We Knew Warmers Were Wacko...But Really?

[Wuwei]

lets tale the discussion out of the hypothetical and make it real....lets plug some numbers into it representing actual temperatures

Solve for P which is the radiating power of our radiator, What is the radiating power of P. Hint: It is a one word answer.

You still don't understand what everyone is telling you. This is what the hyperphysics site - A Good Absorber is a Good Emitter - says about your formula. The site says that T is the temperature of an object. However they give the only valid definition of Tc as:

"In this relationship the term with Tc represents the energy absorbed from the environment. This expression explicitly assumes that the same coefficient e applies to both the emission into the environment and the absorption from the environment."​

SSDD, Every object simultaneously emits and absorbs radiation The object does not just exhibit a reduced emission.

 

[SSDD]

If another object is nearby, it is also radiating at P=kT4. The net energy exchange is Pnet= Pwarm - Pcool. Both objects are still radiating at P=kT4.

So you say...simply tacking net onto an expression, however, does not mean that you are calculating net. Where is the expression for incoming radiation from that other object that changes P? I don't see it...where is it? If we are looking at an equation describing a net energy exchange, there must be an expression for energy coming in as well as going out...where is it?

Either you are saying that the SB law is wrong and you are right...or that there is an expression of incoming radiation in that equation that I am not seeing....which is it?

 

[SSDD]

You still don't understand what everyone is telling you. This is what the hyperphysics site - A Good Absorber is a Good Emitter - says about your formula. The site says that T is the temperature of an object. However they give the only valid definition of Tc as:

"In this relationship the term with Tc represents the energy absorbed from the environment. This expression explicitly assumes that the same coefficient e applies to both the emission into the environment and the absorption from the environment."​

SSDD, Every object simultaneously emits and absorbs radiation The object does not just exhibit a reduced emission.

I understand precisely what everyone is telling me....I also understand that the equation

is a description of a gross energy flow...the power of which is determined by the difference in the temperature of the radiator and the temperature of its surroundings. Now, either you can state where within that equation one would find the expression describing the amount of radiation coming in from another radiator which would indeed make it an expression describing net energy flow...or you can't, in which case, my claim that it is an expression of gross energy flow is correct. In that case you and Ian and others are making the claim that the Stefan Boltzman law is incorrect and that the equations associated with it are wrong. Surely there is a Nobel in it for someone who can prove that a physical law is incorrect.

So take the above equation apart and tell me where the information describing the incoming energy from another radiator is hiding...because that information is necessary if you are going to have an equation describing net energy flow.

 

[SSDD]

By the way....Tc = the temperature of the radiator's surroundings...there is no information there whatsoever about energy being absorbed from the environment...and certainly nothing there regarding any amount being absorbed which would be required for an equation revealing a net energy flow. Simply saying a thing does not make it true.

 

[Toddsterpatriot]

By the way....Tc = the temperature of the radiator's surroundings...there is no information there whatsoever about energy being absorbed from the environment...and certainly nothing there regarding any amount being absorbed which would be required for an equation revealing a net energy flow. Simply saying a thing does not make it true.

Science 24 May 1963:
Vol. 140 no. 3569 pp. 870-877
DOI: 10.1126/science.140.3569.870

In a practical situation and room-temperature setting, humans lose considerable energy due to thermal radiation. However, the energy lost by emitting infrared light is partially regained by absorbing the heat flow due to conduction from surrounding objects, and the remainder resulting from generated heat through metabolism. Human skin has an emissivity of very close to 1.0 . Using the formulas below shows a human, having roughly 2 square meter in surface area, and a temperature of about 307 K, continuously radiates approximately 1000 watts. However, if people are indoors, surrounded by surfaces at 296 K, they receive back about 900 watts from the wall, ceiling, and other surroundings, so the net loss is only about 100 watts.

