Breakthrough thorium-229 nuclear clock could reveal changes in fundamental constants

A major breakthrough in atomic physics came with the development of the first nuclear clock. This clock, based on the thorium-229 nucleus, achieved a level of precision that could help test whether the fundamental constants of physics change over time. This remarkable advance was achieved by a research team led by Jun Ye, a distinguished physicist at JILA in Boulder, Colorado.

Discovery

On a fateful night in May 2024, graduate student Chuankun Zhang of JILA detected a long-awaited signal from a thorium-229 nucleus, a key moment in the search for a nuclear clock. The signal, which shows the nucleus switching between two states, was celebrated by Zhang and his lab colleagues after rigorous verification. Jun Ye, known for his work creating the world’s most accurate atomic clock, was moved to tears when he saw the results.

The Importance of the Nuclear Clock

The unique properties of the thorium-229 nucleus make it exceptionally sensitive to changes in the fundamental constants of nature. These constants, such as the speed of light and the gravitational constant, are fundamental to our understanding of the universe. A precise measurement of the thorium-229 transition, which is a million times more precise than previous attempts, could reveal whether these constants change over time.

Scientific context

The discovery of the thorium-229 nuclear clock has its roots in earlier research. In the 1970s, scientists discovered an unusual nuclear state of thorium-229 that required less energy to excite compared to other nuclei. This property makes it a prime candidate for a highly sensitive clock that can probe the stability of fundamental constants.

Future Consequences

This groundbreaking discovery opens up new avenues for exploring fundamental physics. Scientists like Eric Hudson of the University of California, Los Angeles, and Hannah Williams of Durham University have noted that the precision of the thorium-229 nuclear clock could eventually allow scientists to detect subtle changes in the laws of physics that were previously undetectable.