Time to be redefined as scientists design most accurate clock ever

Possibly originating with the English poet Geoffrey Chaucer’s “time and tide wait for no man,” the idea that time waits for no man has been around for a long time.

But time, or at least the latest best measurement of it, has waited 20 years for the latest “most accurate” clock ever made – an ion or atomic “quantum logic” timepiece that measures to the 19th decimal place, making the priciest wristwatch seem like a sundial in comparison.

In work published in the journal Physical Review, developers based at the US National Institute of Science and Technology (NIST) said the device uses quantum computing techniques to “pair an electrically charged aluminium atom (ion) with a magnesium ion.”

NIST claimed the new clock to have accuracy “41% greater than the previous record” and to show “a threefold reduction in instability” compared to the previous best atomic clocks.

The previous record-holder, developed by NIST and the University of Colorado Boulder, could “detect the effects of gravity predicted by the theory of general relativity at the microscopic scale,” NIST said in 2024.

The record-busting new clock has been “under continuous development for 20 years,” according to NIST, which said the work would help define the second more accurately, a development it believes could herald “new scientific and technological advances.”

The new clock’s ticks are more stable than those of caesium, the provider of the current scientific definition of the second, according to NIST’s David Hume.

Hume’s colleague Mason Marshall believes that fine-tuning the measurement of time “can push the field of physics and our understanding of the world around us.”

Listed since 1960 as “an international standard unit of measurement for time,” the second was at first defined or measured by the rotation of the Earth relative to the cosmos.

But because that rotation can slow down and speed up depending on factors such as the pull of the Moon – posing “a challenge for accurate timekeeping,” according to NIST – the definition was changed in 1967 to one based on energy levels in atoms.

Another redefinition is likely over the coming decade, NIST said in 2023.

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