 

[SSDD]

By the way....Tc = the temperature of the radiator's surroundings...there is no information there whatsoever about energy being absorbed from the environment...and certainly nothing there regarding any amount being absorbed which would be required for an equation revealing a net energy flow. Simply saying a thing does not make it true.

Science 24 May 1963:
Vol. 140 no. 3569 pp. 870-877
DOI: 10.1126/science.140.3569.870

In a practical situation and room-temperature setting, humans lose considerable energy due to thermal radiation. However, the energy lost by emitting infrared light is partially regained by absorbing the heat flow due to conduction from surrounding objects, and the remainder resulting from generated heat through metabolism. Human skin has an emissivity of very close to 1.0 . Using the formulas below shows a human, having roughly 2 square meter in surface area, and a temperature of about 307 K, continuously radiates approximately 1000 watts. However, if people are indoors, surrounded by surfaces at 296 K, they receive back about 900 watts from the wall, ceiling, and other surroundings, so the net loss is only about 100 watts.

All you need do is show me where in the SB equations there is an expression that states how much radiation is coming in from another source besides the radiator referenced by P....such an expression would be necessary for the equation to be one describing net energy flow...absent an expression describing incoming radiation the equation only describes gross energy flow.

You can provide as many thought experiments as you like but it is not going to alter the fact that at present, you are claiming that the equations describing the SB law and, in fact, the SB law itself is incorrect. You claim it is describing net energy movements but the equations associated with it only describe gross energy movement. Either you or the SB law is wrong...I am going to guess that it is you since we both know that you can't point to any reference within the law to incoming radiation from another source.

 

[IanC]

perhaps it is time to just play SSDD's game of semantics. so what IS the Stefan-Boltzmann Law? it describes how all objects warmer than zero degrees Kelvin radiate. all the other knock-on equations are just mathematical variations, and not the S-B Law.



Radiation Heat Transfer

The radiation energy per unit time from a blackbody is proportional to the fourth power of the absolute temperatureand can be expressed with Stefan-Boltzmann Law as

q = σ T4 A (1)

where

q = heat transfer per unit time (W)

σ = 5.6703 10-8 (W/m2K4) - The Stefan-Boltzmann Constant

T = absolute temperature Kelvin (K)

A = area of the emitting body (m2)


SSDD's favourite version,

is not the S-B Law.

it is a mathematically rearranged equation to give the net radiation transfer

Net Radiation Loss Rate
If an hot object is radiating energy to its cooler surroundings the net radiation heat loss rate can be expressed as

q = ε σ (Th4 - Tc4) Ac (3)

where

Th = hot body absolute temperature (K)

Tc = cold surroundings absolute temperature (K)

Ac = area of the object (m2)



I looked at quite a few references for the S-B Law, and they all described how an object radiated according to its temperature. there was no discussion at all about the temperature of the surroundings, just the object's temp and emissivity.

 

[Toddsterpatriot]

By the way....Tc = the temperature of the radiator's surroundings...there is no information there whatsoever about energy being absorbed from the environment...and certainly nothing there regarding any amount being absorbed which would be required for an equation revealing a net energy flow. Simply saying a thing does not make it true.

Science 24 May 1963:
Vol. 140 no. 3569 pp. 870-877
DOI: 10.1126/science.140.3569.870

In a practical situation and room-temperature setting, humans lose considerable energy due to thermal radiation. However, the energy lost by emitting infrared light is partially regained by absorbing the heat flow due to conduction from surrounding objects, and the remainder resulting from generated heat through metabolism. Human skin has an emissivity of very close to 1.0 . Using the formulas below shows a human, having roughly 2 square meter in surface area, and a temperature of about 307 K, continuously radiates approximately 1000 watts. However, if people are indoors, surrounded by surfaces at 296 K, they receive back about 900 watts from the wall, ceiling, and other surroundings, so the net loss is only about 100 watts.

All you need do is show me where in the SB equations there is an expression that states how much radiation is coming in from another source besides the radiator referenced by P....such an expression would be necessary for the equation to be one describing net energy flow...absent an expression describing incoming radiation the equation only describes gross energy flow.

