Also in 1928 he found a connection between relativity and quantum mechanics, his famous spin-1/2 Dirac equation. In 1929 he made his first visit to the United States, lecturing at the Universities of Wisconsin and Michigan.
Sa 1929 siya ay ginawa ng isang tao ng St John's College, Cambridge at, sa parehong taon, siya ay hihirangin upang angkinin ang isang paglelektyur sa Mathematics sa University of Manchester.