Look up at the night sky. Every star you see, every glowing galaxy, every shimmering nebula—all of it, from the smallest atom of hydrogen to the brightest supernova, makes up only a fraction of what truly exists. Scientists believe that about 80 percent of the universe’s mass is hidden in a form we cannot see, touch, or directly measure. This invisible substance is called dark matter, and without it, the universe as we know it could not exist.
Dark matter is not simply a curiosity. It is the glue that holds galaxies together, the unseen scaffolding shaping the cosmic web. Without it, stars would fly apart from galaxies, and planets like Earth might never have formed. Yet, for all its importance, we know almost nothing about what it really is. Its nature remains one of the most profound mysteries in physics.
Why Dark Matter Remains Elusive
For decades, physicists have tried to capture traces of dark matter. They know it does not emit light, and it does not interact with ordinary matter in the same way that protons, electrons, or photons do. But it does leave fingerprints: its gravitational pull bends the paths of galaxies, distorts light from distant stars, and influences the cosmic microwave background—the faint glow left over from the Big Bang.
The problem is that dark matter does not reveal itself easily. Standard detectors have mostly searched for dark matter particles similar in mass to known elementary particles, such as protons or electrons. But what if dark matter lies outside that range? What if its particles are far lighter, so light that the best detectors of today—often massive, liquid xenon–filled tanks buried deep underground—cannot even sense them?
Despite years of experiments, no direct detection has been achieved. And paradoxically, this silence has been incredibly valuable. Every non-detection rules out possibilities, narrowing the vast landscape of theories. The hunt continues, sharper and more refined with each passing year.
A Breakthrough with New Technology
Recently, a team of physicists from the University of Zurich, led by Laura Baudis, Titus Neupert, Björn Penning, and Andreas Schilling, unveiled a device that may open an entirely new chapter in this search. Their tool, published in Physical Review Letters, is an improved superconducting nanowire single-photon detector (SNSPD)—a device so sensitive it can probe dark matter particles that are lighter than the electron itself.
This is groundbreaking. Until now, the possibility of dark matter with such small masses was nearly impossible to explore. But with this new detector, researchers can reach into territory that has long remained hidden. The SNSPD can pick up extremely low-energy photons, tiny packets of light that may be produced when dark matter collides with ordinary matter.
Here’s how it works: a superconducting wire, chilled to near absolute zero, allows electricity to flow without resistance. But when even a single photon strikes the wire, it disrupts the superconductivity for a fleeting moment. The wire briefly becomes a normal conductor, and the resulting change in resistance can be measured. That tiny disturbance could be the signature physicists have been waiting for.
Detecting the Lightest Shadows
In their latest experiments, the researchers refined the device further. Instead of nanowires, they used superconducting microwires, which increased the surface area available for interactions. They also designed the detector in a flat, thin shape, enhancing its sensitivity to directional changes. This matters because Earth itself is moving through a kind of invisible “wind” of dark matter particles as it orbits the galaxy. A detector capable of noticing shifts in the particle’s incoming direction can distinguish genuine dark matter signals from background noise.
The implications are staggering. For the first time, scientists can systematically search for dark matter particles with masses below one mega electron volt (MeV)—around one-tenth the mass of an electron. Above this threshold, the team has already shown that such light dark matter is highly unlikely to exist. Below it lies uncharted territory, where current models face new challenges and constraints from astrophysics and cosmology.
The Next Steps in the Search
The researchers are not stopping here. They envision deploying these detectors deep underground, far from cosmic rays and environmental radiation that might mimic signals. Shielded by Earth itself, the detectors could reach even greater sensitivity, perhaps capturing the faintest whispers of dark matter.
Titus Neupert explained that further refinements in SNSPD technology might even allow us to detect signals from particles lighter than anything we have yet imagined. This opens the possibility of exploring entirely new physics, beyond the standard models that currently guide our understanding of the cosmos.
Why It Matters for All of Us
At first glance, this might sound like a distant, abstract pursuit, far removed from everyday life. But the search for dark matter is not just about filling in a missing piece of the cosmic puzzle. It’s about answering the most fundamental questions: What is the universe made of? Why does it look the way it does? How do we fit into this grand structure?
Every discovery in physics has historically led to revolutions in technology and thought. Electricity, quantum mechanics, relativity—all once seemed purely theoretical, yet they transformed the world. Unlocking the mystery of dark matter could one day lead to insights we cannot yet imagine, reshaping not only science but also our place within the universe.
The Poetry of the Unknown
Perhaps the most profound aspect of this journey is not the answers we already have but the vast ocean of questions still ahead. Dark matter humbles us. It reminds us that the universe is far richer and stranger than our current knowledge. For every experiment that narrows the possibilities, for every device that stretches the boundaries of sensitivity, humanity inches closer to the truth.
Physics is not just about equations or detectors—it is about wonder. The wonder of knowing that we are chasing something unseen, something that silently shapes galaxies and whispers through the night sky. Dark matter is a reminder that even in an age of dazzling technology and deep understanding, the universe still keeps secrets.
And so the search continues. Somewhere, hidden in the shadows, lies the substance of most of the cosmos. Each new experiment is a candle lit in the dark, guiding us toward a truth that will one day reshape the way we see everything.
More information: Laura Baudis et al, First Sub-MeV Dark Matter Search with the QROCODILE Experiment Using Superconducting Nanowire Single-Photon Detectors, Physical Review Letters (2025). DOI: 10.1103/4hb6-f6jl
