A new theory from Dartmouth physicists proposes that dark matter formed when high-energy, massless particles collided, cooled, and suddenly became heavy—shedding new light on the origin of the universe’s invisible architecture.
Key Points at a Glance
- Dark matter may have originated from massless particles bonding and rapidly gaining mass.
- This process mirrors how Cooper pairs function in superconductivity.
- The theory provides a simple, testable explanation for both mass increase and energy drop in the universe.
- It predicts a unique signature on the Cosmic Microwave Background (CMB).
- Existing data from observatories could potentially verify the theory.
The origins of dark matter—the mysterious substance believed to make up 85% of the universe’s mass—have puzzled scientists for decades. But a new theory from researchers at Dartmouth College could offer one of the most elegant answers yet: dark matter may have emerged when light-like, high-speed particles collided, paired up, and suddenly became incredibly heavy.
Published in Physical Review Letters, the theory comes from physics professor Robert Caldwell and undergraduate physics and math double-major Guanming Liang. Their model begins in the chaos following the Big Bang, when the universe was dominated by high-energy, massless particles, zipping through space at the speed of light, much like photons. These particles, according to the theory, had a natural tendency to pair up—especially when their spins pointed in opposite directions, similar to magnetic poles attracting.
The key moment came when these paired particles began to cool. An imbalance in spin states triggered a dramatic drop in energy—what Liang compares to steam instantly condensing into water. At this point, the once massless particles condensed into a new, massive form, and dark matter was born.
“It’s almost like a cosmic phase transition,” Caldwell explains. “They went from behaving like light to behaving like lumps—cold, slow, and massive.”
This transition could explain not only where dark matter came from, but why the universe’s energy density has plummeted since its fiery beginning, even as mass-based structures like galaxies emerged. The mathematical simplicity of the model is what makes it especially appealing.
“You don’t need to create an exotic, convoluted framework,” says Liang. “Our theory builds naturally on established physics and cosmological history.”
The theory’s physical plausibility draws support from an unexpected place: the physics of superconductors. Specifically, the researchers point to Cooper pairs—pairs of electrons that behave in a superconductive way when cooled. In superconductors, these pairs allow for resistance-free flow of electricity. But the crucial parallel is that they, too, experience a dramatic drop in energy as they form.
“If electrons can pair up and shift into a new energy state, then perhaps early-universe particles could do something similar,” Caldwell notes.
And this transformation would leave a trace. According to Caldwell and Liang, the slow, pressureless nature of the newly formed particle pairs should leave a distinct signature on the Cosmic Microwave Background (CMB)—the ancient light of the Big Bang that still permeates space.
This means the theory is testable. Data from major cosmic observatories like the Simons Observatory in Chile or future experiments such as CMB Stage 4 could reveal whether these signals exist, providing a potential breakthrough in dark matter detection.
The inspiration for the theory came when Liang, intrigued by a 2023 paper on quantum condensates in the early universe, realized the authors hadn’t considered non-zero temperatures. Armed with new mathematical tools from a solid-state physics course, he and Caldwell began running the equations—and a full theory emerged.
“It was like the math just told the whole story,” Liang says. “We could see a rich evolutionary arc, from high-temperature chaos to the cold structure of today’s universe.”
The result is a model that not only reframes our understanding of dark matter but may help explain the current energy-to-mass distribution in the cosmos. While it remains hypothetical, it offers a compelling, testable framework that could one day crack one of the greatest mysteries of modern physics.
“It’s exciting,” says Caldwell. “We’re not just theorizing—we’re proposing a way to finally see dark matter for what it is.”
Source: Dartmouth College
