The year 2021 is expected to be the shortest in decades. The last time an average day was less than 86,400 seconds in a full year was in 1937.
According to the calculations, an average day in 2021 will be 0.05 milliseconds shorter than 86,400 seconds. Throughout the year, atomic clocks will have accumulated a lag of about 19 milliseconds.
Accelerated rotation
The length of an average solar day can vary in milliseconds (1 millisecond equals 0.001 seconds). But Earth's rotation speed varies constantly due to the complex motion of its molten core, oceans and atmosphere, as well as other effects. Official measurements of day length are made by the International Earth Rotation and Reference Systems Service (IERS).
To determine the actual length of a day, IERS scientists determine the exact speed of Earth's rotation by measuring the precise times a fixed star passes a given location in the sky each day. This measure is expressed as Universal time (UT1), a type of solar time.
Before 2020 began, for example, The shortest day since 1973 was July 5, 2005, when the Earth's rotation took 1.0516 milliseconds less than 86,400 seconds.
However, in mid-2020, lEarth broke that record no less than 28 times. The shortest day of all came on July 19, when Earth completed its rotation in 1.4602 milliseconds short of 86,400 seconds. 2021, if the calculations are confirmed, will break this record.
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The news
The year 2021 will be the shortest in decades: the Earth has been rotating more rapidly lately
was originally published in
Xataka Science
by
Sergio Parra
.