Earth’s inner core rotating slower than surface, study suggests 


Some uncertainties with this topic. Researchers here propose a 70-year cycle, but other theories say 20-30 years, or even no cycle at all.
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Earth’s inner core, a hot iron ball the size of Pluto, has stopped spinning faster than the planet’s surface and might now be rotating slower than it, research suggested on Monday.

Roughly 5,000 kilometers (3,100 miles) below the surface we live on, this “planet within the planet” can spin independently because it floats in the liquid metal outer core, says Phys.org.

Exactly how the inner core rotates has been a matter of debate between scientists—and the latest research is expected to prove controversial.

What little is known about the inner core comes from measuring the tiny differences in seismic waves—created by earthquakes or sometimes nuclear explosions—as they pass through the middle of the Earth.

Seeking to track the inner core’s movements, new research published in the journal Nature Geoscience analyzed seismic waves from repeating earthquakes over the last six decades.

“We believe the inner core rotates, relative to the Earth’s surface, back and forth, like a swing,” the study’s authors, Xiaodong Song and Yi Yang of China’s Peking University, told AFP.

“One cycle of the swing is about seven decades,” the authors said.

The inner core started rotating slightly faster than the rest of the planet in the early 1970s, the study said.

But it had been slowing down before coming in sync with Earth’s rotation around 2009, it added.

There has been a “negative trend” since, the study said, meaning the inner core is now rotating slower than the surface.

The researchers predicted the next change would occur in the mid-2040s.

They said this rotation timeline roughly lines up with changes in what is called the “length of day”—small variations in the exact time it takes Earth to rotate on its axis.

Stuck in the middle

So far there is little to indicate that what the inner core does has much effect on surface dwellers.

But the researchers said they believed there were physical links between all Earth’s layers, from the inner core to the surface.

“We hope our study can motivate some researchers to build and test models which treat the whole Earth as an integrated dynamic system,” they said.

Experts not involved in the study expressed caution about its findings, pointing to several other theories and warning that many mysteries remain about the center of the Earth.

Full article here.

via Tallbloke’s Talkshop

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January 25, 2023 at 07:47AM

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