  We study the radion stability and radion mass in the framework of the
Horava-Witten (HW) heterotic M-Theory on $S^{1}/Z_{2}$, and find that the
radion is stable and its mass can be of the order of GeV. The gravity is
localized on the visible brane, and the spectrum of the gravitational
Kaluza-Klein (KK) modes is discrete and can have a mass gap of TeV. The
corrections to the 4D Newtonian potential from the higher order gravitational
KK modes are exponentially suppressed. Applying such a setup to cosmology, we
find the generalized Friedmann-like equations on each of the two orbifold
branes.
