Scientists say the Earth’s rotation is slowing down, affecting the timing of negative leap seconds. (Shutterstock)
[The Epoch Times, March 29, 2024](Comprehensive report by Epoch Times reporter Li Yan) Changes in the earth’s rotation are threatening our sense of time, clocks, and computerized society in an unprecedented way. It was only a one-second difference, but it left scientists scratching their heads.
A study published Wednesday (March 27) in the journal Nature investigated how changes in the Earth’s rotation have a huge impact on how we measure time, because our calendars and clocks are based on how long it takes for the Earth to rotate. definite.
The paper found that melting polar ice caps are redistributing large amounts of water from the Arctic and Antarctic to the world’s oceans, causing the Earth’s rotation to slow significantly. It’s like a spinning skater slowing down as he extends his arms to the sides.
Therefore, as more and more water weight is transferred away from the poles and distributed around the center of the Earth’s bulge, the Earth’s rotation slows down.
Yet at the same time, an opposing force has been accelerating the Earth. For about 50 years, the movement of the Earth’s core has been causing the Earth to accelerate. After modeling the effects of these two conflicting forces, the study’s lead author, geophysicist Duncan Carr Agnew, calculated that by 2029 we will need A “negative leap second”, when the world’s clocks will go back one second for the first time in history.
“This has never happened before and poses a significant challenge to ensuring that all global timing infrastructure displays the same time,” Agnew wrote in a statement to Global News. “This once again emphasizes the importance of In an era of unprecedented changes.”
Dennis McCarthy, retired director of the U.S. Naval Observatory, said, “We are heading towards a ‘negative leap second’.”
He was not involved in the study. “It’s just a matter of time,” he said.
It takes approximately 24 hours for the Earth to rotate once. Both Agnew and Judah Levine, a physicist in the Time and Frequency Division of the National Institute of Standards and Technology, say that the Earth has generally been slowing down over thousands of years, with the speed varying from time to time.
McCarthy said the slowdown is primarily caused by tidal effects, which are caused by the moon’s gravity.
A fight of one second
To understand why “negative leap seconds” may be necessary, we first need to understand how the world keeps time.
Before the invention of the atomic clock, a second was defined as 1/86,400 of a day, and a day was defined as one rotation of the Earth. The only problem is that the Earth’s rotation may speed up or slow down, which means the length of a second in each day may be different.
In 1967, timekeepers introduced the atomic clock as a means of precisely defining the second, based on the oscillations of cesium particles emitting radiation. It is conceivable that this quantum process is more stable than the movement of a small ball weighing 500 billion kilograms in space.
This establishes two versions of time – astronomical time and atomic time – but they don’t match. Astronomical time lags behind atomic time by 2.5 milliseconds per day. Over time, every few years there will be a difference of a full second between the two. Starting in 1972, international timekeepers decided to add a “leap second” in June or December in order to allow astronomical time to catch up with atomic time, jumping directly from 11:59:58 to midnight. This is the coordinated world time (UTC).
Between 1972 and 2016, a total of 27 leap seconds were added as the Earth slowed down. But the rate at which the Earth is slowing down is gradually slowing down.
“In 2016 or 2017, maybe 2018, the deceleration rate had slowed to the point where the Earth was actually speeding up,” Levine said.
Agnew said the Earth is accelerating because of its hot liquid core – a giant ball of molten fluid that moves in unpredictable ways, with eddies and flows.
Agnew said the center of the Earth has been causing an acceleration (of the Earth’s rotation) for about 50 years, but the rapid melting of polar ice since 1990 has masked this effect. The reason is as stated earlier in this article.
Agnew calculated that without the impact of melting ice, Earth would need a negative leap second in 2026 instead of 2029.
For decades, astronomers have tied universal time and astronomical time together through these little leap seconds. But adding those capabilities isn’t easy with the precision technology the world now relies on, computer systems operators say. Experts say that in 2012, some computer systems mishandled leap seconds, causing problems for Reddit, Linux, Qantas and others.
McCarthy asked, “Why is it necessary to adjust the timing when it creates so many problems?”
But Agnew and McCarthy said Russian satellite systems rely on astronomical time, so eliminating leap seconds would cause problems for them. Astronomers and others want to preserve the system, which adds a leap second whenever the difference between atomic and astronomical time approaches one second.
In 2022, the world’s timekeeping agencies decided that starting in the 2030s, they would change the standards for inserting or deleting leap seconds, greatly reducing the possibility of using leap seconds.
Tech companies such as Google and Amazon unilaterally developed their own leap second solutions, adding incrementally a few tenths of a second to the day, Levine said.
Agnew said “negative leap seconds” must also be taken into account. McCarthy said skipping a second may be more difficult because software programs are designed to add time, not subtract it.
But Levine doesn’t think negative leap seconds are really needed. He said the overall slowing trend in tides has been around for centuries and is continuing, but the Earth’s core also changes.
“In this process, the past is not a good predictor of the future. Anyone making long-term predictions about the future is untenable,” Levine said. ◇
(This article refers to the Associated Press report)
Editor in charge: Ye Ziwei#
#Slowing #Earths #rotation #change #humans #time #Epoch #Times
2024-03-29 02:57:59
