[Origin]

So you think you already understand it?
Explain yourself.

I asked if you are any clearer on what temperature is after these 10 pages of discussion.  I didn't say anything about my understanding.  So what do you think, any clearer?

[Eternal Student]

Hi.
     A few people, including myself, are just getting a bit uncertain what it is you ( @hamdani yusuf )  are trying to do.
As @Origin has mentioned there are 10 pages of stuff here now.   If you (Hamdani) get an opportunity perhaps you could think about and write down a summary of the situation so far.    You might include the following:
    1.   A short summary of what has been said or done so far and what you're happy with.
    2.   Some indication of what you're still uncertain of or would like to continue to discuss.
    3.   Some indication of your ultimate goal.  For example, do you wish to present new ideas about what a temperature is?

    You don't have to do this, you can obviously do whatever you want.   It's just that several people (including me) aren't following the thread well, several things are getting repeated and future comments are at risk of becoming off-target.

Best Wishes.

[hamdani yusuf (OP)]

How much can we remove until the difference can no longer be ignored?

It depends what you are doing.

Looks like what we've got here is a failure to communicate.

Let's get this straight. If I do X, then a lot of frequency spectra can be removed without changing the status as thermal radiation. On the other hand, if I do Y, then a slight changes of frequency spectra will make the radiation no longer thermal. The question will be, what are the criteria for actions in X and Y category?

[hamdani yusuf (OP)]

So you think you already understand it?
Explain yourself.

I asked if you are any clearer on what temperature is after these 10 pages of discussion.  I didn't say anything about my understanding.  So what do you think, any clearer?

Do you realize that this thread is placed in New Theories section?

[hamdani yusuf (OP)]

Hi.
     A few people, including myself, are just getting a bit uncertain what it is you ( @hamdani yusuf )  are trying to do.
As @Origin has mentioned there are 10 pages of stuff here now.   If you (Hamdani) get an opportunity perhaps you could think about and write down a summary of the situation so far.    You might include the following:
    1.   A short summary of what has been said or done so far and what you're happy with.
    2.   Some indication of what you're still uncertain of or would like to continue to discuss.
    3.   Some indication of your ultimate goal.  For example, do you wish to present new ideas about what a temperature is?

    You don't have to do this, you can obviously do whatever you want.   It's just that several people (including me) aren't following the thread well, several things are getting repeated and future comments are at risk of becoming off-target.

Best Wishes.

For me, the point of this thread so far is to see if my idea is new, at least some part of it, and for forum members who follow this. To do that, I need to know how the concept of temperature is currently understood by most people.
Here are some points I've learned.
- Temperature is mostly described as a measure of the kinetic energy of particles, which is related to their movements.
- But sometimes, temperature is also treated as potential energy, such as the case with Carnot engine and heat pump.

- It's also realized that not all kinetic energy is classified as thermal. Synchronized particle movements are usually not considered as temperature, such as translation of the whole object.

[Bored chemist]

Looks like what we've got here is a failure to communicate.

Yes.
We are not communicating because you keep ignoring the reply.

Let's get this straight. If I do X, then a lot of frequency spectra can be removed without changing the status as thermal radiation. On the other hand, if I do Y, then a slight changes of frequency spectra will make the radiation no longer thermal. The question will be, what are the criteria for actions in X and Y category?

Quote from: Bored chemist on 11/04/2022 13:12:55
Quote from: Bored chemist on Yesterday at 13:12:17
It depends what you are doing.

Whether or not a particular spectrum would be considered "thermal" or not, depends on the context.

Temperature is mostly described as a measure of the kinetic energy of particles, which is related to their movements.

Not really.
Thermal energy is any sort of energy.
So, the random movement of the particles of a gas is thermal energy
But so is the energy of vibrations of the molecules of the gas.
And half the time, that energy is potential energy stored in the springiness of the molecules.
The rotational energy is considered separately- because it doesn't exist for single atoms, only molecules.
And the electronic energy is also part of thermal energy- so the energy in oxygen carried by the excited singlet state of O2 is also thermal energy (Though that's not a big contributor at room temperature).
And in principle, you need to consider the potential energy due to magnetic moments
https://en.wikipedia.org/wiki/Magnetic_refrigeration


And it's only "thermal" energy if the energy is (ideally)  equally shared out between all these various forms.

So, did you not read the stuff about equipartition, or did you not understand it?

[Origin]

deleted.

