Earth's inner core slowing down, could change day's length

NEW DELHI: A recent study published in Journal Nature suggests that the length of one day could be changed by fractions of a second as "unambiguous evidence" indicates that the Earth's inner core, a solid sphere composed of iron and nickel, began to slow down its rotation in 2010 relative to the planet's surface.
The inner core is suspended within the liquid outer core, which is made of molten metals, and is held in place by gravity.These two layers, along with the mantle and crust, form the three layers of the Earth.
"When I first saw the seismograms that hinted at this change, I was stumped. But when we found two dozen more observations signalling the same pattern, the result was inescapable. The inner core had slowed down for the first time in many decades," said John Vidale, a professor of Earth Sciences at the University of Southern California, US.
Researchers usually study the core by analyzing seismograms, recordings of waves generated by earthquakes, as it is physically inaccessible.
The researchers examined seismic data recorded from 121 repeating earthquakes that occurred in the same location between 1991 and 2023 in the South Sandwich Islands, a remote archipelago in the South Atlantic Ocean known for its violent earthquakes for the this study.
The analysis also included data from twin Soviet nuclear tests between 1971 and 1974, as well as multiple French and American nuclear tests from other studies of the inner core.
The slowing down of the inner core is a topic of debate within the scientific community, with some studies even proposing that it rotates faster than the Earth's surface.
The spin of the inner core is known to be influenced by the magnetic field generated in the outer core and the gravitational effects within Earth's mantle.
Additionally, it is believed that the inner core is reversing and backtracking relative to the surface because it is rotating slower than the mantle for the first time in approximately 40 years.