The theory of relativity introduces several effects that need to be taken into account when dealing with precise time measurements. According to special relativity, time passes differently for objects in relative motion. That is known as kinetic time dilation : in an inertial reference frame, the faster an object moves, the slower its time appears to pass (as measured by the frame's clocks). General relativity takes into account also the effects that gravity has on the passage of time. In the context of GPS the most prominent correction introduced by general relativity is gravitational time dilation : the clocks located deeper in the gravitational potential well (i.e. closer to the attracting body) appear to tick slower.