Neutrino geophysics

Neutrinos have no charge and very little mass, and interact but rarely. Underground neutrino detectors can never theless record these ghostly particles (or their antiparticles) originating from the Sun, from cosmic rays, and from nuclear reactors. Now, the Kamioka liquid scintillator antineutrino detector (KamLAND) in Japan has registered the presence of candidate antineutrinos coming from radioactive decays of uranium-238 and thorium-232 inside Earth. A statistical analysis of data gathered over 749 days revealed between 4.5 and 54.2 such particles at the 90% confidence level. Geoscientists accept that Earth’s tectonic plates are kept in motion by a reservoir of energy deriving from two principal sources: residual energy from Earth’s formation and additional energy from subsequent radioactive decays. The rudimentary inventory of geoneutrinos observed so far is consistent with the theory.

(T. Araki et al., Nature 436 , 499, 2005 http://dx.doi.org/10.1038/nature03980 .)