  We present a minimal model for the quantum evolution of matter under the
influence of classical gravity in the Newtonian limit. Based on a continuous
measurement-feedback channel that acts simultaneously on all constituent masses
of a given quantum system, the model scales and applies consistently to
arbitrary mass densities, and it recovers the classical Newton force between
macroscopic masses. The concomitant loss of coherence is set by a model
parameter, does not depend on mass, and can thus be confined to unobservable
time scales for micro- and macroscopic systems alike. The model can be probed
in high-precision matter-wave interferometry, and ultimately tested in recently
proposed optomechanical quantum gravity experiments.