You can provide as many thought experiments as you like but it is not going to alter the fact that at present, you are claiming that the equations describing the SB law and, in fact, the SB law itself is incorrect. You claim it is describing net energy movements but the equations associated with it only describe gross energy movement. Either you or the SB law is wrong...I am going to guess that it is you since we both know that you can't point to any reference within the law to incoming radiation from another source.

Wuwei already showed you.

"In this relationship the term with Tc represents the energy absorbed from the environment."

 

[SSDD]

perhaps it is time to just play SSDD's game of semantics. so what IS the Stefan-Boltzmann Law? it describes how all objects warmer than zero degrees Kelvin radiate. all the other knock-on equations are just mathematical variations, and not the S-B Law.

The law is described by the associated equations...no more...no less. If the law meant something else, then the equations would reflect something else.



Radiation Heat Transfer

The radiation energy per unit time from a blackbody is proportional to the fourth power of the absolute temperatureand can be expressed with Stefan-Boltzmann Law as

q = σ T4 A

(1)

That equation describes a perfect black body radiating into a vacuum at 0 degrees K. You always fail to mention that.

SSDD's favourite version,

is not the S-B Law.

But it is derived from the law and represents a radiator other than a perfect black body radiating into surroundings that are above 0 degrees K...in essence...the real world as opposed to the fantasy of a black body radiating into perfectly empty space.

it is a mathematically rearranged equation to give the net radiation transfer

No it isn't and you know perfectly well that it isn't. You are well versed enough in mathematics to know that that equation is not describing a net energy transfer...if it were, there would be an expression representing the amount of incoming energy from an outside source....it isn't there and therefore it is not, and never was intended to give net anything.

I looked at quite a few references for the S-B Law, and they all described how an object radiated according to its temperature. there was no discussion at all about the temperature of the surroundings, just the object's temp and emissivity.

Then you didn't look very hard...In the above equation P is the radiation emitted from the radiator and P varies with the difference in the temperature between itself T and its surroundings Tc....like it or not, that is what the equation says and the fact that it doesn't jibe with your claims makes your claims suspect while the equation supports my position 100%

 

[SSDD]

Wuwei already showed you.

"In this relationship the term with Tc represents the energy absorbed from the environment."

wuwei is wrong...and his source is wrong. Describe how the difference between the temperature of a radiator and the temperature of its surroundings describes incoming radiation. Like it or not, the information is not there... If the equation were about incoming radiation, then the expression would be for incoming radiation rather than simply the temperature of the surroundings...the equation is describing gross energy movement...not net energy transfers.

 

[Toddsterpatriot]

Wuwei already showed you.

"In this relationship the term with Tc represents the energy absorbed from the environment."

wuwei is wrong...and his source is wrong. Describe how the difference between the temperature of a radiator and the temperature of its surroundings describes incoming radiation. Like it or not, the information is not there... If the equation were about incoming radiation, then the expression would be for incoming radiation rather than simply the temperature of the surroundings...the equation is describing gross energy movement...not net energy transfers.

You have yet to provide a single source that explicitly states an object above 0K ever stops radiating.
I've provided multiple sources that state objects receive energy radiated from sources cooler than themselves.
In fact, several of your recent sources have disagreed with your claim and agreed with me.

Go find a source that says an object stops radiating near a warmer object or admit your error.

 

[SSDD]

You have yet to provide a single source that explicitly states an object above 0K ever stops radiating.
I've provided multiple sources that state objects receive energy radiated from sources cooler than themselves.
In fact, several of your recent sources have disagreed with your claim and agreed with me.

Of course I have...you failed to solve for P in the equation above...solve for P and P =0 whether you like it or not. If the equations associated with the law itself aren't good enough for you then what is? The fact that you can't even do such basic math...or that you refuse to accept the answer you get when you do the math is irrelevant....the answer is zero and the equation is describing gross energy flow...since none of you seem to be able to show any real expression of incoming radiation which would be required to formulate an equation showing net energy flow.

