Leap second that crashed Reddit and LinkedIn plus knocked out Qantas's booking system

SIXTY-six million years ago, days were about twenty-three-and-a-half hours long. Professor Claire Nichols, associate professor of the geology of planetary processes at Oxford University, said: "Tyrannosaurus Rex had half-an hour less than us to go about his business. The planet was rotating faster because the Earth had more energy. "Earth formed around 4.5 billion years ago, and there was a lot more energy in the solar system then. So everything was rotating very, very rapidly. The moon was much closer to us. But Earth has slowed down and the Moon has moved further away over the last 4.5 billion years as the solar system loses energy. The energy is being dissipated basically by the interactions between all the bodies in the solar system. It's really surprising that we're currently speeding up and the days are getting fractionally shorter. This means that the days and months have been getting longer and longer over geological time." By fractionally shorter, Prof Nichols means a shift of around a millisecond and a half, which doesn't sound like a massive problem. Even Earth's fastest day on record, set in July 2024, was only 1.66 milliseconds short of 24 hours. And this month, turning back the clocks to British wintertime will not be the only changing time we need to be concerned about. To see more of the stories you love from The Mirror and to find them easily in Google then make us your preferred source. Free and easy-to-do, just click on the link here to find more from The Mirror at the top of your feed. For, between October 13 and 15, at the 28th meeting of the General Conference on Weights and Measures, international timekeepers will address the future of the leap second at the Palais des Congrès de Versailles in France The leap second that delegates from around the world are due to vote on retiring is the extra second that’s been added to the world's clocks every few years since 1972, to keep them in step with the Earth's uneven spin. Throughout most of human history, the sun set the length of a day. That changed with the railways, when Britain adopted a single standard time, so that a timetable in Bristol matched a timetable in London. In 1955, scientists at the National Physical Laboratory in Teddington built an atomic clock based on the vibrations of caesium atoms, accurate to within a second every 300 years. By 1967, the second itself had been redefined around caesium, ending thousands of years of timekeeping by the stars. Mathematician Kit Yates says it is easy to confuse leap seconds with leap years, though the two work differently. Leap years, he said, adjust the calendar for the Earth's orbit around the sun, while leap seconds adjust the clock for the Earth's rotation on its own axis. Over a hundred years, Kit said, losing 24 days to the calendar would be hard to miss, but a midday shift of a minute or so from leap seconds would not. Setnam Shemar, principal scientist at the National Physical Laboratory, said it brings forward a decision the world's measurement authorities already made in 2022, when they agreed leap seconds would stop by 2035. Meanwhile, applying the leap second hasn't always gone smoothly. Setnam said different systems can apply it slightly differently, causing timing conflicts between networks. The last time it went badly was in 2012, when the extra second crashed Reddit and LinkedIn, and knocked out Qantas's booking system for around two hours, forcing staff to check passengers in by hand. Accurate time is used across the country, Setnam said, by telecommunications, electrical grid operators, banks timestamping financial transactions, transport, positioning and emergency services, much of it critical national infrastructure. Most of those users get their time from satellite navigation systems such as GPS, he said, but the most critical ones get it directly from the lab. Until now, every leap second has worked the same way, adding a second because the Earth was running slow against the clocks. Setnam said it has become more urgent because the Earth's rotation has been speeding up, meaning the next adjustment would have to go in the opposite direction from normal, a negative leap second that has never been applied before. One estimate puts the odds of that happening by 2035 at 30 per cent. At midnight on New Year's Eve, Setnam said, a negative leap second would mean skipping the 59th second entirely, jumping straight from 58 to the next minute. What's on the table in October would avoid that altogether, by letting the gap between atomic time and the Earth's spin grow far wider before anyone has to touch the clocks at all, from one second to as much as an hour. Setnam said that would take thousands of years to add up. Why it's happening now comes down to what's going on deep inside the Earth. "This kind of wobble will have happened before," Prof Nichols said. "Lots of things slightly change the rotation rate of the Earth. "We have a solid inner core and a liquid outer core, and there's observations that suggest that the solid inner core is actually kind of rotating slightly, either ahead of the rest of the planet or behind the rest of the planet. And it seems to do that on kind of a 70 year time scale, roughly. And so if it gets slightly ahead of us, it makes the days go slightly faster. And if it gets slightly behind us, it makes the days go slightly slower." Tectonic plates shifting across the surface change how the planet's mass is spread out too, alongside the ice sheets and oceans moving around it. "You can imagine it being like an ice skater spinning," Prof Nichols said. "If you stick your arms out compared to kind of crouching inwards, that will change how quickly you spin." The same core also generates the Earth's magnetic field, which plays its own part in changing the length of the day. "I guess it's either speeding up or slowing down always, but it's really interesting that it's actually causing enough of an issue now that we're kind of having to fix the length of the day. And it's also actually manifest in what the magnetic field is doing. So the magnetic north pole has been wandering very, very rapidly from Canada over to Siberia. We've had to keep updating the model of the magnetic field so we can all still navigate using our phones. So actually we're seeing lots of effects of this in real life. So it's always nice to feel like we have a purpose." Prof Nichols also points to why any of this matters outside a lab. "We rely on the fact that the day and the night happen at predictable times, the months match with the changing seasons, for all manner of things. From kids being able to walk to school in the daylight, to ensuring we have enough fuel for heating when the weather gets colder in the winter." Looking further ahead, Prof Nichols expects the balance to tip back the other way. "We should start slowing down again in the next few decades. So over our lifetime, we'll probably go back to having a slightly slower day. It will take a lot, lot longer. But there are more sinister consequences for the whole solar system before we actually stop rotating. It's a pretty slow process." Even though the changes are tiny, Professor Nichols say they help remind us what an incredible place the solar system is. She added: "As a planetary geologist, the thing I would like people to remember is that we're on a planet that's rapidly spinning and hurtling around the Sun in space. We very rarely have reminders of the fact that we're part of a very complex, dynamic and fast moving solar system, so I think this is a nice reminder."