  MOG is a fully relativistic modified theory of gravity based on an action
principle. The MOG field equations are exactly solvable numerically in two
important cases. In the spherically symmetric, static case of a gravitating
mass, the equations also admit an approximate solution that closely resembles
the Reissner-Nordstrom metric. Furthermore, for weak gravitational fields, a
Yukawa-type modification to the Newtonian acceleration law can be obtained,
which can be used to model a range of astronomical observations. Without
nonbaryonic dark matter, MOG provides good agreement with the data for galaxy
rotation curves, galaxy cluster masses, and gravitational lensing, while
predicting no appreciable deviation from Einstein's predictions on the scale of
the solar system. Another solution of the field equations is obtained for the
case of a a spatially homogeneous, isotropic cosmology. MOG predicts an
accelerating universe without introducing Einstein's cosmological constant; it
also predicts a CMB acoustic power spectrum and a mass power spectrum that are
consistent with observations without relying on non-baryonic dark matter.
Increased sensitivity in future observations or space-based experiments may be
sufficient to distinguish MOG from other theories, notably the LCDM "standard
model" of cosmology.