 

[Toddsterpatriot]

You have yet to provide a single source that explicitly states an object above 0K ever stops radiating.
I've provided multiple sources that state objects receive energy radiated from sources cooler than themselves.
In fact, several of your recent sources have disagreed with your claim and agreed with me.

Of course I have...you failed to solve for P in the equation above...solve for P and P =0 whether you like it or not. If the equations associated with the law itself aren't good enough for you then what is? The fact that you can't even do such basic math...or that you refuse to accept the answer you get when you do the math is irrelevant....the answer is zero and the equation is describing gross energy flow...since none of you seem to be able to show any real expression of incoming radiation which would be required to formulate an equation showing net energy flow.

Of course I have

I must have missed it, provide it again.

you failed to solve for P in the equation above...solve for P and P =0 whether you like it or not.

When net equals zero, neither object stops radiating.

If the equations associated with the law itself aren't good enough for you then what is?

The equations are fine, your confusion is not.

the answer is zero and the equation is describing gross energy flow..

You just won't provide a source that says so explicitly.

...since none of you seem to be able to show any real expression of incoming radiation

But of course I did. It's the same equation for both objects, because both objects above 0k radiate continuously.
You have to add them together to get the net. Addition, apparently, is too difficult for you.

Still waiting for your source that says objects above 0K stop radiating. Ever.
It will take me only moments to find sources that disagree with your claim, why can't you find any that agree?

 

[SSDD]

I must have missed it, provide it again.

In your eyes an equation, derived from the SB law where P=0 is not proof to you? So you are saying that the SB law is incorrect. OK.

When net equals zero, neither object stops radiating.

Since you could provide no evidence of an expression in the equation which gave any actual amount of incoming radiation from another source which would be required if one were going to write an equation showing a net energy exchange...it is clear that the equation is a description of gross energy flow. Your failing at basic math doesn't change the fact.....the equation is not showing net anything.

The equations are fine, your confusion is not.

Of course the equations are fine...and my position on them is fine...your insistence that they are describing net energy flow, when you are unable to show any expression that could be construed as providing precise information about incoming radiation from another source clearly demonstrates that it is you who is confused....or perhaps just not grown up enough to admit that you are wrong. Continuing to claim that the equations are describing net energy flow when it is obvious to anyone who has even a small grasp of math only makes you look like a whining baby demanding that up is down and right is left. Grow up and describe how one might derive any information whatsoever about the output of an unknown radiator or radiators simply by having the temperature of the surroundings.

Here...the surrounding temperature is 58 degrees F. What is the amount of radiation that one, or any number of radiators are putting out. Clearly, you can't have any idea and yet, you believe that you can provide just that from nothing more than a temperature within an equation....that assumption and it is an assumption based on an unsupportable belief that the equation is providing a net energy flow even though it is not written in any form that would provide information about a net flow...it is no better than writing Pnet=Tnet-Tcnet....simply saying net does not make it net. If you can prove net with the law itself and not your unfounded claims, then by all means do it by telling me how much radiation the unknown radiator or radiators are putting out in order to make the air temperature 58 degrees. You might start by telling me the area of the radiators...that would be a good start...how will you get that from nothing other than the temperature?

You just won't provide a source that says so explicitly.

The equation is the ultimate source...the only source that is unimpeachable...sorry that you aren't able to recognize that fact.

But of course I did. It's the same equation for both objects, because both objects above 0k radiate continuously. You have to add them together to get the net. Addition, apparently, is too difficult for you.

Further demonstration of your mathematical ineptitude...the mere temperature of the surroundings do not give you anything like an incoming watts per square meter of incoming radiation....that whole equation is necessary to determine the radiation output of P and you think you can derive the radiation output of an unknown radiator or radiators from a simple temperature? You really don't get this do you. How far must you dig before you finally admit that you are wrong and have been wrong from the start?

