  With Einstein's inertial motion (free-falling and non-rotating relative to
gyroscopes), geodesics for non-relativistic particles can intersect repeatedly,
allowing one to compute the space-time curvature $R^{\hat{0} \hat{0}}$ exactly.
Einstein's $R^{\hat{0} \hat{0}}$ for strong gravitational fields and for
relativistic source-matter is identical with the Newtonian expression for the
relative radial acceleration of neighboring free-falling test-particles,
spherically averaged.--- Einstein's field equations follow from Newtonian
experiments, local Lorentz-covariance, and energy-momentum conservation
combined with the Bianchi identity.
