It used to be that the inner core of Earth was spinning faster than the rest of the planet. Now it seems that the solid iron core in the middle of the planet is rewinding its rotation. This is a significant development and the implications are potentially far reaching because it means that Earth’s outer core will possibly slow down, decelerate, or even (theoretically) stop spinning altogether.
Seismologists are using seismic waves to examine the inner core of the planet. These waves travel through the Earth and reflect off its solid and liquid layers. They have been measured and analysed from the 1960s to the present day. The study found that the core of the earth has slowed down in the past decade.
The study also showed that the fastest direction of motion tilted 10 degrees away from the axis of the spin. What this means is that the inner core of the planet was spinning faster than the surface of the planet, but not as fast as the mantle.
This is the first time scientists have been able to accurately measure the speed of the core’s rotation. This is thanks to the immense gravitational field created by the mantle, which slows the planet’s spin.
This is just one piece of the puzzle. Other studies have shown that Earth’s magnetic field changes over time. But no one knows why these reversals occur. Some researchers think the reversals are due to the exchange of angular momentum. Others believe that they are due to gravitational coupling.