First Thorium Nuclear Clocks Begin to Tick

Researchers in Vienna and Beijing have independently built the first nuclear clocks based on oscillations inside thorium nuclei, marking a major milestone for a field that could eventually produce highly portable, ultra-precise timekeepers. The clocks are already precise enough to lose only about a second over millions of years. The New York Times reports: The first nuclear clocks are not going to immediately supplant the worldwide network of atomic clocks, whose steady ticking we rely on for GPS and the definition of a second.