Still waiting for your source that says objects above 0K stop radiating. Ever.

Solve for P. If you can't accept equations derived from the SB law you must be claiming that it is wrong.

It will take me only moments to find sources that disagree with your claim, why can't you find any that agree?

The law itself agrees with me...and the equations associated with it support my position, what else do I need?....any source that disagrees with the fact that P=0 in the example I gave you and that one can not derive any real information about incoming radiation from an unknown radiator or radiators merely by having the temperature of the surroundings is simply as wrong as you. The equations are what they are and they say what they say....and the fact that you can't accept what they say on their own terms speaks volumes about you

 

[Toddsterpatriot]

I must have missed it, provide it again.

In your eyes an equation, derived from the SB law where P=0 is not proof to you? So you are saying that the SB law is incorrect. OK.

When net equals zero, neither object stops radiating.

Since you could provide no evidence of an expression in the equation which gave any actual amount of incoming radiation from another source which would be required if one were going to write an equation showing a net energy exchange...it is clear that the equation is a description of gross energy flow. Your failing at basic math doesn't change the fact.....the equation is not showing net anything.

The equations are fine, your confusion is not.

Of course the equations are fine...and my position on them is fine...your insistence that they are describing net energy flow, when you are unable to show any expression that could be construed as providing precise information about incoming radiation from another source clearly demonstrates that it is you who is confused....or perhaps just not grown up enough to admit that you are wrong. Continuing to claim that the equations are describing net energy flow when it is obvious to anyone who has even a small grasp of math only makes you look like a whining baby demanding that up is down and right is left. Grow up and describe how one might derive any information whatsoever about the output of an unknown radiator or radiators simply by having the temperature of the surroundings.

Here...the surrounding temperature is 58 degrees F. What is the amount of radiation that one, or any number of radiators are putting out. Clearly, you can't have any idea and yet, you believe that you can provide just that from nothing more than a temperature within an equation....that assumption and it is an assumption based on an unsupportable belief that the equation is providing a net energy flow even though it is not written in any form that would provide information about a net flow...it is no better than writing Pnet=Tnet-Tcnet....simply saying net does not make it net. If you can prove net with the law itself and not your unfounded claims, then by all means do it by telling me how much radiation the unknown radiator or radiators are putting out in order to make the air temperature 58 degrees. You might start by telling me the area of the radiators...that would be a good start...how will you get that from nothing other than the temperature?

You just won't provide a source that says so explicitly.

The equation is the ultimate source...the only source that is unimpeachable...sorry that you aren't able to recognize that fact.

But of course I did. It's the same equation for both objects, because both objects above 0k radiate continuously. You have to add them together to get the net. Addition, apparently, is too difficult for you.

Further demonstration of your mathematical ineptitude...the mere temperature of the surroundings do not give you anything like an incoming watts per square meter of incoming radiation....that whole equation is necessary to determine the radiation output of P and you think you can derive the radiation output of an unknown radiator or radiators from a simple temperature? You really don't get this do you. How far must you dig before you finally admit that you are wrong and have been wrong from the start?

Still waiting for your source that says objects above 0K stop radiating. Ever.

Solve for P. If you can't accept equations derived from the SB law you must be claiming that it is wrong.

It will take me only moments to find sources that disagree with your claim, why can't you find any that agree?

The law itself agrees with me...and the equations associated with it support my position, what else do I need?....any source that disagrees with the fact that P=0 in the example I gave you and that one can not derive any real information about incoming radiation from an unknown radiator or radiators merely by having the temperature of the surroundings is simply as wrong as you. The equations are what they are and they say what they say....and the fact that you can't accept what they say on their own terms speaks volumes about you

In your eyes an equation, derived from the SB law where P=0 is not proof to you?

That is proof. Proof that net energy transfer is zero.
Still waiting for you to prove that means both stopped radiating.

