Few of us think about the fact that the Earth rotates until a sudden movement, earthquake or volcanic eruption brings us to mind. Geologists, however, have a little more insight into Earth’s internal dynamics and have discovered that Earth’s solid inner iron core, which normally spins in a molten outer crust with almost no friction, appears to have slowed down. It’s not the first recording of such an event, with no one panicking and chasing after a terrifying sci-fi movie from 20 years ago, hoping to find a solution to such an event in hopes of inspiring it. This is not even a first in recent history.

“We show surprising observations that the inner core has almost stopped spinning in the last decade and may be experiencing a reversal in perennial oscillations, with another turning point in the early 1970s,” said geophysicists Yi Yang and Xiaodong Song from Beijing. The university in Beijing writes in their published papers.

That the Earth’s inner core rotates with respect to the mantle above it has been known for only a few decades, since it was confirmed in 1996 by Song of Columbia University and his seismologist colleague Paul Richards. Prior to his work, the idea that the Earth’s inner core rotates separately from the rest of the planet was an unproven theory predicted by an unproven model of Earth’s magnetic field. Since then, scientists have been trying to figure out how fast or slow the inner core spins from a distance of 5,100 kilometers (or 3,170 miles).

The inner core was originally thought to make a complete revolution every 400 years, with electromagnetic torque and balanced gravitational force. But other scientists soon theorized that it rotated much more slowly and took 1,000 years or more to complete a full rotation. The speed of this turn and whether it has changed is still debated. However, the inner core continues on its merry way, unaware of the heated discussion above.

Deciding, Song went back to the same method he and Richards had used to conclude that the inner core had rotated. In 1996, the duo monitored seismic wave readings from repeating earthquakes, called doubles, that passed through the inner core from the south Atlantic to Alaska between 1967 and 1995.

If the inner core had not moved, the shock waves would have followed the same path. However, Song and Richards showed that seismic waves accelerated by fractions of a second from the 1960s to the 1990s. Now, in a new study with Young, Song has reviewed this old data, comparing it to more recent patterns of nearly identical seismic waves that show the inner core slows to a halt and can even reverse. They found that since about 2009, paths that previously showed significant time variation have changed little as seismic waves pass through the core and exit on the other side. Any time difference is gone.

“This globally consistent pattern suggests that the rotation of the inner core has recently stopped,” Yang and Song write.

Also, Yang and Song say that this recent closure of the inner core appears to be related to a change in rotation, as the hard iron sphere shifted the other way as part of a seventy-year oscillation.

According to his calculations, a small imbalance of electromagnetic and gravitational forces would be enough to slow and then reverse the rotation of the inner core, as observed.

Not all researchers point out that the seventy-year lapse coincides with other periodic changes seen on the Earth’s surface, such as day length and magnetic field, both of which have a periodicity of sixty to seventy years. The decade-old patterns of climate observations, global average temperature, and sea level rise also seem to be in strange harmony.

According to Yang and Song, this frequent, slow, barely perceptible oscillation, oscillating back and forth every 60-70 years, seems to point to “a system of resonances in different layers of the Earth” – as if the entire planet hums in the same way. tuning

Because the Earth’s inner core is believed to be dynamically connected to its outer layers, electromagnetically linked to the outer core and connected to the mantle by gravitational forces, the study could also help us understand how processes occurring deep within our planet affect our planet. its surface – the thin crust that sits on top of the swirling internal environment on which we live.

“These observations show a dynamic interaction between Earth’s layers, from the deepest depths to the surface,” Yang and Song said.