(color online) (a) The angular velocity of the torsion balance turntable at the 10th hour (black line). (b) The angular velocity of the torsion balance turntable versus time during the whole experiment. The green line is the fitting line of the angular velocity. It is clear that the angular velocity of the torsion balance turntable undergoes not only the whole quadratic slow drift but also the cosine oscillation fluctuation.