Achi news desk-
The changing spin of the Earth threatens to toy with our sense of time, clocks and computerized society in an unprecedented way – but only for a moment.
For the first time in history, the world’s timekeepers may have to consider removing a second from our clocks in a few years because the planet is rotating a little faster than it used to. Clocks may have to skip a second – known as a “negative leap second” – around 2029, a study in the journal Nature said on Wednesday.
“This is an unprecedented and very large situation,” said study lead author Duncan Agnew, a geophysicist at the Scripps Institution of Oceanography at the University of California, San Diego. “It’s not a huge change in the Earth’s rotation that’s going to lead to some disaster or anything, but it’s something notable. It is yet another sign that we are in very unusual times.”
Melting ice at both poles of the Earth has been counteracting the planet’s speed burst and is likely to have delayed this global moment of reckoning by about three years, Agnew said.
“We’re headed for a negative leap moment,” said Dennis McCarthy, retired weather director for the US Naval Observatory who was not involved in the study. “It’s a matter of time.”
It is a complex situation involving physics, global power politics, climate change, technology and two kinds of time.
The Earth takes about 24 hours to rotate, but the key word is about.
For thousands of years, the Earth has been generally slowing down, with the rate varying from time to time, said Agnew and Judah Levine, a physicist for the time and frequency division of the National Institute of Standards and Technology.
The slowdown is mainly caused by the effect of tides, which are caused by the pull of the moon, McCarthy said.
This did not matter until atomic clocks were adopted as the official time standard more than 55 years ago. Those didn’t slow down.
That set up two versions of time – astronomical and atomic – and they didn’t match. Astronomical time fell 2.5 milliseconds behind atomic time each day. That meant the atomic clock would say it was midnight and for Earth it was midnight a fraction of a second later, Agnew said.
Those daily fractions of seconds added up to whole seconds every few years. Starting in 1972, international timekeepers decided to add a “leap second” in June or December for astronomical time to catch up to atomic time, known as Coordinated Universal Time or UTC. Instead of turning 11:59 and 59 seconds at midnight, there would be another second at 11:59 and 60 seconds. A negative leap second would go from 11:59 and 58 seconds directly to midnight, skipping 11:59:59.
Between 1972 and 2016, 27 separate leap seconds were added as the Earth slowed down. But the rate of slowdown was decreasing.
“In 2016 or 2017 or maybe 2018, the rate of deceleration had slowed to the point that the Earth was actually accelerating,” Levine said.
The Earth is accelerating because its hot liquid core – “a big ball of molten liquid” – is acting in unpredictable ways, with varying offsets and flows, Agnew said.
Agnew said the core had been driving acceleration for about 50 years, but the rapid melting of ice at the poles since 1990 masked that effect. Melting ice moves the mass of the Earth from the poles to the center of gravity, which slows the rotation much like a spinning ice skater slows down by extending their arms out to their sides, he said.
Without the effect of melting ice, Earth would need that second negative jump in 2026 instead of 2029, Agnew calculated.
For decades, astronomers had been keeping universal and astronomical time along with those handy little leap seconds. But computer system operators said those additions aren’t easy for all the very technology the world now relies on. In 2012, some computer systems abused the second jump, causing problems for Reddit, Linux, Qantas Airlines and others, experts said.
“What is the need for this adjustment at a time when it causes so many problems?” McCarthy said.
But Russia’s satellite system relies on astronomical time, so eliminating leap seconds would cause problems for them, Agnew and McCarthy said. Astronomers and others wanted to keep the system that would add a leap second whenever the difference between atomic time and astronomical time approached a second.
In 2022, the world’s timekeepers decided that, starting in the 2030s, they would change the standards for inserting or removing a leap second, making it much less likely.
Tech companies like Google and Amazon unilaterally established their own solutions to the second leap issue by gradually adding fractions of a second over a full day, Levine said.
“The fight is so serious because the stakes are so small,” Levine said.
Then add the “weird” effect of pulling, not adding a jump moment, Agnew says. It’s likely harder to skip a moment because software programs are designed to add, not subtract, time, McCarthy said.
McCarthy said the trend towards needing a second negative jump is clear, but he believes it has more to do with the Earth becoming rounder from geological changes from the end of the last ice age.
Three other outside scientists said Agnew’s study made sense, calling his evidence compelling.
But Levine doesn’t think there will really be a need for a negative leap moment. He said the general tidal slowing trend has been around for centuries and continues, but the shorter trends in the Earth’s core come and go.
“This is not a process where the past is a good predictor of the future,” Levine said. “Anyone who makes a long-term prediction about the future is on very, very shaky ground.”
(This story has not been edited by News18 staff and is published from a syndicated news agency feed – Associated Press)
