Thomas precession: Where is the torque?

Special relativity appears to violate the conservation of angular momentum L since it predicts that an accelerated gyroscope will precess, i.e., L will change in the absence of any applied torque. The paradox is resolved in a simple example by demonstrating that there is a torque present. The mass distribution in the gyroscope undergoes a relativistic distortion, and the center of mass is displaced away from the position of the accelerating force. The resulting torque τ=dL/dt. The model also shows the physical origins of spin-orbit coupling and of the ‘‘oscillating term.’’ A related calculation shows why a moving magnetic dipole has an electric dipole moment.