0
0
For decades, scientists expected Earth’s rotation to slow down gradually. Instead, recent measurements show the planet is spinning faster than anticipated, completing a full rotation in slightly less than 24 hours. Researchers suspect processes deep within Earth’s interior are responsible for this unexpected acceleration.
A Day Shorter Than 86,400 Seconds
In theory, a day lasts exactly 86,400 seconds. Yet Earth’s rotation has never been perfectly constant. For much of the past century, the planet typically took one to three milliseconds longer than 24 hours. Since 2020, however, Earth has been rotating faster, shaving off fractions of a millisecond each day.
“This is somewhat surprising,” says geophysicist Roland Pail of the Technical University of Munich. “All signs actually pointed toward a slowdown.”
The Moon’s Braking Effect
The Moon acts like a cosmic handbrake. Its gravitational pull gradually slows Earth’s spin. Evidence from coral reefs and sediments shows that 500–600 million years ago, a day lasted only 21 hours. Over time, the “Moon’s brake” has steadily lengthened the day.
Climate change was also expected to slow the Earth further. As polar ice melts, water shifts toward the equator. Like a figure skater extending her arms during a spin, this redistribution should reduce rotational speed. Yet Earth has defied these predictions.
Mantle and Core Out of Sync
Instead of slowing, Earth has accelerated. Measurements from the Technical University of Vienna confirm the trend. Pail suspects the cause lies beneath our feet: the mantle and core may currently be rotating at slightly different speeds. While this phenomenon is known, it remains poorly understood and difficult to model. “The long-term behavior is absolutely unknown,” Pail admits.
Imperceptible to Humans
For everyday life, the effect is negligible. “We’re talking about a hundredth of the blink of an eye,” says Pail. Such fluctuations have occurred throughout Earth’s history without noticeable impact on human activity.
Atomic Clocks and Leap Seconds
Ultra-precise atomic clocks, however, do detect the shorter days. Since the 1970s, scientists have occasionally added “leap seconds” to keep Coordinated Universal Time (UTC) aligned with Earth’s rotation. The last leap second was added at the end of 2016. Now, for the first time, experts are debating whether a negative leap second might be required.
Fears of Computer Crashes
Unlike adding a second, subtracting one poses serious risks. Many computer systems are not designed to handle negative time adjustments. “Nobody is prepared for that,” warns Pail. While the physical discrepancy of a few milliseconds may be trivial, the potential for widespread computer failures is far more concerning.
- Hector Pascua with reports from orf.at/picture: pixabay.com
This post has already been read 5 times!
