The Chandler wobble and Solar day

TL;DR

This paper clarifies the physical origin of the Chandler wobble, emphasizing its independence from Earth's rotational axis motion and highlighting the role of gravitational effects in zenith distance measurements.

Contribution

It refines previous interpretations of the Chandler wobble by analyzing the gravitational influences on zenith distance variations and challenges the notion of Earth's rotation axis motion as its cause.

Findings

Chandler wobble is independent of Earth's rotation axis motion.

Zenith distance variations are influenced by gravitational effects, especially lunar perigee.

The analysis refutes the idea that the wobble is a phantom phenomenon.

Abstract

This work supplements the main results given in our paper "The Chandler wobble is a phantom" (eprint arXiv:1109.4969) and refines the reasons for which researchers previously failed in interpreting the physical meaning of observed zenith distance variations.The main reason for the Chandler wobble problem emergence was that, in analyzing time series with the step multiple of solar day, researchers ignored the nature of the solar day itself. In addition, astrometric instruments used to measure the zenith distance relative the local normal are, by definition, gravity independent, since the local normal is tangential to the gravitation field line at the observation point. Therefore, the measured zenith distances involve all the instantaneous gravitational field distortions. The direct dependence of the zenith distance observations on the gravitational effect of the Moon's perigee mass enables us to conclude that the Chandler wobble is fully independent of the possible motion of the Earth's rotation axis within the Earth.