= Frame dragging
<Frame dragging> is the influence of <mass>-<energy> currents, especially rotation, on local inertial directions in <general relativity>. In a stationary axisymmetric <metric tensor>, an observer with zero <angular momentum> has coordinate <angular velocity> $\omega=-g_{t\phi}/g_{\phi\phi}$ when the other spatial coordinates are held fixed. Around a rotating source this can be nonzero even without an applied azimuthal <torque>.
<Gravity Probe B> tested the effect with four cryogenic <gyroscopes> in Earth orbit, comparing their <spin> directions with a guide-star reference. Its analysis separated the much larger <geodetic precession> from the smaller rotation-dependent drift. This tests a change of inertial orientation, rather than ordinary frictional dragging of the spacecraft.<Gravity Probe B: Final Results of a Space Experiment to Test General Relativity by C. W. F. Everitt and others>[Abstract and gyroscope experimental method]{ref}
Back to article page
