Today’s textbooks of electromagnetism give the particular solution to Maxwell’s equations involving
the integral over the charge and current sources at retarded times. However, the texts fail to
emphasise that the choice of the incoming-wave boundary conditions corresponding to solutions of the
homogeneous Maxwell equations must be made based upon experiment. Here we discuss the role of these
incoming-wave boundary conditions for an experimenter with a hypothetical charged harmonic
oscillator as his equipment. We describe the observations of the experimenter when located near a
radio station or immersed in thermal radiation at temperature T . The classical physicists at the
end of the 19th century chose the incoming-wave boundary conditions for the homogeneous Maxwell
equations based upon the experimental observations of Lummer and Pringsheim which measured only the
thermal radiation which exceeded the random radiation surrounding their measuring equipment; the
physicists …