Rotation of Earth's core has slowed, now moving in reverse direction: Experts

The rotation of Earth's inner core, a solid metal ball, which is independent of the spinning of our planet has slowed down and is now turning possibly in reverse direction, scientists have confirmed.

An increasing body of evidence from research on its movement, rotation speed and direction, suggests the speed of the core's rotation has changed dramatically in recent years.

The research published June 12 in the journal Nature has provided bolstering evidence confirming the core slowdown and supports the 2023 proposal that the deceleration of the core is part of a decades-long pattern of slowing down and speeding up.

The Earth has three parts consisting of the crust (outer layer), the mantle and the inner and outer cores. This inner core has been part of decades-long research since its discovery by Danish seismologist Inge Lehmann in 1936.

Situated about 3,200 miles (5,149 km) below the Earth’s crust, the solid inner core is separated from the semi-solid mantle by the liquid outer core, allowing the inner core to rotate at a different speed from the rotation of the Earth itself.

However, scientists remain divided on its long-term impact on our planet. The problem mainly lies in the location of the Earth's core as it is impossible to observe or sample it directly.

Seismologists have tried to gather information about the inner core’s motion by examining the behavior of waves from large earthquakes. Scientists measured the changes in the inner core’s position and calculated its spin with the variations between waves of similar strengths that passed through the core at different times.

“Differential rotation of the inner core was proposed as a phenomenon in the 1970s and ’80s, but it wasn’t until the ‘90s that seismological evidence was published,” Dr Lauren Waszek, a senior lecturer of physical sciences at James Cook University in Australia was quoted as saying by CNN.

However, the researchers are divided on the interpretation of these findings, “primarily due to the challenge of making detailed observations of the inner core, due to its remoteness and limited available data,” Waszek said.

As a result, “studies which followed over the next years and decades disagree on the rate of rotation, and also its direction concerning the mantle,” she added. Some researchers even proposed that the core didn’t rotate at all.

In 2023, one model showed promising evidence that the inner core had spun faster than Earth itself in the past but was now spinning slower. After that, the scientists said the core’s rotation matched Earth’s spin following which it became slower until the core was moving backwards relative to the fluid layers around it.

Earth’s core has a radius of of almost 2,200 miles (3,540km) which is about the size of Mars, and is made up of mostly iron and nickel, and contains about one-third of Earth’s mass.

According to experts, the Earth's composition is changing continuously every day. The inner part of the planet can be divided into three different layers: crust, mantle, and core. Earth's core is the hottest part of the planet, equivalent to that of the Sun's surface.