What’s going on? One idea is that two giant powers are fighting for control of the core of the world. Earth’s magnetic field, generated by the swirling iron currents in the liquid outer core, pulls on the inner core, causing it to rotate. This thrust is resisted by the mantle, the mucous layer above the outer core and under the Earth’s crust, by the enormous gravitational field that holds the inner core and slows its rotation.
By studying the underlying subduction seismic waves recorded from the 1960s to the present day, Dr. Song Wei Yang, another seismologist at Peking University and co-author of the study, posits that this massive tug of war causes the inner core to rotate backwards. And back and forth in a cycle of about 70 years.
In the early 1970s, to a person standing on Earth’s surface, the inner core was not spinning. Since then, the inner core has gradually rotated faster eastward, eventually outpacing the rotational speed of Earth’s surface. After that, the inner core’s rotation slowed until it appeared to have stopped at some point between 2009 and 2011.
The inner core is now gradually rotating westward relative to Earth’s surface. It will likely speed up and then slow again, hitting another apparent standstill in the 40s and completing its latest east-west spin.
This 70-year rhythm, if it exists, could have a measurable impact on parts of the Earth. deeper bowels. But they may only be able to provoke a relatively minor perturbation near the surface – perhaps by causing slight shifts in the planet’s magnetic field, or even by slightly tweaking the length of the day, which is known to increase and decrease by a fraction of a millisecond every six. Years.
This is just one of several competing models that explain the irregular waves’ journeys up to the core. It is also possible that the deeper layer of the Earth is present oscillate. Conversely, Earth’s iron core may have a metamorphic surface, twisting any seismic waves that penetrate it. “No matter which model you like, there is some data that you don’t agree with,” said Dr. Vidal.
Due to the inaccessibility of this immemorial world, he might escape interpretation forever. “It’s certainly possible that we may never find out,” said Dr. Vidal. But he added: “I am optimistic. The pieces will fall into place one day.”