Microscopic magnet powers search for dark matter in the universe

In a chilled lab where temperatures drop close to absolute zero, a speck of magnet hovers in place. This tiny magnet, levitating silently inside a special trap, may hold answers to one of the greatest mysteries in science—dark matter. While no direct signals appeared in this first search, the experiment marks a bold step into a new frontier of physics.

Dark matter doesn’t emit, absorb, or reflect light. You can’t see it, but scientists believe it makes up most of the universe’s mass. Without it, galaxies would spin apart. Yet, after decades of searching, no one has directly detected it.

Now, researchers are turning to an unusual and delicate tool—a magnetically levitated particle. A new experiment led by scientists from Rice University has launched the first search for ultralight dark matter using this technique. The study focuses on a form of dark matter that behaves more like a soft background wave than a single particle.

Ultralight dark matter, if it exists, might flow through Earth like a ripple in space. These ripples could tug very gently on certain types of matter. But this force would be incredibly small—so faint that only ultra-sensitive equipment could spot it.

That’s why the team suspended a microscopic magnet inside a cold, superconducting trap. The magnet floated in midair, completely untouched by friction or heat. By creating such a quiet space, the magnet could wiggle if nudged by these ghostly dark matter waves.

“Our approach brings dark matter detection into a new realm,” said physicist Christopher Tunnell, one of the study leaders. “By suspending a tiny magnet in a frictionless environment, we’re giving it the freedom to move if something nudges it.”

The experiment used a neodymium magnet less than a millimeter wide. This small piece was placed in a trap cooled to near -459.67°F. That’s almost as cold as anything can get. The setup reduced noise so much that it could detect movements smaller than the size of a single hydrogen atom.

The researchers watched closely, searching for a signal at a specific frequency—26.7 cycles per second. That’s the rate at which ultralight dark matter in a certain mass range would likely cause oscillations, or tiny repeated movements. Despite the incredible precision, they found no signal.

Still, this result helps. It sets a new limit on how dark matter can interact with regular matter. The study focused on interactions based on a property in particle physics known as “B minus L.” This stands for the difference between the number of baryons (like protons and neutrons) and leptons (like electrons). These numbers often stay constant during particle reactions.

In this study, the scientists searched for forces that would act differently depending on these numbers. By not finding any effect, they were able to narrow the possible strength of such dark matter interactions. They ruled out a coupling strength higher than 2.98 × 10⁻²¹, which is among the strictest limits ever set in this area.

“Every time we don’t find dark matter, we refine the map,” said Tunnell. “It is like searching for a lost key in your house—when you do not find it in one place, you know to look elsewhere.”

The idea for this novel experiment began in an unexpected place: a climate protest. Two physicists met there, talked about their ideas, and even danced a traditional dance known as the polonaise. That moment sparked the name for their next project—POLONAISE.

This next-generation experiment will improve on the current design in several ways. It will use heavier magnets, which respond more to force. The team also plans to boost the stability of the levitation and scan a wider range of frequencies. That means they’ll be able to look for more types of dark matter than before.

“Our future setup won’t just listen more closely, it’ll be tuned to hear things we’ve never even tried listening for,” said Tunnell. Dorian Amaral, the study’s lead author, helped lay the theoretical foundation for the measurement. He worked closely with other physicists to design this bold test.

“We’re not just testing a theory, we’re laying the groundwork for an entire class of measurements,” said Amaral. “Magnetic levitation gives us a fundamentally new tool to ask the universe big questions.”

This setup isn’t only useful for dark matter. It’s sensitive enough to detect forces as small as 0.2 femtonewtons per square root of hertz. That’s comparable to the weight of a single virus. Reaching this level of sensitivity opens the door to many kinds of future discoveries in physics.

The team hopes to improve their system over time. Short-term upgrades will help smooth the levitation and reduce noise. In the medium term, they’ll add better sensors and stronger magnetic materials. In the long run, the final version of POLONAISE could lead the world in dark matter sensitivity across a wide mass range.

Even though this first attempt didn’t spot dark matter, the value of the experiment goes far beyond a single result. The setup proves that magnetic levitation in a superconducting trap works as a quantum sensor. And that opens up new paths in physics, many of which scientists haven’t yet explored.

The research team worked with scientists from multiple universities and received support from the National Science Foundation. Together, they built something not just cutting-edge—but potentially revolutionary.

Each new search like this one brings the world a little closer to understanding the unseen matter that shapes the universe. Whether or not it was found this time, the dark remains a little less mysterious now.