Dynamics of the Moon

Abstract

Koziel’s results on the librations have been rediscussed. Some serious departures from independence of the errors were detected and have been allowed for. The results are

$$ \beta = 0.0006271 \pm 0.0000010 $$

$$ \gamma = 0.0002362 \pm 0.0000082 $$

These do not differ much from Koziel’s values but the uncertainties are larger. Both are consistent with results previously derived by comparison of results of different authors, and γ is consistent with a reinterpretation of a result of Yakovkin.

The effect of elasticity is considered. It is shown that the elastic strain does not contribute to the librations but would affect the perturbations of a satellite. Allowance for this difference reduces Michael’s estimate of 0.4015 for C/Ma ² to 0.4001 ± 0.0030, which would be consistent with either uniform density or with the value I found in 1936 after allowance for compressibility and a possible thin surface layer, namely 0.3971 ± 0.0007.