A small team at the National University of Singapore's Centre for Quantum Technologies has built the world's most accurate atomic clock using a single ion of lutetium, a rare earth metal. The clock is so precise it would lose one second every 260 billion years, nearly 20 times the age of the universe, and is approximately four times more accurate than the previous record holder, a calcium-ion clock developed by China's Academy of Sciences. It also surpasses a US NIST aluminium-ion clock unveiled last year. Lutetium's unusual properties give it key advantages: it is highly resistant to temperature and magnetic field changes, remaining stable across the full range of temperatures found on Earth, and can remain in an excited state for about a week compared to just minutes for strontium, giving researchers more time to measure its frequency. To verify accuracy, the team built two independent lutetium clocks and compared them over 200 hours, achieving agreement to within 5.7 parts in 10¹⁹, the most precise comparison between two atomic clocks ever reported. The research is published in Nature.