---
title: "Thorium Nuclear Clocks: Vienna Scientists Create a Device with an Error of One Second in 30 Million Years"
description: "Scientists at the Vienna University of Technology have introduced a thorium nuclear clock capable of operating for a day without intervention and losing only one second every 30 million years."
date: 2026-10-17T17:11:38.498Z
lang: en
url: https://xab.info/en/posts/thorium-nuclear-clocks-vienna-scientists
tags: [nuclear-clocks, thorium, precision-timing, physics, vienna-technology-institute, nature-journal]
author: "Alexander Buran"
publisher: "XAB.info"
---

# Thorium Nuclear Clocks: Vienna Scientists Create a Device with an Error of One Second in 30 Million Years

![A group of Vienna University of Technology scientists in the laboratory examine the new thorium nuclear clock prototype](https://xab.info/media/2026/10/17/yadernye-chasy-toriya-venskie-uchenyie/yadernye-chasy-toriya-venskie-uchenyie-1.webp)

## Key Points

- Vienna scientists have created a thorium-based nuclear clock prototype capable of running for more than 24 hours without external intervention
- The device's accuracy is around 10⁻¹⁵ — an error of one second in 30 million years
- Self-stabilization is ensured by thorium nuclei absorbing laser light only at a strictly defined frequency
- Atomic nuclei are 10,000 times smaller than whole atoms, making the system more resistant to external disturbances
- The result currently lags behind the best optical atomic clocks, but is a record for the first prototype

Scientists at the Vienna University of Technology (TU Wien) have presented a prototype of a nuclear clock capable of autonomously correcting its own errors and operating for more than a day without any external human intervention. The device, reported in a recent publication in the journal Nature, uses nuclear transitions of the thorium isotope as a time standard, which fundamentally distinguishes it from traditional optical atomic clocks based on electronic energy levels. According to RBC-Ukraine, the prototype's accuracy is on the order of 10 to the minus fifteenth power, which is equivalent to an error of one second over 30 million years of operation.

### The Principle of Self-Stabilization: Why Thorium Became the Key to Reliability

Any laser clock measures time using a light beam; however, temperature, vibrations, and other external factors can cause the laser to slightly shift its working frequency, leading to the accumulation of error. To eliminate this problem, researchers placed a special crystal containing thorium atoms inside the device. The uniqueness of thorium, which has interested physicists for decades, lies in the fact that two of its nuclear energy levels are located incredibly close to each other. Thanks to this configuration, a laser beam can easily transition the nucleus from one state to another, and it is this physical phenomenon that ensures the self-stabilization of the system.

### How the Clock "Hears" Laser Drift

The self-regulation mechanism works on the following principle: thorium nuclei absorb laser light only at a strictly defined frequency. If the laser begins to deviate from the norm, the light absorption intensity immediately drops. The clock detects this decrease and automatically corrects the laser's operation without requiring connection to any external reference devices. Thus, the device forms a closed feedback loop in which the thorium crystal itself acts simultaneously as both the measurement object and the calibration tool.

### Why Nuclei Are More Reliable Than Whole Atoms

The researchers emphasize that the main advantage of the new approach lies in scale: atomic nuclei are more than 10,000 times smaller than whole atoms. This means they react much more weakly to external disturbances—electromagnetic fields, thermal fluctuations, mechanical impacts—making the entire system fundamentally more resistant to frequency drift. This is why the nuclear standard is seen as a potential successor to optical atomic clocks in ultra-precise timing tasks.

### Current Limitations and Future Plans

Measurements taken over the course of a single day confirmed the prototype's accuracy at approximately 10⁻¹⁵. Although this result currently lags behind the world's best optical atomic clocks, for a first-generation device of this class, it is, according to the researchers themselves, exceptionally telling. In the future, the team intends to significantly increase accuracy by using more powerful lasers and thorium crystals with improved purity and homogeneity characteristics. The successful implementation of these plans could pave the way for a new generation of time standards for navigation systems, fundamental physics experiments, and the synchronization of global networks.

## Fact-Check & Sources

- [Ошибка в 1 секунду за 30 млн лет: как ученые создали самые точные ядерные часы](https://www.rbc.ua/ukr/news/pomilka-1-sekundu-30-mln-rokiv-k-vcheni-stvorili-1791802126.html) - Primary source containing all key facts: accuracy 10⁻¹⁵, thorium self-stabilization principle, publication in Nature, improvement plans. All data in the article matches the source text.

## FAQ

### What is a nuclear clock and how does it differ from a regular atomic clock?

A nuclear clock uses transitions between energy levels of atomic nuclei to measure time, whereas conventional optical atomic clocks rely on electronic levels of whole atoms. Since nuclei are 10,000 times smaller than atoms, they react less to external disturbances, which increases system stability.

### What is the accuracy of the Vienna nuclear clock prototype?

The accuracy is on the order of 10 to the minus fifteenth power, equivalent to an error of one second in 30 million years of continuous operation. For a first prototype of this type, this is an exceptional result, although the best optical atomic clocks are currently more precise.

### How does the device self-stabilize the laser operation?

Thorium nuclei in the crystal absorb laser light only at a strictly defined frequency. If the laser shifts, absorption drops, the clock registers this, and automatically adjusts the laser frequency without connecting to external references.

### When were the research results published?

The results were published in the journal Nature. A summary of the research was published by RBC-Ukraine. The exact publication date in Nature is not specified in the provided materials.