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

The Discovery

On a notable night in May 2024, graduate student Chuankun Zhang at JILA detected a long-sought signal from the thorium-229 nucleus, marking a key moment in the quest for a nuclear clock. The signal, which shows the nucleus switching between two states, was celebrated by Zhang and his lab mates after rigorous verification. Jun Ye, known for his work in creating the world’s most precise atomic clock, was moved to tears upon seeing the results.

Significance of the Nuclear Clock

The thorium-229 nucleus’s unique properties allow it to be exceptionally sensitive to variations 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. The precise measurement of the thorium-229 transition, which is a million times more accurate than previous attempts, could reveal if these constants change over time.

Scientific Context

The discovery of the thorium-229 nuclear clock is rooted in earlier research. In the 1970s, scientists discovered thorium-229’s unusual nuclear state, which 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 Implications

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