Teams in Vienna and Beijing build thorium nuclear clock prototypes

Researchers in Vienna and Beijing have built working thorium-229 nuclear clock prototypes, Popular Science reported, with studies published this week in Nature. The clocks stabilize a laser's frequency using changes between energy states inside thorium nuclei, rather than the electron transitions used by atomic clocks. Testing reportedly shows the Chinese version is about six times as stable as the Vienna clock. The Vienna prototype is reportedly the first nuclear clock to stabilize itself in the manner of atomic clocks. The technology still trails established timekeepers: researchers estimate the new prototype may drift by about one second every 30 million years, roughly 10 times worse than the cesium clocks defining the official second.