NEW DELHI: A groundbreaking study has found “clear evidence” that the Earth’s inner core has slowed its rotation relative to the planet’s surface since 2010, potentially affecting the length of a day by a fraction of a second.
The inner core, a solid sphere of iron and nickel, is encased within the liquid outer core and stabilized by gravity. Researchers typically study the core through seismograms, which record waves generated by earthquakes.
“When I first saw the seismograms showing these changes, I was shocked,” said John Widale, Earth sciences professor at the University of Southern California. “But after finding dozens more observations with the same pattern, the conclusion was inescapable. The inner core has slowed down for the first time in decades,” added Widale, co-author of the study published in Nature.
The slowdown of the inner core’s rotation is a subject of debate among scientists, with some studies suggesting it may be spinning faster than the Earth’s surface. The core’s rotation is influenced by the magnetic field generated by the outer core and gravitational forces in the Earth’s mantle.
“For the first time in 40 years, the inner core has slowed relative to the surface,” said Widale. The study used seismic data from 121 repeated earthquakes in the South Sandwich Islands between 1991 and 2023, as well as data from Soviet nuclear tests in the 1970s.
Duncan Agnew, a geophysicist at the University of California San Diego, suggests that the Earth’s liquid core slows its rotation, causing the solid Earth to spin faster to counteract this effect. He notes that fewer “leap seconds” have been needed in recent decades to correct Coordinated Universal Time (UTC) for Earth’s variable rotation speed.
The findings highlight how changes in the inner core’s rotation could have subtle but measurable impacts on global timekeeping and Earth’s geophysical processes.
Read Now:EPFO Reforms Under Review: Automation, Efficiency, and Social Security Expansion
