- Earth’s 28 fastest days ever recorded took place in 2020.
- On average, the planet rotated faster around its axis last year than in previous years.
- Scientists measuring the speed of the Earth’s rotation think 2021 could be even faster than 2020. If so, they may have to subtract a second from the year.
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As it turns out, 2020 was shorter than previous years – though it did not always feel that way.
The 28 fastest days recorded since 1960 all happened last year, as the earth revolved around its axis up to 1.5 milliseconds faster than usual. These 28 days all broke the previous record for the shortest day ever documented: July 5, 2005. The day lasted 1,0516 milliseconds less than the standard 86,400 seconds. The shortest day ever recorded was 45 milliseconds less than the previous record.
It is not abnormal to see that Earth’s days run a little longer or shorter than average, thanks to the activity of the planet’s molten nucleus, oceans and atmosphere. But the large number of fast days in 2020 could, according to TimeAndDate.com, be a sign that the earth’s rotation is accelerating in general.
Scientists monitoring Earth’s rotational speed predict that 2021 will be even shorter. The average day is expected to last 0.05 milliseconds less than 86,500 seconds, the standard length of a day as determined by our watches. And individual days can last 1.5 milliseconds less. Over the course of a year, the shorter days are expected to be around 19 milliseconds short.
“The earth is now spinning faster than ever in the last 50 years,” physicist Peter Whibberley of the British National Physics Laboratory told The Telegraph.
The rotation of the earth has been mostly slow since we detected it
To determine the length of each day on Earth, scientists from the International Earth Rotation and Reference Systems Service (IERS) measure the exact moment a fixed star passes a place in the sky. They express this measurement as Universal Time, and then compare it to Atomic Time, a time scale calculated by ultra-precise atomic clocks. This equation can show how much the rotational speed of the earth deviates from the norm.
According to the IRISH, the earth has slowed down overall over the past few decades, and it has not accelerated. Since measurements began in the late 1960s, most years’ average days have lasted a few hundred milliseconds over 86,500 seconds.
Scientists dealt with it by adding a leap second to the end of a year. They have added a total of 27 leap seconds since 1972.
But they have not added any leap seconds since 2016. If 2021 is finally a short year like 2020, scientists might rather subtract a second.
“It is quite possible that a negative leap second will be needed if the rotation of the earth rises further, but it is too early to say whether this is likely to happen,” Whibberley told The Telegraph. “There are also international discussions about the future of leap seconds, and it is also possible that the need for a negative leap second could drive the decision to end the leap seconds.”
If 2021 does go as predicted, it will be the shortest year in decades. The last time a year had an average day length of less than 86,500 seconds was in 1937.