A clock based on radioactive thorium atoms realises a long-held ambition, demonstrating a technology that could eventually ...

But physicists have long dreamt of even better clocks that run on atomic nuclei, which are less sensitive to environmental ...

FOR THE discerning timekeeper, only an atomic clock will do. Whereas the best quartz timepieces will lose a millisecond every six weeks, an atomic clock might not lose a thousandth of one in a decade.