Negative Kelvin temperature? (Recent Science paper)

[Khashishi]

It doesn't change the result.

If you put two objects at different temperatures together, the reciprocal of temperature of both objects will spontaneously move toward each other. (The amount one moves versus the other depends on the thermal mass, aka the heat capacity.)

 

[h1a8]

Why not give a direct answer?
What happens to the negative temperature object (not the positive one) when it comes in contact with the positive temperature object? Which one?
The temperature would remain the same.
The temperature would become more negative.
The temperature would become less negative.

 

[Khashishi]

If you put a negative temperature object in contact with a positive temperature object, the negative temperature object will cool down and the positive temperature object will heat up. See reply #34 for what happens when the negative temperature object cools down.

 

[h1a8]

Does cooling down mean the temperature becomes less negative? Or more negative?

 

[Khashishi]

Read the second sentence of #34.

 

[h1a8]

Sorry, I see now. Thanks!

So this actually makes no sense (Unless there is a maximum possible temperature and lowest negative temperature). At what point does the negative temperature switches to a positive temperature without a limit?

 

[mfb]

See the old posts. It is much easier to consider the inverse temperature, where you don't have such a jump.

0, approached from positive values, is the lowest possible temperature, and 0, approached from below, is the highest possible temperature. If you keep cooling an object with negative temperature, its temperature will go down, it will approach "infinite temperature (no meaningful sign here)" and then have a positive temperature afterwards.

 

[h1a8]

And what else that doesn't make sense is if 2 negative temperature (different) objects come in contact then the greater negative temperature object would become warmer until it reaches absolute 0.

 

[jbriggs444]

And what else that doesn't make sense is if 2 negative temperature (different) objects come in contact then the greater negative temperature object would become warmer until it reaches absolute 0.

The very negative temperature object becomes warmer only until it reaches the temperature of the less negative temperature object. They will both settle toward a medium-negative value.

The continuum of temperature values is from 0 up through +/- infinity and on up toward zero. Absolute zero is both the limit to which negative temperatures cannot reach from below and to which positive temperatures cannot sink from above. As has been suggested, consider inverse temperatures with + and - infinity as the limits on either end of the scale and "zero" in the middle and it is the exact same thing.

 

[h1a8]

Ok I understand. One more question.

Can anyone touch an object of negative temperature feel and just feel a comfortable warmth they touch it? Meaning, it will not severely burn or disintegrate, them but just feel warm to the touch?

 

[mfb]

If thermal conductivity is low enough, it could work. But then you are actually touching an object where the surface has a normal positive temperature, while the interior might still have a negative one.

That is purely hypothetical - I don't think you can have a normal solid material that you could actually touch at a negative temperature.