Inner Core Gravity Tug-of-War Explains Decadal Shifts in Day Length
A new study published in Nature identifies gravitational torque from Earth's inner core as the primary driver of multidecadal changes in the length of a day. Researchers Huifeng Zhang and Mathieu Dumberry found that this gravitational influence competes with electromagnetic and topographic forces at the core-mantle boundary, which act as resisting mechanisms. These deep interior interactions have altered the day's length by several milliseconds between 1964 and 2019, providing new constraints on the physical properties of Earth's deep layers, including the viscosity of the inner core and the conductivity of the lowermost mantle.
