Scientists: Earth’s inner core begins to move in the opposite direction

Deep within the Earth lies a solid metal ball of iron and nickel the size of the moon, rotating independently of our planet’s rotation, and shrouded in mystery.

Since its discovery by Danish seismologist Inge Lehmann in 1936, the inner core has fascinated scientists. Its motion – including the speed and direction of its rotation – has been the subject of decades of debate.

Mounting evidence suggests that the core’s spin has changed dramatically in recent years, but scientists are still divided over exactly what’s happening and what it means.

At one point, the core’s rotation matched the Earth’s, but then it began to slow down even more, moving backward relative to the surrounding fluid layers, the scientists reported.

The new paper also supports a theory that the change is part of a long-observed pattern of slowing and accelerating.

But what exactly is driving this change?

Researchers used information from earthquakes and Soviet nuclear tests to analyze the motion of the inner core.

Specifically, they compiled seismic data from 121 earthquakes that occurred in the same location at different times between 1991 and 2023.

“The matching waveforms reveal the times when the inner core reoccupies the same position, relative to the mantle, as it did at some point in the past,” the scientists wrote. “This pattern shows that the inner core rotated gradually from 2003 to 2008, and then from 2008 to 2023 rotated two to three times more slowly once more along the same path.”

Scientists suggest that the movement of the inner core is driven by the Earth’s magnetic field, causing it to rotate.

At the same time, the mantle and the liquid outer core exert their own influence on the iron ball (the inner core), creating a push-pull effect. Scientists believe this has caused the inner core to slow down over time.

The new study, led by Dr. John Vidal, professor of earth sciences at the University of Southern California’s Dornsife College of Letters, Arts and Sciences, reveals that changes in rotation speed follow a 70-year cycle.

“We’ve been arguing regarding this for 20 years, and I think we’ve succeeded,” he said. “I think we’ve settled the debate regarding whether the inner core is moving, and what its pattern has been over the past two decades.”

The implications of the slowing inner core and how it affects us remain a mystery, although some link it to the Earth’s magnetic field.

Studies suggest that a slower-spinning core might affect Earth’s magnetic field, the protective shield that protects the planet from deadly solar radiation, and might also partially shorten the length of the day.

The scientists say the change will be imperceptible in our lifetimes, with the total time added to the length of the day amounting to only milliseconds. However, the findings add to a growing body of evidence that the length of days is changing.

Previous studies have determined that days may eventually extend to 25 hours, which might take 200 million years from now.

Source: The Sun