Talk:Radiant exitance

You might want to touch on the topic of radiant emittance being dependent upon ambient temperature. The equations you've got only apply for maximum radiant emittance, ie: if the surface was emitting to a 0 K ambient.

Evenminded...

You should know that the person undoing the edits, using the nym 'Evenminded' believes that all objects emit as though they're in a 0 K ambient. That's why he's undone the edit for a real-world object's S-B equation... and done a poor job of it.

He claims that for an ambient temperature of 287.64 K, and a surface temperature of 303.15 K, the surface will emit 479 W / m^2... in reality, it'll emit 84.96925 W / m^2 (for an emissivity of 0.93643).

https://i.imgur.com/8XzwMRQ.png

He remains clue repellent, even when it's pointed out that his σ T^4 S-B equation is equivalent to the object emitting into a 0 K ambient with an emissivity of 1: q = 1 σ (T_h^4 - 0 K) 1 m^2 = σ T^4

He can't seem to differentiate between a hypothetical blackbody and a real-world object.

Here's physicist Dr. Charles R. Anderson, PhD proving that this kook's blather violates Stefan's Law: https://objectivistindividualist.blogspot.com/2018/08/the-nested-black-body-shells-model-and.html It also violates 1LoT and 2LoT. 71.135.36.192 (talk) 05:00, 7 February 2021 (UTC)

You are confusing the amount of radiation emitted by a surface with the net amount of heat transferred from the surface. The latter is the radiant exitance minus the irradiance. Evenminded (talk) 05:07, 7 February 2021 (UTC)

I'm confusing nothing. You're confusing real and hypothetical. Your blather has already been proven to violate Stefan's Law, 1LoT, 2LoT, etc. You claim energy can flow from any energy density to any other energy density without work being done. You're confused on a fundamental level. 71.135.36.192 (talk) 05:13, 7 February 2021 (UTC)

You may not listen to reason, but this is established science. https://infraredtraininginstitute.com/thermograpahy-information/black-body-radiation/ Evenminded (talk) 05:15, 7 February 2021 (UTC)

Hello, please stop reverting others' edits repeatly. You both should have seen the warning in your talk pages. If this continues, I might need to report this. Please be civil, thanks. ~ Ase1este^t@lk_c0ntribs 05:20, 7 February 2021 (UTC)

Tell the kook to stop denying reality... the original text specified a "real surface", and a "real surface" does not emit as though it's in a 0 K ambient. Evenminded's blather has been proven to violate 1LoT, 2LoT and Stefan's Law by physicist Dr. Charles R. Anderson, PhD. (link above). He does it (and he's done it for years) because he has a theory that continual 2LoT violations cause catastrophic global warming... except a macroscopic 2LoT violation has never been empirically observed, and 2LoT is even more rigorously observed at the quantum scale: https://www.pnas.org/content/112/11/3275 71.135.36.192 (talk) 05:23, 7 February 2021 (UTC)

You will need to report this. The other person is a troll that is vandalizing the page. This is a fundamental concept. Objects emit radiation according to their emissivity and their temperature. They also absorb radiation from their surroundings. The heat transferred from the object is the first minus the second. This is basic stuff. The exitance is not the exitance minus the irradiance, it is simply the exitance. Evenminded (talk) 05:24, 7 February 2021 (UTC)

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Your blather claims that lower energy density photons emitted by a cooler object (or cooler ambient) will be incident upon and absorbed by a warmer object of higher energy density. You'll get right on detailing exactly how that doesn't violate 2LoT in the Clausius Statement sense:

2LoT (in the Clausius Statement sense... "No process is possible whose sole result is the transfer of heat from a cooler to a hotter body") states that energy cannot flow from a lower to a higher-energy region without external work being done upon the system... not via conduction, not via radiative means, not macroscopically, not at the quantum scale [1], not ever. Do keep in mind the definition of heat: "an energy flux". Thus: "No process is possible whose sole result is an energy flux from a cooler to a hotter body" without external energy doing work upon the system.

It requires energy (an energy gradient) to perform work, to provide the impetus for any action.

