A Gravitational Battle Within the Earth Is Changing the Length of Days

Scientists have shown that the inner core’s gravity and its misalignment with mantle mass irregularities drive small, long-term changes in Earth’s rotation speed. By combining seismic data on inner-core rotation with outer-core flow models, the study reproduced observed day-length variations from 1964 to 2019, revealing a previously unrecognized internal torque that subtly accelerates or decelerates the planet’s spin.