Remarks on Clock Synchronization
Space-time coordinates, like any other physical quantity, should be given by their own operational definitions. This means that we should point out a physical process which can be used to measure them by comparison with standard phenomena defining the system of units. In particular, in order to be able to measure time at distant points in a unique way we must synchronize all clocks present in the system. The choice of synchronization method defines the model of space-time obtained and significantly influences its properties, physical as well as mathematical, including the structure of the space-time symmerty group [1,2].