Earth is continuously bombarded by cosmic rays—extremely energetic particles (mostly protons and atomic nuclei) coming from space. When these particles strike Earth’s atmosphere, they create cascades of secondary particles, including muons, which can travel deep underground or underwater.
Detectors like KM3NeT can observe these muons far below the sea surface.
Far below the surface of the Mediterranean Sea, a network of sensors watches the darkness. Suspended in deep water, the instruments of the KM3NeT Neutrino Telescope search for faint flashes of light produced when a neutrino collides with matter. Such events are rare. Neutrinos, among the lightest and most elusive particles known, pass through planets, stars, and human bodies with barely any interaction. Their neutrality and near masslessness allow them to travel across the universe almost undisturbed.
The first clear insight often takes shape in silence. Deep rock, deep water, and deep time frame the latest effort to understand a particle that reaches Earth from every direction. Two new facilities, JUNO in Guangdong and KM3NeT in the Mediterranean, now supply fresh data that sharpen long-standing questions about neutrino mass, flavor transitions, and the engines that drive high-energy particle streams across the cosmos.
