  Knowing the magnitude of the energy flow inherent to zero-point radiation
allows us to approach the question of its possible interaction with particles
of matter. Its photons are not different from the rest, and must in principle
be subject to the Compton effect and the Klein-Nishima-Tann formula for its
cross section. On this assumption, it is shown here that zero-point radiation
may be powerful enough to explain Poincar\'e's tensions and to supply an
efficient cause for gravitation. This could be only the case if the classic
radius of the electron measures $8.143375\times10^{20}q_\la$, where $q_\la$ is
the minimum wavelength for electromagnetic radiation, and if the wavelength of
the most energetic photon in the actual zero-point radiation is
$5.275601\times10^{27}q_\la$. To the first of these numbers there corresponds
the energy $3.5829 \times10^{23}$ MeV for the photon whose wavelength is
$1q_\la$. This gives also the relation $q_\la=(2 \pi \al)^{1/2}L_P$, where
$L_P$ is the Planck Length. Finally the relation between the force of gravity
and the electrostatic force is explained by the equations obtained in this
paper.