[1] https://www.pnas.org/content/112/11/3275

"The Stefan-Boltzmann relationship is also related to the energy density in the radiation in a given volume of space." [2]

[2] http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/stefan.html#c1

As physicist Dr. Charles R. Anderson, PhD wrote in debunking Evenminded's blather (with Evenminded socked up as Anonymous in the comments, which he later admitted was him): "The problem, as I have shown in a simple thought experiment with two closely spaced parallel walls is that this requires a violation of Stefan's Law for the energy density uniformly in the volume of the black body cavity. Photons emitted by one wall according to the Stefan-Boltzmann equation as though the temperature of the other wall was T = 0K applied to both walls doubles the energy density in the black body cavity volume that is known from Stefan's Law when you apply your idea of one photon emitted and one absorbed by each wall." [3]

[3] https://objectivistindividualist.blogspot.com/2018/08/the-nested-black-body-shells-model-and.html

"This means that, at every point of the region of space that is in (pointwise) radiative equilibrium, the total, for all frequencies of radiation, interconversion of energy between thermal radiation and energy content in matter is nil (zero)." [4]

[4] https://en.wikipedia.org/wiki/Radiative_equilibrium

As physicist Hendrik (Hans) Kramers wrote: "Another point which, this time, lies quite within the domain where our formulae are significant refers to the scattering of light by an elastically bound electron. Consider again our assembly of harmonic oscillators of frequencies k which we may imagine to take the discrete but very finely distributed values determined by [ kL - η(k) = π N (N = 1, 2, 3... ) ]. Let all of them be in the ground state (energy 3/2 ħ k) with the exception of one (frequency k') which has the energy 5/2 ħ k', the vibration parallel to - say - the x-axis being excited by one quantum ħ k'. In this situation light of frequency k' coming from all directions is continuously scattered by the electron.

...the light quanta in the external field... which are affected by the presence of the electron through the appearance of the phase shift η. We might also call them phase shifted light quanta..."

The electric field of a non-resonant photon, ~100,000,000 times smaller than the Coulomb field seen by the bound electron(s), slightly changes the phase of the bound electron(s), as equally as it changes the phase of the incident photon... no energy is exchanged if the photon is not absorbed, only the phase is shifted. This is how reflection from a step potential works. This is dependent upon the differential between energy density of the photon and atom / molecule. In the case of absorption, the photon constructively interferes with the available resonant quantum states of the atom or molecule. No phase shift.

Just as in a cavity at thermodynamic equilibrium (remember that blackbody radiation was once called cavity radiation), between two objects at thermodynamic equilibrium, each object emits blackbody radiation, which sets up a standing wave between the objects. No energy is exchanged, that'd violate 1LoT, 2LoT, Stefan's Law, etc. Neither object can do work upon the other at thermodynamic equilibrium, thus no energy can be transferred between them. Evenminded claims energy can flow without work being done because he misunderstands the meaning of free energy.

If one object changes temperature, the standing wave will travel toward the object of lower temperature, with the group velocity of that traveling wave proportional to the temperature differential of the two objects, the operating principle behind it all being radiation pressure, which Evenminded denies exists.

A standing wave results from two waves of the same frequency with different vectors within the same medium. Thermodynamic equilibrium between two objects means energy emitted by each object is identical in frequency distribution, and since the objects emit into the shared space between the objects, the medium is the same.

Thus, photons from one object won't be absorbed by the other, they'll be reflected. This increases the energy density of the standing wave until it equals that of the objects. Thus at thermodynamic equilibrium the objects cannot emit nor absorb photons, they can only reflect the photons still in the standing wave from when the objects were approaching thermodynamic equilibrium. — Preceding unsigned comment added by 71.135.36.192 (talk) 12:41, 7 February 2021 (UTC)

At thermodynamic equilibrium, the Helmholtz Free Energy is zero: F = U - TS Where: F = Helmholtz Free Energy U = internal energy T = absolute temperature S = final entropy TS = energy the object can receive from the environment

If U > TS, F > 0... energy must flow from object to environment. If U = TS, F = 0... no energy can flow to or from the object. If U < TS, F < 0... energy must flow from environment to object.

