or curiosity concerning the matter. All that other stuff should be kept out of the lede. IMBNMHO JonRichfield ( talk) 19:24, 10 April 2012 (UTC)
And yes, there are people who speak loosely of hot electrons and hot atoms, but it is bad physics to do so. It is rather like people speaking of mass being converted to energy. Strictly speaking it never is (matter is, mass is not), but even physicists can be loose with language. S B H arris 18:57, 25 March 2012 (UTC)
No, kinetic energy in systems behaves much more like potential energy, since more than two particles not moving in the same direction are involved, and this results in an invariant quality that includes some kinetic energy (unlike the case with single particles). The system gets a certain invariant mass which is related to the system/object's COM frame, exactly as with a potential energy system (where potential energy stored in the system adds to invariant mass also). The kinetic addition in systems happens even in systems with a temperature and no potential energy at all, like a (massless) bottle of hot monatomic ideal gas (for example). Kinetic energy (KE) systems have a certain minimal KE in their COM frame, and you can't go below that, so it's not entirely relative, once you get a system of more than two particles in different directions. And the COM temperature is the maximal object temperature from any reference frame, also. However, temperature, unlike invariant mass is not Lorentz invariant. Temperature is a scalar, and I know of no invariant scalars, except for invariant mass. There is an invariant "heat 4-current," with 3 components that are the usual spacial-direction heat flows/currents, and the time component is the thermal energy in the COM frame. But I don't know what the 4-vector equivalent of this is, for temperature. S B H arris 00:50, 26 March 2012 (UTC)
This discussion is merely repeating the discussion about the energy of a single particle at the Boltzmann constant [ [9]]. And if anyone wishes to insist that the expression from Reif :- 1/2mv2 = 3/2KBT 'doesn't apply to a single particle', I expect them to explain what minimum number of particles is needed to make it valid, at present I am quite unable to see how this minimum number can be different from '1'. -- Damorbel ( talk) 06:08, 26 March 2012 (UTC)
Yu began talking about chemical reactions, and the transition I was talking about is the one in the transition state theory of chemical reaction rates. See specifically collision theory where the Maxwell-Bolzmann distribution is used to deduce the fraction of molecules at a given temperature that have the required kinetic energy to reach the activation energy and thus reach transition state and go on to undergo the chemical reaction. Usually, it's just a tiny fraction of molecules in the "fast tail" of the M-B distribution.
Your statement above says nothing about equilibrium but obviously assumes it. An object with two temperatures will obviously have an internal heat flow, and this is an important subject in heat transfer and engineering. See heat equation.
Finally, for examples of how temperature in systems of small numbers of particles depends on the number of particles, even with total energy and average total energy fixed, see canonical ensemble. Also there is one example of a formula for small numbers of particles which depends on time-averages here: [11]. Note that the general temperature of the system only approaches what we normally think of as the temperature, in the limit that the number of particles becomes "large." Finally, note that the equations for 1/2mv^2 = 3/2kT all rely on v_rms, which means "root mean square." All your texts should have the same. S B H arris 16:11, 30 March 2012 (UTC)
No, you miss the point. The reason the 1/2mv_rms^2 = 3/2k_B*T equation isn't valid for one particle isn't because of problems with calculating the v_rms for one particle, but the problems in calculating temperature for one particle. Temperature must have a statistical distribution of energies, and is not valid for one particle which never changes energies. Furthermore, following one particle as it changes energies over time in a system, is essentially sampling a large number of particles of different energies in a thermal system that it impacts with, and thus (again) you are (indirectly) measuring a thermal distribution, by sampling it. The variance of such a set of samples tells you something you need to know, to even DEFINE temperature. Why? Because for any temperature above absolute zero you must have an entropy-change associated with the thermal energy change for the temperature, and you cannot do that with one particle, which (in isolation) has an entropy of zero, no matter how fast the particle is moving. S = k_B ln (1) = 0. Thus, you can increase the energy of one particle and its entropy does not change, and is still zero, so dQ/dS = dE/dS = T = undefined since dS = 0. Which makes your proposed definition of T as the KE of one particle untennable. You disagree with thermodynamic definitions of T.
IOW, the "logical argument" why a huge number of particles is required" (at a thermal distribution of different energies) to define a temperature to some narrow value, is that the laws of thermodynamics don't work unless temperature is defined in terms of heat input (or thermal energy content change) per unit of entropy-change, and entropy requires disorder, and disorder requires a system of particles, not one particle.
