After World War II, he began to study methods for detecting neutrinos emitted, first, from nuclear reactors and later, in the 1960s, from the Sun (see Solar Neutrino Unit), utilizing reactions of the neutrinos with the isotope chlorine-37 to produce argon-37. This work earned him a share of the 2002 Nobel Prize in Physics. Davis also used the decay of chlorine-36 to argon-36 to estimate the time that meteorites, including Lost City, had spent in space.