Image of the Sun taken through the Earth, in “neutrino light”, at the Super-Kamiokande detector (Japan). The image has been obtained with a 503 days exposure, by registering neutrinos emitted from the solar core and detected in a 50 000-ton water pool located 1 km underground. At night, neutrinos were transparently traversing the whole earth before being registered in this image.



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A neutrino is an elementary matter particle of almost zero mass, only interacting through weak nuclear forces and gravity, leading to its unimpeded traveling through ordinary solid matter at almost the speed of light. During a rare interaction between a neutrino and an electron in the water, the electron is accelerated at a speed greater than the speed of light in water, producing a pulse of light -called Cherenkov radiation- similar to a supersonic boom. These pulses are detected by thousands of light amplifiers disposed everywhere on the pool surface.