Recent studies have confirmed that Earth inner core is slowing down in terms of angular velocity as compared to the outer shell. This slowdown started over a decade ago, more specifically around the year 2010, and this is the first time it has been observed by scientists.

The central solid core is a dense and hot part of the earth, and it includes iron and nickel with a temperature of approximately 5,500 °C. Lies more than 3,000 miles beneath the surface of the Earth, enclosed within the melt iron-nickel outer core; this solid core is as big as the moon. Although scientists are unable to physically observe it or even visit it, there are ways of studying it, such as by analyzing seismic waves that result from earthquakes.

Earth inner core
Image Source: Shiksha

Scientists from the University of Southern California have successfully shown that the Earth’s inner core is slowing down, implying a backward movement. This was specifically named “Inner core backtracking by seismic waveform change reversals” and was released in Nature on the 12th of June.

The researchers stated, "The pattern of matches, together with previous studies, demonstrates that the inner core gradually super-rotated from 2003 to 2008, and then from 2008 to 2023, it sub-rotated two to three times more slowly back through the same path.”

John Vidale, who holds the position of Dean's Professor of Earth Sciences at the USC Dornsife College of Letters, Arts, and Sciences, expressed the following statement, as quoted on the official website:

When I first saw the seismograms that hinted at this change, I was stumped. But when we found two dozen more observations signaling the same pattern, the result was inescapable. The inner core had slowed down for the first time in many decades. Other scientists have recently argued for similar and different models, but our latest study provides the most convincing resolution.”

According to the official announcement, the inner core is believed to be undergoing a reversal and backward movement compared to the Earth's surface due to its slightly slower pace than the Earth's mantle, marking the first occurrence of this phenomenon in approximately four decades.

This shift could potentially impact the planet's rotation, leading to longer days. However, any noticeable effects are expected to primarily affect the geomagnetic field.

"It's very hard to notice, on the order of a thousandth of a second, almost lost in the noise of the churning oceans and atmosphere,” said Vidale. Vidale also mentioned that the backward movement of the inner core might cause slight changes in the length of a day, possibly by fractions of a second.

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