Comparing Relativistic Theories Against Observed Perihelion Shifts of Icarus and Mercury

Abstract

This paper compares the post-Newtonian approximation (PNA) to general relativity (GR) for the relativistic perihelion shift calculations. Nelson’s PNA predicts 5/6 of GR’s perihelion shift. Using the original Universal Time (UT), Shapiro’s accurate, highly elliptical orbit for Icarus corroborates PNA while GR exceeds the error boundary. The Icarus result was λ = 0.75 ± 0.08 where λ=1 for GR and λ=0 for Newtonian theory. Studies of Mercury’s perihelion shift used timescales equivalent to lunar Ephemeris Time (ET) with the present Système International (SI) second, the basic time unit for all atomic timescales like International Atomic Time (TAI). Atomic timescales run faster than UT, because the SI second is 2.468E-8 s shorter than the original UT second. This is confirmed by the two observational reports using the original calibration data of 1955-1958, by the Improved Lunar Ephemeris used in the original calibration, by the linear divergence of TAI versus UT during 1958-1998, and by the 2.1 ms mean excess between a UT day and TAI day during 1958-1998. Time dilation was not included in the lunar theory, which is confirmed by timekeeping authorities. So, the undilated lunar ET second is shorter than Earth’s proper UT second. An ET timescale creates an additional, artificial perihelion shift for Mercury of 6.433”/cy. Other renowned relativists used a 1973 update for Earth’s general precession that now excludes the GR prediction while including the PNA prediction if the artificial Mercury shift is included in the calculations. Apparently, Nelson’s PNA is more accurate than GR.