Earth's inner core rotates at a different speed than the rest of the planet.

Earth's inner core is a solid sphere of iron and nickel roughly 70% the size of the Moon. It is suspended within the liquid iron outer core, which acts as a fluid buffer. This lack of a rigid connection allows the inner core to rotate at a different rate than the mantle and crust, a phenomenon known as differential rotation. Research published in 'Nature Geoscience' in 2023 by scientists Yi Yang and Xiaodong Song suggests this rotation follows a multidecadal cycle.In the 1990s, seismologists first discovered that the inner core was rotating faster than the surface by about 1 degree per year. However, more recent data from seismic waves generated by earthquakes indicates that this rotation slowed down significantly around 2009. This shift suggests that the core may undergo a periodic oscillation, speeding up and slowing down every 60 to 70 years. This cycle appears to correlate with small changes in the length of a day and variations in Earth's magnetic field.The rotation is driven by the electromagnetic torque generated by the geodynamo in the outer core and balanced by gravitational tugs from the mantle. Understanding these movements is crucial because the interaction between the inner and outer core generates the magnetosphere. This magnetic shield protects the planet from harmful solar radiation and cosmic rays. Continued monitoring of seismic data helps scientists map the deep interior processes that keep our planet habitable.