Earth Rotation: Measurement of TT-UT, -720 to +1950

Abstract

We present figures and tables of our results for DT=TT-UT in the period -720 to +1950 obtained principally from analyses of historical records of solar eclipses (-720 to +1600) and timings of lunar occultations ( + 1600 to + 1950) [1], These show changes in the Earth’s rate of rotation as measured in changes of the length of the day (lod). There is a long-term deceleration producing an increase in the lod of +1.72 ms cy-1. There are also centennial fluctuations in the lod of amplitude 3 ms. After +1600 the data are precise enough to reveal decade fluctuations of up to an amplitude of 4 ms.