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Trending science: Our last ‘leap second’?

‘If only I had more time’, so goes the popular refrain. Well this week, we all had a smidge more time – one extra ‘leap second’ to be precise.

Just before midnight GMT on Tuesday our clocks paused and the planet gained one second – automatic clocks read 23:59:60 and then ticked forward to 00.00.00. As the Earth’s rotation is gradually slowing, the ‘leap second’ allows us to realign Coordinated Universal Time (UCT) with solar time. This can lead to anxiety among the financial markets and the tech industry – after all when the last leap second was added in 2012, several sites crashed and, according to the Guardian, in Australia, more than 400 flights were grounded as the Qantas check-in system went down. Peter Whibberley, a senior scientist at the National Physical Laboratory (NPL) in the UK, spoke to the Guardian about tech concerns: ‘There are consequences [to] tinkering with time. Because leap seconds are only introduced sporadically it is difficult to implement them in computers and mistakes can cause systems to fail temporarily.’ Speaking to the BBC, Mr Whibberley added, ‘Getting leap seconds wrong can cause loss of synchronisation in communication networks, financial systems and many other applications which rely on precise timing.’ He continued, ‘Whenever a leap second occurs, some computer systems encounter problems due to glitches in the code written to handle them. The consequences are particularly severe in the Asia-Pacific region, where leap seconds occur during normal working hours.’ Linus Torvalds, the main force behind the Linux kernel which now runs so many of the leading Internet services, elaborated in WIRED on the software problems encountered with the leap second, ‘Almost every time we have a leap second, we find something. It’s really annoying, because it’s a classic case of code that is basically never run, and thus not tested by users under their normal conditions.’ According to the Guardian, the need for leap seconds is, in a sense, because official timekeeping has become so precise: ‘Atomic clocks are roughly a million times better at keeping time than the rotation of the Earth, which fluctuates day-to-day and in the long term is slowing down, due to a phenomenon known as “moon drag” … Without the correction, civil time would very slowly drift away from time based on the Earth’s rotation, meaning that about 800 years from now the sun would be at its highest point in the sky at 1pm rather than noon.’ The practice began 1972 and Tuesday’s leap second was the first one in three years. There is disagreement between the world’s timekeepers over whether the practice of adding leap seconds should be continued considering the potential risk to our financial, communication and even transport systems. WIRED argues against the keeping the practice for the sake of human comfort: ‘We keep the leap second because, well, it makes us feel good. We don’t like the idea of the sun being directly overhead when it’s not noon. We bristle at the thought of it going down when the clock reads, say, 3 pm. But even if we drop the leap second, this sort of thing won’t happen for centuries. And that gives us plenty of time to prepare for some other way to put the world’s clocks and computers back in sync with the earth’s rotation.’ There was no talk of market shocks or tech meltdowns on Wednesday morning so this year’s leap second may have passed off without incident. However it may well have been our last extra second as the world’s timekeepers will be discussing whether to maintain the practice or not at the World Radiocommunication Conference in Geneva in November. For further information, please visit:


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