In planetary systems, the problem arises whether gravity attracting the planets towards the central star has an instantaneous action or propagates with finite velocity. Laplace noticed that, if gravity propagated with finite velocity, planets motion would become unstable due to a torque originating from time lag of the gravitational interactions. Given that equations describing gravitational interaction are formally the same describing electrostatic interactions, we have performed an experiment meant to measure the time/space evolution of the electric field generated by a uniformly moving set of electrons. The results we obtain seem compatible with an electric field rigidly carried by the beam itself.
