We present the structure of space-time as an oscillating Hubble Scale Mass (HSM) particle in a viscous fluid of Planck mass relics. Due to this particle oscillations and its interaction with a residual Planck mass, spacetime is undergoing a damped harmonic oscillation. This means that spacetime has a physical structure and is therefore foamy on small scales. Applying our damped harmonic oscillator model to cosmology we rediscover the Friedman-Lemaitre equations for an expanding Universe. From the expanding Universe model we predict that cosmic acceleration, driven by an oscillating HSM and its gravitational interaction with a cosmic medium or Planck mass relics, manifests as the universe’s expansion accelerating over time, with a corresponding acceleration of roughly 10-10m/s2. Depending on the model, the “damping” aspect of the oscillator is interpreted as a constant dark gravity force which is also a representation of dark energy, a mysterious force causing the universe’s expansion to accelerate. We derive an estimate of the strength of this extra force in terms of the Gravitational constant, Planck mass, Hubble acceleration scale ???????????? , fine structure constant, cold dark matter ???????? , dark energy ????? and baryon density ???????? and provide evidence for the fact that this ‘dark gravity force’ explains the observed phenomena for an accelerating expansion of the Universe currently attributed to dark energy. Lastly we present a model for an accelerating expanding universe in the early Universe using an oscillating Planck mass particle in a viscous fluid of a Hubble scale mass as our space-time model.