"Electron neutrinos, muon neutrinos and tau neutrinos. Each type is associated with an antiparticle, called an "antineutrino", which also has neutral electric charge and half-integer spin. Whether or not the neutrino and its corresponding antineutrino are identical particles has not yet been resolved, even though the antineutrino has an opposite chirality to the neutrino. Most neutrinos passing through the Earth emanate from the Sun. About 6.5Ã—1010 solar neutrinos per second pass through every square centimeter perpendicular to the direction of the Sun in the region of the Earth."