Scientists have recorded the shortest day on Earth since its rotation period began to be recorded with high-precision atomic clocks: on June 29, 2022, Earth’s rotation completed in 1.59 milliseconds in less than 24 hours.
A day is 24 hours long because the Earth completes a full rotation on its axis approximately every 8,640,000 milliseconds. In the short term, this speed can fluctuate by fractions of a millisecond from one day to the next. This means that the length of a day can vary, but usually only by a small amount.
Our planet is also undergoing long-term changes. Previously, the planet was observed to rotate more slowly and take longer to complete a day. As a result, with each passing century, the Earth has taken a few more milliseconds to complete a revolution.
Related: How Fast is the Earth Moving?
In recent years, however, this long-term trend has been reversed. The Earth appears to be speeding up and taking progressively less time to complete its rotation, meaning the days are getting shorter.
As of December 2020, the website Date and time reported (opens a new tab) that during that year Earth had experienced its 28 shortest days since scientists began measuring the length of a day with atomic clocks in the 1960s.
July 19, 2020 was a record short day that year with Earth completing one rotation in 1.47 milliseconds in less than 24 hours. The record stood unchallenged through 2021 before being broken by a day of minus 1.59 milliseconds on June 29, 2022.
And July 19, 2020 wouldn’t stay in the second fastest day position for long either. Just one month after the record for the fastest day was broken, that second-place day was further dethroned when Earth experienced a day of -1.50 milliseconds on July 26, 2022.
Scientists have several ideas about what could be causing the Earth to start speeding up its rotation and shortening its days suddenly. These ideas may involve processes in the inner or outer layers of the planet, oceans, tides or even its climate.
A team of researchers thinks that the shortening of days could be related to a small irregular movement in the Earth’s geographic poles and its axis of rotation that shifts them by a tiny amount across its surface called a “wobble of Chandler.”
“The normal amplitude of the Chandler wobble is about three to four meters on the Earth’s surface, but from 2017 to 2020 it disappeared.” HSE University Associate Professor Leonid Zotov said Time and Date. (opens in a new tab)
If the decrease in day length continues, it may be necessary to introduce a negative leap second to maintain “civil time” as measured by highly reliable atomic clocks synchronized with solar time, the movement of the sun across the sky from sunset to sunrise.
Zotov is not convinced that this measure, which could cause difficulties for some computer systems, is necessary. He thinks the length of the days may not get much shorter.
“I think there’s a 70 percent chance that we’ll be at the bottom and we won’t need a second negative jump,” he said.
This week Zotov and his colleague will present their hypothesis to the Asia Oceania Geoscience Society 2022 Annual Meeting (opens in a new tab) which is broadcast online.
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