A groundbreaking study challenges our understanding of nearly 70% of the universe's composition. New simulations suggest that dark matter with magnetic-like properties could be driving cosmic expansion.
In the late 1920s, astronomer Edwin Hubble revolutionized astronomy by discovering that all galaxies are receding from us—and from each other. In essence, the universe is expanding. Picture a chocolate chip muffin baking in the oven: as it rises, the chips move farther apart.
Decades later, in the 1990s, researchers found another surprise: the galaxies' escape velocity from the Milky Way is increasing over time. This means not only is the universe expanding, but the expansion is accelerating.
To account for this, scientists proposed a repulsive force countering gravity, dubbed "dark energy." Calculations indicate it makes up about 68% of the universe's total energy density. Like dark matter, its existence is inferred only through indirect gravitational effects—no direct evidence yet.
Given the stakes in unraveling its physics, exploring alternatives is crucial. In a recent study, University of Copenhagen researchers posed a provocative question: What if dark energy doesn't exist? What if dark matter alone drives this accelerated expansion?
"We don't know much about dark matter other than that it's heavy, slow-moving particles. But we wondered—what if it had a quality analogous to magnetism? What would happen?" explains lead author Steen Harle Hansen.
This idea fueled a new computer model. By removing dark energy and endowing dark matter with magnetic-like properties, the team simulated the universe's behavior. Remarkably, it replicated dark energy's effects on cosmic expansion.
"If accurate, this would upend our view that nearly 70% of the universe doesn't actually exist," Hansen emphasizes.
These findings require validation through more sophisticated models accounting for additional factors. "Honestly, it might just be a coincidence," Hansen admits.
"But if not, it's revolutionary. This could redefine the universe's makeup. Right now, magnetized dark matter and dark energy are equally speculative—only precise observations will decide."
Dark energy remains the leading theory, with ongoing efforts to probe it. The DESI instrument has been mapping millions of galaxies' motions for months. Meanwhile, ESA's Euclid mission—now in testing—features a 1.2-meter telescope with a visible-light imager (VIS) and near-infrared spectro-imager (NISP). Its launch was slated for 2022.
These tools may finally answer: Where did we come from, and where are we headed?
