Leap second for 2015

THE year 2015 will be one second longer under the orders of a French body.

The International Bureau of Weights and Measures, based in Sèvres, has ordered the extra second to harmonise the two main clocks that measure time on Earth.

Atomic clocks, which measure time by the number of vibrations of Cesium 133, have proved too accurate and can gradually fall out of synch with the Earth’s natural rotation which is slowing down due to gravitational influences and the ‘wobble’ of tides.

A one-second difference between atomic time and astronomical time can mean a difference of 500m to ships navigating by traditional, non-GPS, methods (albeit an increasingly small problem).

The decision to add the second to Coordinated Universal Time is taken on the advice of the head of the Paris-based International Earth Rotation and Reference Systems Service, Daniel Gamblis.

He told Le Figaro he was “a little bit of a master of time” but would get rapped on the knuckles if he let the two clocks run out of synch by more than a second.

Given the prevalence of GPS and the complications that the leap second can cause with technological equipment being synchronised around the world, the head of the International Bureau of Weights and Measures, Felicitas Arias has said this could be the last leap second the world sees, as the group investigates different methods of synchronisation.

Photo: Flickr/Robert Couse-Baker