Length Of A Second About To Change

Time is running out for the current length of second after an “optical clock” was sent into space for the first time. Such clocks are up to 1,000 times more accurate than the current international standard, which dates back to 1967 and is based on the natural oscillation of an atom of caesium, rather than the swing of a traditional pendulum. While no one would notice the difference in everyday life, optical clocks would be extremely useful for a number of reasons. For example, it would enable GPS navigation to be accurate to within a few centimeters. But changing the way a second is defined – currently 9,192,631,770 cycles of the microwave signal produced by caesium – to about 429,000 billion cycles form a strontium atom used in some optical clocks, would also inevitably introduce a tiny error, changing its length ever so slightly. Writing in Optica, researchers described how they had successfully sent an optical clock into space – a journey they would need to survive if they were to be used on the satellites providing GPS signals. This device represents a corner-stone in the development of future space-based precision clocks and metrology. The optical clock had about a tenth the accuracy of the current atomic clocks. Researchers plan to develop an improved version next year.