If U = TS, p_photon = u/3 = p_object, energy cannot flow because no work can be done. Photon chemical potential is zero.

You can see the Schrodinger equation in operation detailing exactly what was stated above: https://physics.weber.edu/schroeder/software/BarrierScattering.html

So it's not that the warmer object is absorbing radiation from the cooler object (or cooler ambient) (which would violate 2LoT) which slows the cooling rate of the warmer object; it's the radiation pressure of the cooler object (or cooler ambient) which reduces the radiative emission rate from the warmer object and thus slows its rate of cooling. 71.135.36.192 (talk) 07:21, 7 February 2021 (UTC)

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Stop playing the victim. You reverted my correct edit to come into line with your blather that all objects emit as though they're in a 0 K ambient, and you claim that energy can flow without work being done. You're fundamentally confused. 71.135.36.192 (talk) 05:29, 7 February 2021 (UTC)

@71.135.36.192:, @Evenminded:. In any case, if anyone makes another edit from this point on, I will report this to Wikipedia:Administrators' noticeboard/Edit warring. Keep in mind that being civil is as important as being right. ~ Ase1este^t@lk_c0ntribs 05:27, 7 February 2021 (UTC)

I say being right is priority one... you are, after all, supposed to be an encyclopedia. Do you side with people who make up hobby theories then twist facts and edit pages to align them with their pet theory, despite the fact that it can be shown that their blather violates the fundamental physical laws? 71.135.36.192 (talk) 05:29, 7 February 2021 (UTC)

I'll allow others to determine who has been civil in this interaction. Here is yet another link explaining that the amount of radiation emitted by a surface depends only on its temperature and emissivity. https://web.mit.edu/16.unified/www/FALL/thermodynamics/notes/node135.html Evenminded (talk) 05:31, 7 February 2021 (UTC)

And here is another http://www.mhtl.uwaterloo.ca/courses/ece309_mechatronics/lectures/pdffiles/summary_ch12.pdf Evenminded (talk) 05:33, 7 February 2021 (UTC)

Again, you are fundamentally confused. Stefan and Boltzmann came up with this equation for a reason: q = ε σ (T_h^4 - T_c^4) A_h And if we assume emissivity = 1 and T_C = 0, we get: 1 σ (T_h^4 - 0 K) 1 m^2 = σ T^4 71.135.36.192 (talk) 05:36, 7 February 2021 (UTC)

I just provided a textbook reference on the topic. Evenminded (talk) 05:39, 7 February 2021 (UTC)

As usual, you take references and quotes out of context to fit your hobby theory. Real surfaces do not emit as though in a 0 K ambient, which is why you were wrong about the surface at 303.15 K emitting into a 287.64 K ambient... you claimed it'd emit 479 W/m^2, when in reality it emits 84.96925 W / m^2 (for an emissivity of 0.93643). So not only are you claiming all objects emit into a 0K ambient, you're claiming all objects have emissivity of 1... IOW, that ALL OBJECTS ARE HYPOTHETICAL BLACKBODIES. 71.135.36.192 (talk) 05:44, 7 February 2021 (UTC)

See Eqs. 11-3 and 11-34. https://kntu.ac.ir/DorsaPax/userfiles/file/Mechanical/OstadFile/Sayyalat/Bazargan/cen58933_ch11.pdf Evenminded (talk) 05:51, 7 February 2021 (UTC)

And now you're confusing blackbody radiation and blackbody objects. Again, you are fundamentally confused. The dominant source of blackbody radiation is transient oscillating dipoles induced by inter-molecular thermal vibrations within a material. Solids, liquids, plasma of sufficient density and gases of sufficient density can emit blackbody radiation, but our atmosphere cannot simply because the gas molecules spend the majority of their time relatively distant from each other, and thus they cannot sustain the inter-molecular oscillations necessary for blackbody radiation. As gas density increases, blackbody radiation production increases and eventually dominates the discrete emission spectra. Similarly, as gas density increases, blackbody absorption increases and eventually dominates the discrete absorption spectra. Simply because an object emits blackbody radiation does not make that object a hypothetical blackbody object. 71.135.36.192 (talk) 05:56, 7 February 2021 (UTC)

