Earth records shortest days since atomic clocks existed

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On June 29, 2022, the Earth completed one rotation in 1.59 milliseconds in less than 24 hours. This is the latest in a series of Earth speed records since 2020.

In general, over long periods, the Earth’s rotation slows down. Each century, the Earth takes about a few milliseconds to complete one rotation (where 1 millisecond equals 0.001 seconds).

However, in this general pattern, the speed of rotation of the Earth fluctuates. From day to day, the time it takes Earth to complete one rotation increases or decreases by a fraction of a millisecond, reports

Scientists who study the Earth’s rotation use the term “daylength” to refer to the speed or slowness of Earth’s rotation. The length of a day is the difference between the time it takes the Earth to rotate once on its axis and 86,400 seconds (24 hours).

The longer the day length increases, the slower the Earth rotates. When it decreases and becomes a negative number, the Earth spins faster.

In recent years, the Earth has accelerated. In 2020, it had reached its shortest 28 days since accurate daily measurements with atomic clocks began in the 1960s. The shortest day of all in 2020 was -1.47 milliseconds on July 19.

The Earth continued to spin rapidly in 2021, although the shortest day of the year in 2021 was a fraction longer than in 2020.

This year, on June 29, Earth set a new record for the shortest day in the atomic clock era: -1.59 milliseconds. Earth broke its record again a month later, recording a day length of -1.50 milliseconds on July 26, according to measurements by the National Physical Laboratory in England.

Ordinary fluctuations in day length are the result of the Moon’s monthly orbit around the Earth. The longest and mildest waves, with the shortest days in or around July each year, are related to the movements of the Earth’s atmosphere.

The current downward trend in the length of the shortest day could be linked to processes in the inner or outer layers of the Earth, the oceans, the tides or even the climate. Scientists are unsure and struggle to make day length predictions more than a year in advance.

If the Earth’s rapid rotation continues, it could lead to the introduction of the first negative leap second. This would be necessary to keep civil time, which is based on atomic clocks, in sync with solar time, which is based on the movement of the Sun across the sky.

A negative leap second would mean that our clocks skip a second, which could create problems for various technologies. “I think there’s a 70 percent chance that we’re at the minimum ‘day length reduction,’ said Leonid Zotov, an Earth rotation expert at Lomonosov University, “and we won’t have no need for a negative leap second”.

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