The new record-holder for the most precise timekeeper could tick off the 13.7-billion-year age of the universe to within 4 seconds.

The optical clock monitors the oscillation of a trapped atom of aluminium-27. It is more than twice as precise as an earlier version, reported in 2008, and was built at the National Institute of Standards and Technology in Boulder, Colorado. “It’s extremely impressive,” says Patrick Gill of the UK’s National Physical Laboratory, who was not involved with the work.

The second is currently defined by caesium atomic clocks, but optical clocks promise higher precision because their atoms oscillate at the frequencies of light rather than in the microwave band, so they can slice time into smaller intervals. Such clocks could help spot tiny changes in physical constants over time.

Journal reference: arxiv.org/abs/0911.4527