June 29 was the shortest day on our planet since the 1960s, since records began. The cut of 1.59 milliseconds with respect to the usual 24-hour turn raises the possibility that a leap second will have to be used to keep the clocks as they have been until now. This would be the first time that global clocks have accelerated.
In general, the Earth rotates once every 24 hours. However, the length of the day has variability due to various factors that can make it longer or shorter.
Earth’s rotation has been known to slow down, with 27 leap seconds, needed to keep atomic time accurate since the 1970s. The last one was on New Year’s Eve 2016, when clocks stopped for a second to allow Earth to catch up.
Atomic clocks have recently revealed that the Earth’s rotation is accelerating rapidly. In fact, a 50-year phase of shorter days could be starting right now. Scientists note that 2020 had the shortest 28 days since 1960. The shortest day in 2021 was longer than in 2020, reversing the trend of the previous year.
But on June 29, 2022, our planet made the fastest rotation in its history, and on July 26, 2022, there was a day that apparently lasted 1.50 milliseconds less.
Why does it seem that the Earth’s spin is accelerating?
On longer term, geological time scales, the Earth is actually spinning more slowly than before. If we turn back the planet’s clock 1.4 billion years, a day would pass in less than 19 hours. On average, therefore, Earth days grow longer rather than shorter, by about 74,000 of a second each year. The moon is the main culprit for the effect: the gravitational pull slightly distorts the planet, producing tidal friction that constantly slows Earth’s rotation.
As we’ve discussed, to keep clocks in line with the planet’s spin, the International Telecommunication Union , a United Nations body, adds occasional leap seconds and tells countries when leap seconds should be added or removed, with six months in advance. The next opportunity is December 2022, though with the Earth spinning so fast lately, that’s unlikely to be necessary.
Mind you, if the trend of shorter days were to continue for long, it could give rise to the possibility of the first “negative leap second” . Instead of adding a second to clocks, civil time would jump a second to keep up with the faster-spinning planet.
This tool, very useful for keeping time, has recently been criticized by the Internet giants Facebook, Google, Amazon and Microsoft, since the introduction of an additional second can occasionally break the software.
