Understanding Planck Units: The Impact of kB in Temperature Definition

[Sunfire]

Hello,

Planck units are defined here
http://en.wikipedia.org/wiki/Planck_units

Length, mass and time are defined via G, c and \hbar and do not involve k_B;
But temperature contains all G, c and \hbar and k_B;

Perhaps this is okay; just seems "uneven" that k_B appears with a zero power in the definitions of length, mass and time but with nonzero power in the definition of temperature.

It seems a bit "ad hoc"... Would anyone have a comment on these definition choices?

 

[mfb]

Mass, space and time are connected both via gravity and via quantum theory. This is not true for temperature. It is just (directly) related to energy.

It is not a choice. If you set all those constants to 1, you have no choice how to get Planck units (apart from constant prefactors).

 

[Sunfire]

The reason I am asking is I read this thread (thread) on Planck units.

It says that c, G and \hbar form a "vector basis" (1,0,0) (0,1,0) and (0,0,1) where adding vectors corresponds to multiplication of units.

It is interesting that adding k_B happens only for temperature, as if temperature has a "4-dimensional" unit, while L, T, M are less-dimensional. Wondering what the implications of this could be.