中国科学家研究发现 地球内核的自转可能已暂停(图)

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The rotation of Earth's core may have paused, scientists in China have suggested.

The rotation of Earth's core may have paused, scientists in China have suggested.


The rotation of Earth’s inner core may have paused and it could even go into reverse, new research suggests.


The Earth is formed of the crust, the mantle and the inner and outer cores. The solid inner core is situated about 3,200 miles below the Earth’s crust and is separated from the semi-solid mantle by the liquid outer core, which allows the inner core to rotate at a different speed from the rotation of the Earth itself.


With a radius of almost 2,200 miles, Earth’s core is about the size of Mars. It consists mostly of iron and nickel, and contains about about one-third of Earth’s mass.


In research published in the journal Nature Geoscience on Monday, Yi Yang, associate research scientist at Peking University, and Xiaodong Song, Peking University chair professor, studied seismic waves from earthquakes that have passed through the Earth’s inner core along similar paths since the 1960s to infer how fast the inner core is spinning.

在1月23日发表在《自然地球科学》( Nature Geoscience)杂志上的一项研究中,北京大学科学家杨毅和宋晓东研究了自20世纪60年代以来沿着相似路径穿过地球内核的地震产生的地震波,以推断内核旋转的速度。

What they found was unexpected, they said. Since 2009, seismic records, which previously changed over time, showed little difference. This, they said, suggested that the inner core rotation had paused.


“We show surprising observations that indicate the inner core has nearly ceased its rotation in the recent decade and may be experiencing a turning-back,” they wrote in the study.


“When you look at the decade between 1980 and 1990 you see clear change but when you see 2010 to 2020 you don’t see much change,” added Song.


The spin of the inner core is driven by the magnetic field generated in the outer core and balanced by the gravitational effects of the mantle. Knowing how the inner core rotates could shed light on how these layers interact and other processes deep in the Earth.


However, the speed of this rotation, and whether it varies, is debated, said Hrvoje Tkalcic, a geophysicist at the Australian National University, who was not involved in the study,“The inner core doesn’t come to a full stop,” he said. The study’s finding, he said, “means that the inner core is now more in sync with the rest of the planet than a decade ago when it was spinning a bit faster.”

然而,这种旋转的速度,以及它是否有所变化,是有争议的。澳大利亚国立大学的地球物理学家Hrvoje Tkalcic说,他没有参与这项研究。他说,“这项研究发现内核并没有完全停止自转,这意味着,与十年前相比,现在的内核与地球其他部分的同步程度更高,当时它的旋转速度略快。”

“Nothing cataclysmic is happening,” he added.


Song and Yang argue that, based on their calculations, a small imbalance in the electromagnetic and gravitational forces could slow and even reverse the inner core’s rotation. They believe this is part of a seven-decade cycle, and that the turning point prior to the one they detected in their data around 2009/2010 occurred in the early 1970s.


Tkalcic, who is the author of “The Earth’s Inner Core: Revealed by Observational Seismology,” said the study’s “data analysis is sound.” However, the study’s findings “should be taken cautiously” as “more data and innovative methods are needed to shed light on this interesting problem.”


Song and Yang agreed that more research was needed.


Studying the Earth’s core


Tkalcic, who dedicates an entire chapter of his book to the inner core rotation, suggested the inner core’s cycle is every 20 to 30 years, rather than the 70 proposed in the latest study. He explained why such variations occur and why it was so difficult to understand what happens in the innermost reaches of the planet.


“The objects of our studies are buried thousands of kilometers beneath our feet,” he said.


“We use geophysical inference methods to infer the Earth’s internal properties, and caution must be exercised until multi-disciplinary findings confirm our hypotheses and conceptual frameworks,” he explained


“You can think of seismologists like medical doctors who study the internal organs of patients’ bodies using imperfect or limited equipment. So, despite progress, our image of the inner Earth is still blurry, and we are still in the discovery stage.”


原载2023年1月25日CNN网站Earth’s inner core may have stopped turning and could go into reverse, study suggests作者Lianne Kolirin,皮建华试译。 阅读原文

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