For an example of the converse, consider my example of a perfect crystal cooled to absolute zero, then made somehow to travel at the v_rms speed of an air molecule (you could accelerate the entire thing, or merely change reference frames). Does it make sense to now speak of the "temperature" of all these fast atoms, since each is now moving at the (exact same) high velocity? You say yes. But the correct answer is no!, for this makes hash of all thermodynamics equations that involve temperature and entropy and energy. If such an emsemble has a "temperature" then none of the laws of thermodynamics regarding temperature and work-cycle efficiency are valid. Since such a crystal has zero entropy, then the kinetic energy of such a crystal, like the kinetic energy of a single atom in flight, can be converted to useful work with 100% efficiency. In a Carnot cycle such a temperature of such a mass therefore doesn't look like room temperature for such a mass, but rather it looks like the absolute zero that it (in fact) is. Thus, your proposed definition of temperature is WRONG and nobody agrees with you. Sorry, but you're just being ignorant of the basics of Thermo 101 here, and I would ask you to stop editing this article until you educate yourself. S B H arris 17:22, 2 April 2012 (UTC)
You pick me a single particle and I can find a reference frame for which it has no kinetic energy and thus a temperature of zero in your system. I can also find a reference frame or observer for which a collection of atoms in a crystal with zero entropy in its own rest frame, has a temperature as large as you like, which makes no thermodynamic sense, as its entropy is the same in all frames. This, this notion is wrong, and you are wrong.
Your references from hyperphysics above actually don't say what you think they do, and you should look at them again. Your Temperature definition says: A convenient operational definition of temperature is that it is a measure of the average translational kinetic energy associated with the disordered microscopic motion of atoms and molecules. Read that three times. Or you could look in the WP article on thermodynamic temperature which give the meaning of your equation with the Boltzmann constant: The thermodynamic temperature of any bulk quantity of a substance (a statistically significant quantity of particles) is directly proportional to the mean average kinetic energy of a specific kind of particle motion known as translational motion. Read that again, too. S B H arris 18:05, 3 April 2012 (UTC)
That is correct. Individual photons do not have a temperature. An energy, yes; a temperature, no. The photons from the Sun have an equivalent temperature only because they come with a spread-out blackbody spectrum at many frequencies, so we can assign them a temperature of 5780 K and after thermalizaton thermodynamically they act like heat at that temperature. If they all came with the same frequency, they also would have no temperature. A laser beam has no temperature and no entropy.
Unlike sunlight, a laser beam could be converted into work with 100% efficiency, even without an entropy dump. Sunlight cannot. Because of entropy, efficiency of conversion to usable energy on Earth from sunlight is never better than (5760-300)/5760 = 95%. That's far better than solar cells or plants actually do, so we don't notice the themodynmic limitation, but it's there, all the same. Since the entropy of the Sunlight energy has to go somewhere when you convert it to work, at least 5% of it must wasted, making heat at 300 K (Earth temp). All this doesn't happen with laser beams or monochromatic light. If we were able to dump heat into space at 2.7 K our efficiency could go up to (5780-2.7)/5780 = 99.95%. But still not 100%. Once Sunlight has been thermalized on the Sun, you can't ever get all its energy back. Some of it always has to stay as thermal energy (randomized energy) at some lower temp. That's the second law of thermodynamics. THe second law is the whole idea behind temperature. It's not only kinetic energy that defines temperature, but (much more importantly) the fact that the energy has been randomized in direction and amount. Once spread out in phase space, it cannot be put back. S B H arris 21:27, 3 April 2012 (UTC)
“ | Information is stored in a Planck-sized remnant:
|
” |
I'm sorry, but you simply cannot claim that two collections of particles with the same average kinetic energy but different energy distributions (and thus different entropies) have the same temperature. I already gave you an example of a perfect crystal at absolute zereo which you can accelerate in any direction, giving it a lot of kinetic energy and all of its atoms a large velocity (or you can do this by looking at it from a different reference frame), but its temperature will remain zero because its entropy remains zero. All that kinetic energy of all those atoms does not count toward temperature because it hasn't been thermalized. It's a little harder to see why one cannot speak of the temperature of box of gas molecules flying in random directions, all with exactly the same energy, but the basic reason is that this is not a system in equilibrium, yet. As it equilibrates to a Maxwell-Boltzmann energy distribution (thermalizes) its entropy will increase also (although this time, it doesn't start from zero). But the molecules enter more states in phase-space. This is a bit like allowing an already-thermalized gas to expand into a larger volume without doing work. Here, energy (and this time also temperature) stay the same but entropy also increases, as the system reaches equilibrium by expanding in phase space in another way.
