Scientists Build the World's First Working Nuclear Clocks Using Thorium-229

Scientists have built the world's first working nuclear clocks using thorium-229, marking a major step beyond current atomic timekeeping.

How It Works

Atomic clocks use electrons, which are easily disturbed by room temperatures or electric and magnetic fields. A nuclear clock uses an atom's nucleus instead, which is safely hidden by the electron cloud. While a nucleus usually needs strong X-rays or gamma rays to change states, the thorium-229 isotope has a much lower transition energy that an ultraviolet laser can trigger. The clock counts the fast-moving cycles of the laser's electric field just like a pendulum swinging back and forth. If the laser drifts and hits the nuclei less often, a computer instantly corrects it.

Research and Uses

Research teams in Beijing and Shanghai put thorium-229 inside calcium fluoride crystals and used an ultraviolet laser to build a compact, portable design. Meanwhile, separate teams from Austria and Germany built a thorium-229 clock to hunt for dark matter. They ran it side by side with a ytterbium atomic clock, looking for tiny changes in their tick rates caused by fluctuating physics constants. While they did not find a dark matter signal this time, the tests proved the new design works. These early models are not yet as precise as the top atomic clocks, but better laser power and crystal quality will help them take the lead.

Context

Timekeeping devices like atomic clocks form the invisible backbone of modern technology, running everything from global navigation systems to synchronized power and communication networks. Nuclear clocks use the strong forces inside an atom's core, offering a much more stable platform that resists external environmental disturbances.