# Vienna Team Builds First Self-Stabilizing Nuclear Clock, Running 24 Hours Unattended

*2026-10-11 18:00 UTC · Science · 1 min read*

> TU Wien and PTB build the first self-stabilizing thorium-229 nuclear clock, which ran over 24 hours unattended.

Researchers at TU Wien and PTB Braunschweig report the world's first nuclear clock that stabilizes itself, without a conventional atomic clock as reference. It ran for more than 24 hours without intervention, according to a paper in Nature.

The clock uses thorium-229, whose nucleus has two states with an unusually small energy gap that a laser can drive. A laser shines on a thorium-containing crystal, and the nuclei absorb light only at one precise frequency. When the laser drifts, absorption drops, and a feedback loop steers it back.

Measured relative precision is about 10^-15, roughly one second of error in 30 million years. It does not yet match the best optical atomic clocks, but nuclei are over 10,000 times smaller than atoms and less sensitive to outside disturbances, so the approach could eventually surpass them.

## Sources

- [sciencedaily.com](https://www.sciencedaily.com/releases/2026/10/261008102701.htm)

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TechTools News · https://techtools.cz/tools/news/article/2499-vienna-team-builds-first-self-stabilizing-nuclear-clock-running-24-hours
Česká verze: https://techtools.cz/tools/news/clanek/2573-vidensky-tym-postavil-prvni-samostabilizujici-se-jaderne-hodiny-bezely-24-hodin