The answer to your question of how many particles does it take, has already been answered: more than one. You can calculate a "temperature" for a system of two molecules so long as they are not traveling in the exact same direction, and they have had a chance to thermally equilibrate by hitting or interacting with each other enough times (just as you can calculate an invariant mass (or system mass) for two or more photons also, as long as they are not moving in the same direction). Now, the temperature you get from this will not be a very good one. It will be a number like any sample average, with a very wide confidence limit. Temperatures are sample averages (kinetic energy averages). How good the average is (what its confidence limits are) depends on your sample size. If you sample two people on their yearly income, you get a crappy answer for the country, but at least it's a real answer for "average income." One person will not give you an average income at a given time. If that one person moves around the country and works at 4000 widely different jobs like Mike Roe, however, you can take his mean salary, and start to get a better number for the average income of people who have jobs. And if you sample 4000 people randomly around the country you can get the average income to a percent of the number you get if you got this info from every person. Temperature usually involves systems with such a huge number of particles that we forget the confidence limits on the number, because they are so small. But they do exist, and they show up with small numbers of particles. Okay? S B H arris 18:41, 4 April 2012 (UTC)
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I don't like this idea that matter exchanges heat with cooler matter. Matter gives off heat to its surrounding environment. If it's radiant it gives it off equally in all directions. If you want some of it, you have to arrange your physical condition so as to intercept whatever amount you think you need. You can get closer. or in the focus of a parabolic collector. Or get in contact with other matter that has received some of the radiated energy. It's obviously a part of nature's energy dissipation process. And the majority of natures spacial volume is evidently at a temperature of only about 3 degrees kelvin. And so you're used to existing at a temperature of 98.6 degrees Fahrenheit (+296 degrees kelvin), you have to arrange to acquire heat from your environment to reach that goal. But each system of matter delivers heat to its surrounding environment. WFPM ( talk) 22:20, 17 March 2012 (UTC)
The way that systems of matter get rid of excessive heat and energy to the surrounding environment is by the progressive interaction between their constituent particles which results in the smallest particles acquiring an equal amount of the momentum of the larger particles but getting practically all the v squared Kinetic energy. Thus the emitted particles are a matter efficient way to get rid of excess kinetic energy from a physical process. If these particles are intercepted the contained kinetic energy can be either reincorporated into the matter of the receiving substance or else reflected away without adsorption. WFPM ( talk) 02:08, 19 March 2012 (UTC)
To see how efficient and far reaching this system of heat energy dissipation exists, I refer you to an image of the Whirlpool Galaxy, where the individual matter systems (stars) can be seen giving off heat energy at a distance 4 million times as that from the earth to the sun. And the image shows a process that was occurring approximately 30 million years ago.
And to give you the big picture of all this, you can note that our Milky Way galaxy plus the Andromeda galaxy and the Whirlpool galaxy are all located within a cubic volume of space which only accounts for maybe 1 billionth of the estimated size of the universe. WFPM ( talk) 11:51, 19 March 2012 (UTC)
Dear Andrewedwardjudd, your recent edit (21:30, 18 March 2012) to the lead of the present article on heat is a good faith edit but it does not conform to normal Wikipedia requirements for editing.
Your edit was a change in the lead which was not a summary of the article.
Your edit was not supported by any citation of reliable sources. For historical statements such as those in your edit should be supported by concordant secondary and tertiary sources; primary sources by themselves are not enough for the present purposes.
You edit sought to change the direction of thinking of the article, but it did not express your thoughts in terms of classical thermodynamics, while the main drift of the present article is framed in those terms. Your edit therefore is in some ways incoherent with the rest of the article. An edit should not make an article incoherent.
You have some valid things to say, but if you want to say them, you should do so in accord with normal Wikipedia editing requirements. You should read WP:RS, WP:OR, WP:SYN, WP:POV and related Wikipedia policy articles, and thoroughly digest their contents. You seem at present not to have read or understood or followed them. Till now you have ridiculed my comments along these lines, apparently because you have not absorbed Wikipedia editing policy. Ridiculing my comments may be amusing but does not exempt you from the need to follow Wikipedia policy.
The article on heat at present does not discuss enthalpy, and at present the Wikipedia article on enthalpy has considerable room for improvement. Your idea of heat content is closely related to the idea of enthalpy, which is a quantity of classical thermodynamics, and is sometimes called 'heat content'.
Enthalpy is derivable from internal energy by a Legendre transform, which changes the independent variables of a fundamental thermodynamic equation. This would be made clear in a suitable edit.
It may perhaps be that you can properly edit the article making use of the relation between your idea of heat and the classical thermodynamic idea of enthalpy. This should be done in the body of the article and if it is successfully done there, it will be right to summarize it in the lead.
You may wish to write an edit that sort out or clarify the partly dubious term thermal energy. For this purpose you would need to read, summarize, and cite a good range of suitable secondary and tertiary sources.
Your edit uses special historical terms, such as vis viva, in the lead, but they are not adequately defined in the body of the article. The lead should summarize, not introduce new undefined terms.
