Earth S Inner Core

Study links decades-long shifts in Earth's day length to inner core gravity

Researchers Hao Zhang and Mathieu Dumberry report in Nature that gravitational coupling between Earth's solid inner core and its mantle explains multidecadal changes in day length of a few milliseconds. They combined seismological data on inner-core rotation with a model of outer-core flow derived from magnetic field measurements to reach this conclusion.

nature.com · 2026-09-23

Study links Earth's day-length changes to core-mantle torque forces

A study published in Nature reports that small variations in the length of Earth's day, on the order of milliseconds over decades, can be explained by competing gravitational, mechanical and electromagnetic forces between Earth's solid inner core, molten outer core and rocky mantle. Researchers, including geophysicist Mathieu Dumberry, had long suspected core-mantle interactions caused these fluctuations but lacked clarity on which specific forces were responsible.

nature.com · 2026-09-23