Abstract
Variations in the rate of rotation of the Earth are determined from the comparison of the mean UT1 against an atomic time scale for the period of 7 years from 1956 to 1962. The mean UT1 is that obtained from the weighted mean of the data of eleven observatories which have kept good time observations for the period from 1955.5 to 61.5, and for-the remainning period from 1961.5 to 62.9 only the data of the Tokyo UT1 is used instead Corrections for the longitude variation which are used to obtain the true UT1 are calcu-lated from the instantaneous pole's coordinates of the Earth determined by the same authors solely from the time observation data. While, the atomic time scale is principally based on cesium frequency standards at the N. P. L. (England) and the N. R. L. (U. S. A.).
As a result of this comparison correction for the seasonal variation in the rate of rotation of the Earth is separated as follows,
where t is the fractions of year. As for the residual variations the general aspect of the clock-face of the “Earth Clock” may be represented by five pieces of straight lines with different inclinations for the fractional periods, 1956.057.2 (-115 × 10-10), 1957.2-58.5 (-165 × 10-10), 1958.5-60.4 (-150 × 10-10), 1960.4-62.3 (-130 × 10-10) and 1962.3- (-155 × 10-10 ?). In these residual variations, moreover, the existence of a periodic term of some 5.5 years is plausible, although it is not yet definite.
