In 2023, neutrino detectors in the Mediterranean Sea picked up something that shouldn't exist: a particle with roughly 100,000 times more energy than anything we can produce at the Large Hadron Collider. No known cosmic process should be able to generate such energies. And yet, there it was.
Now, a team of physicists at UMass Amherst thinks they know what produced it: an exploding primordial black hole.
If they're right, this single detection could confirm three of the most profound mysteries in physics all at once—the existence of primordial black holes, the reality of Hawking radiation, and the nature of dark matter itself.
That's a lot riding on one neutrino. So let's be clear about what we're dealing with here.
The Anomaly
The detection came from the KM3NeT Collaboration, a network of underwater neutrino detectors off the coast of Sicily. Neutrinos are notoriously difficult to catch—trillions pass through your body every second without interacting. But when one does collide with an atom, it can produce a telltale flash of light.
This particular flash indicated an ultra-high-energy neutrino—far beyond what should be possible from known sources like supernovae or active galactic nuclei. Andrea Thamm, an assistant professor of physics at UMass Amherst and lead author on the new paper, saw an opportunity.
"Our dark-charge model is more complex, which means it may provide a more accurate model of reality," Thamm said.
The research, published in Physical Review Letters, proposes that the neutrino came from the explosive death of a quasi-extremal primordial black hole—a black hole formed in the first fraction of a second after the Big Bang.
The Physics: Hawking Radiation on Steroids
Here's where it gets elegant. Stephen Hawking predicted in 1974 that black holes aren't completely black—they emit radiation due to quantum effects near the event horizon. This is incredibly faint for large black holes. For a solar-mass black hole, the temperature is about 60 billionths of a degree above absolute zero.
