Ojan · Public domain

The first physicist ever awarded the Fields Medal, mathematics' highest honor, in 1990, for insights spanning string theory and knot theory — his 1981 proof of the positive energy theorem settled a long-open question in general relativity. A driving force behind M-theory's unification of competing string theories in the 1990s, he has spent his career at Princeton's Institute for Advanced Study, and his work continues to reshape both physics and pure mathematics.