An unprecedented breakthrough in nuclear physics has emerged from a research team at JILA in Boulder, Colorado, as they successfully detected a long-sought signal from the thorium-229 nucleus. This pivotal moment, which took place in May 2024, marks the advent of the “nuclear clock,” a tool that could potentially unravel the mysteries of fundamental constants in physics.

On a seemingly ordinary night, graduate student Chuankun Zhang witnessed a remarkable event on his monitor. As he observed a peak rising from the static, he quickly shared the screenshot with his lab mates. The excitement was palpable as they gathered to verify the authenticity of the signal, which indicated a transition between two states of the thorium-229 nucleus. After confirming their findings, the group celebrated this significant milestone at 3:42 a.m. with a selfie, capturing the moment of scientific triumph.

The following morning, during their routine meeting with group leader Jun Ye, renowned for creating the world’s most precise atomic clock, the team maintained a calm demeanor. However, the atmosphere shifted dramatically when Zhang unveiled a slide showcasing the long-anticipated peak. Overwhelmed with emotion, Ye was moved to tears, and the team toasted to their achievement with champagne at 9:30 a.m.

This groundbreaking measurement, detailed in a September 2024 publication in the journal Nature, represents the third observation of the thorium-229 transition in just four months. However, what sets this measurement apart is its extraordinary precision, being millions of times more accurate than previous results reported from Germany and California. This achievement concludes a lengthy pursuit to determine the exact laser frequency necessary to trigger the nuclear clock transition.

Experts in the field have hailed this achievement as a remarkable technical feat. Hannah Williams, a physicist at Durham University in the UK, noted the significance of the work, emphasizing its potential implications for future research.

Beyond its technical achievement, this discovery opens the door to a new frontier in physics. Researchers are now poised to utilize the thorium-229 transition to explore whether the fundamental laws of physics are subject to change over time, a concept supported by various theoretical frameworks in fundamental physics. The unique characteristics of the thorium-229 nucleus, which exhibit an almost perfect cancellation of two of nature’s four forces, render the nuclear clock transition exceptionally sensitive to variations in these forces.

This sensitivity suggests that by measuring the thorium-229 transition at different intervals, scientists could potentially uncover fluctuations in the fundamental constants of physics. Asimina Arvanitaki, a theoretical physicist at the Perimeter Institute for Theoretical Physics in Canada, expressed her enthusiasm for the discovery, viewing it as the commencement of an exciting journey in scientific exploration.

The implications of this nuclear clock extend beyond mere curiosity; they could reshape our understanding of time and the fundamental principles governing the universe. As researchers embark on this new chapter, the potential for groundbreaking discoveries looms large.

In summary, the detection of the thorium-229 nuclear clock transition represents a significant milestone in the field of nuclear physics. With its unprecedented precision and the potential to probe the stability of fundamental constants, this discovery not only celebrates a technical achievement but also sets the stage for future explorations that could redefine our comprehension of the universe.