Earth had the shortest day on record this summer, thanks to a wobble on its axis that meant it completed a single spin in a fraction of a second in less than 24 hours.
June 29 was 1.59 milliseconds shorter than 86,400 seconds, or exactly 24 hours, according to the website timeanddate.com.
In recent decades, Earth has been more likely to slow down, resulting in marginally longer days. But in recent years this trend has been reversed and the days have been getting shorter and shorter.
If the Earth continues to accelerate, this could cause the first requirement to subtract a second from atomic clocks.
The Earth is not perfect
It’s no wonder the Earth wobbles: the spin we experience night and day doesn’t always happen exactly in line with its axis, the line between the north and south poles.
This is because it is not a precise sphere.
The planet has a bulge at the equator, while the poles are slightly squashed, meaning the Earth is slightly elliptical.
Other factors can also interfere with the spin, including ocean tides and the Moon’s gravity.
“Chandler’s Wobbling”
Leonid Zotov, a mathematics professor, believes the Earth may be spinning faster due to a periodic motion called the “Chandler wobble.”
The wobble was first detected in the late 1880s, when astronomer Seth Carlo Chandler noticed that the poles wobbled over a period of 14 months.
That swing began to slow in the early 2000s, hitting record lows since 2017, according to The Telegraph.
And between 2017 and 2020, it “disappeared,” Zotov told timeanddate.com.
Zotov is to present this hypothesis to the Asia Oceania Geosciences Society, per timeanddate.com. It has not yet been peer reviewed.
Earth’s wobbles don’t change much from day to day. But it’s important to keep track of it, so the atomic clock can remain accurate to precisely coordinate GPS and Earth observation satellites.
This article was originally published by Business Insider.
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