gjm comments on Entropy and Temperature - Less Wrong

26 Post author: spxtr 17 December 2014 08:04AM

You are viewing a comment permalink. View the original post to see all comments and the full post content.

Comments (96)

You are viewing a single comment's thread. Show more comments above.

Comment author: gjm 22 January 2015 04:43:37PM 1 point [-]

Temperature in the thermodynamic sense (which is the same as the information-theoretic sense if you have only ordinary macroscopic information) is the same as average energy per molecule, which has a lot to do with phase changes for the obvious reason.

In exotic cases where the information-theoretic and thermodynamic temperatures diverge, thermodynamic temperature still tells you about phase changes but information-theoretic temperature doesn't. (The thermodynamic temperature is still useful in these cases; I hope no one is claiming otherwise.)

Comment author: spxtr 22 January 2015 08:00:24PM 2 points [-]

You probably know this, but average energy per molecule is not temperature at low temperatures. Quantum kicks in and that definition fails. dS/dE never lets you down.

Comment author: gjm 22 January 2015 10:05:33PM 0 points [-]

Whoops! Thanks for the correction.

Comment author: Lumifer 22 January 2015 05:05:03PM 0 points [-]

Aha, thanks. Is information-theoretic temperature observer-specific?

Comment author: gjm 22 January 2015 05:18:38PM 0 points [-]
Comment author: dxu 22 January 2015 08:26:00PM 0 points [-]

I am somewhat amused that you linked to the same post on which we are currently commenting. Was that intentional?

Comment author: gjm 22 January 2015 10:02:00PM 0 points [-]

Actually, no! There have been kinda-parallel discussions of entropy, information, probability, etc., here and in the Open Thread, and I hadn't been paying much attention to which one this was.

Anyway, same post or no, it's as good a place as any to point someone to for a clarification of what notion of temperature I had in mind.