Eq. 11-34 was for arbitrary bodies. Evenminded (talk) 05:58, 7 February 2021 (UTC)

Again, you're confusing concepts... that equation calculates the emissivity, that ratio of what a surface DOES emit as compared to what a hypothetical blackbody WOULD emit... but again, you claim that all objects must be hypothetical blackbodies with emissivity of 1 and emitting as though in a 0 K ambient because they emit blackbody radiation. You are fundamentally confused. I've tried for years to educate you, but you refuse to learn anything except what bolsters your hobby theory. 71.135.36.192 (talk) 06:03, 7 February 2021 (UTC)

Guys. You can't keep reverting the article back and forth. It doesn't matter who is right. Reverting an article repeatedly will get you blocked. If I were an admin, I'd have blocked you both already. I'm sure one will do so shortly. --Srleffler (talk) 06:05, 7 February 2021 (UTC)

@Srleffler: - Then someone has to step in and make a decision. This is textbook stuff and I am going to revert it back to the textbook definition. Here is a video for beginners that provides this definition: https://www.youtube.com/watch?v=fIjs9zjmF0U Evenminded (talk) 13:59, 7 February 2021 (UTC)

That is not the textbook definition for a "real surface", it is the textbook definition for a hypothetical blackbody, which assumes emissivity of 1 and T_c = 0 K. You do no one any good deed by misleading them. At the very least, you should remove the "real surface" blurb and specify that the σ T^4 applies only to hypothetical blackbodies. The notion that a body must absorb all radiation incident upon it (which is posited to offset radiant emission as though into a 0 K ambient) violates 2LoT in the Clausius Statement sense. See above. q = ε σ (T_h^4 - T_c^4) A_h = 1 σ (T_h^4 - 0 K) 1 m^2 = σ T^4 71.135.36.192 (talk) 14:12, 7 February 2021 (UTC)

Indeed it is the textbook definition of the radiation emitted. If you believe otherwise, then cite a textbook that states as such. The formula you continue to post is the net heat transfer, not the radiation emitted. Evenminded (talk) 19:06, 7 February 2021 (UTC)

I see that this is an external dispute you two have been having in the comments section of Charles R. Anderson's blog (links above). Don't bring your argument here. According to Charles R. Anderson, the view being promoted by User:71.135.36.192 is contrary to the "so-called settled science treatment". That's sufficient for me: we'll stick with the settled science treatment, thank you very much. See Wikipedia:No original research for the relevant policy.--Srleffler (talk) 19:07, 7 February 2021 (UTC)

No, the view promoted by me is exactly the view of physicist Dr. Charles R. Anderson, PhD... the view of Evenminded violates the fundamental physical laws, not least of which is 2LoT in the Clausius Statement sense.

71.135.36.192 (talk) 19:13, 7 February 2021 (UTC)

Yes, exactly. You're promoting the view of one guy, who admits that his view is contrary to the "so-called settled science treatment" (direct quote from his blog.) That's not what we do at Wikipedia. See Wikipedia:No original research.--Srleffler (talk) 19:14, 7 February 2021 (UTC)

Indeed. In addition, see Wikipedia:Fringe theories. Also, in my experience, calling someone "Dr. So-and-so, PhD" is not just a logically fallacious appeal to authority, but also a pretty good counter-indicator.... XOR'easter (talk) 19:15, 8 February 2021 (UTC)

Your claimed "non-consensus view" used mathematics and concepts from the book Thermal Physics[1] by Philip M. Morse (Professor of Physics at MIT, co-founding editor of Annals of Physics, co-founder of MIT Acoustics Laboratory, first Director of Brookhaven National Laboratory, founder of MIT Computation Center) to show the "consensus view" violates Stefan's Law. That the "consensus view" demonstrably violates Stefan's Law doesn't magically make it right just because some purported 'majority' subscribes to it... it just makes that purported 'majority' wrong.