Since you could provide no evidence of an expression in the equation which gave any actual amount of incoming radiation from another source which would be required if one were going to write an equation showing a net energy exchange

P = εAσ(255^4)

This is the equation showing the energy radiated by an object at 255K into a vacuum with surroundings at 0K.

P = εAσ(250^4)

This is the equation showing the energy radiated by an object at 250K into a vacuum with surroundings at 0K.

When you put them next to each other, P = εAσ(255^4 - 250^4) shows the net energy lost by the warmer object and gained by the cooler object.
Because they are both radiating, all the time.
And you have yet to provide a source that agrees with your silly claim that any object over 0K stops radiating, ever.
Why such a long term failure to find a source that agrees with you?
I mean, even your own sources disagreed with you.
That's hilarious!

Of course the equations are fine...and my position on them is fine...

You just can't find a single source that agrees with you.

The equation is the ultimate source

If your confusion was correct, you'd have thousands of sources describing objects above 0K that suddenly stopped radiating, instead of zero sources.

any source that disagrees with the fact that P=0 in the example I gave you

I don't have any sources that disagree that net energy exchange is zero in the example you gave. Do you?

If only you had a source that agrees all radiating ceased in your example.......

 

[IanC]

the original data for development of the S-B Law came from heating (and cooling) a crucible with a small aperture. the inside was coated in carbon soot to make it as close as possible to a blackbody, the radiation leaving the aperture was analyzed for amount and wavelength.

trial and error led to the discovery that the radiation was proportional to the 4th power of temperature measured in Kelvin which starts at absolute zero (-273.15 C). a lot of scientists were involved, including Max Planck who introduced a 'granularity' constant to get rid of the ultraviolet catastrophe, which set the whole quantum theory ball rolling.

the point is.....all objects radiate according to their temperature, at all times. THAT is the S-B law.

all the other variations in the equations for S-B are just that, variations.

SSDD's favourite is

which is the same as P= kAT^4 - kATcool^4 , no difference just rearranged terms

the visual representation of that is -

everything under the pink curve is a one-to-one exchange between the warm object and the cool one. the area between the blue and pink curves represents the amount of radiation that is flowing from warm to cool. the overlapped area on the curves doesnt disappear, its effects just cancel out, leaving zero net change.

 

[IanC]

the other thing to think about is what causes objects to shed radiation.

kinetic movement forces particles to collide, or at least graze each other. kinetic energy is turned into potential energy by distorting the electron clouds and such. when the particles separate the distortions return to normal releasing the potential energy as photons. that's why cool objects have an upper limit to the wavelength they can emit. slower moving particles produce lower energy photons, on average.

SSDD says the radiation stops. but that means the collisions stop. and that makes no sense unless the temperature drops to absolute zero.

every facet of SSDD's explanation leads to logical exclusion. all objects radiate all the time, just like the S-B Law states.

 

[SSDD]

In your eyes an equation, derived from the SB law where P=0 is not proof to you?

That is proof. Proof that net energy transfer is zero.
Still waiting for you to prove that means both stopped radiating.

I see you couldn't tell me how much radiation an unknown radiator or radiators were emitting when the temperature of the air is 58 degrees. I guess you can't derive any such information from a mere temperature which is all that the SB equation gives about its surroundings....clearly it is not an equation that gives information about net anything...simply claiming that it is net when the equation clearly is not net just keeps on giving up information about you.

Since you could provide no evidence of an expression in the equation which gave any actual amount of incoming radiation from another source which would be required if one were going to write an equation showing a net energy exchange

P = εAσ(255^4)

This is the equation showing the energy radiated by an object at 255K into a vacuum with surroundings at 0K.

P = εAσ(250^4)

This is the equation showing the energy radiated by an object at 250K into a vacuum with surroundings at 0K.

When you put them next to each other, P = εAσ(255^4 - 250^4) shows the net energy lost by the warmer object and gained by the cooler object.

