A Faster Spinning Earth May Cause Timekeepers to Subtract a Second from World Clocks

This image provided by NOAA/NASA In This May 31, 2018 satellite image shows the Earth's western hemisphere at 12:00 p.m. EDT on May 20, 2018, made by the new GOES-17 satellite, using the Advanced Baseline Imager (ABI) instrument. (NOAA/NASA via AP, File)
This image provided by NOAA/NASA In This May 31, 2018 satellite image shows the Earth's western hemisphere at 12:00 p.m. EDT on May 20, 2018, made by the new GOES-17 satellite, using the Advanced Baseline Imager (ABI) instrument. (NOAA/NASA via AP, File)
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A Faster Spinning Earth May Cause Timekeepers to Subtract a Second from World Clocks

This image provided by NOAA/NASA In This May 31, 2018 satellite image shows the Earth's western hemisphere at 12:00 p.m. EDT on May 20, 2018, made by the new GOES-17 satellite, using the Advanced Baseline Imager (ABI) instrument. (NOAA/NASA via AP, File)
This image provided by NOAA/NASA In This May 31, 2018 satellite image shows the Earth's western hemisphere at 12:00 p.m. EDT on May 20, 2018, made by the new GOES-17 satellite, using the Advanced Baseline Imager (ABI) instrument. (NOAA/NASA via AP, File)

Earth’s changing spin is threatening to toy with our sense of time, clocks and computerized society in an unprecedented way — but only for a second.

For the first time in history, world timekeepers may have to consider subtracting a second from our clocks in a few years because the planet is rotating a tad faster than it used to. Clocks may have to skip a second — called a "negative leap second" — around 2029, a study in the journal Nature said Wednesday.

"This is an unprecedented situation and a big deal," 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 catastrophe or anything, but it is something notable. It’s yet another indication that we’re in a very unusual time."

Ice melting at both of Earth’s poles has been counteracting the planet's burst of speed and is likely to have delayed this global second of reckoning by about three years, Agnew said.

"We are headed toward a negative leap second," said Dennis McCarthy, retired director of time for the US Naval Observatory who wasn’t part of the study. "It’s a matter of when."

It’s a complicated situation that involves, physics, global power politics, climate change, technology and two types of time.

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 slowing is mostly caused by the effect of tides, which are caused by the pull of the moon, McCarthy said.

This didn’t matter until atomic clocks were adopted as the official time standard more than 55 years ago. Those didn’t slow.

That established two versions of time — astronomical and atomic — and they didn't match. Astronomical time fell behind atomic time by 2.5 milliseconds every day. That meant the atomic clock would say it’s midnight and to 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 the atomic time, called Coordinated Universal Time or UTC. Instead of 11:59 and 59 seconds turning to 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 Earth slowed. But the rate of slowing was tapering off.

"In 2016 or 2017 or maybe 2018, the slowdown rate had slowed down to the point that the Earth was actually speeding up," Levine said.

Earth’s speeding up because its hot liquid core — "a large ball of molten fluid" — acts in unpredictable ways, with eddies and flows that vary, Agnew said.

Agnew said the core has been triggering a speedup for about 50 years, but rapid melting of ice at the poles since 1990 masked that effect. Melting ice shifts Earth’s mass from the poles to the bulging center, which slows the rotation much like a spinning ice skater slows when extending their arms out to their sides, he said.

Without the effect of melting ice, Earth would need that negative leap second in 2026 instead of 2029, Agnew calculated.

For decades, astronomers had been keeping universal and astronomical time together with those handy little leap seconds. But computer system operators said those additions aren’t easy for all the precise technology the world now relies on. In 2012, some computer systems mishandled the leap second, causing problems for Reddit, Linux, Qantas Airlines and others, experts said.

"What is the need for this adjustment in time when it causes so many problems?" McCarthy said.

But Russia’s satellite system relies on astronomical time, so eliminating leap seconds would cause them problems, Agnew and McCarthy said. Astronomers and others wanted to keep the system that would add a leap second whenever the difference between atomic and astronomical time neared a second.

In 2022, the world’s timekeepers decided that starting in the 2030s they’d change the standards for inserting or deleting a leap second, making it much less likely.

Tech companies such as Google and Amazon unilaterally instituted their own solutions to the leap second issue by gradually adding fractions of a second over a full day, Levine said.

