‘Nuclear clocks’ tick closer to reality

After decades of research, physicists are confident that the first tick of a ‘nuclear clock’ is imminent. This device would keep time by measuring energy transitions in the radioactive isotope thorium-229, which could make it the most precise clock on the planet. Last week, scientists at the American Physical Society Global Physics Summit compared notes on their progress toward assembling the clock’s components, including efforts to build a laser that can make the clock ‘tick’.