  Flat space-time has not heretofore been thought a suitable locus in which to
construct model universes because of the presumed necessity of incorporating
gravitation in such models and because of the historical lack of a theory of
gravitation in flat space-time. It is here shown that a Lorentz-invariant
theory of gravitation can be formulated by incorporating in it the mass-energy
relation. Such a theory correctly predicts the well-known relativistic effects
(advance of perihelion, gravitational refraction, gravitational red shift, echo
delay of sun-grazing radio signals, and others). The equations of motion,
properly stated, are also seen to be identical to those of electromagnetism and
lead to the correct prediction of gravitational radiation. Therefore Milne's
kinematic model of the universe, mappable into his dynamical (or Newtonian)
model, offers a unique alternative to the general relativistic models which are
encumbered with both theoretically and observationally objectionable features.