Perhaps your interest is more directly historical than physical. If so, your edits should be based on secondary and tertiary sources which are explicitly historical. Ancillary citations of primary sources would then be fitting, in order to back up and exemplify the historical conclusions of the secondary and tertiary sources that are cited as the main reliable sources. For example, you may find statements that support your views in the book by Truesdell on the early history of thermodynamics; Truesdell is an example of a secondary or tertiary historical source. Partington is also often useful. It will be best if you find several more concordant explicitly historical secondary and tertiary sources. Your own reading of primary sources does not by itself constitute reliable sourcing as defined by Wikipedia policy. Chjoaygame ( talk) 23:56, 18 March 2012 (UTC)
Andrewedwardjudd ( talk) 05:46, 19 March 2012 (UTC)andrewedwardjudd
What is this 'explanation' [ [2]] doing in the article? Is this the return of ' Caloric'. "A potentially confusing term is thermal energy, loosely defined as the energy of a body that increases with its temperature. Thermal energy, even when not in transit or motion, is sometimes referred to as heat or heat content"? 'Loosely' defined is it? What is this editor trying to say?
Reif ( Fundamentals of Statistical and Thermal Physics ) has been cited, so? On page 269 Reif has:- 1/2mv2 = 3/2KBT.
Read further if you wish but it is quite clear from this that Reif is a fully signed up believer in classical kinetic theory where heat, measured by temperature, is directly related to the energy of moving particles by the Boltzmann constant (KB). -- Damorbel ( talk) 16:19, 19 March 2012 (UTC)
Diatomic gas | CV, m (J/(mol·K)) | CV, m / R |
---|---|---|
H2 | 20.18 | 2.427 |
CO | 20.2 | 2.43 |
N2 | 19.9 | 2.39 |
Cl2 | 24.1 | 3.06 |
Br2 (vapour) | 28.2 | 3.39 |
Damorbel, having failed to read the article on heat capacity, actually believes it is a constant for any given material, and not a function of temperature, so that thermal energy is linearly dependent on temperature. Well, it isn't. And 1 gram of any matter at 1000 K will have a hugely larger thermal capacity than 1000 grams of the same matter at 1 K, where the heat capacity will be reduced to almost nothing. See Einstein solid and Debye model. S B H arris 07:56, 21 March 2012 (UTC)
You know, you could read the article on temperature. Temperature is very simply a measure of the mean kinetic energy per particle in a system in thermal equilibrium. The two would be measured with the same scale if it weren't for the fact that they (temperature and energy units) were developed historically independently. So now, because of that, we now need a scaling factor between kinetic energy (in joules) and temperature (in kelvins), which are related linearly. That simple scaling factor, which is not a law of nature but just a sacling factor between historical scales, is the Bolzmann constant gives you kinetic energy per particle per kelvin, and the gas constant for kinetic energy per mole per kelvin. That's all they are, and we're done.
Much of the rest of this is obfuscation by Dramorbel, who hasn't "got" the idea that neither heat nor thermal energy are (necessarily) kinetic energy. His equation (3/2)kT = kinetic E, gives how much kinetic energy there is in an object with a temperature, but it doesn't say that this is where all the thermal energy is. It's not all kinetic. Thermal energy is a different sort of energy, of which kinetic energy of atoms may only be a part, depending on the number of degrees of freedom for thermal partition in the system. In a monatomic ideal gas, heat is all kinetic energy, but that's one of the few systems for which that is true. In systems where atoms are bound to each other with chemical bond, or there is electronic exitation, or electrons themselves participate as particles, a lot of heat is other types of energy, often potential. Thus, there is no linear translation from temperature to thermal energy, as there is between temperature and mean kinetic energy. The ratio of the thermal energy (or heat input) to temperature is heat capacity, which is a nonlinear complicated business, although the heat capacities of most substances in practice fall into a fairly narrow range per particle (no more than a factor of 2 differece per particle), at least at higher temperatures (ie, well over the Einstein or Debye temps for that substance, if it is a solid, and another corresponding substance specific reduced temperature if it is a polyatomic gas).
The other problem with this article is that heat has many colloquial uses (one of which is temperature) and many historical uses in physics (on of which we now call thermal energy content). But that hsould simply be pointed out in the lede (as it now actually is, though not optimally), and the historical changes in usage (like how Lord Kelvin used the word "heat") can be left for the history section. When scientists say the word "meter" today, they don't mean what they did in 1890 or 1990. But we leave most of that for the historical section on that subject. S B H arris 17:32, 21 March 2012 (UTC)
As described so clearly by Planck in the reference I provided on the main article page, classically a thermometer measured degree of heat, or the ability of heat to flow from one object to another of a lower temperature. But the thermometer gives no measure of the amount of heat that can flow, nor does it measure degree of heat accurately between the arbitarily inscribed marks between the two reference temperatures that produce the scale of the thermometer.
