Electromagnetic waves, developing in vacuum or into matter, produce dynamical alterations of the space-time metric. This is a consequence of Einstein's equation, that we are able to solve explicitly in some circumstances. Solutions are in fact obtained by plugging on the right-hand side of the equation some appropriate energy tensors. Hence, the passage of a wave generates both electrodynamics and 'gravitational' (local and temporary) modifications of the molecular lattice of a dielectric. If the wave or the dielectric body are asymmetric, we could theoretically obtain a distribution of Newtonian-like forces with nonzero resultant. This hypothesis suggested a laboratory experiment where an electromagnetic signal applied to a ring with a particular geometry imparts a directional thrust in apparent violation of the action-reaction principle. This test was recently realized with success. Therefore, the present theoretical approach, once appropriately refined, may constitute a crucial referring point for further developments.