Why has the Earth’s core slowed down so much that it is receding according to experts?

A study published last year in Nature suggested that the earth’s inner core—the spinning mass at the center of the planet—may have stopped rotating. Scientists had previously hypothesized that the planet’s outer layer spins at a different rate from the inner core, which is suspended within a layer of molten iron. The inner core’s relative speed is thought to play a role in maintaining the magnetic fields on Earth, but the new findings suggest that something is changing beneath our feet.

Now, a few months after that initial study was published, Nature has released another study conducted by Dr. John Vidale, a professor of Geophysics at Johns Hopkins University, that shows the behavior of the core to be normal. However, that does not mean that scientists understand the mechanisms at play. Dr. Vidale and his team found that while the slowing of the earth’s core had been happening over the last few decades, they expect it to be spinning faster in the coming years and decades. The researchers identified a 70-year cycle that the core follows, thus making it easier to project the speed at which the metallic ball will be moving in the future.

The fact that the core should speed up again is good news, considering that the article published in 2023 suggested that if it continued to slow, it could impact the length of the day.

What is the earth’s inner core?

The Earth’s core was discovered in 1936 when researchers investigated how earthquakes spread across the planet. They found that the planet has a 7,000 km-wide core, consisting of a solid center surrounded by a layer of molten iron, nickel, and other elements. The inner core is suspended by a layer of liquid, allowing it to spin independently of the rest of the planet. In 1996, researchers found that the travel time of seismic waves could change, indicating that the inner core was rotating at a different speed from the rest of the planet.

The scientists believed that the inner core was moving in a ‘super-rotation,’ i.e., one that is faster than the speed at which the earth’s surface rotates. The difference was only around one-tenth of a degree per year, but it was enough to influence how earthquakes travel and is thought to be related to the earth’s magnetic fields.