• [1] https://archive.org/details/thermalphysics00mors

71.135.38.119 (talk) 06:41, 9 February 2021 (UTC)

Ah, but your promoting a view that demonstrably violates the fundamental physical laws... that's alright? See above. Think for yourself... how exactly does a photon with a lower energy (from a cooler object or cooler ambient) get absorbed by a warmer object without external energy doing work upon the system to push that energy against the energy gradient? And how exactly is the Stefan-Boltzmann equation (which takes into account field radiation pressure, as explicated in the links above) not the "consensus view"? 71.135.36.192 (talk) 19:19, 7 February 2021 (UTC)

An individual photon does not know what temperature the object it came from was. The photon has energy that corresponds to its frequency. A 1.2 eV photon might come from near the peak of a 3000 K blackbody emission spectrum or from the infrared tail of a 6000 K spectrum. There is no way to tell, and it doesn't make any difference to the photon. Whether the photon is absorbed by the surface depends solely on the properties of the photon and the surface. The second law of thermodynamics is preserved by the balance between all the photons absorbed by the surface and all the photons emitted from it. The law always holds; the fact that a photon can be absorbed is inextricably linked to the fact that photons can be emitted from the surface. The net energy flow between two surfaces at different temperatures will always satisfy the law.--Srleffler (talk) 20:57, 7 February 2021 (UTC)

As Planck wrote in his "The Theory of Heat Radiation", the amount of radiation emitted by an object does not depend on the temperature of what it is emitting to, "A body A at 100 C emits toward a body B at 0 C exactly the same amount of radiation as toward an equally large and similarly situated body B′ at 1000 C". Evenminded (talk) 19:50, 7 February 2021 (UTC)

Again, you take quotes out of context in furtherance of your hobby theory... Planck was discussing an idealized blackbody object, which assumes emission to a 0 K ambient and emissivity of 1... real-world objects do not act in that manner, which is why Stefan and Boltzmann created the S-B equation which takes into account field radiation energy density via taking into account T_c. We are not discussing idealized blackbody objects in the section in question, we are discussing (and I quote) "real surfaces". 71.135.36.192 (talk) 19:55, 7 February 2021 (UTC)

No, Planck was talking about real-world objects, "the coefficient of emission ε depends, apart from the frequency ν and the nature of the medium, only on the temperature T". Evenminded (talk) 19:56, 7 February 2021 (UTC)

You two need to work this out before making changes to the article text, or you will be blocked for longer next time. If you can't reach agreement between the two of you, please seek outside dispute resolution help. GorillaWarfare (talk) 20:07, 7 February 2021 (UTC)

Dueling WP:SPAs

Sorry I didn't see this sooner; you should have both been blocked a hundred edits ago. Srleffler, thanks for reverting to before them. Dicklyon (talk) 02:19, 12 February 2021 (UTC)

Radiant Emittance and Emissive power

Copying over from Talk:Stefan–Boltzmann_law#Scope_of_expansion

Is radiant emittance same as emissive power? Ref: Emissivity#Emittance If yes, then can it be mentioned in the intro section of this page? Yashpalgoyal1304 (talk) 17:58, 28 March 2021 (UTC)

No, emissive power would be the same as radiant flux.--Srleffler (talk) 23:20, 28 March 2021 (UTC)

In most basic words, Radiant flux is mentioned as energy per unit time, while Emissive Power is mentioned as energy per unit time per unit area. So, how can these two be same?? While Radiant Emittance is mentioned as flux per unit area which seems to equal emissive power. Can u please recheck? Yashpalgoyal1304 (talk) 11:13, 29 March 2021 (UTC)

I'm taking emissive power as a synonym for radiant power, which is energy per unit time. --Srleffler (talk) 21:56, 3 April 2021 (UTC)

i get that, but i am saying that wont what u're saying be wrong? as emissive power is energy per unit time per unit area Yashpalgoyal1304 (talk) 08:51, 26 April 2021 (UTC)

Yep, certainly as defined on the page to which you've linked, emissive power is a synonym for radiant excitance. --Srleffler (talk) 02:33, 28 April 2021 (UTC)