In a study of fundamental quantum interactions which models the generation of discrete waveform/particles as a local oscillatory function of an expanding inertial spacetime continuum, beta decay constitutes the propagation of a portion of the energy and power of the characteristic fundamental oscillation beyond its boundaries as the discrete waveform of the electron,. The expansion of spacetime results in a drop in its linear inertial density over time that is equal to a drop in its mechanical impedance over distance, where time and distance are related by the speed of wave propagation. This drop produces a change in wave force at the boundary of the fundamental, resulting in a wave transmission recognized as the electron and concomitantly in a frequency change for the fundamental from that of the neutron to that of the proton. The value of this change in force can be quantified as the rest mass energy of the electron divided by its rest angular wavelength, i.e. its reduced Compton wavelength, and the corresponding rate of change in the linear inertial density/mechanical impedance is shown to be equal to the Hubble rate, thereby coupling beta decay to the cosmic expansion rate which is shown to be exponential. The derivative of the fundamental oscillation wave force with respect to the expansion stress is shown to be the basis of quantum gravity. The Planck scale is shown to be a differential scale, and implications for the cosmic age are investigated.