Scientists have developed new clocks that measure time by monitoring changes in the atomic nuclei of thorium, a heavy radioactive element, marking a significant advance in timekeeping technology. Two independent research teams, based in Vienna and Beijing, achieved this breakthrough by constructing the first nuclear clocks, which rely on the oscillations of thorium nuclei rather than the electron transitions used in conventional atomic clocks.

Reported in the journal Nature, these nuclear clocks exhibit extraordinary precision, losing only one second over the course of several million years. This level of accuracy surpasses many existing timekeeping devices but still falls short of the best atomic clocks currently in use. State-of-the-art atomic clocks are far more precise, capable of maintaining accuracy without losing a second for more than 100 billion years.

Nuclear clocks operate on a fundamentally different principle than atomic clocks. While atomic clocks measure the frequency of electron oscillations, nuclear clocks track transitions within atomic nuclei, which are believed to be less affected by environmental factors, potentially allowing for even greater stability and accuracy in future iterations.

Although these nuclear clocks are unlikely to replace the global fleet of atomic clocks in the near term, researchers see significant potential for their future applications. The nuclear clock design could eventually yield devices that are smaller and more portable than current atomic clocks, enhancing their usability in various scientific and technological settings.

Moreover, the unique sensitivity of nuclear clocks to interactions affecting the thorium nucleus opens possibilities for detecting dark matter—a mysterious form of matter that constitutes about 83 percent of the universe’s matter content but remains difficult to observe. If particles of dark matter were to pass through the thorium nuclei, they could induce subtle disturbances in the nuclear clock’s steady rhythm, providing a novel tool for studying this elusive cosmic component.

Experts recognize the development as a major milestone that may pave the way for a new generation of ultraprecise timekeeping instruments with applications ranging from fundamental physics research to enhancing navigation and communication systems. However, further refinement and testing are necessary before nuclear clocks can achieve practical deployment and potentially surpass the precision and reliability of current atomic clocks.