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The Earth’s shifting rotation threatens to upend our perceptions of time, clocks, and electronic society in new ways, but only for a second.
For the first time in history, timekeepers around the world may have to consider deducting a second from our clocks in a few years since the planet is rotating slightly faster than before.
Clocks may need to skip a second – known as a “negative leap “second”—around 2029, according to a study published Wednesday in Nature.
“This is an unprecedented situation and a major event,” said Duncan Agnew, the study’s principal author and geophysicist at the Scripps Institution of Oceanography at the University of California, San Diego. “It’s not a significant alteration in the Earth’s rotation that will trigger a disaster or anything, but it is noticeable. It’s another sign that we’re living in a really strange period.”
Melting ice at Earth’s two poles slowed the planet’s acceleration, likely delaying the second global assessment by around three years, Agnew said.
“We’re heading toward a negative second,” said Dennis McCarthy, weather director at the United States Naval Observatory, who was not involved in the study. “The question is when.”
This is a complicated problem that includes physics, global power politics, climate change, technology, and two forms of weather. The Earth rotates in about 24 hours, however the keyword is “approximately”.
According to Ms. Agnew and Judah Levine, a physicist in the National Standards Institute’s Time and Frequency Division, the Earth has been slowing down for thousands of years, with the rate altering per period.
McCarthy explained that the slowing is primarily due to the effect of tides, which are generated by the moon’s pull. This didn’t matter until about 55 years ago, when atomic clocks were designated as the official time standard. They have not slowed down.
Two forms of time were thus created: astronomical and atomic, although they did not correspond to one another. Every day, astronomical time trailed atomic time by 2.5 milliseconds. That is, the atomic clock indicated it was midnight, but it was midnight on Earth a fraction of a second later, Agnew explained.
These everyday fractions of seconds accumulated up to entire seconds every few years. Beginning in 1972, worldwide timekeepers decided to add a “leap second” in June or December to bring astronomical time into sync with atomic time, known as Coordinated Universal Time (UTC). There would be an extra second at 11:59:60 rather than 11:59:59 at midnight. A negative leap second would jump from 11:59:58 to midnight, skipping 11:59:59.
Between 1972 and 2016, 27 more leap seconds were added as Earth slowed. However, the pace of the decline has reduced. “In 2016, 2017 or maybe 2018, the rate of slowdown slowed to the point where the Earth started speeding up ,” Levine said in a statement.
Earth is speeding fast because its hot liquid core – “a big ball of molten fluid” – behaves unexpectedly, with swirling and varying flows, according to Agnew.
According to Mr. Agnew, the core has been causing an acceleration for nearly fifty years, but the rapid melting of ice at the poles since 1990 has obscured the effect. Melting ice pushes the Earth’s bulk from the poles to the domed center, slowing the rotation in the same way that an ice skater would stretch his arms to the sides.
Mr. Agnew calculated that without the influence of melting glaciers, the Earth would need this negative leap second in 2026 rather than 2029.
Astronomers have been able to align universal and astronomical time for decades because to these extremely useful leap seconds. However, computer system operators stated that the additions were difficult to make given the precision of today’s technology. Experts suggest that in 2012, several computer systems handled the leap second incorrectly, causing issues for Reddit, Linux, Qantas Airlines, and others.
“What’s the point of this time adjustment when it causes so much trouble?” Mr. McCarthy asked.
However, because Russia’s satellite system is based on astronomical time, removing leap seconds would be problematic, according to Mr. Agnew and Mr. McCarthy. Astronomers and others sought to keep the method of adding a leap second whenever the discrepancy between atomic and astronomical time approaches one second.
In 2022, timekeepers around the world agreed that beginning in the 2030s, they would revise the requirements for adding or removing a leap second, considerably reducing the possibility of it occurring.
According to Mr. Levine, tech corporations like Google and Amazon have applied their own solutions to the leap second problem by progressively adding fractions of a second over the course of a day.
“The arguments are so serious because the stakes are so small,” Mr. Levine explained.
Then, Ms. Agnew continued, add the “bizarre” effect of subtracting rather than adding a leap second. Mr. McCarthy believes it will be more difficult to skip a second because software is meant to increase time rather than subtract it.
Mr. McCarthy stated that the trend toward the need for a negative leap second is apparent, but he believes it is due to the Earth becoming rounder as a result of geological changes at the conclusion of the last ice age.
Three additional outside experts agreed that Agnew’s work made logic and his evidence was strong.
However, Mr. Levine believes that a negative leap second is unnecessary. The main tidal slowing tendency has existed for ages and continues, he claims, although shorter trends in the Earth’s core come and go.
“This is not a process where the past is a good prediction of the future ,” Mr. Levine went on to say. “Anyone who makes a long-term prediction about the future is on very, very shaky ground.”
