07:30 GMT27 January 2021
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    It takes the Earth 24 hours to revolve around its axis, however, even such a beautiful world like our planet is not perfect and the length of its rotation can vary by milliseconds, with the Earth speeding up or slowing down.

    It felt like 2020 would never end, but it turns out the previous year was the quickest in decades, with our planet revolving around its axis up to 1.5 milliseconds faster than usual. According to the website TimeAndDate.com, 2020 had the 28 shortest days since 1960. The shortest one occurred on 19 July, with our planet completing a rotation 1.4 milliseconds less than the usual 24 hours.

    Scientists monitoring the planet’s rotation say that the trend may continue and that this year may set new records. An average day is expected to last 0.05 milliseconds less than usual. The last time our planet was spinning that fast was in 1937. Physicist Peter Whibberley from the UK's National Physics Laboratory said the Earth is now spinning faster than at any time in the last 50 years.

    How Do Scientists Determine the Rotation Speed?

    Researchers at the International Earth Rotation and Reference Systems Service (IERS) first measure the exact moment a fixed star passes a location in the sky. They call this measurement Universal Time, which they then compare to International Atomic Time, a time scale that combines data from 200 ultra-precise atomic clocks located in laboratories across the world. The result tells scientists how far the planet has deviated from the norm.

    Sometimes the Earth slows down. Since the second part of the 20th century, when scientists began measuring the Earth’s rotation, most years' days exceeded the norm by a few hundred milliseconds, which prompted scientists to introduce a leap second to atomic clocks. Since 1972, researchers at IERS have added 27 leap seconds. However, no leap seconds have been added since 2016 and if this year turns out to be shorter than 2020, scientists may even subtract a second.


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    International Earth Rotation and Reference Systems Service, 2020, rotation, Earth
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