Based on the hypothesis that the combined matter and radiation energy of the universe is balanced by an equivalent amount of negative gravitational energy, a novel formulation of the Friedmann equation is examined. The hypothesis opens new avenues for studying the evolution of the universe. The expansion, initiated by the event of a vacuum fluctuation, is driven by the continuous occurrence of new positron-electron pairs. The current acceleration of expansion, gexp = 1,066·10-11 m/s2, emerges as a result of the study. It is mathematically shown that gexp causes a cosmic Coriolis effect responsible for the rotary velocity deviations in the galaxies. The effect eliminates the need for dark matter. The MOND theory is explained on a purely physical basis.