  The union of high-energy particle theories and gravitation often gives rise
to an evolving strength of gravity. The standard picture of the earliest
universe would certainly deserve revision if the Planck mass, which defines the
strength of gravity, varied. A notable consequence is a gravity-driven, kinetic
inflation. Unlike standard inflation, there is no potential or cosmological
constant. The unique elasticity in the kinetic energy of the Planck mass
provides a negative pressure able to drive inflation. As the kinetic energy
grows, the spacetime expands more quickly. The phenomenon of kinetic inflation
has been uncovered in both string theory and Kaluza-Klein theories. The
difficulty in exiting inflation in these cases is reviewed. General forms of
the Planck field coupling are shown to avoid the severity of the graceful exit
problem found in string and Kaluza-Klein theories. The completion of the model
is foreshadowed with a suggestion for a heating mechanism to generate the hot
soup of the big bang.
