The gravitationally-induced collapse time expressed in (4) has also been derived in other ways. The original proposal is due to Diósi, who gets it from a master equation with gravitational damping term. It also arises from a conflict between quantum superposition and the equivalence principle of general relativity when one considers the wave function phases of systems evolving in accelerated and free-fall frames. The collapse time in (4) is strictly valid for stationary states. Tackling the dynamical evolution of the collapse would require solving the Diósi master equation.