Tucked away at the National Physical Laboratory in Teddington, south-west London, there is a clock which takes up most of a room – and which is so accurate it could actually redefine the second.

At the heart of the clock is an ion of strontium, trapped by a ‘lattice’ of lasers inside a vacuum, with its orbiting electrons working like a pendulum.

It’s so accurate that had it been ticking since the beginning of the universe, 14 billion years ago, it would only have lost or gained one second.

Before this decade is over, it (and other clocks like it) might have redefined low long a second lasts, says one of the experts working with the machine.

The point of this remarkable device isn’t just to measure time, however.

Instead, the ultra-fast oscillator could open new frontiers in science, being used for space navigation, and even to ‘sense’ gravity, according to Leon Lobo Strategic Business Development Manager, Time and Frequency, at the laboratory.

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It could also lead to GPS systems which are accurate down to the centimetre, paving the way for a new generation of self-driving cars and drones.

‘The clock is so accurate that you could use it to detect gravity waves,’ says Lobo,

‘If you were to raise it by a centimetre, the accuracy would change. You could use it as a mobile gravity detector, to detect sinkholes under the ground, or measure the sea level with high accuracy.’

View photos Vacuum chamber for the atomic fountain (NPL) More

The clock is not unique: it’s one of dozens around the world using similar technology, known as ‘optical atomic clocks’ or ‘optical lattice atomic clocks’.

They ‘tick’ much faster than traditional microwave atomic clocks, a network of which provide the official global definition of the second today, Lobo explains.

Britain’s National Physical Laboratory unveiled the first microwave atomic clock in 1955, and it became the basis of the official definition of a second a decade later.

Previously, seconds had been based on ‘mean solar time’, a mathematical calculation based on the passage of the sun over the meridian at noon.

But irregularities in Earth’s rotation mean that’s imprecise: hence the switch to atomic clocks, and the subsequent drive towards more and more accurate models.

‘The optical atomic clock measures electronic transitions of particular species of atom,’ Lobo says, ‘At NPL we use strontium and ytterbium.

‘You can use the frequency of that signal as a regulator. It’s very, very stable.’

View photos NPL More

‘The optical clock is the next generation of clock, which will take us beyond the definition of a second that we use globally.

‘The current international definition under the International System of Units is based on caesium, which oscillates at 9.2 billion cycles per second. But the optical clock operates at five orders of magnitude higher frequency.’

Because optical atomic clocks operate at such high frequencies, they can ‘split’ seconds into far smaller fractions – trillions per second.

It could lead to much more accurate satellite navigations, with satellites able to triangulate positions down to the centimetre.

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