  The probability distribution function for thermodynamics and econophysics is
obtained by solving an equilibrium equation. This approach is different from
the common one of optimizing the entropy of the system or obtaining the state
of maximum probability, which usually obtains as a result the Boltzmann
distribution. The Gamma distribution is proposed as a better equation to
describe the blackbody radiation in substitution of Planck's radiation
equation. Also, a new form of entropy is proposed, that maintains the correct
relation with the Clausius' formula.
