  A quantum-mechanical theory of gravitation is presented, where the motion of
particles is based on the optics of de Broglie waves. Here the large-scale
geometry of the universe is inherently flat, and its age is not constrained to
< 13 Gyr. While this theory agrees with the standard experimental tests of
Einstein's general relativity, it predicts a different second-order deflection
of light, and measurement of the Lense-Thirring effect in the upcoming NASA
experiment Gravity Probe B.
