Overview

• An international team from Peking University and the University of Southern California reports seismic evidence that the solid inner core’s relative rotation has decelerated based on data from 1990 to 2021.
• The analysis of global earthquake wave travel times indicates a slowdown to near standstill relative to the mantle and crust, with a possible reversal of direction.
• The finding aligns with earlier indications of a roughly 70‑year rhythm in inner‑core behavior.
• Potential effects include subtle changes in Earth’s day length by milliseconds and gradual adjustments in the geomagnetic field that could influence satellites, communications and animal navigation.
• Researchers emphasize that impacts would develop over years to decades and that further analyses and independent confirmation are needed to refine estimates.