To measure the amount of heat transferred by a tested object at say 100C, you need to transfer an amount of heat to a reference object of 0C, for example water is reference object, where you have a reference temperatures of 100C and 0C for state changes in water and reference heat content of water, and observe the temperature rise. You can then have a calibration table of known power transfers to the reference water to know how much energy was transferred to the water to create the observed temperature change. You then know how much heat energy was transferred from the object under test and then construct tables of relative sensible heat contents for certain temperatures.
So you have two different things.
1. is a measure of hotness or degree of heat by temperature
2. Is a measure of amount of hotness or amount of heat which involves using temperature.
So if you say that temperature is a measurement of heat you are not being clear what you mean
Similarly if you say that temperature is not a measure of hotness or degree of heat you are really mangling our language, to the point that nobody can understand what you are talking about unless they realise you have decided to use the word heat only for what we call amount of heat.
For example when we look at the picture of the Sun in the main article and it begins 'Heat generated by the sun' we are not looking at the amount of heat. We are looking at the degree of heat and we know that is incredibly hot. If you want to be picky the caption should be 'thermal energy generated by the sun, that is being transferred away from the sun as heat'?
Otherwise, maybe somebody who is very strict can help me with my understanding on why heat is being used in the first word of that description? Andrewedwardjudd ( talk) 07:00, 20 March 2012 (UTC)andrewedwardjudd
Andrewedwardjudd ( talk) 07:00, 20 March 2012 (UTC)andrewedwardjudd
' Greenhouse effect' has difficulty with heat and thermal effects in general, frequently GHE editors do not engage in discussion, some have been banned for abuse of contributions from other editors. -- Damorbel ( talk) 17:03, 22 March 2012 (UTC)
The term "thermal energy" is not a standard term strictly defined by standard texts that I am familiar with. I think some homework needs to be done on this term so that this term should be well sourced from reliable sources, or that it should be made explicitly clear in the article that it is not to be found in reliable sources, or that the term should be removed from the article. Chjoaygame ( talk) 03:48, 24 March 2012 (UTC)
Work and the technical definition of
heat share something in common in that they are process quantities. Most people tend to think of heat as a kind of energy, as opposed to a kind of work. So how about this distinction then: Let's have the articles
Heat (work) and
Heat (energy). Anyone in favor say Aye! or Support.
siNkarma86—Expert Sectioneer of Wikipedia
86 = 19+9+14 + karma = 19+9+14 +
talk
04:01, 24 March 2012 (UTC)
Heat (energy) suggests that there is some other kind of heat that is NOT energy, which is also wrong. S B H arris 17:55, 24 March 2012 (UTC)
Splitting this page up, without consensus to do so is unacceptable. Please don't do it again; it has been undone, wasting people's time William M. Connolley ( talk) 19:55, 24 March 2012 (UTC)
Well, we do in fact have two articles on work. One is work (physics) which is synonymous with force x distance = mechanical work. It probably includes (as a subset) electrical work, even though when you charge a battery that's hardly mechanical work. The action of electrical fields on charges, however, gives a "force" and one actually does move such a charge through a distance when charging a battery, so this is very similar. Other types of work with forces other change mechanical/contact forces (like gravitational work when a book falls off a table inside a closed room) can be treated similarly.
The other article is work (thermodynamics) which defines this term as any energy change to a system that isn't a thermal/heat change. So this "work" includes chemical potentials in systems, which are not mechanical work, but are something like changing a dead battery for a fresh one in a system, rather than charging the dead one from a battery charger (which of course does electrical work on it). Whether changing a battery is using a "mechanical and/or quasi-mechanical external device with a number small enough to count on your fingers and toes" depends on your perspective. A fresh battery is ONE thing, to be sure, bui it consists of many mols of fresh/different atoms all in a different state, so in that sense, you've done a lot of switching. The fact that in a battery you can do this all at the "same time" instead of by means of a zillion different mechanical "strikes" of hot atoms (heat transfer) is related to the fact that changing a battery, like charging a battery, doesn't change entropy (much), and need not change it at all.
The problem with "radiation" (let us just examine electromagnetic radiation) is that you can add it thermally or not. Clearly, if you irradiate a cold system with radiant heat at some blackbody temperature (like the Sun does for Earth) you are adding "heat." But if you irradiate the body with a monochromatic laser beam, you are not. (To be sure, such energy can be converted to heat immediately, but unlike the other heat, it need not be, and could be stored (in theory) a photon at a time to increase some chemical potential and never appear as thermal energy at all). So, light energy delivered by laser has no entropy and no temperature. What kind of work is it?
