  Newton's inverse-square law of universal gravitation assumes constant mass.
But mass increases with speed and perhaps with gravity. By SR, mass is
increased over the rest mass by gamma. Rest mass is here postulated to increase
under gravity, by 1/alpha =1+GM/rc^2. We examine the consequences of
introducing this changing mass into Newton's law in flat spacetime. This
variable mass affects the metric, relative to an observer away from the
influence of gravity, contracting both lengths and times (as measured) by
alpha/gamma. The gravitational force, as in orbital calculations, differs from
Newton's law by the factor (gamma/alpha)^3, and is not quite inverse square.
Without adjustable parameters, this accounts fully for the classical tests of
GR. The postulated "fifth force" appears at the 10^-9 g level.
Gravitationally-influenced space remains Euclidean, but the mass-metric changes
make it seem curved when measured.
