  The atomic scale is the only relevant thermodynamic scale in our universe,
since quantum properties restrict classical considerations of subatomic physics
and disappear for larger scales. Then the characteristic energy that dictates
the value of the unit of temperature can be the classical thermal energy
defined for simplest atoms. It is shown that vibrational frequency of a
classical model hydrogen atom, of the radius of its Rydberg wavelength, is in
far-infrared range and from its quantum of energy one can obtain the value of
Boltzmann's constant that serves as the measure of the absolute temperature in
kelvins.