Much the same thing happens with molecular/atomic impacts. You can warm a system by bathing it in a gas at some temperature, and that guarantees heat transfer. But if, instead, you project molecules at it, each one of which are at exactly the same velocity, now you're not transfering entropy unless some process that makes it happens. You could in theory (even without a Maxwell Demon) catch all those atoms, or charge them, and use their monochromatic kinetic energy to raise the potential of the system in a way that didn't increase its entropy. Put these zillions of atoms into lumps, and it's like firing bullets at the system. By the time you get to one "bullet" (or one piston) it's clear you now are doing mechanical work on it. So where does the "fingers and toes" number come in, inasmuch you can divide your mechanical impacts into as many subunits as you like, just as in the case of the (one) fresh battery composed of many, many new chemically altered atoms? Again, the fact that you CAN do this has to do with the low phase-space content of your addition. That's what allows you to collect it into a "fingers and toes" number like with ONE battery or ONE bullet or ONE piston (or ONE set of photons all in the same state, as in a laser beam). But you don't HAVE to do it. With heat, you do have to do it; the fact that you can't collect the hot particles in the same way, or transfer their kinetic energy in the same way, is intrinsically connected with the higher entropy of the (kinetic) energy that they carry. S B H arris 18:13, 27 March 2012 (UTC)
The English language does not require an article (such as 'the' or 'a') by automatic default. An article is not needed here, and it is idiomatic not to use it in this case. Chjoaygame ( talk) 10:56, 24 March 2012 (UTC)
Thank you for your comments. I think that nature and art agree here. The sentence in question is "Quantity of heat transferred can be estimated by ..." The word 'the' would point to an instance already defined, which does not exist for this sentence. The word 'a' would be permissible, because this sentence might be regarded as creating an instance, but, I think unhappily, it would seem to demand a further 'a' for the "direct measurement" and perhaps for the "heat" and perhaps a "some" for the "calculations". Better with no article, I feel. Chjoaygame ( talk) 20:31, 24 March 2012 (UTC)
I have undone the redirect by Kmarinas86 of 19:41, 24 March 2012. That redirect was not nearly adequately justified and might be considered as some kind of misbehaviour. A redirect like that would need plenty of notice and consensus. Chjoaygame ( talk) 19:58, 24 March 2012 (UTC)
http://en.wikipedia.org/?title=Heat&diff=483739254&oldid=483738800
I was told to see the talk page about this one, but I see nothing here about it yet.
siNkarma86—Expert Sectioneer of Wikipedia
86 = 19+9+14 + karma = 19+9+14 +
talk
20:50, 24 March 2012 (UTC)
I don't think the edit that read "Estimates of the transfer of heat can be conducted ..." is better. The added word "conducted" serves only a grammatical function, not a substantial one; likewise for the added word "methods". And the removed word "quantity" gave direct continuity with the preceding sentence. And the subject of the sentence was made to be "transfer of heat" instead of "quantity of heat transferred", which is not an improvement, because the key idea here is "quantity". Chjoaygame ( talk) 20:54, 24 March 2012 (UTC)
There is a new edit of the lead of the article on heat. The new edit is concerned with the possible meanings of the word heat and how they should appear in the article. There arise concerns about the present-day and about classical physical principles, and about historical readings.
The newly edited words are
The words which the new edit has replaced are
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The questions at issue are whether this new edit should stand as it is in the lead, and whether its content or similar content should be entered somewhere in the body of the article, from which a summary entry might be put into the lead, and what sourcing is needed. Chjoaygame ( talk) 07:18, 19 March 2012 (UTC)
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Rethink I decline to comment on the preferable form of the definitions etc and their relative equivalence or superiority. I do however object to the discussion of the history or any other details that do not directly assist in the immediate understanding of what the core subject matter of the article is intended to cover. You could say what heat is, as the first paragraph does, and you might add brief statements of what heat is not (with suitable links to terminology). You might for example say briefly in what way heat is not not temperature or internal energy etc, but that is that. All the other stuff, if you do not think that it is good to confine the discussion to respective related sections, can go into an introductory overview section. Most of the current lede belongs in such an overview section if it is to be retained at all. Keep the lede short enough and specific enough to satisfy anyone who elects not to read the article after having read the lede, and informative enough to keep anyone reading, who has any functional interest or curiosity concerning the matter. All that other stuff should be kept out of the lede. IMBNMHO JonRichfield ( talk) 19:24, 10 April 2012 (UTC)
And yes, there are people who speak loosely of hot electrons and hot atoms, but it is bad physics to do so. It is rather like people speaking of mass being converted to energy. Strictly speaking it never is (matter is, mass is not), but even physicists can be loose with language. S B H arris 18:57, 25 March 2012 (UTC)
