Rotation, Equivalence Principle, and GP-B Experiment

The ultra-precise Gravity Probe B experiment measured the frame-dragging effect and geodetic precession on four quartz gyros. We use this result to test WEP II (Weak Equivalence Principle II) which includes rotation in the universal free-fall motion. The free-fall E"otv"os parameter eta for rotating body is < = 10**(-11) with four-order improvement over previous results. The anomalous torque per unit angular momentum parameter lambda is constrained to (-0.05 ± 3.67) \times 10**(-15) s-1, (0.24 ± 0.98) \times 10**(-15) s-1, and (0 ± 3.6) \times 10**(-13) s-1 respectively in the directions of geodetic effect, frame-dragging effect and angular momentum axis; the dimensionless frequency-dependence parameter {\kappa} is constrained to (1.75 ± 4.96) \times 10**(-17), (1.80 ± 1.34) \times 10**(-17), and (0 ± 3) \times 10**(-14) respectively.