Earth’s Inner Core Slowing Down: What It Means for Our Days


A recent study has confirmed that Earth’s inner core has been rotating more slowly than usual since 2010.

This change, known as “backtracking,” could slightly affect Earth’s overall rotation, potentially lengthening our days, though the difference would be imperceptible to us.

What’s Happening in Earth’s Core?

The Earth is made up of several layers, much like a Russian nesting doll.

At the center lies the inner core, a solid ball of iron and nickel about the size of the moon, located over 3,000 miles (4,800 kilometers) below the surface.

This inner core is surrounded by a liquid outer core, a solid mantle, and the crust we live on.

While the entire Earth rotates, the inner core can spin at a different speed than the mantle and crust because of the liquid outer core’s viscosity.

For the past 40 years, scientists have observed that the inner core was rotating slightly faster than the Earth’s outer layers.

However, new research shows that since 2010, the inner core has been slowing down and now rotates more slowly than the rest of the planet.

How Do We Know This?

Researchers discovered this change by analyzing seismic data from over 100 “repeating earthquakes.”

These are seismic events that occur repeatedly at the same location, allowing scientists to map the inner core’s position relative to the mantle.

By comparing these measurements over time, they observed a consistent pattern indicating the inner core’s slowdown.

John Vidale, a seismologist at the University of Southern California, Dornsife, noted that the findings were initially surprising.

But after observing the same pattern in multiple cases, the evidence became undeniable.

What Does This Mean for Us?

If the inner core continues to decelerate, its gravitational pull could cause Earth’s outer layers to slow down slightly, potentially lengthening our days by a few thousandths of a second.

However, this change would be so minor that it would be “very hard to notice,” according to Vidale.

Therefore, we won’t need to adjust our clocks or calendars for this difference, especially if the slowdown is temporary.

Why Is This Happening?

The exact cause of the inner core’s slowdown is still unclear.

Researchers suggest it could be due to the movement of liquid iron in the outer core or gravitational pulls from dense regions in the mantle.

It’s also possible that the inner core’s spin constantly speeds up and slows down over long periods, but more data is needed to understand these long-term trends.

The Mystery Continues

The inner core remains one of Earth’s most mysterious layers.

Recent technologies have revealed more about it, such as its slight lopsidedness, unexpected softness, potential wobble off Earth’s axis, and the presence of a separate innermost core.

Researchers will continue to study seismic data to uncover more about the inner core and its changes over time.

“The dance of the inner core might be even more lively than we know,” Vidale said.