In Cambridge, Massachusetts, Russian mathematician Grigori “Grisha” Perelman presented the proof of the Poincaré Conjecture, formulated in 1904: every compact and simply connected three-manifold (i.e., on which every closed path can be reduced to a point) is homeomorphic (i.e., topologically identical) to the three-sphere; he later refused the million-dollar prize because “it doesn’t interest him.”
