World's most accurate clock

An atomic clock at the UK's National Physical Laboratory (NPL) has the best long-term accuracy of any in the world, research has found.

The clock would lose or gain less than a second in some 138 million years.

The UK is among the handful of nations providing a "standard second" that keeps the world on time.

However, the international race for higher accuracy is always on, meaning the record may not stand for long.

The NPL's CsF2 clock is a "caesium fountain" atomic clock, in which the "ticking" is provided by the measurement of the energy required to change a property of caesium atoms known as "spin".

By international definition, it is the electromagnetic waves required to accomplish this "spin flip" that are measured; when 9,192,631,770 peaks and troughs of these waves go by, one standard second passes.

Complete news.