Keeping time sounds simple until you try to do it perfectly. Now a team of physicists in Europe has built a new kind of clock that could one day push timekeeping further than ever.
Researchers at the Vienna University of Technology (TU Wien) report that they have built the world’s first self-stabilizing nuclear clock. It ran on its own for more than 24 hours, according to a report published Oct. 10 by ScienceDaily based on the university’s announcement. The work appears in the journal Nature.
What makes it different
Today’s best clocks are atomic clocks. They keep time by tracking tiny energy jumps made by electrons orbiting an atom.
The new clock goes deeper. It uses the nucleus, the tiny core of the atom, which is more than 10,000 times smaller than the atom itself. The team used a special isotope called thorium-229.
Here’s the basic idea. A laser shines on a special crystal containing thorium, made at TU Wien. The thorium nuclei absorb the laser light at one very precise frequency. A feedback loop watches that absorption and constantly nudges the laser back on target whenever it drifts. The nuclei act like a built-in referee.
How accurate is it?
In its day-long test, the clock reached a relative precision of about 10⁻¹⁵. That works out to roughly one second of error over 30 million years.
To be clear, nobody ran it for 30 million years. That number is a way of expressing how stable it was during the 24-hour run.
It’s not yet as precise as the very best optical atomic clocks. But the team says that’s not the point of a first prototype.
“For a first prototype it is a fantastic result,” said Prof. Thorsten Schumm of TU Wien’s Institute of Atomic and Subatomic Physics, according to ScienceDaily. He added that with atomic nuclei, “much higher precision is possible in principle.”
Why ‘self-stabilizing’ is the big deal
In 2024, Schumm’s team and collaborators at PTB Braunschweig, Germany’s national measurement institute, first managed to excite the thorium nucleus with a laser. Later that year they connected their thorium setup to a conventional atomic clock.
But leaning on another clock isn’t the goal. “What you really want is a self-stabilizing nuclear clock,” Schumm said. That’s what this new device does. It keeps its own frequency steady without help from an atomic clock.
What it could mean down the road
The researchers describe the payoffs in general terms: more precise timekeeping, better measurements of other physical quantities, and sharper tools for studying the basic laws of nature.
The team plans to improve precision with more powerful lasers and higher-quality thorium crystals.
Why should a self-reliant reader care? Because better measurement is the foundation of better tools. This is early-stage science, and the researchers aren’t promising specific gadgets. But a clock that can keep itself on track, using something as stable as the core of an atom, is the kind of building block engineers like to have on the shelf.
The bottom line
A small team working with a laser, a special crystal and a lot of patience has built a clock that keeps time using the core of an atom, and it ran on its own for a full day. It’s an early prototype, not a product, and it isn’t beating the best atomic clocks yet.
But it’s a genuine first, and a reminder that basic science still produces real surprises. The team says the next steps are stronger lasers and better crystals. Keep an eye on this one.
Sources
- ScienceDaily: Scientists build a nuclear clock that could make atomic clocks obsolete (Oct. 10, 2026)
- Journal reference: L. Toscani De Col et al., “A thorium-229 optical nuclear clock with feedback loop,” Nature, 2026. DOI: 10.1038/s41586-026-11084-4