The rotation speed of the Earth is mysteriously increasing

The rotation speed of the Earth is mysteriously increasing

The rotation speed of the Earth is mysteriously increasing

The length of the day is defined as the difference between the time it takes for the Earth to complete one full rotation on its axis and 24 hours (ie 86,400 seconds). If this duration increases, it means that our planet rotates more slowly; on the contrary, if it decreases, it indicates that the Earth is rotating faster. It is known that in the long run our planet tends to slow down. This is also why the Paris-based International Earth Rotation and Reference Systems Service (IERS) has introduced a “leap second”, an annual adjustment aimed at aligning Coordinated Universal Time (UTC) with astronomical reality. However, in recent years, we have observed the opposite phenomenon: the Earth is spinning on itself faster and faster.

  • The fastest spin ever

Evidence of this acceleration was particularly abundant in 2020 – scientists recorded the shortest 28 days since the 1960s that year! On July 19, 2020, the Earth completed a rotation in 24 hours minus 1.4602 milliseconds. It was the last record until this year, until this year: on June 29, the rotation was even faster by 0.13 milliseconds. It was the shortest day on record since atomic clocks were used to measure the rotation speed of the Earth.

rotation

Day length fluctuation from 2019 (data provided by the International Earth Rotation and Reference Systems Service). Credits: timeanddate.com

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This new record was almost beaten the following month: on July 26, 2022, the length of the day was 24 hours minus 1.5 milliseconds. The longest day of the year (so far) occurred on May 14: the rotation lasted 24 hours and 0.68 milliseconds.

It is generally believed that a day lasts 24 hours: this definition is also the basis of watchmaking. But in reality, this is not entirely accurate: in terms of standard time, each day is usually slightly longer or slightly shorter than 24 hours (as can be seen in the graph above). Due to the tidal effect exerted by the presence of the Moon, which changes the shape of the Earth, its rotation gradually slows down. So every century the Earth typically takes a few milliseconds or more to complete one rotation.

  • The climate or internal processes potentially involved

As of August 24, 2022, the expected length of the day was 23 hours, 59 minutes and 59.9986509 seconds (i.e. 24 hours minus 1.3491 milliseconds), specify the time and date of the site. How do you explain these recent accelerations, which have become increasingly frequent since 2020? If the exact origin of the phenomenon is currently unknown, scientists are putting forward several hypotheses, in particular related to climate change or internal geological processes.

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The melting of glaciers at the poles – and the mass fluctuation they cause – movements within the Earth’s mantle or even the planet’s seismic activity could be possible explanations.

These point accelerations could also be due to the Chandler Oscillation, which refers to the irregular movement of the Earth’s geographic poles with respect to its surface, whose period is fourteen months. This hypothesis was suggested by Leonid Zotov and his collaborators during the annual meeting of the Asia Oceania Geosciences Society. ” The normal amplitude of the Chandler oscillation is about three to four meters on the Earth’s surface, but from 2017 to 2020 it disappeared “He said, according to comments reported by timeanddate.

  • Will we have to go back in time?

Nothing to worry about: these accelerations are still anecdotal and the phenomenon of slowdowns remains predominant for the moment. If, on the other hand, the length of the day continues to decrease, to keep Coordinated Universal Time closer to standard time, the IERS may soon decide to enter a negative leap second for the first time since 1972. – date on which the leap second system was introduced.

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However, inserting a negative leap second would result in our watches being set back by one second, which could potentially cause computer systems to malfunction. However, Professor Zotov wants to be reassuring: ” I think there is a 70% chance that we are at a minimum and we will not need a negative leap second “He said.

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