No, kinetic energy in systems behaves much more like potential energy, since more than two particles not moving in the same direction are involved, and this results in an invariant quality that includes some kinetic energy (unlike the case with single particles). The system gets a certain invariant mass which is related to the system/object's COM frame, exactly as with a potential energy system (where potential energy stored in the system adds to invariant mass also). The kinetic addition in systems happens even in systems with a temperature and no potential energy at all, like a (massless) bottle of hot monatomic ideal gas (for example). Kinetic energy (KE) systems have a certain minimal KE in their COM frame, and you can't go below that, so it's not entirely relative, once you get a system of more than two particles in different directions. And the COM temperature is the maximal object temperature from any reference frame, also. However, temperature, unlike invariant mass is not Lorentz invariant. Temperature is a scalar, and I know of no invariant scalars, except for invariant mass. There is an invariant "heat 4-current," with 3 components that are the usual spacial-direction heat flows/currents, and the time component is the thermal energy in the COM frame. But I don't know what the 4-vector equivalent of this is, for temperature. S B H arris 00:50, 26 March 2012 (UTC)
This discussion is merely repeating the discussion about the energy of a single particle at the Boltzmann constant [ [9]]. And if anyone wishes to insist that the expression from Reif :- 1/2mv2 = 3/2KBT 'doesn't apply to a single particle', I expect them to explain what minimum number of particles is needed to make it valid, at present I am quite unable to see how this minimum number can be different from '1'. -- Damorbel ( talk) 06:08, 26 March 2012 (UTC)
Yu began talking about chemical reactions, and the transition I was talking about is the one in the transition state theory of chemical reaction rates. See specifically collision theory where the Maxwell-Bolzmann distribution is used to deduce the fraction of molecules at a given temperature that have the required kinetic energy to reach the activation energy and thus reach transition state and go on to undergo the chemical reaction. Usually, it's just a tiny fraction of molecules in the "fast tail" of the M-B distribution.
Your statement above says nothing about equilibrium but obviously assumes it. An object with two temperatures will obviously have an internal heat flow, and this is an important subject in heat transfer and engineering. See heat equation.
Finally, for examples of how temperature in systems of small numbers of particles depends on the number of particles, even with total energy and average total energy fixed, see canonical ensemble. Also there is one example of a formula for small numbers of particles which depends on time-averages here: [11]. Note that the general temperature of the system only approaches what we normally think of as the temperature, in the limit that the number of particles becomes "large." Finally, note that the equations for 1/2mv^2 = 3/2kT all rely on v_rms, which means "root mean square." All your texts should have the same. S B H arris 16:11, 30 March 2012 (UTC)
No, you miss the point. The reason the 1/2mv_rms^2 = 3/2k_B*T equation isn't valid for one particle isn't because of problems with calculating the v_rms for one particle, but the problems in calculating temperature for one particle. Temperature must have a statistical distribution of energies, and is not valid for one particle which never changes energies. Furthermore, following one particle as it changes energies over time in a system, is essentially sampling a large number of particles of different energies in a thermal system that it impacts with, and thus (again) you are (indirectly) measuring a thermal distribution, by sampling it. The variance of such a set of samples tells you something you need to know, to even DEFINE temperature. Why? Because for any temperature above absolute zero you must have an entropy-change associated with the thermal energy change for the temperature, and you cannot do that with one particle, which (in isolation) has an entropy of zero, no matter how fast the particle is moving. S = k_B ln (1) = 0. Thus, you can increase the energy of one particle and its entropy does not change, and is still zero, so dQ/dS = dE/dS = T = undefined since dS = 0. Which makes your proposed definition of T as the KE of one particle untennable. You disagree with thermodynamic definitions of T.
IOW, the "logical argument" why a huge number of particles is required" (at a thermal distribution of different energies) to define a temperature to some narrow value, is that the laws of thermodynamics don't work unless temperature is defined in terms of heat input (or thermal energy content change) per unit of entropy-change, and entropy requires disorder, and disorder requires a system of particles, not one particle.
For an example of the converse, consider my example of a perfect crystal cooled to absolute zero, then made somehow to travel at the v_rms speed of an air molecule (you could accelerate the entire thing, or merely change reference frames). Does it make sense to now speak of the "temperature" of all these fast atoms, since each is now moving at the (exact same) high velocity? You say yes. But the correct answer is no!, for this makes hash of all thermodynamics equations that involve temperature and entropy and energy. If such an emsemble has a "temperature" then none of the laws of thermodynamics regarding temperature and work-cycle efficiency are valid. Since such a crystal has zero entropy, then the kinetic energy of such a crystal, like the kinetic energy of a single atom in flight, can be converted to useful work with 100% efficiency. In a Carnot cycle such a temperature of such a mass therefore doesn't look like room temperature for such a mass, but rather it looks like the absolute zero that it (in fact) is. Thus, your proposed definition of temperature is WRONG and nobody agrees with you. Sorry, but you're just being ignorant of the basics of Thermo 101 here, and I would ask you to stop editing this article until you educate yourself. S B H arris 17:22, 2 April 2012 (UTC)
You pick me a single particle and I can find a reference frame for which it has no kinetic energy and thus a temperature of zero in your system. I can also find a reference frame or observer for which a collection of atoms in a crystal with zero entropy in its own rest frame, has a temperature as large as you like, which makes no thermodynamic sense, as its entropy is the same in all frames. This, this notion is wrong, and you are wrong.
