μ muonic \ myü-​ˈä-​nik \ adjective - having the characteristics of muons, a type of unstable subatomic particle, with a half life of 2 microseconds. Muons weigh about 207 times more than an electron. They were discovered in 1936 in cosmic ray observations.

// "π → μ - when high energy cosmic ray protons hit atoms in the upper atmosphere, pions (π ) are created. Pions decay often quickly into Muons (μ), which travel in the same direction as the cosmic rays, close to the speed of light, at a density of one particle per square centimeter a minute. Muons, like neutrinos, are unusually penetrative and pass through us and meters deep into rocks. They are observed in deep underground and deep underwater detectors. Muon radiation is used also for imaging (muography) in archeology, to look inside the ground, inside pyramids, but also inside volcanos.