Sources, transmitters, Hertz potentials, and radiation fields

The essay is concerned with that class of dynamical systems sufficiently isolated that the gravitational fields that they produce are asymptotically flat. It is argued that as far as the definitions of multipole moments and radiation fields are concerned, whether electromagnetic or gravitational, the original curved manifold is an unsuitable arena for their description. Instead, physical laws are to be formulated in space-times of image points. An example is the equality between the time rate of change of the gravitational quadrupole moment and the spin-2 Hertz potential. (author)