  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 emphasize the role played by the
choice of the boundary conditions corresponding to solutions of the homogeneous
Maxwell equations. Here we discuss the role of these 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 homogeneous boundary
conditions for Maxwell's equation based upon the experimental observations of
Lummer and Pringsheim which measured only the thermal radiation which exceeded
the random radiation surrounding their measuring equipment. Today at the
beginning of the 21st century, classical physicists must choose the homogeneous
boundary conditions for Maxell's equations to correspond to the full radiation
spectrum revealed by the recent Casimir force measurements which detect all the
radiation surrounding conducting parallel plates, including the radiation
absorbed and emitted by the plates themselves. The random classical radiation
spectrum revealed by the Casimir force measurements includes electromagnetic
zero-point radiation, which is missing from the spectrum measured by Lummer and
Pringsheim, and which cannot be eliminated by going to zero temperature. This
zero-point radiation will lead to zero-point energy for all systems which have
electromagnetic interactions. Thus the choice of the boundary conditions on the
homogeneous Maxwell equations is intimately related to the ideas of zero-point
energy and non-radiating ground states which are introduced in classes of
modern physics.
