Researchers from the United States and China have confirmed that the Earth’s inner core has slowed down, a process that began in 2009. Using seismic data from earthquakes, scientists determined that the rotation of the core is not constant, as previously believed, but fluctuates in cycles lasting several decades.
The Earth’s core lies thousands of miles beneath the surface and is composed mainly of iron and nickel. It has two parts: a liquid outer core, which helps generate Earth’s magnetic field, and a solid inner core, where temperatures can reach 5,700 degrees Celsius. The outer core begins about 1,800 miles down, while the inner core starts around 3,200 miles beneath the crust.
For many years, scientists assumed the core rotated steadily. New findings show that the inner core sometimes slows down until it moves almost in sync with the crust, creating the appearance of a standstill. In reality, the core never stops, but its relative speed changes. Evidence suggests that these fluctuations follow a cycle of about 70 years, with the core’s rotation relative to the crust reversing roughly every 35 years.
The slowdown of the inner core may cause tiny changes in the length of days, though these are measured in milliseconds and are not noticeable in daily life. Such fluctuations can, however, affect astronomical measurements, satellite data, and navigation systems. Scientists also suggest possible links to variations in Earth’s magnetic field and climate, though more research is needed.
The phenomenon shows how little is known about Earth’s deepest layers. While the changes in core rotation are unlikely to affect people directly, they provide insight into the complex interactions between the Earth’s interior, surface, and atmosphere.