A day is supposed to last 24 hours, but Earth does not keep time quite that neatly.
A new study found that forces deep inside the planet are subtly speeding up and slowing down Earth’s rotation, changing the length of a day by milliseconds over the course of decades, Gizmodo reported.
In a Nature paper published Wednesday, researchers argued that a long-running question about multidecadal changes in Earth’s rotation may be explained by processes inside the planet.
The explanation involves three competing mechanisms — gravitational, electromagnetic, and topographic coupling — that help account for those changes.
According to Huifeng Zhang, a University of Alberta doctoral candidate and the study’s first author, gravitational coupling between the inner core and the mantle appears to produce most of the shift, while the other two mechanisms push in the opposite direction, the outlet noted.
Zhang and co-author Mathieu Dumberry reached that conclusion by comparing statistical models with observational records spanning roughly six decades.
The effect is tiny but detectable.
Observational data cited in the study shows core-driven processes changed day length by a few milliseconds between the early 1970s and 2021, per Gizmodo. Scientists already knew that Earth’s rotation can vary and that the reason depends on the timescale being studied.
Over short periods, the atmosphere and oceans play a major role. Over millions of years, tidal interactions with the moon can drive long-term changes.
(Yahoo News)
Monday, September 28, 2026