The Moon is wobbling our planet so much that it's currently deciding how long our days are.
April 15, 2026
Original Paper
Lunar nutation effect defines the sign of the Earth rotation rate for now, but this may change soon
arXiv · 2604.11126
The Takeaway
We usually think of the Earth's rotation as slowing down gradually over millions of years, but this paper shows that our current day-length changes are actually being driven by an 18.6-year 'lunar nutation' cycle. The Moon's gravitational tug causes the Earth to wobble, and right now, that wobble is the main factor in whether we need to add a 'leap second' to our clocks. The study warns that this trend is about to shift, which could mess up the precision timing systems that run our GPS and internet. It’s a reminder that we aren't just spinning in a vacuum; the Moon is actively 'tuning' our planet’s speed like a cosmic dial.
From the abstract
The Earth slowly decelerates in its rotation due to the energy dissipation caused by the interaction to the Moon. This leads to the continuous increasing of the length of the mean solar day (aka, length-of-day, or, LOD) relatively to 86400 solar seconds at average secular rate of +1.8 ms per century. But, on a shorter time scale the process is uneven. A positive leap second is used to be introduced on regular basis to support a consistency between the astronomical and atomic time scales. However