World's most accurate clock created

2019-03-06 06:18:01

By Eugenie Samuel An optical atomic clock that promises to be a thousand times more accurate than the current standard has been created in the United States. For the last 50 years, world time has been kept by a network of atomic clocks based on the caesium atom. These clocks are vital not just to physicists requiring high precision to test their theories but also to the performance of satellite navigation systems. These include the Global Positioning System that enables users to pinpoint positions to within about 20 metres. Caesium clocks consist of a microwave laser tuned to a resonant frequency in a caesium atom. They are accurate to within one part in 1015 per day, meaning that they gain or lose than a tenth of a nanosecond in 24 hours. But now researchers at the US National Institute of Standards and Technology have made an atomic clock, based on a much faster optical resonance in a mercury atom. The accuracy of spacecraft and satellite navigation systems should benefit by several orders of magnitude. “Clocks are always a fundamental limitation on navigation because light signals travel 30 centimetres in a nanosecond, limiting accuracy to a few metres for the caesium clocks,” says John Laverty, who directs timekeeping in the UK at the National Physical Laboratory in Middlesex. Although the team have not yet proven that different mercury clocks will keep the same time – a key requirement before world time can be based on the new design – researchers agree the mercury based system is probably stable enough to work. “They’ve got their act together first,” says Patrick Gill who was also working to develop the first optical atomic clock at the National Physical Laboratory. Jim Bergquist of the NIST team says he is hopeful for his design. “The atom is held in a trap very gently so external perturbations don’t matter and so it should be reproducible.” If Bergquist turns out to be right, Gill says standards researchers will have to redefine the second,