Earth is "falling out" of its 24-hour rhythm – what scientists discovered

Scientists have found that the length of Earth's day changes by several milliseconds due to the movement of the planet's inner core. Researchers from the University of Alberta compared three mechanisms with data from 1964 to 2019 and concluded that the gravitational pull of the inner core may be the primary driver of multi-decade variations.

Scientists have discovered that the length of Earth's day changes by several milliseconds due to the movement of the planet's inner core. Researchers from the University of Alberta — PhD student Huifeng Zhang and Professor Mathieu Dumberry — compared three possible mechanisms with observed changes in day length from 1964 to 2019. They examined magnetic forces at the core-mantle boundary, the movement of liquid iron in the outer core, and the gravity of the inner core. According to a model based on seismic wave data, the inner core may rotate about 2.35 degrees in one direction and then swing back relative to the mantle, like a pendulum. The full cycle takes about seven decades. The gravitational torque matched the data both in magnitude and temporal dynamics. The authors concluded that the gravitational influence of the inner core may be the main mechanism behind multi-decade changes. The height of irregularities on the core's surface is estimated at 11–29 meters, and the core's displacement relative to the mantle is about 0.12 degrees per year. Seismologist John Vidale noted that none of the existing models fully explain all observations yet.