Consider a hydrogen atom, with orbitals describing movement of an electron about a proton, together bound by the electromagnetic force. Next consider an equivalent "atom" made up of two massive neutral particles, where the gravitational force at a given separation is the same as the Coulomb force between the above proton and electron, and with a similar center of mass as hydrogen. Is the quantum interpretation for the trajectories of the latter case essentially the same as that of the hydrogen atom? How does the spectrum appear, and is it of gravitational radiation rather than electromagnetic? Otherwise, is the situation now correspondently classical?