The MOND theory (Modified Newtonian Dynamics) initiated by Milgrom has established itself as the most important model for explaining the measured rotation curves of galaxies without the aid of ominous dark matter. The core element of MOND is the so-called fundamental acceleration a0 with a value of approx. 1.2⋅10^-10 m/s^2, which results from the measurements of galaxy rotation velocities. At accelerations close to or below this value, neither Newton's nor Einstein's gravitational models work reliably.Critics of the MOND theory argue that this value is an ad-hoc "fudge factor" that was not derived from a fundamental consideration of space and time. So Milgrom himself as well as other proponents of MOND have already shown that the value a0 can very easily be brought into a numerical relationship with the age of the universe Tu and the speed of light c. In this paper, I would now like to show that this numerical correlation is no coincidence, but can be derived by consistent application of Heisenberg's energy-time uncertainty relation on a cosmic scale. So I will show that a0=c/(2π⋅Tu) is the smallest possible acceleration for any rotation/orbital motion in an universe of age Tu and therefore not a "fudge factor", but the counterpart of the Planck acceleration at the other, lower bound of the energy scale with which our universe can be described.