Newman was a prominent contributor to the golden age of general relativity (roughly 1960-1975). In 1962, together with Roger Penrose, he introduced the powerful Newman/Penrose formalism for working with spinorial quantities in general relativity. In 1963, Newman and two coworkers discovered the NUT vacuum, an exact vacuum solution to the Einstein field equation which has become a famous "counterexample to everything". In 1965, he discovered the Kerr-Newman electrovacuum, one of the best known of all exact solutions.
Newman has continued to make important contributions. Some of his most interesting recent work has involved the problem of reconstructing the gravitational field within some region from observations of how optical images are lensed as light rays pass through the region.