Practical implications of relativity for a global coordinate time scale

Frontiers of technology now need synchronization between remote clocks to an accuracy of about a nanosecond. Rate changes arising from the velocity and gravitational potential of a transported clock used for synchronization of a network must be accounted for. In addition, one cannot assume that the earth is an inertial frame, i.e., not spinning. If classical Einstein synchronization is used, where from the midpoint between clocks at A and at B, one simultaneously sends light pulses to A and B to synchronize them, two problems arise. First, the synchronization process will not be transitive; i.e., if A is synchronized with B and B with C, then A will not necessarily be synchronized with C. Second, starting at a point on the equator and transporting a portable clock eastward (westward), while establishing a synchronized time grid on the way, will result in a discontinuity upon returning to the original point of about −200 ns (+200 ns); minus (−) means that the portable clock will be late. This paper will discuss the construction of a coordinate clock network on the earth's surface which does not have these problems; i.e., synchronization is transitive, and there is no discontinuity. This may be done by adjusting clocks to read coordinate time on an underlying nonrotating local inertial frame. The theoretical and practical implications of setting up such a coordinate clock network using either electromagnetic signals (e.g., laser, Loran‐C) or portable clocks will be discussed. It will be shown how this network may be applied in making UTC or any other global scale more useful for state‐of‐the‐art navigation and communication systems.