Earth's rotation fluctuates due to core and mantle interactions

Research into Earth's rotation reveals that the length of a day can fluctuate by several milliseconds due to complex interactions deep within the planet. While a day is generally considered to be 24 hours, the actual time it takes for the planet to rotate on its axis varies over decades.

While surface phenomena such as hurricane winds, rising sea levels from melting glaciers, and intense earthquakes can redistribute mass and affect rotation, scientists have identified deeper causes. The liquid outer core, composed primarily of iron and nickel, rotates at a different rate than the layers above it. This differential rotation between the outer core and the mantle involves the exchange of angular momentum and energy.

These shifts are driven by electromagnetic forces, gravitational torque, and angular momentum transfer. Observations suggest that the lowermost mantle may conduct electricity, allowing the flow of the molten outer core to exert electromagnetic stress on it, effectively coupling the two layers and influencing the planet's overall spin.