[alancalverd]

ES's theoretical test object at 0K raises some interesting questions. Since theory predicts that you can't bring an object to 0K, it rather looks like dividing 0 by 0 with a predetermined idea of the result instead of admitting that the result is undefined. In other words,  ES has devised a "thought experiment" that can't be done and is therefore not an experiment!

[Bored chemist]

Then the next question is what is thermal energy?

The same as it was when you started this thread 4 years ago.
What have you learned in the meantime?

[paul cotter]

"Same as it ever was", as the song said(David Byrne-Talking Heads for those not familiar).

[paul cotter]

Following up on the test tube with water being heated, here is something NOT to do and I repeat NOT. Faced with a dirty pyrex boiling tube which resisted cleaning I added water to a depth of about 2 inches and added conc sulphuric acid to a depth of about 1 inch and applied vigorous heating at the base. Some time later I was surprised that boiling had not ensued and I gave the tube a slight shake and whoosh, the entire contents of hot acid and boiling water exploded out of the tube. The acid had not mixed significantly with the water and with a boiling point in the region of 300c it was not going to boil for quite some time and shaking the tube led to mixing and a subsequent runaway reaction.  My mistake was a failure to thoroughly mix acid and water before heating.

[hamdani yusuf (OP)]

ES's theoretical test object at 0K raises some interesting questions. Since theory predicts that you can't bring an object to 0K, it rather looks like dividing 0 by 0 with a predetermined idea of the result instead of admitting that the result is undefined. In other words,  ES has devised a "thought experiment" that can't be done and is therefore not an experiment!

What is 0 in numerator, and 0 in denominator refer to?

[hamdani yusuf (OP)]

Then the next question is what is thermal energy?

The same as it was when you started this thread 4 years ago.
What have you learned in the meantime?

What is it?
Do you have any information that ChatGPT doesn't?

[alancalverd]

Then the next question is what is thermal energy?

The kinetic energy of the particles inside a boundary.

[hamdani yusuf (OP)]

Then the next question is what is thermal energy?

The kinetic energy of the particles inside a boundary.

That would include rotational motion of a spinning magnet.

[hamdani yusuf (OP)]

Following up on the test tube with water being heated, here is something NOT to do and I repeat NOT. Faced with a dirty pyrex boiling tube which resisted cleaning I added water to a depth of about 2 inches and added conc sulphuric acid to a depth of about 1 inch and applied vigorous heating at the base. Some time later I was surprised that boiling had not ensued and I gave the tube a slight shake and whoosh, the entire contents of hot acid and boiling water exploded out of the tube. The acid had not mixed significantly with the water and with a boiling point in the region of 300c it was not going to boil for quite some time and shaking the tube led to mixing and a subsequent runaway reaction.  My mistake was a failure to thoroughly mix acid and water before heating.

Thanks for sharing your experience. People say that experience is the best teacher. But we should not rely on our own experience in learning about safety issues. We need to learn from someone else's mistakes. We won't have enough time to make them all ourselves.

[hamdani yusuf (OP)]

What I have learned so far, is that there are different usages of the term temperature, such as thermodynamics temperature, noise temperature, antenna temperature. The concept itself was meant to predict the direction of energy transfer between two objects when they are allowed to interact.
Thermodynamics temperature is mostly measured by heat conduction between the measured object and the thermometer. While antenna temperature is specifically measured by electromagnetic radiation between the measured object and the receiving antenna. It's an analogy to thermodynamics temperature, which was introduced first.

[hamdani yusuf (OP)]

Here's a thought experiment. A pair of large centrifuge tubes containing a heavy gas, eg SF6 at 1 bar absolute, 300K, isolated and freely floating in outer space. The centrifuge is spinning at 100 rps, with effective radius of 1 meter. The gas particles move slower the closer they are from the axis of rotation, and faster the further away from the axis. This creates temperature gradient within the system, which can be used  by a thermoelectric generator. The electricity is then used to power a laser beam aimed to outside of the system.
How the system will deplete its internal energy?
What happens to its angular momentum? Will it be conserved?

[hamdani yusuf (OP)]

The atoms within your rod have no idea how fast the rod is travelling in space if the speed is constant, but they do know what happens when they bash into each other. If you decelerate the rod by crashing into a brick wall, the energy transferred to the wall will be the  0.5mv2 component of the rod plus its heat content, but we are no longer talking about the original bounded ensemble.

Perhaps some variations of this experiment can improve our understanding.

We can use cooled magnet. Or a superconductor as the stopper.

[Bored chemist]

What happens to its angular momentum? Will it be conserved?

Yes.
And I didn't need to read the rest of your post.
So, we can work back from that fact.
Thus we deduce that you are wrong somewhere in your argument.
Feel free to find out where.

[hamdani yusuf (OP)]

Thus we deduce that you are wrong somewhere in your argument.

What makes you think that there's something wrong?
I haven't even made any conclusion.

[Bored chemist]

I haven't even made any conclusion.

How the system will deplete its internal energy?

You can't ask how something happens without concluding that the thing happens.

Are you sure that energy is available to drive a laser?

Are you sure that there will be a change in angular momentum?

[alancalverd]

The gas particles move slower the closer they are from the axis of rotation, and faster the further away from the axis.

Why use a gas? The molecules of any spinning wheel are moving faster at the edge, so you can extract energy  by fixing a thermocouple to any rotating object. Problem is that nobody else can!

Your fallacy is in confusing gross motion of a body with thermal motion of the particles inside it..

[hamdani yusuf (OP)]

You can't ask how something happens without concluding that the thing happens.

A conclusion is

a judgment or decision reached by reasoning.

the necessary consequence of two or more propositions taken as premises

You are confused between conclusion and proposition.

[hamdani yusuf (OP)]

Are you sure that energy is available to drive a laser?

As long as the extractable energy is non-zero, the system can be upscaled until it's enough to drive a laser.

[hamdani yusuf (OP)]

What happens to its angular momentum? Will it be conserved?

Yes.
And I didn't need to read the rest of your post.

Are you sure that the laser doesn't carry away some of the system's angular momentum?

[hamdani yusuf (OP)]

The gas particles move slower the closer they are from the axis of rotation, and faster the further away from the axis.

Why use a gas? The molecules of any spinning wheel are moving faster at the edge, so you can extract energy  by fixing a thermocouple to any rotating object. Problem is that nobody else can!

Because the thermometer can be stationary in the frame of reference of the tubes, while in relative motion against the gas particles to exchange their thermal energy.
The gas is chosen for the simplicity of equation connecting its temperature and its kinetic energy.
E=nRT d/2