Made-in-China clock loses a second in twice the age of the universe

2026.03.21 06:20 Researchers from University of Science and Technology of China in Hefei have built this strontium optical lattice clock. Photo: CCTV China has joined the global top-tier timekeeping club with a new optical clock that could help it play a leading role in redefining the second. A team, led by Pan Jianwei at the University of Science and Technology of China in Hefei, has built a strontium optical clock that would lose or gain less than one second over about 30 billion years – more than twice the age of the universe. The clock’s key parameters, known as stability and uncertainty, both surpassed the level of 10 to the power of minus 19, a feat achieved by only a handful of labs worldwide, including the National Institute of Standards and Technology in the US and Germany’s national standards laboratory, the team wrote in the journal Metrologia this month. Its precision exceeds the threshold required for redefining the second, potentially “allowing China to play a leading role in the effort”, according to state broadcaster CCTV. The work also provided a practical path for China to develop more stable and portable optical clocks, as well as space-based versions, said Dai Hanning, a co-author from Pan’s team. “It lays a solid foundation for using optical clocks to test fundamental physics, improve next-generation satellite navigation and build a unified ultra-precise global time standard,” Dai told CCTV on March 7. Optical clocks are the most precise timekeeping devices available. They use lasers to trap atoms such as strontium and rubidium at very low temperatures, and measure time from the frequency of light emitted as their electrons jump between energy levels. Compared with today’s microwave-based atomic clocks, which define the current second, optical clocks are about 10,000 times more precise thanks to their much higher operating frequencies. Global timekeeping currently relies on a network of about 450 atomic clocks across 80 labs worldwide, including

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