By The Arusha News Reporter
We may not have noticed it, but 22nd July was the second-shortest day of the year, as the Earth completed its rotation around its axis in slightly less than the usual 24 hours, according to timeanddate.com.
Scientists describe the Earth as an almost perfect and reliable timekeeper. On average, it completes one full rotation in exactly 86,400 seconds — a period referred to as the Length of Day (LOD)—with a variation of plus or minus a millisecond (ms), a tiny measurement made possible by the advent of atomic clocks in the 1950s. Simply put 86,400 seconds equals to 24 hours.
However, since 2020, scientists have observed that the Earth appears to be accelerating its rotation, particularly during mid-year months such as July and August. This results in slightly shorter days — though not shorter nights. The cause remains unclear, though some researchers suggest climate change could be a factor.
The first short day of this year occurred on 9th July, when the Earth completed its rotation 1.23 milliseconds faster than usual. On 22nd July, it shaved off 1.34 milliseconds. A third short day is anticipated on 5th August, with a predicted time saving of 1.25 milliseconds. For context, a millisecond is 0.001 seconds — significantly faster than the blink of an eye, which typically lasts around 100 milliseconds.
The shortest recorded LOD, as measured by atomic clocks, occurred in 2020 at 1.05 milliseconds shorter than average. Since then, it seems the Earth has been racing to beat its own record, with progressively shorter days suggesting an increase in rotational speed. Scientists also note that short-term LOD variations are influenced by the Moon’s orbit.
According to researchers, the Earth spins slightly faster when the Moon is positioned farther north or south of the equator. Interestingly, the Moon was near its maximum distance from the equator on both 9th and 22nd July, and is expected to reach that position again on 5th August. Why exactly this affects Earth’s speed — or whether it will slow down again — remains uncertain.
“Nobody expected this,” says Leonid Zotov, a leading expert on Earth’s rotation at Moscow State University. “The cause of this acceleration is not yet explained,” he concludes. Nevertheless, many scientists believe the phenomenon may be linked to Earth’s complex core dynamics, as well as interactions with the oceans and atmosphere.
