The rotation of Earth's inner core is slowing down

An illustrated globe of the Earth is cut open at its center, revealing different layers the higher up until a solid orange ball represents the core.

The rotation of Earth's inner core began to slow down more than a decade ago, altering the length of our days by fractions of a second. 

Researchers from the University of Southern California (USC) created renderings of the inner core's movement using seismic data recorded from various earthquakes and nuclear tests, both of which send vibrations through the planet. By measuring the speed and interaction of the seismic waves within the Earth's layers, researchers can estimate the position and movement of the inner core.