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Earth Rotation Variations and the Moon Apsidal-Nodal Effects
Earth rotation in recent epoch shows anomalies: its rotation velocity reached decadal maximum in 2024; the Chandler wobble (CW) of the rotation axis disappeared in 2018–2020, then resumed with a phase changed by 180^\circ
◦; the ampli-tude of the Free Core Nutation (FCO) decreased since 2021 as well. We analyzed the CW amplitude modulations since the 1850s and found out that they could be synchronized with the changes of the big moon (syzygies in perigee) events occur-ring at different celestial declinations. The series of such events, depending on the line of apsides direction, drifts over the 18.6-year lunar orbital precession cycle. Big full moons replace big new moons at the same phase of precession, with a{\sim}93∼93-year interval. Particular configurations coincide with CW minimums of the 1930s and 2020s. 433 (434)-day period of the Chandler wobble differs from the 412-day period of big full moon events, possibly producing a 23 (22)-year cycle in their mutual directions. Thus, the observed periods of amplification and decrease of the Chandler wobble and length of day (LOD) could naturally follow from the tidal variability as a result of the apsidal-nodal effects. The total {\sim} 186∼186-year cycle of conjunctions of perigee, the ascending node of the Moon and vernal equinox, with the latest event happening in 2024, could modulate other geophysical processes.