After decades of spinning slightly ahead of the surface, Earth’s inner core has started to lag behind it — a shift visible only via earthquake data, linked to millisecond variations in day length and to deep-planet processes that also shape the magnetic field

A hidden ball of iron deep beneath our feet has reversed its rotation, a shift that may reshape our understanding of how Earth's interior works. The post After decades of spinning slightly ahead of the surface, Earth’s inner core has started to lag behind it — a shift visible only via earthquake data, linked to millisecond variations in day length and to deep-planet processes that also shape the…