On 31 December an extra second will be added before midnight, senior research scientist Peter Whibberley explains. Since the 1960s we have used atomic clocks to keep track of time, as they are more accurate than the old method of using the Earth, as the Earth randomly speeds up and slow down. But to make sure that the atomic clock is in line, an extra second is needed every so often to ensure many of modern societies functions like the internet and mobile phones can work.