"The fights are so serious because the stakes are so small," Levine said.

Then add in the "weird" effect of subtracting, not adding a leap second, Agnew said. It’s likely to be tougher to skip a second because software programs are designed to add, not subtract time, McCarthy said.

McCarthy said the trend toward needing a negative leap second is clear, but he thinks it’s more to do with the Earth becoming more round from geologic shifts from the end of the last ice age.

Three other outside scientists said Agnew's study makes sense, calling his evidence compelling.

But Levine doesn’t think a negative leap second will really be needed. He said the overall slowing trend from tides has been around for centuries and continues, but the shorter trends in Earth’s core come and go.

"This is not a process where the past is a good prediction of the future," Levine said. "Anyone who makes a long-term prediction on the future is on very, very shaky ground."



Prince William Takes Early-Morning Nature Walk Near South Africa’s Table Mountain

 Prince William, Prince of Wales talks to Megan Taplin, Park Manager for Table Mountain National Park during his visit at Signal Hill on November 05, 2024 in Cape Town, South Africa. (Ian Vogler/Pool via Reuters)
Prince William, Prince of Wales talks to Megan Taplin, Park Manager for Table Mountain National Park during his visit at Signal Hill on November 05, 2024 in Cape Town, South Africa. (Ian Vogler/Pool via Reuters)
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Prince William Takes Early-Morning Nature Walk Near South Africa’s Table Mountain

 Prince William, Prince of Wales talks to Megan Taplin, Park Manager for Table Mountain National Park during his visit at Signal Hill on November 05, 2024 in Cape Town, South Africa. (Ian Vogler/Pool via Reuters)
Prince William, Prince of Wales talks to Megan Taplin, Park Manager for Table Mountain National Park during his visit at Signal Hill on November 05, 2024 in Cape Town, South Africa. (Ian Vogler/Pool via Reuters)

Prince William went on an early-morning nature walk near South Africa's Table Mountain on Tuesday to promote the work of conservation rangers in a unique urban national park.

The Prince of Wales and heir to the British throne met with some of the rangers who guard the Table Mountain National Park, an 85-square-mile (220-square kilometer) area that overlooks Cape Town and spills into the city's suburbs in some areas.

William didn't go to the top of the famous flat-topped mountain, instead strolling through nature trails on Signal Hill, a foothill that sits by the ocean's edge.

The prince was accompanied on the walk by Megan Taplin, the park manager, and Robert Irwin, an Australian conservationist. William met with rangers, park firefighters and members of a K-9 dog unit.

“He got to learn about what they do on a daily basis and what challenges they face,” Taplin said. “We also spoke a lot about ranger wellness and how that's really important that rangers are supported, that their families are supported, because they are doing quite dangerous work and difficult work.”

William is in South Africa to promote his annual Earthshot Prize, which awards $1.2 million in grants to five entrepreneurs or organizations for innovative ideas that help the environment and combat climate change. William set up the Earthshot Prize in 2020 through his Royal Foundation and the awards ceremony will be held in Cape Town — the first time it's been in Africa — on Wednesday night.

The prince's four-day visit is a kind of environmental roadshow and is heavily focused on climate and conservation, though he did break away from those issues on his first day in Cape Town on Monday to attend a rugby practice at a local high school and play a little of South Africa's favorite sport with some of the kids.

William was also due to meet with South African President Cyril Ramaphosa at the president's Cape Town residence on Tuesday.

William has a range of engagements planned in South Africa's second-biggest city, including meetings with young environmentalists, attending a wildlife summit, visiting a botanical garden and spending time at a sea rescue institute and with a Cape Town fishing community.

William last visited Africa in 2018 but he has a strong connection to the continent. He traveled there as a boy after the death of his mother, Princess Diana, in a Paris car crash in 1997. He and his wife, Kate, got engaged at a wildlife conservancy in Kenya in 2010. And he said he came up with the idea for the Earthshot awards while in Namibia in 2018.

Before the visit, William said that Africa has always had “a special place in my heart.” William's brother Prince Harry visited South Africa and neighboring Lesotho last month for a charity he set up in southern Africa.

William's wife Kate, the Princess of Wales, and their children Prince George, Princess Charlotte and Prince Louis did not travel to South Africa. Kate only recently returned to some public duties after completing treatment for an undisclosed type of cancer.