Comparisons of et (solar) , ET (lunar), ut, and Tdt

Abstract

A fundamental dynamical scale, ET(solar), was formed from absolute, meridian circle observations, from 1835 to 1982. At 1967.0 the ET(solar) and SI seconds were equal to 1 part in 10⁹ and, from Morrison's (1979a) ET(lunar) scale, the ET(ILE) and SI seconds were equal to 1 part in 10¹⁰. The long term fluctuation in the Earth's rotation has been parabolic, instead of sinusoidal, for at least 350 y.