Neutrino

Hypothesized as the explanation for continuous electron energy spectrum in beta decay in 1930 by .

First observed directly by the Cowan-Reines neutrino experiment.

Because they interact weakly with matter and mostly just escape out of nuclear reactors, you can likely locate all nuclear reactors on Earth by measuring neutrino flows:The CIA must love that shit, they must have had it years prior to this public paper.