Einstein's $R^{\hat{0} \hat{0}}$ equation for non-relativistic sources   derived from Einstein's inertial motion and the Newtonian law for relative   acceleration
  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. 
Christoph Schmid (ETH Zurich, Institute for Theoretical Physics, 8093   Zurich, Switzerland)
gr-qc