Imagine Earth’s thick inner core as a heavy metal ballerina. This is how dense our planet is. This iron-rich dancer can pirouet at a variety of speeds.
That core could be on the verge of a significant transformation. Seismologists announced Monday in the journal Nature Geoscience that the inner core changes how it spins — relative to the motion of the Earth’s surface — potentially once every few decades, after brief but strange pauses. One such turnaround may be taking place right now.
This may sound like the premise for a massively successful blockbuster film. But don’t worry: this planetary spin cycle, which has been going on for ages, will produce nothing apocalyptic.
Instead, the academics who put out this theoretical model hope to improve knowledge of Earth’s most sacred region and how it interacts with the rest of the planet.
According to Xiaodong Song, a seismologist at Peking University in Beijing and one of the study’s authors, the inner core is similar to “a world within a planet, therefore how it moves is obviously very important.”
Scientists have been perplexed by the discovery made by Danish seismologist Inge Lehmann in 1936 that a solid metal marble is enclosed in Earth’s liquid outer core.
Seismologist John Vidale of the University of Southern California, who was not involved in the study, said: “It’s weird that there’s a solid iron ball kind of floating in the middle of the Earth.”
Scientists believe that at some point in Earth’s recent history, after the planet’s interior blaze had sufficiently cooled, the core formed out of a molten metal soup.
Although the inner core cannot be directly sampled, intense seismic waves from strong earthquakes and nuclear bomb testing conducted during the Cold War have penetrated the inner core, shedding light on some of its characteristics. This 1,520-mile-long ball, which is primarily made of iron and nickel, is said to be about as hot as the sun’s surface.
But a problem was also produced by these waves. The journeys of core-diving waves from nearly similar earthquakes and nuclear explosions would never alter if the core were inert, but over time, they do.
This is just one of several competing models explaining the erratic voyages of waves that reach the core. It is also possible that Earth’s innermost layer is wobbling about. Conversely, Earth’s ferrous nucleus may have a metamorphosing surface, twisting any seismic waves that pierce it.
Song and Yi Yang, co-authors of the paper and two other Peking University seismologists, propose that this enormous tug of war causes the inner core to spin back and forth on a cycle of about 70 years by analysing core-diving seismic waves collected from the 1960s to the present.
Early in the 1970s, the inner core was not rotating with respect to a person standing on Earth’s surface. Since then, the inner core has progressively spun more quickly in an eastward direction, eventually surpassing the rate of rotation of the Earth’s surface. The inner core’s spin then slowed until it looked that its rotation ceased somewhere between 2009 and 2011.
In relation to the Earth’s surface, the inner core is currently beginning to progressively spin westward. It is likely to speed up, then slow down once again, coming to a stop again in the 2040s and ending its most recent eastward-westward spin cycle.
If there is a 70-year pattern, it may have a real impact on the Earth’s deepest viscera. It might only be able to significantly alter the length of a day, which is known to vary by a fraction of a millisecond every six years, or cause minute changes in the planet’s magnetic field to cause relatively modest turbulence closer to the surface.
“No matter whatever hypothesis you want, some data contradicts it,” Vidale added.
This abyssal world may perpetually evade explanation due to its inaccessibility.
“It’s possible we’ll never find it out,” Vidale admitted. “I’m an optimist,” he continued. Someday, the pieces will come into place.”