The phenomenon could force to add a negative second in the clocks for the first time
This summer, Earth had the shortest day in its history due to its fastest recorded rotation speed. Experts say that it possibly happened thanks to a wobble in its axis that made it complete a single turn in a tiny fraction of a second less than usual.
Specifically, on June 29, 2022, the planet made a complete turn in 1.59 milliseconds less than the usual 24 hours (86,400 seconds), according to the website timeanddate.com. And this July he was about to break the barrier: July 26 was 1.50 milliseconds shorter than 24 hours.
To measure the actual length of a day, scientists determine the exact speed of Earth’s rotation by measuring the precise times a fixed star passes a certain location in the sky each day.
It’s not the first time
And it is that, indeed, the Earth has increased its speed in recent years. In 2020, our planet experienced its shortest month ever measured, since the 1960s. As if she herself wanted to end that pandemic year faster, the Earth in 2020 rotated faster than usual. In fact, our planet broke the previous record for the shortest astronomical day, set in 2005.
The shortest day of that year, July 5, saw the Earth complete a rotation of 1.0516 milliseconds faster than 86,400 seconds, which is the time it takes to rotate relative to the Sun, which is equivalent to 24 hours or a mean solar day. Instead, the shortest day of 2020 was July 19, when the planet completed a spin 1.4602 milliseconds faster than 86.400 seconds. Additionally, 2020 included the shortest 28 days since 1960. The following year, the Earth continued to rotate at a generally higher speed, although it did not break records. Until now.
Despite the punctual increases in recent times, in general, the rotation of the Earth slows down. Every century, the Earth takes a couple of milliseconds or so to complete one rotation (where 1 millisecond equals 0.001 seconds). Still, within this general pattern, the Earth’s spin rate fluctuates. From day to day, the time it takes for the Earth to complete one rotation increases or decreases by a fraction of a millisecond. Thus, in recent years, this trend has been reversed and the days are getting shorter.
Why is the Earth speeding up or slowing down?
Although the cause of the different rotational speeds of the Earth, and therefore the variable length of days, is unknown, theories abound. The most accepted is that this is due to several factors.
As reported Business Insider, the spin that we experience as night and day does not always occur exactly in line with its axis, the line between the north and south poles. Also, the planet has a bulge at the equator, while the poles are slightly squashedwhich means that the Earth is slightly elliptical.
There’s also other factors that can alter the rotation, such as ocean tides and the Moon’s gravity. In the same way, there are those who point out that the melting of the glaciers causes that there is less weight in the poles, among other theories. However, there are scientists who point to a main reason, apparently more accepted.
On June 29, 2022, the planet made a complete revolution in 1.59 milliseconds less than 86,400 seconds.
Chandler’s Wobble
Experts suggest that the reason for the trend of shorter days could be related to the Chandler wobble, a small deviation in the Earth’s axis of rotation. According to scientists Leonid Zotov, Christian Bizouard and Nikolay Sidorenkov, who presented the hypothesis at the Asia-Oceania Society of Geosciences, this phenomenon is similar to the tremor seen when a spinning top begins to gain momentum or slows down.
The wobble was first detected in the late 1880s, when astronomer Seth Carlo Chandler observed that the poles wobbled over a period of 14 months. “The normal amplitude of the Chandler wobble is about three or four meters at the surface of the Earth & rdquor ;, said the Zotov, “but from 2017 to 2020 it disappeared & rdquor ;, he added.
If the rapid rotation of the Earth continues, could lead to the introduction of the first negative additional second in history. This would be necessary to keep civil time – which is based on the super-steady rhythm of atomic clocks – in step with solar time, which is based on the Sun’s movement across the sky. An additional negative second would mean that our clocks would skip a second, which could create problems in computer systems.
To measure 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 certain location in the sky each day. This measurement is expressed as Universal Time (UT1), a type of solar time.
UT1 is then compared to International Atomic Time (TAI), a highly accurate time scale that combines the output of some 200 atomic clocks maintained in laboratories around the world. The actual length of a day is expressed by the deviation of UT1 from the TAI over 24 hours. Currently, the IERS does not show any new leap seconds scheduled to be added.
According to the service’s Earth Orientation Center leap seconds have their pros and cons. They are useful for making sure astronomical observations are in sync with clock time, but can be a nuisance for some data logging applications and telecommunications infrastructure. Some scientists at the International Telecommunications Union have suggested letting the gap between astronomical and atomic time widen until a “leap hour” is needed, which would minimize disruption to telecommunications.
Reference Articles:
https://www.timeanddate.com/news/astronomy/shortest-day-2022https://www.infobae.com/america/ciencia-america/2022/08/03/la-tierra-esta-girando-mas-rapido-de-lo-normal-y-registro-su-dia-mas- short/
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