No...those both only give you information about how much energy they are radiating into a vacuum at 0 degrees K...neither gives any information at all about any sort of incoming radiation...they are radiating into an empty vacuum so there is no need for information about any other radiator.....if there were two radiators in the vacuum, then the temperature wouldn't be zero....would it?...and another equation would be required.

they are both radiating, all the time.p.quote]

If each is a perfect black body alone in a vacuum at zero degrees K....you really don't know what the equations are saying do you?

And you have yet to provide a source that agrees with your silly claim that any object over 0K stops radiating, ever.p.

The fact that you don't know what the equations are describing doesn't alter the fact that they are describing a perfect black body radiator all alone in a vacuum at 0 degrees K...if the two were in the same space, the temperature wouldn't be zero degrees K and a different equation would be required...if you can't even grasp what the equations are describing, how do you suppose you can be right about an assumption on your part....you have failed on the basics...any assumption you make will be the result of an incorrect grasp of the basics.

Why such a long term failure to find a source that agrees with you?p.

The law itself agrees with me...what else do I need...P=0 in the equation I provided...you can provide no evidence whatsoever that proves that the equation is yielding a net energy flow because you can provide no evidence that there is any information about incoming radiation...your proof so far has been to provide information about two radiators, each alone in their own vacuum at 0 degrees K....if they were together, the temperature would not be zero...fail again.

You just can't find a single source that agrees with you.

Except the SB law itself...that is enough for me. Again, how much radiation is an unknown radiator or radiators emitting when the air temperature is 58 degrees? That is all the information about the surroundings that the equations give you...How much?

If your confusion was correct, you'd have thousands of sources describing objects above 0K that suddenly stopped radiating, instead of zero sources.

Can you provide a single observed, measured example of net radiative transfer? Of course not...since you can't provide a single observed, ,measured example of back radiation.

I don't have any sources that disagree that net energy exchange is zero in the example you gave.

Since there is no information about incoming radiation from another radiator, the question is moot....clearly the equation is providing information about gross energy movement....the closest you came to giving any sort of an answer was an epic fail...you give an equation that describes a theoretical perfect black body all alone radiating in a vacuum with a temperature of 0 degrees K twice and claim that is some sort of proof. The absurdity is amazing.

If only you had a source that agrees all radiating ceased in your example.......

The equation itself says P=0 and the best you can do is provide examples that simply assume net...lets see the proof that the equation is deriving net. Not just saying net but mathematically proving net.

 

[SSDD]

the original data for development of the S-B Law came from heating (and cooling) a crucible with a small aperture. the inside was coated in carbon soot to make it as close as possible to a blackbody, the radiation leaving the aperture was analyzed for amount and wavelength.

trial and error led to the discovery that the radiation was proportional to the 4th power of temperature measured in Kelvin which starts at absolute zero (-273.15 C). a lot of scientists were involved, including Max Planck who introduced a 'granularity' constant to get rid of the ultraviolet catastrophe, which set the whole quantum theory ball rolling.

So you are acknowledging that the equation in question is deriving information about gross energy flow. Thanks.

the point is.....all objects radiate according to their temperature, at all times. THAT is the S-B law.

When they are perfect black bodies radiating along in a vacuum at 0 degrees K...and even then not only according to their temperature but their size as well. Take them out of the vacuum and raise the temperature of their surroundings and then P varies with the temperature of its surroundings...not simply according to its own temperature.

all the other variations in the equations for S-B are just that, variations.

SSDD's favourite is

which is the same as P= kAT^4 - kATcool^4 , no difference just rearranged terms

And yet, the amount of radiation emitted from P varies with that temperature...and the equation is still only describing gross energy movement from P. There is not enough information there to derive net anything.

t

 

[IanC]

now you are telling us their experiments were done in a vacuum at zero Kelvin? hahahahaha

the gross flow of radiation from any object is kT^4. it is always there.

net flow is kT^4 minus the amount of radiation the object receives back from the environment.