The blackbody radiation is an open problem, in the sense that there is no classical counterpart to describe the spectrum in physical terms. The usual derivation of Planck implicitly assumes that the spectral density is a mean for a special kind of exponential distributions. There is however a case where the classical statistics makes sense for the spectrum, if we consider the spectral density as a probability density for the values of the frequency at a certain temperature. We show here this case and illustrate it on contemporary COBE-FIRAS data, pointing out to a special tensor nature of the cosmic background radiation. Some conclusions about the measurement process and about the progress in general are drawn.