Accelerometers are used alongside gyroscopes in inertial navigation systems. Symmetry between inertial and gravitational mass results in general relativity. The direction of the velocity vector, relative to inertial axes is formula 49. Sciama referred to the effect of the acceleration dependent term as Inertial Induction. Consider a rigid body rotating about a fixed axis in an inertial reference frame. The missile uses inertial + terminal active radar guidance. Dynamic aeroelasticity studies the interactions among aerodynamic, elastic, and inertial forces. The measurement of time dilation by two observers in different inertial reference frames is mutual. Optical tracking helps to cope with a drift of inertial tracking. Classical theories that use the Galilean transformation postulate the equivalence of all inertial reference frames. For example, consider a stationary object in an inertial frame. This essentially means that the statistics are scale-invariant in the inertial range. In addition, the plasmoids density must be between the inertial and magnetic fusion criteria. Navigation is via both GPS and an inertial navigation system. An accelerating parcel of fluid is subject to inertial effects.