Examination of the Change in the Earth's Rotation Rate From Ancient Chinese Observations of Lunar Occultations of the Planets.

摘要

A study is made of fifty-eight records of naked eye observations of occultations of the planets by the Moon chosen from the Chinese dynastic histories. These records cover the period from 68 B.C. to 575 A.D. Fifty-three of these records fall in the time period between 100 A.D. and 575 A.D., a period with no other known observations useful for Earth rotation studies. The observations are compared to topocentric ephemerides computed using Bretagnon's planetary theories VSOP82 and the Chapront-Touze lunar theory ELP2000-85. The area of the Earth from which an individual lunar occultation is observable is too large to produce a useful value of the acceleration parameter, C (Cr2=ET- UT), from untimed occultation records. However, the entire series of observation records produces a weak estimate for the value of C (12.6 s cy-2 to 35.7 s cy-2). The uncertainty in C is difficult to estimate. Overall, the check on the change in the rotation rate is very weak, but it represents the limit of what can be done with known, untimed occultation records.