Why this year will be longer than last year – by a leap second

http://www.theguardian.com/science/shortcuts/2015/jan/07/why-this-year-longer-than-last-leap-second

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Good news! This year is to last a second longer than 2014. The decision was made this week by the International Earth Rotation Service (IERS). A leap second is to be inserted at the very end of 30 June. You will probably be asleep. You could set your alarm, but you’d better wake at its first beep or the second will have gone.

Leap seconds are surprisingly common. Since their introduction in 1972, we have gained 25 seconds and lost none. (The bonus second in June will be the 26th.) So why are leap seconds necessary?

Unfortunately, there is no answer at the IERS in Paris. But the UK’s leap-second expert is Peter Whibberley, of the National Physical Laboratory in Teddington. Think of him as a time lord. “Over centuries, the Earth has been slowing down,” he says. Surely in 2015 someone can invent a clock that keeps time accurately? Alas, that seems to be the problem.

“Atomic clocks keep much better time than the Earth itself,” Whibberley says. “They are more than a million times more stable.” Coordinated Universal Time, which the world abides by, comprises the average time of 400 caesium atomic clocks globally, all ticking away at the highest level of accuracy.

“Previously the Earth was the ultimate reference and man-made clocks were adjusted to match,” says Whibberley. “From the beginning of the 1960s, atomic clocks became the ultimate reference. They were adjusted to keep in step with the Earth. Then, in 1972, it was decided that, instead of adjusting how fast the clocks ticked, they would be left to tick away at the atomic rate and the leap second would be introduced.”

Why not save all the leap seconds and have a leap minute in 2115? Then you could go really crazy. But leap seconds mess with technical systems. In 2012, the leap second delayed 400 Qantas flights and disrupted websites including Reddit and LinkedIn. “If you move to minute adjustments, you simply make the problems bigger,” says Whibberley.

A second may seem trivial, the 1p coin of time, but the leap second is a matter of great controversy. Some of the 170 countries represented at the International Telecommunication Union - the US, France, Mexico and Japan, for instance - want to end the leap second and simply let atomic clocks run away from Earth. In centuries, when all those missed leap seconds make an hour, each country could simply shift their clock forward or back. Russia and the UK want to defend it.

“The debate started in 2000,” says Whibberley, which shows that time moves slowly in this field. But the fate of the leap second may become clear at the next World Radiocommunication Conference in November.

It seems wrongheaded to devise a means of measuring time accurately, and then decide that the Earth is out of sync with it. The Earth’s timekeeping is unpredictable. It slows down and speeds up. But that doesn’t mean we can’t follow it. The Earth’s supremacy on one hand; an inconvenience to LinkedIn users on the other. It’s a tough call.

Finally, Daniel Gambis, director of the IERS, returns the Guardian’s call. A second, he says, is not to be undervalued. “In one second, satellites can advance 7km. In one second, someone could buy Greece.” So he is in favour of the leap second? “It’s important to maintain the contact with astronomy and not only physics,” he says. “We are living on Earth.”

How to spend your extra second

Watch the atomic clock change to 00:59:60 (British Summer Time)

Instagram the second

Make a Vine of you Instagramming the second

Have a micro lie-in

Wink at someone

• This article was amended 9 January 2015 because an earlier version said since the introduction of leap seconds, we have gained 15 seconds and the bonus second in June will be the 16th. This has been corrected to say we have gained 25 seconds, and the leap second in June with be the 26th.