Earth Rotation - GoKawiil

Study: Inner core's gravity pull tied to Earth's shifting day length

Researchers publishing in Nature propose that gravitational interactions between Earth's inner core and mantle help explain decades-long changes in the length of a day. Because the inner core rotates at a slightly different rate than the rest of the planet, it becomes misaligned with mass irregularities in the mantle, and the resulting gravitational pull works against other core-mantle interactions. Geophysicist Mathieu Dumberry and colleagues say this tug-of-war produces small accelerations and decelerations in Earth's spin over time.

wired.com · 2026-09-26

Study links Earth's inner core gravity to decade-scale day-length shifts

Researchers analyzed length-of-day (LOD) records from 1964 to 2019, after removing known effects from the atmosphere, oceans, tides and surface mass changes, to isolate multidecadal variations. They modeled these residual variations using torque equations that account for gravitational pull from the inner core alongside electromagnetic and topographic coupling at the core-mantle boundary, finding that gravitational torque from the inner core contributes to the slow, multidecadal changes in how long a day lasts.

nature.com · 2026-09-23