Your references from hyperphysics above actually don't say what you think they do, and you should look at them again. Your Temperature definition says: A convenient operational definition of temperature is that it is a measure of the average translational kinetic energy associated with the disordered microscopic motion of atoms and molecules. Read that three times. Or you could look in the WP article on thermodynamic temperature which give the meaning of your equation with the Boltzmann constant: The thermodynamic temperature of any bulk quantity of a substance (a statistically significant quantity of particles) is directly proportional to the mean average kinetic energy of a specific kind of particle motion known as translational motion. Read that again, too. S B H arris 18:05, 3 April 2012 (UTC)
That is correct. Individual photons do not have a temperature. An energy, yes; a temperature, no. The photons from the Sun have an equivalent temperature only because they come with a spread-out blackbody spectrum at many frequencies, so we can assign them a temperature of 5780 K and after thermalizaton thermodynamically they act like heat at that temperature. If they all came with the same frequency, they also would have no temperature. A laser beam has no temperature and no entropy.
Unlike sunlight, a laser beam could be converted into work with 100% efficiency, even without an entropy dump. Sunlight cannot. Because of entropy, efficiency of conversion to usable energy on Earth from sunlight is never better than (5760-300)/5760 = 95%. That's far better than solar cells or plants actually do, so we don't notice the themodynmic limitation, but it's there, all the same. Since the entropy of the Sunlight energy has to go somewhere when you convert it to work, at least 5% of it must wasted, making heat at 300 K (Earth temp). All this doesn't happen with laser beams or monochromatic light. If we were able to dump heat into space at 2.7 K our efficiency could go up to (5780-2.7)/5780 = 99.95%. But still not 100%. Once Sunlight has been thermalized on the Sun, you can't ever get all its energy back. Some of it always has to stay as thermal energy (randomized energy) at some lower temp. That's the second law of thermodynamics. THe second law is the whole idea behind temperature. It's not only kinetic energy that defines temperature, but (much more importantly) the fact that the energy has been randomized in direction and amount. Once spread out in phase space, it cannot be put back. S B H arris 21:27, 3 April 2012 (UTC)
“ | Information is stored in a Planck-sized remnant:
|
” |
I'm sorry, but you simply cannot claim that two collections of particles with the same average kinetic energy but different energy distributions (and thus different entropies) have the same temperature. I already gave you an example of a perfect crystal at absolute zereo which you can accelerate in any direction, giving it a lot of kinetic energy and all of its atoms a large velocity (or you can do this by looking at it from a different reference frame), but its temperature will remain zero because its entropy remains zero. All that kinetic energy of all those atoms does not count toward temperature because it hasn't been thermalized. It's a little harder to see why one cannot speak of the temperature of box of gas molecules flying in random directions, all with exactly the same energy, but the basic reason is that this is not a system in equilibrium, yet. As it equilibrates to a Maxwell-Boltzmann energy distribution (thermalizes) its entropy will increase also (although this time, it doesn't start from zero). But the molecules enter more states in phase-space. This is a bit like allowing an already-thermalized gas to expand into a larger volume without doing work. Here, energy (and this time also temperature) stay the same but entropy also increases, as the system reaches equilibrium by expanding in phase space in another way.
The answer to your question of how many particles does it take, has already been answered: more than one. You can calculate a "temperature" for a system of two molecules so long as they are not traveling in the exact same direction, and they have had a chance to thermally equilibrate by hitting or interacting with each other enough times (just as you can calculate an invariant mass (or system mass) for two or more photons also, as long as they are not moving in the same direction). Now, the temperature you get from this will not be a very good one. It will be a number like any sample average, with a very wide confidence limit. Temperatures are sample averages (kinetic energy averages). How good the average is (what its confidence limits are) depends on your sample size. If you sample two people on their yearly income, you get a crappy answer for the country, but at least it's a real answer for "average income." One person will not give you an average income at a given time. If that one person moves around the country and works at 4000 widely different jobs like Mike Roe, however, you can take his mean salary, and start to get a better number for the average income of people who have jobs. And if you sample 4000 people randomly around the country you can get the average income to a percent of the number you get if you got this info from every person. Temperature usually involves systems with such a huge number of particles that we forget the confidence limits on the number, because they are so small. But they do exist, and they show up with small numbers of particles. Okay? S B H arris 18:41, 4 April 2012 (UTC)