Ghosts from within

摘要

The decay of unstable isotopes of chemical elements within the Earth produces heat that contributes to its overall energy output ― a fact recognized shortly after Henri Becquerel first discovered radioactivity in 1896. More than 100 years on, Araki et al. (page 499 of this issue) report the first measurement of antineutrinos produced by radioactive β~- -decay at the heart of the Earth. The results obtained from these so-called geoneutrinos are consistent with geochemical and geophysical models of the planet, and provide a new way of determining where the unstable isotopes ― radionuclides ― are stored inside the Earth, and in what concentrations.