Deep Sea Telescope Detects the Undetectable

Deep in the Mediterranean Sea, off the coasts of France and Sicily, a team of physicists found evidence of an ultrahigh-energy neutrino – an elusive subatomic particle – in a discovery that could point back to the cosmic accelerators that launched them at unimaginable speeds.

“What we have discovered is, we think, the most energetic neutrino ever recorded on Earth,” explains Paul de Jong, a physicist at the University of Amsterdam and current spokesperson for the global collaboration of roughly 350 scientists involved in the discovery. “Now, we know these neutrinos are not just predicted. They’re there. They’re real.”

A neutrino is nearly weightless, doesn’t carry an electrical charge, doesn’t regularly collide, repel, or otherwise interact with matter, and flows through virtually everything without a trace. In February 2023, the Kilometer Cube Neutrino Telescope, or KM3NeT, picked up traces of a muon, another subatomic particle created when the neutrino bumped into rock or seawater nearby, at lightning-fast speed, leaving a trail of bright blue photons. After two years of analysis, physicists confirmed the neutrino carried 220 million billion electronvolts of energy—tens of thousands of times more than CERN’s Large Hadron Collider can produce.