Earth’s inner core slows its rotation

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In the mid-1990s, scientists found evidence of it Earth’s inner core, a superheated iron ball slightly smaller than the Moon, was rotating at its own speed, slightly faster than the other planets. A study has now been published Natural Earth Sciences In 2009, the The core spun its rotation in sync with the surface for a while – now it’s lagging behind.

The provocative findings come after years of research and deep scientific disagreement about the core and how it affects some fundamental aspects of our planet, including the length of a day and fluctuations in Earth’s magnetic field.

Three thousand miles below the surface, a blazing hot ball of solid iron floats inside a liquid outer core. Geologists believe that the energy released by the inner core causes fluid in the outer core to move, creating currents that create a magnetic field around the planet. This magnetic shield protects life on the surface from the most damaging cosmic radiation.

Don’t panic. The deceleration of the core is not the beginning of the end times. The same thing seems to have happened in the late 1960s and early 1970s, study authors from Peking University in China say. This will cause the 70-year cycle to speed up and slow down the central cycle.

But while other experts applaud the rigor of the analysis, the study will sharpen, not resolve, a serious scientific debate about what it is. Mysterious metal sphere Up to the center of the earth.

“It’s controversial because we can’t find it,” said John Vidal, a geophysicist at the University of Southern California. “It’s probably benign, but we don’t want to have things deep in the Earth that we don’t understand.”

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The new study was led by Geologist Xiaotong Zhang of Peking University, whose work was first presented in 1996. Proof that the core is doing its own thing. Buried beneath the mantle and crust, the core is too deep to see directly, but scientists can use seismic waves triggered by earthquakes to infer what’s happening in the planet’s interior. Seismic waves travel at different speeds depending on the density and temperature of the rock, so they act as a kind of X-ray to the Earth.

It studied the seismic waves that travel from earthquake sites to sensors on the other side of the planet, passing through the epicenter on the way. By comparing waves of similar earthquakes that hit the same location over the years, scientists were able to look for and analyze time delays and disturbances in the waves that gave them indirect information about the core — or, as some scientists call it, the planet inside. Our planet.

“The inner core is the deepest layer of the Earth, and its rotation is one of the most intriguing and challenging problems in deep Earth science,” Chang said in an email.

Scientists are slowly unlocking the secrets of Earth’s mysterious hums

The core’s behavior can be linked to minute changes over the length of a day, although the precise details are a matter of debate. The length of a day has been increasing by milliseconds over the centuries due to other forces, including the pull of the Earth by the Moon. But ultraprecise atomic clocks have measured mysterious fluctuations.

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These variations may line up with changes in the center’s rotation, Song and colleagues argue. While they eliminate predictable fluctuations in the length of a day due to the moon’s tidal forces, the new paper finds changes in the rotation of the inner core that appear to track 70-year oscillations.

Paul Richards, a seismologist The Lamont-Doherty Earth Observatory at Columbia University, along with Chang, presented the first evidence that the core rotates faster than the rest. Planet.

“Most of us assume that the inner core rotates at a constant rate slightly different from Earth’s,” Richards said. “The evidence is piling up, and this paper shows that the evidence is there [faster] The cycle was strong prior to 2009, and will die down in later years.

However, he cautioned that things can quickly become speculative when trying to understand the center’s influence on other phenomena. This is because the behavior of the core is still a contested question—simplifying assumptions have been increasingly refined over the years.

For example, there is evidence to support other ideas about how the Earth’s core works. Vidal of USC studied the generated seismic waves Nuclear explosionsAnd he likes short, six-year swings to the center’s rotation rate.

Liangxing Wen, a seismologist at Stony Brook University, completely rejects the idea that the core rotates independently. He argues that change over time surface of the inner core A more plausible interpretation of seismic data.

“This study misinterprets seismic signals caused by episodic changes in the Earth’s inner core surface,” Wen said in an email. The idea that the inner core rotates independently of the surface, he added, “gives an inconsistent explanation for the seismic data even if we assume it’s true.”

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What geologists agree is that as more data have accumulated, many early ideas about the behavior of the core have grown more complex.

“Ultimately I don’t think that things are complicated is a problem in the geosciences,” Elizabeth Day, a geophysicist at Imperial College London, said in an email. “We know the surface of our planet is complex … so it’s reasonable to assume that the deep interior is complex too! We need to collect as much data as possible to say for sure how the inner core rotates relative to the outer layers of the planet.

The stakes in this scientific debate are high in part because at the core is a mystery that, unsolved, hits close to home.

“It’s not going to affect potato prices tomorrow,” Richards said. But the debate speaks to deeper questions about Earth’s formation and how its inner layers support life on its surface, which could aid studies of life on rocky planets orbiting other stars.

“When you think about … what our planet consists of and what its history is,” Richards said, “a deeper understanding of the inner core is ‘How did all these rifts of Earth form?’

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