What’s the time?
Physicists at the US National Institute of Standards and Technology (NIST) claim they have built an atomic clock that is twice as precise as the previous best example.
The new clock, based on a single aluminium ion trapped by electric fields and vibrating at ultraviolet light frequencies, is the second version of NIST's 'quantum logic clock'. In addition to demonstrating that aluminium is now a better timekeeper than mercury, the latest results confirm that optical clocks are widening their lead – in some respects – over the NIST-F1 caesium fountain clock, which currently keeps time to within 1s in about 100million years.
The aluminium based clock is said to neither lose nor gain a second in 3.7billion years.
However, because the international definition of the second (in the SI realm) is based on the caesium atom, caesium clocks remain the 'ruler' for official timekeeping and, technically, no clock can be more accurate than caesium based standards such as NIST-F1.
Pictured with the atomic clock is NIST postdoctoral researcher James Chin-wen Chou.
