The Earth’s center does slow down its rotation!

A study published in the journal nature The University of Southern California demonstrated the deceleration of the Earth’s inner core through seismic wave analysis on June 12, 2024. The core is more than 2,900 kilometers deep, and it is now easier to send a satellite to Jupiter than to explore below the Earth’s surface!

The first ball, with a temperature fluctuating between 3800 and 5500°C, consists of molten iron and nickel and forms the Earth’s core. Inside floats another ball, called the seed (or inner core). Its composition is similar, but this one is solid. To reach it, you have to dig 5,150 km deep!

The seeds spin on their own within the liquid core. This rotation creates a strong magnetic field, called the magnetosphere. It protects our planet from the potentially dangerous effects of the solar wind and cosmic radiation.

The inner core’s motion has been debated in the scientific community for two decades, with some studies suggesting the inner core rotates faster than the planet’s surface. New research from the University of Southern California provides evidence that the inner core began to slow down around 2010, moving slower than the planet’s surface.

To resolve inconsistencies in previous models, the study analyzed more than 120 earthquakes that occurred in the South Sandwich Islands, a special seismic zone, between 1991 and 2023. The scientists also used data from two Soviet nuclear tests, as well as French and American nuclear tests, between 1971 and 1974. The team carefully analyzed seismograms to detect changes in PKIKP waves.

name «PKIKP» Describes the path that seismic waves take through the different layers of the Earth. This seismic wave is divided into several types of waves. P waves travel through the Earth’s crust and upper mantle, while K waves travel through the Earth’s outer core. I waves travel through the seed, or inner core. Seismic waves penetrate the Earth from both sides, allowing scientists to learn about the Earth’s internal structure.

The corresponding pattern, as well as previous studies, showed that the inner core’s rotation speed gradually increased from 2003 to 2008, and then from 2008 to 2023 it began to slow down by two to three times over the same path. The inner core was then seen to reverse and move backwards relative to the planet’s surface!

“When I first saw seismograms suggesting this change, I was confused”John Vidale, professor of geosciences in the USC Dornsife College of Letters, Arts and Sciences, said in a statement. “But when we found two dozen other sightings reporting the same pattern, the result became inevitable. The inner core was slowing down for the first time in decades. Other scientists have recently proposed similar and different models, but our latest study provides the most convincing solution.”

Researchers are not at all sure about the effects of such an event. According to John Vidale, the slowing of the inner core could affect the length of a day by a fraction of a second. An infinitesimally small change that would almost disappear “In the din of sea and air”.