According to the latest data disclosed recently, on June 29, the earth completed a rotation 1.59 milliseconds less than the standard 24 hours, which is the fastest time since atomic clocks began to record the earth's rotation in the 1960s.

　　According to reports, this record gave the earth "the shortest day ever" and also showed once again that the earth has been spinning faster in recent years.

However, the exact cause of Earth's accelerated rotation remains a mystery.

In fact, since 2020, Earth has broken the record for the fastest rotation more than 20 times, reversing a previous long cycle that lasted for decades.

　　Scientists who study the earth's rotation use the term "diurnal variation of the earth's rotation" to describe how fast the earth rotates, referring to the difference between the time it takes the earth to make one revolution around the earth's axis and 86,400 seconds, or 24 hours.

When the "day change in Earth's rotation" increases, the Earth's rotation slows; when it decreases and becomes negative, the Earth's rotation increases.

　　For a long time before, the rotation speed of the earth has been "slowing", and it usually takes a few milliseconds more time to complete one rotation (1 millisecond is equivalent to 0.001 seconds).

But the speed of Earth's rotation fluctuates, and the time it takes to complete one rotation increases or decreases by a fraction of a millisecond.

　　The scientists explained that the Earth is not a perfect sphere and its rotation is always affected by many factors, including its internal structure, the tidal influence of the moon and climate change.

At this year's annual meeting of the "Asia-Oceania Geoscience Society", Dr. Leonid Zotov of Moscow State University pointed out that the current "change in the diurnal length of the Earth's rotation" may be related to the "Chandler wobble".

　　A "Chandler wobble" is a small movement of the Earth's axis of rotation relative to the Earth's surface.

"The normal amplitude of the Chandler wobble is about 3 to 4 meters at the Earth's surface," Dr Zotov said, "but between 2017 and 2020 it disappeared."

　　Professor Matt King, who specialises in Earth observation at the University of Tasmania, said clearly something had changed, "but this change is something we haven't seen since precision radio astronomy began in the 1970s. "

　　If Earth's days continue to get shorter, scientists may eventually have to add a "negative leap second" to ensure that Earth's orbit around the sun matches what atomic clocks measure.

This would be the first example of a "negative leap second" in history.

　　It is reported that manually adding or subtracting a leap second will cause serious losses to those industries that have high requirements on time accuracy, such as aerospace, communications, and finance.

It also requires a lot of manpower and material resources to allow organizations around the world to provide services based on time to add or subtract a leap second at the same time.

　　However, Dr Zotov said: "There is a 70% chance that the Earth's rotation has already reached its lowest level of variation in day length, so we don't need negative leap seconds."

　　Chengdu Business Daily - Red Star News reporter Xu Huan

　　Intern Li Zhaoxin