  In 1917 F. Klein proposed his work on projective geometry to A. Einstein for
further developments of general relativity. Klein had a peculiar way to
consider the relationship between mathematics and physics, based on his
Erlanger Programm and geometrical modeling of physical phenomena. He was aiming
at a physical foundation for non Euclidean geometry. However, the letters he
wrote to Einstein had no sequel.
  We think that F. Klein's ideas still deserve some attention, as they can be
useful for modeling Maxwell's equations with a radically different approach
than resorting to field theories. One reason for looking for alternatives is
that current field theories use geometry exclusively as a formal technique
thereby inhibiting human intuition from grasping the physical world.
  This article collects cues that we deem relevant for a model of
electromagnetic received signals. In the first two chapters we highlight a few
features of classical physics, namely the trajectories of mass points, and the
differences in treating rotations between statics and dynamics. In the third
chapter, we finally review F. Klein's approach toward geometrical modeling of
electromagnetism and special relativity.
