What is Negative Temperature and How Does it Work?

[hagopbul]

so is it impossible to Reich the 0 Kelvin or not

 

[christianjb]

3rd law of thermodynamics says yes. You can only get asymptotically close.

 

[vivesdn]

You would need something below zero to cool your system up to 0K. But 0K is the lowest temperature possible. So there are no means you can use to get to 0K.

 

[daniel_i_l]

According to QM the answer is no, because if the momentum of all the particles is known to be 0 then you have no knowlage of the position of the particles - but if you know where they are then there's always some uncertainty in their momentum.

 

[Crosson]

Fix an object at temperature x. Now, if I have several other objects of lower temperatures $$y_1,y_2,...,y_n$$. What do these y values represent?

The answer is that the objects with the smaller y values will absorb more heat in a given amount of time. The problem of course with a zero temperature object is that it would absorb infinite heat in an arbitrarily short time i.e. for any objects x, y and any amount of wattage there are temperatures the objects could have could have so as to exchange energy at that rate.

Negative temperature is not a contradiction, these are systems that become "cooler" when you heat them up, that is they become more willing to receive energy at from another object of given temperature.