A study led by Wei Wang and John E. Vidale reveals that the Earth's inner core rotates relative to the mantle, with a super-rotation from 2003 to 2008, followed by a slower sub-rotation back to its original position from 2008 to 2023. The research uses 143 pairs of repeating earthquakes from the South Sandwich Islands, analyzed through PKIKP waves recorded by seismic arrays in northern North America. Waveform changes and reversals indicate the inner core's movement, with precise tracking of its progression and regression. The findings suggest that the inner core's rotation is more complex than previously thought, with a reversal in direction near 2010. The study also highlights the need for new models to explain the dynamics between the inner core, outer core, and mantle. The results confirm the inner core's slow, smooth rotation along a reversing path, with the sub-rotation being less than half as fast as the super-rotation. The study provides the most definitive evidence that the inner core moves relative to the rest of the Earth, with implications for understanding Earth's magnetic field and core dynamics. The research also notes that changes in the inner core boundary or outer core are unlikely, as PKP waveforms do not show significant changes. The study's methods and observations support the idea that the inner core's rotation is influenced by gravitational coupling with mantle density anomalies and core-mantle boundary topography. The findings contribute to the ongoing debate about the inner core's motion and its relationship with Earth's magnetic field.A study led by Wei Wang and John E. Vidale reveals that the Earth's inner core rotates relative to the mantle, with a super-rotation from 2003 to 2008, followed by a slower sub-rotation back to its original position from 2008 to 2023. The research uses 143 pairs of repeating earthquakes from the South Sandwich Islands, analyzed through PKIKP waves recorded by seismic arrays in northern North America. Waveform changes and reversals indicate the inner core's movement, with precise tracking of its progression and regression. The findings suggest that the inner core's rotation is more complex than previously thought, with a reversal in direction near 2010. The study also highlights the need for new models to explain the dynamics between the inner core, outer core, and mantle. The results confirm the inner core's slow, smooth rotation along a reversing path, with the sub-rotation being less than half as fast as the super-rotation. The study provides the most definitive evidence that the inner core moves relative to the rest of the Earth, with implications for understanding Earth's magnetic field and core dynamics. The research also notes that changes in the inner core boundary or outer core are unlikely, as PKP waveforms do not show significant changes. The study's methods and observations support the idea that the inner core's rotation is influenced by gravitational coupling with mantle density anomalies and core-mantle boundary topography. The findings contribute to the ongoing debate about the inner core's motion and its relationship with Earth's magnetic field.