New research has revealed that Earth’s inner core, a solid metal sphere rotating independently of the planet, has significantly slowed down and even reversed its direction. This discovery, published in the journal Nature, has raised questions about the potential effects on Earth’s magnetic field, although scientists remain uncertain about the exact implications.
The inner core, located about 3,220 miles beneath the Earth’s surface, is primarily composed of iron and nickel and reaches temperatures similar to the sun’s surface—approximately 9,800 degrees Fahrenheit. Its rotation is influenced by Earth’s magnetic field, gravity, and the flow of the fluid outer core and mantle.
Danish seismologist Inge Lehmann first discovered the inner core in 1936. Since then, scientists have debated its rotation speed and direction. Recent studies indicate that the core’s rotation varies over a 70-year cycle, sometimes spinning faster than the planet itself and, more recently, slowing down significantly.
Analysis of seismographic data suggests that the core began decelerating around 2008 and reversed direction relative to the mantle by 2023. Researchers predict that the inner core will begin to accelerate again within the next five to ten years.
The study’s coauthor, Dr. John Vidale, Dean’s Professor of Earth Sciences at the University of Southern California, stated, “I think we’ve ended the debate on whether the inner core moves, and what’s been its pattern for the last couple of decades.” However, the precise effects of this slowdown and reversal on Earth remain unclear.
One theory posits that a slower-spinning core could slightly alter the length of a day. Additionally, the movement of metal-rich fluid in the outer core generates electrical currents that sustain Earth’s magnetic field, which shields the planet from harmful solar radiation. A change in the core’s rotation could potentially impact this magnetic field.
Dr. Lauren Waszek, a senior lecturer of physical sciences at James Cook University in Australia, noted that the phenomenon of differential rotation was proposed in the 1970s and ’80s, with seismological evidence emerging in the ’90s. She emphasized the need for more data and interdisciplinary tools to better understand the potential effects.
Waszek also commented on the practical implications, stating, “In terms of that effect in a person’s lifetime? I can’t imagine it means much.” While the long-term consequences remain a subject of scientific investigation, the immediate impact on daily life appears minimal.
