Earth records its shortest day ever

Earth records its shortest day ever

If you feel that there is not enough time in the day, there may be a reason.

Earth experienced its shortest day since records began last month, cutting 1.59 milliseconds from its usual 24-hour rotation on June 29 – raising the possibility that a negative leap second will soon be needed to keep the hours matching the sky.

Normally, the average rotational speed of the Earth decreases slightly over time. Timers have been forced to add 27 leap seconds to atomic time since the 1970s as the planet slowed.

But since 2020, this phenomenon has reversed – speed records have been repeatedly broken over the past two years.

The previous day’s fastest was 1.47 ms under 24 hours on July 19, 2020. It was almost broken again on July 26, when the day was -1.50 ms shorter.

While the effect is too small to be observed by humans, it can accumulate over time — potentially affecting modern satellite communications and navigation systems that rely on time consistent with the traditional positions of the sun, moon and stars.

This means that it may soon be necessary to remove the time, add a negative leap second, and speed up the world clocks for the first time ever.

“Chandler and Bobble”

Scientists have been left confused as to why, although experts have suggested that a phenomenon known as “Chandler’s Wobble” may have an effect.

The speed of the Earth’s rotation varies constantly due to the complex movement of its molten milk, oceans and atmosphere, as well as the influence of celestial bodies such as the Moon.

Tidal friction and the change in the distance between the Earth and the Moon cause daily variations in the planet’s rotation speed on its axis.

“Chandler Wobble” is the change in the Earth’s rotation about its axis and usually causes the Earth’s rotation to increase, which means it takes longer to complete a turn. But in recent years, the rotation has become less volatile.

Dr. Leonid Zotov, of the Sternberg Institute of Astronomy at Lomonosov Moscow State University, believes this lack of oscillation may be behind the faster days and will present the theory next week at the annual meeting of the Asia Oceania Society for Geosciences.

“The normal amplitude of the Chandler Wobble is about three to four meters at the Earth’s surface, but it disappeared from 2017 to 2020,” Dr. Leonid Zotov told Timeanddate.

In the early 2000s, Chandler and Bobble’s breadth started declining and in 2017-20 reached its historic low just as day length began to shrink.

Global warming is a small contributing factor

Other factors that could have an effect on the annual variance include the accumulation of snow on mountains in the northern hemisphere in the winter and then melting in the summer.

Global warming is also expected to have an effect by melting ice and snow at higher altitudes, causing the Earth to spin faster, but is considered a relatively small contribution.

Changes in the length of the standard day were only discovered after high-accuracy atomic clocks were developed in the 1960s and compared to fixed stars in the sky.

The last leap second was added on New Year’s Eve in 2016, when clocks around the world stopped for a second to allow the Earth’s rotation to catch up.

Then, BT’s talk clock added a second pause before the third dot, while BBC Radio 4 added an additional dot to the 1am bulletin.

The Paris-based International Earth Rotation Service monitors the planet’s rotation and informs countries when leap seconds should be added or removed six months in advance.

However, the leap second could be canceled entirely next year, when the World Radiocommunication Conference will decide whether it will depend entirely on atomic time.

Britain opposes this move because it will cut off the link to solar time in perpetuity.

Some experts believe that the need for a negative leap second may increase the pressure on the transition to atomic time.

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