For decades, physicists have sought to build a clock based on the atomic nucleus rather than the electrons surrounding it. That ambition has now taken a major step forward with the creation of the first functioning nuclear clocks, a breakthrough that could eventually surpass the accuracy of today’s best atomic clocks and enable new tests of fundamental physics, tells this Nature article.
The achievement centers on the isotope thorium-229, whose nucleus possesses a remarkably low-energy transition that can be accessed using lasers. This unusual property has made thorium-229 the leading candidate for a nuclear clock. Two independent research teams have now demonstrated working devices that measure this nuclear transition, transforming a long-standing scientific concept into a practical experimental technology.
Modern atomic clocks rely on electron transitions to keep time with extraordinary precision. However, electrons are sensitive to external influences such as electromagnetic fields and temperature variations. Nuclear transitions occur deeper within the atom and are shielded from many environmental disturbances. As a result, nuclear clocks could potentially achieve greater stability and accuracy than conventional atomic clocks.
Although the new devices are not yet as precise as the most advanced atomic clocks, researchers view them as an important proof of principle. The work confirms that laser control and measurement of a nuclear transition are possible and provides a foundation for future improvements.
The implications extend well beyond timekeeping. Nuclear clocks could help scientists search for dark matter, investigate whether fundamental constants of nature vary over time, and test theories that go beyond the Standard Model of particle physics. They may also contribute to advances in navigation, communications, and other technologies that depend on highly accurate timing.
The successful demonstration of nuclear clocks marks the beginning of a new chapter in precision measurement. What was once considered a highly ambitious idea is now a working technology with the potential to reshape both metrology and fundamental science.