Far below Earth’s surface, the giant may have begun spinning in a different direction than ours, according to a study whose findings should not end the controversy that has been troubling experts.
The Earth’s core, a Pluto-sized sphere, has stopped spinning and may even have started spinning in the other direction, the study suggests, published today in the journal Nature Geoscience.
This “planet within a planet,” essentially made of iron, about five thousand kilometers from the surface, has free motion as it floats in the liquid shell of the outer core.
The exact mechanism of this rotation continues to be controversial. What little is known is based on the analysis of seismic waves caused by Earth tremors as they pass through the center of the planet.
Analyzing these waves over the past 60 years, Xiaodong Song and Yi Yang of Peking University concluded that the core’s rotation “almost stopped in 2009 and then resumed in the opposite direction.”
“We think that the central core rotates in one direction, then in the other, relative to the surface of the Earth, like a seesaw,” they told AFP.
“A full cycle is about 70 years,” they estimate. The last change in rotation before 2009 occurred in the 1970s, the next, as these scientists always believe, should occur in the 2040s.
This rotation, in his opinion, should be more or less reflected in a change in the length of the day, tiny changes in the additional time it takes the planet to rotate on its axis.
To date, there is little indication of the effect of this rotation on what passes above the Earth’s surface.