Wilhelm Wien

“ For example, If a process were known by which the wavelengths could be changed in a manner such that the entropy increases without an expenditure of work and without absorption, then the distribution of energy in the spectrum of a blackbody would be completely determined from the condition of maximum entropy. As I have shown in an earlier work, it is always possible to state the entropy of radiation of known intensity and color, but for the time being there are no known physical processes that would cause such a change in color. ”

“ Even though the shift in the radiation of a blackbody with temperature, and the distribution over all wavelengths can be derived on the basis of the electromagnetic theory of light in a purely thermodynamic way without the help of any special hypotheses, It has not yet been possible to determine the distribution of the energy itself. ”

“ Now for radiation emitted by a molecule, of velocity , it is completely unknown how the radiation depends on the state of the molecule. The view that the electric charges in the molecules can excite electromagnetic waves is nowadays generally accepted.
We hypothesize that each molecule emits radiation with a wavelength that depends only on the velocity and has intensity that a function of that velocity. ”