Time Scales

Time scales have traditionally provided the time of day and the season of the year, as well as time interval, and if it is to be of universal use the atomic scale must be coordinated with astronomical scales. Two major steps in the coordination have already been taken: the atomic unit has been defined in terms of the second of Ephemeris Time, and the scales were made to agree on 1st January 1958. If the rotation of the Earth were constant the scales would continue to agree, but because of the variations in the rate of rotation the atomic scale will diverge from the astronomical scale unless some adjustments are made to bring them together. The present method of adjustment is to apply a frequency offset from the nominal value to the oscillator from which the 1s timing pulses are derived and when necessary a step adjustment to the epoch of the signals. This method possesses serious disadvantages and it is suggested that all standard transmissions should operate at their nominal values provision being made to supply those users needing astronomical time with the difference between atomic and astronomical time.