In 1956 Clyde Cowan and Frederick Reines deployed a 10‑ton detector, shielded by lead and sand, beside the Savannah River reactor. Their experiment, dubbed Project Poltergeist, captured the first neutrino, confirming Wolfgang Pauli’s 1930 hypothesis of an invisible particle carrying beta‑decay energy. The historical scientific breakthrough proved that particles with near‑zero mass and no charge could be observed despite their ghost‑like nature.

Later, Raymond Davis Jr. placed a 400,000‑liter perchloroethylene tank one and a half kilometers underground at South Dakota’s Homestake mine. Over 25 years the detector recorded far fewer solar neutrinos than theory predicted, creating the solar neutrino problem. Subsequent giant water Cherenkov detectors—Kamiokande, Super‑Kamiokande, and Canada’s Sudbury Observatory—showed neutrinos change flavor, implying they possess mass contrary to existing models.

The newest generation follows the same formula: deep instruments. China’s Jiangmen Underground Neutrino Observatory (JUNO) began data collection in 2025 and released 2026 results that set the tightest limits on oscillation parameters to date. Parallel projects such as Japan’s Hyper‑Kamiokande and the U.S. DUNE experiment aim to map neutrino behavior, turning a once‑theoretical ghost into a probe of fundamental physics.