In a groundbreaking study, physicists have developed a new method for detecting dark matter, an invisible substance believed to account for around 80% of the universe’s mass. Using thorium-229, a radioactive element, this method utilizes the precision of a nuclear clock—a device that measures time by the oscillation of atomic nuclei. The method, published in Physical Review X in July 2025, opens new avenues in the hunt for dark matter, pushing the boundaries of our understanding of the universe’s most elusive substance. The study, spearheaded by scientists from the Weizmann Institute of Science and Germany’s National Metrology Institute, could revolutionize how we detect and study dark matter. It promises to offer insight into one of the most puzzling aspects of physics today—dark matter’s subtle influence on atomic structures.
Unlocking the Mysteries of Dark Matter Through Precision Timekeeping
Dark matter has been one of the most significant mysteries in astrophysics, with scientists exploring numerous approaches to detect and understand it. However, despite decades of research, direct detection has remained out of reach. One of the most promising techniques now lies in the development of a nuclear clock using thorium-229, which could offer unparalleled precision in detecting the effects of dark matter. According to Prof. Gilad Perez of the Weizmann Institute of Science, while scientists have not yet achieved the ultimate goal of constructing a fully functional nuclear clock, they have already made significant strides in identifying a new way to study dark matter’s presence. “We still need even greater precision to develop a nuclear clock,” Perez notes, “but we’ve already identified an opportunity to study dark matter.”
This breakthrough marks a departure from traditional methods of searching for dark matter, which often rely on high-energy particle collisions or cosmic radiation detection. The innovative use of thorium-229 may open the door to studying dark matter with unprecedented accuracy by using atomic nuclei as highly sensitive detectors.
A New Window into the Universe’s Hidden Matter
At the heart of this discovery lies the resonance frequency of thorium-229, a key property of atomic nuclei that allows them to oscillate between quantum states. Just as a pendulum’s swing can be influenced by the forces around it, thorium-229’s quantum “swing” can be altered by the subtle presence of dark matter. Unlike most atomic materials, which require intense radiation to excite their nuclei, thorium-229 has a naturally low resonance frequency, making it ideal for manipulation with standard laser technology. This unique property sets it apart from other nuclear materials, and, as a result, it presents a promising candidate for building a new generation of nuclear clocks.
In this new study, the team proposed a method for detecting minute shifts in thorium-229’s absorption spectrum, a key aspect of its resonance frequency. These shifts could potentially be linked to dark matter’s presence, which, despite its elusive nature, might influence atomic structures at a quantum level. “In a universe made up only of visible matter, the physical conditions and the absorption spectrum of any material would remain constant,” says Perez. “But because dark matter surrounds us, its wave-like nature can subtly change the mass of atomic nuclei and cause temporary shifts in their absorption spectrum.”
Searching for Subtle Deviations: New Approaches to Measuring Dark Matter
The search for dark matter has often been described as a hunt for something that we can neither see nor directly detect. Researchers, therefore, need to identify methods that can reveal its influence without relying on traditional forms of detection. The thorium-229 nuclear clock offers an exciting new possibility, enabling researchers to spot the faintest deviations in resonance frequencies that could indicate the presence of dark matter.
Theoretical calculations, led by Dr. Wolfram Ratzinger, one of the study’s authors, suggest that even if dark matter’s effects are incredibly weak—up to 100 million times weaker than gravity—the tiny shifts in thorium-229’s absorption spectrum could still be measurable. “This is a region where no one has yet looked for dark matter,” says Ratzinger. “Our calculations show that it’s not enough to search for shifts in the resonance frequency alone. We need to identify changes across the entire absorption spectrum to detect dark matter’s effect.”
Although no such shifts have been detected yet, Ratzinger’s team is laying the groundwork to identify and interpret these subtle changes once they appear. The researchers are optimistic that future developments will allow them to pinpoint these shifts and, in turn, understand the nature of dark matter itself.
Thorium-229 Nuclear Clock: The Ultimate Dark Matter Detector
One of the most exciting possibilities arising from this research is the potential for thorium-229 to become the ultimate tool for detecting dark matter. Traditional atomic clocks, which rely on the oscillations of electrons between quantum states, are incredibly precise but vulnerable to electrical interference. This interference can affect the consistency of the clocks and limit their ability to detect subtle forces like those attributed to dark matter.
A thorium-229-based nuclear clock, by contrast, would be far less sensitive to environmental disruptions, making it an ideal candidate for dark matter detection. “When it comes to dark matter,” says Perez, “a thorium-229-based nuclear clock would be the ultimate detector. Right now, electrical interference limits our ability to use atomic clocks in the search.” He further emphasizes that such a clock could detect forces 10 trillion times weaker than gravity, providing a resolution 100,000 times better than current technologies.
The potential for this technology extends beyond just dark matter research. If perfected, it could have profound implications for fields like Earth and space navigation, power grid management, and scientific research, offering a new level of precision in timekeeping that we have never seen before.