  Feynman one of the founders of Quantum Electronic Dynamics (QED) introduced
in his diagrams virtual particles as intermediate states of an interaction
process. Such virtual particles are not observable, however, from the
theoretical point of view they represent necessary intermediate states between
observable real states. Such virtual particles were introduced for describing
the interaction process between an electron and a positron and for much more
complicated interaction processes. Other candidates for virtual photons are
evanescent modes known from optics. Evanescent modes have a purely imaginary
wave number, they represent the mathematical analogy of the tunneling solutions
of the Schr\"odinger equation. Evanescent modes are present in the optical
processes of total reflection and in undersized wave guides for instance. The
most prominent example of the occurrence of evanescent modes is frustrated
total internal reflection at double prisms. In 1949 Sommerfeld
\cite{Sommerfeld} pointed out that this optical phenomenon represents the
analogy of quantum mechanical tunneling. The evanescent modes and tunneling
violate the theory of special relativity, obviously, they represent the
exception which proves the special theory of relativity. We demonstrate the
quantum mechanical behavior of evanescent modes \textbf{with digital microwave}
signals at a macroscopic scale of the order of a meter and show that evanescent
modes are well described by virtual photons as predicted by former QED
calculations.
