(NEXSTAR) — Deep in the center of the Earth is the inner core, which spans about 746 miles and is composed primarily of pure, solid iron, NASA explains. While we’ve long believed — and research has shown — that the inner core rotates, a new study suggests it has “paused” and may even have reversed its spin.
The liquid outer core surrounding the inner core creates the Earth’s magnetic field. According to NASA, as the molten iron and nickel move in the outer core, they create electric currents that result in a magnetic field. The outer core also allows the inner core to spin on its own, explains Nature.
While scientists can’t track the core directly, they can analyze seismic waves created by earthquakes — and Cold War nuclear weapons tests — as they reach the core. That’s what co-authors Yi Yang and Xiaodong Song, seismologists at Peking University in Beijing, did for their new study, which was published Monday in the journal Nature Geoscience.
Based on their analysis of seismic waves generated by similar earthquakes dating back to the 1960s, Yang and Song said they found that the rotation of the inner core appears to have “paused” between 2009 and 2020, and even “by a small amount could reverse.
Sounds worrying, right? Don’t be alarmed – this is probably not the first time our inner core has come to a standstill. Instead, they believe the change is “associated with a gradual reversal of the inner core as part of a oscillation spanning about seven decades.”
According to Yang and Song, the results of their research also point to “a new tilt or a slowdown in rotation around the early 1970s.”
The seismologists said their findings — changes in how fast seismic waves traveled through the inner core — coincide “with changes in several other geophysical observations, especially length of day and magnetic field,” both regions affected by the motion of the inner core. , research has shown.
While the changes are “valid,” what Yang and Song found may not be exactly what’s happening in the depths of our planet. John Vidale, a professor of earth sciences at the University of Southern California who was not involved in the research, noted “several competing ideas” about the Earth’s core in The Wall Street Journal.
This includes theories that the inner core reverses its rotation more often than the 70 years Yang and Song determined and that it stopped spinning in the early 2000s.
“It doesn’t matter which model you like, there’s certain data that disagrees with it,” Vidale told The New York Times.
Vidale recently co-authored a study that showed that the inner core changed spins between 1969 and 1974 and that it appears to oscillate “a few miles every six years.”