The Earth's core stopped spinning and may now be in reverse

The Earth's core – a sphere of almost pure iron more than 5,000 kilometers deep that is hotter than the Sun – has slowed down and it is possible that it is rotating in the opposite direction to the surface of the planet , according to a study published today in Nature Geoscience . This slowdown can have global effects, such as shortening the days by a few fractions of a second and influencing the climate and sea level.

The two authors of the paper are Yi Yang and Xiaodong Song, from Peking University's Institute of Theoretical and Applied Geophysics, in China. Both have tried to solve a current enigma since, a few decades ago, it was confirmed that the Earth contains a planet inside another.

"Differential rotation of Earth's inner core relative to the mantle is thought to occur under the effects of the geodynamo on core dynamics and gravitational core-mantle coupling," wrote study authors Yi Yang  and Xiaodong Song of Peking University.

"This rotation has been inferred from temporal changes between repeated seismic waves that should traverse the same path through the inner core."

"Here we analyse repeated seismic waves from the early 1990s and show that all of the paths that previously showed significant temporal changes have exhibited little change over the past decade."

"This globally consistent pattern suggests that inner-core rotation has recently paused. We compared this recent pattern to the Alaskan seismic records of South Sandwich Islands doublets going back to 1964 and it seems to be associated with a gradual turning-back of the inner core as a part of an approximately seven-decade oscillation, with another turning point in the early 1970s."
Source: EL PAÍS, SL