Earth’s inner core may have started spinning in the opposite direction, a tantalizing new discovery suggests

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A new study reveals that Earth’s solid inner core has paused its rotation and started spinning in the opposite direction instead.

The study, published Tuesday in the journal Nature Geoscience, notes that the research could advance understanding of how processes deep inside the planet affect its surface, including the length of the day.

Previous research has found that the planet’s inner core is separated from the rest of Earth by a liquid outer core, with the magnetic field affecting the rotation of the inner layer along with the gravitational effects of the mantle.

The scientists, including those from Peking University in Beijing, explained that this was previously inferred based on changes in the travel time between repeated seismic waves that must traverse the same path through the inner core.

However, how fast the inner core rotates, and whether it is variable, has remained unclear.

Seismic waves from near-identical earthquakes that have passed through the Earth’s inner core along similar paths since the 1960s were evaluated by researchers, including Yi Yang and Xiaodong Song, for the new study.

They specifically analyzed the variation in the waveform and travel time of these earthquakes and found that since 2009, the trajectories of seismic waves – which previously showed a large variation in travel time – showed “little change”.

“Here we analyze repeated seismic waves from the early 1990s and show that all trajectories that previously showed significant temporal changes showed little change over the past decade,” they wrote in the study.

The results indicate that the rotation of the Earth’s inner core has paused.

This may be related to a reversal of the inner core’s rotation as part of a seven-decade oscillation, indicating a “resonance system across the different layers of the Earth”.

These differences are related to changes in observations at the Earth’s surface, such as the length of the day, according to the study.

They noted that “this multi-decadal periodicity coincides with changes in many other geophysical observations, particularly day length and magnetic field.”

The new findings also shed new light on the interaction between Earth’s different layers.

“These observations provide evidence of dynamic interactions between Earth’s layers, from the deepest interior to the surface,” the scientists said in the study.

According to them, an earlier turning point occurred in the early 1970s.

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