[hamdani yusuf (OP)]

But so is the energy of vibrations of the molecules of the gas.

Isn't vibration a kind of movement?

[hamdani yusuf (OP)]

Whether or not a particular spectrum would be considered "thermal" or not, depends on the context.

What's an example where a particular spectrum would be considered "thermal" in one context, but not in another context?

[Bored chemist]

But so is the energy of vibrations of the molecules of the gas.

Isn't vibration a kind of movement?

And half the time, that energy is potential energy stored in the springiness of the molecules.

OK what I should have said is that half the energy (on average) is not kinetic energy but potential energy.

[hamdani yusuf (OP)]

And it's only "thermal" energy if the energy is (ideally)  equally shared out between all these various forms.

Since the ideal conditions are not usually met, then most of the time it's not considered as thermal?

[Bored chemist]

Whether or not a particular spectrum would be considered "thermal" or not, depends on the context.

What's an example where a particular spectrum would be considered "thermal" in one context, but not in another context?

A xenon arc lamp  gives a fairly good approximation to thermal spectrum- unless you look near the emission lines at the right hand end
https://en.wikipedia.org/wiki/Xenon_arc_lamp#/media/File:Xenon_arc_lamp_profile.png

The visible radiation from the sun is close enough to a thermal spectrum to let us estimate the temperature of the sun's surface.

But the emission lines were what allowed someone to demonstrate the existence of helium

[Bored chemist]

And it's only "thermal" energy if the energy is (ideally)  equally shared out between all these various forms.

Since the ideal conditions are not usually met, then most of the time it's not considered as thermal?

The equipartition  condition is usually met - at least to a very high degree of precision.
So , for example, a tungsten light bulb, a candle , or sunlight is a pretty good approximation to a thermal spectrum.

[hamdani yusuf (OP)]

Whether or not a particular spectrum would be considered "thermal" or not, depends on the context.

What's an example where a particular spectrum would be considered "thermal" in one context, but not in another context?

A bit of information reduces uncertainty by a half.
Your statement contains one bit of information, regardless of its correctness. Namely, thermality of a spectrum is not solely determined by its spectral distribution. There's at least another factor to consider in determining thermality, which you called context. The same exact spectrum can have different thermal status depending on its context. Is there any additional information on the  context which can reduce the uncertainty, and make our knowledge more precise?

[Bored chemist]

Whether or not a particular spectrum would be considered "thermal" or not, depends on the context.

What's an example where a particular spectrum would be considered "thermal" in one context, but not in another context?

A bit of information reduces uncertainty by a half.
Your statement contains one bit of information, regardless of its correctness. Namely, thermality of a spectrum is not solely determined by its spectral distribution. There's at least another factor to consider in determining thermality, which you called context. The same exact spectrum can have different thermal status depending on its context. Is there any additional information on the  context which can reduce the uncertainty, and make our knowledge more precise?

Yes there is.
That is why I provided it.
Did you somehow miss this bit?

A xenon arc lamp  gives a fairly good approximation to thermal spectrum- unless you look near the emission lines at the right hand end
https://en.wikipedia.org/wiki/Xenon_arc_lamp#/media/File:Xenon_arc_lamp_profile.png

The visible radiation from the sun is close enough to a thermal spectrum to let us estimate the temperature of the sun's surface.

But the emission lines were what allowed someone to demonstrate the existence of helium

[hamdani yusuf (OP)]

A xenon arc lamp  gives a fairly good approximation to thermal spectrum- unless you look near the emission lines at the right hand end

It's good approximation where it is, and bad where it is not.
What's the context or factor we need to consider in determining if a spectrum is thermal radiation or not?

[alancalverd]

A thermal spectrum is a continuum. An actual spectrum may have discrete bits added or subtracted, or may be entirely non-thermal.

[alancalverd]

But sometimes, temperature is also treated as potential energy,

No. It is a measure of potential, not energy.

[hamdani yusuf (OP)]

But sometimes, temperature is also treated as potential energy,

No. It is a measure of potential, not energy.

You're right. I should say that objects with higher temperature are some times treated like they have higher potential energy compared to the same/similar objects but at lower temperature.

[hamdani yusuf (OP)]

A thermal spectrum is a continuum. An actual spectrum may have discrete bits added or subtracted, or may be entirely non-thermal.

Take a continuous spectrum, but has flat distribution (up to certain frequency), instead of black body radiation. Is it considered thermal?
What do you mean by entirely non-thermal? Do you have an example?