Question

find the time interval when the object was at rest?​

Answer 1

The time interval dt0 in a stationary frame (earth ground station), is measured by an observer at rest at a particular spatial point L0 in the stationary frame, where dL0=0 in Eq. (13.11). On the moving frame (satellite), the proper time t and time interval dt, and proper length interval L and length interval dL of objects at rest on the moving frame are measured by an satellite-based observer at rest on the moving frame. From Eq. (13.11), with dL0=0, one obtains the relation between the moving frame (satellite) proper time interval dt and the stationary (earth ground station) frame time interval dt0, where