# Tag Info

Yes frame dragging is related to vorticity; consider Kerr spacetime for simplicity in the following. In Kerr space-time one has a time-like Killing field $\xi^{\alpha}$. The congruence of observers $u^{\alpha} = \xi^{\alpha}/|\xi|$ following orbits of $\xi^{\alpha}$ are of course the observers who are at rest with respect to the central mass and hence are ...