Physics question -> Max temperature ?

[The Last Conformist]

col is speaking in terms of the relativistic mass, which is gamma times rest mass.

Personally, I prefer not to speak of relativistic mass, but write out a gamma directly in the formula for kinetic energy.

 

[nonconformist]

Electromagnetic radiation is commonly assigned a temperature, specifically that of a black body that would radiate with the same spectral distribution.

Of course, this only makes sense for radiations that approximate blackbody radiation; others are sometimes called "non-thermal".

I'm saying that Rik said that temperature is the vibration of atoms (or soemthing to that effect) which is correct in terms of conduction and convection, but not in terms of radiation.

 

[The Last Conformist]

I must confess I do not understand what you are getting at.

 

[nonconformist]

Then you never shall.

 

[betazed]

I'm saying that Rik said that temperature is the vibration of atoms (or soemthing to that effect) which is correct in terms of conduction and convection, but not in terms of radiation.

correct. if temperature is defined as a measure of k.e of atoms/molecules (this is usually done when we say the temperature of that hot object is 200 C) then col's explanation of why there cannot be a maximum temperature works.

however, if we define temperature as a measure of radiative energy (this is usually done when talking of stars for example) then col's explanation needs to be modified as to why there is no limit to radiative energy.

 

[The Last Conformist]

Stellar surfaces are close enough to blackbodies that the definitions largely coincide in that context.

 

[aneeshm]

Beyond a point , though , the classical meaning of temperature ceases to be really meaningful ( if the density and temperaure are high enough , particles will dissociate into their constituents ) .

 

[nonconformist]

Beyond a point , though , the classical meaning of temperature ceases to be really meaningful ( if the density and temperaure are high enough , particles will dissociate into their constituents ) .

Thermal decomposition, or plasmas?

 

[betazed]

Stellar surfaces are close enough to blackbodies that the definitions largely coincide in that context.

huh?

how can you have a meaning of temperature in the kinetic energy sense for a black body? All that comes out from a black body (and hence all that you can measure) is a tiny amount of radiation and nothing else.

 

[The Last Conformist]

huh?

how can you have a meaning of temperature in the kinetic energy sense for a black body? All that comes out from a black body (and hence all that you can measure) is a tiny amount of radiation and nothing else.

You aren't confusion a black body with a black hole, are you?

Otherwise I do not see the problem. The radiation from a stellar atmosphere with kinetic energy sense temperature T is very close to black body radiation of temperature T.

 

[betazed]

You aren't confusion a black body with a black hole, are you?

no I am not.

Otherwise I do not see the problem. The radiation from a stellar atmosphere with kinetic energy sense temperature T is very close to black body radiation of temperature T.

to measure T in the k.e sense you need particle emission because particles have k.e.. A black body does not emit particles. it only emits radiation (actually an ideal black body emits nothing but we always make the assumption that it emits a little energy just enough to measure and not enough to change the energy of the body substantially). so you cannot have a T meausre in the k.e sense for a black body.