According to a recent study conducted by researchers from the University of Southern California (USC), seismic data confirms that the rotation of Earth's inner core has been slowing down since around 2010. The research, based on data collected from various earthquakes and nuclear tests, reveals that the inner core's slowing speed is causing subtle changes in the length of our days.

Using seismic waves and measuring their speed and interaction within Earth's layers, the researchers were able to estimate the position and movement of the inner core. Their findings indicate that the inner core is not only moving slower than the Earth's surface but has also been backtracking, marking a significant slowdown compared to previous decades.

"The inner core had slowed down for the first time in many decades," stated John Vidale, co-author of the study and a professor of Earth Sciences at USC. "Other scientists have recently argued for similar and different models, but our latest study provides the most convincing resolution."

The inner core, a hot, dense, and solid sphere made of iron and nickel, resides approximately 3,200 miles (5,150 kilometers) below the Earth's surface. It is surrounded by a liquid iron-nickel outer core and encased by a solid rocky mantle. The study reveals that the inner core's reduced rotation speed is primarily attributed to convection within the liquid iron outer core, which sustains Earth's magnetic field, as well as the gravitational forces exerted by the overlying mantle.

To reach their conclusions, the researchers analyzed seismic data collected from 121 repeating earthquakes occurring around the South Sandwich Islands in the South Atlantic between 1991 and 2023. Additionally, they incorporated data from several nuclear tests conducted worldwide.

This new study provides valuable insights into the dynamic nature of Earth's inner core and its impact on the planet's rotational patterns. While the changes in the length of our days remain subtle, they serve as a reminder of the intricate and interconnected systems that govern our planet. Further research is required to fully understand the implications of this slowing rotation and its potential long-term effects.