The world's first neutrino observation in a hydrogen bubble chamber was found Nov. 13, 1970, on this historical photograph from the Zero Gradient Synchrotron's 12-foot bubble chamber. The invisible neutrino strikes a proton where three particle tracks originate (right). The neutrino turns into a muon, the long center track. The short track is the proton. The third track is a pi-meson created by the collision. This picture is rotated to the original photograph and includes a colored overlay which shows the visible and invisble tracks of the decay. Also the weak neutrino decay is shown on the right hand side. From: Argonne National Laboratory, http://www.anl.gov/Science_and_Technology/History/Anniversary_Frontiers/86photo.html

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