form separate, well-defined atoms. They would all collapse to form a roughly uniform, dense ΓÇ£soup.ΓÇ¥
A proper understanding of the electron and other spin-1/2 particles did not come until 1928, when a theory was proposed by Paul Dirac, who later was elected to the Lucasian Professorship of Mathematics at Cambridge (the same professorship that Newton had once held and that I now hold). DiracΓÇÖs theory was the first of its kind that was consistent with both quantum mechanics and the special theory of relativity. It explained mathematically why the electron had spin 1/2, that is, why it didnΓÇÖt look the same if you turned it through only one complete revolution, but did if you turned it through two revolutions. It also predicted that the electron should have a partner: an antielectron, or positron. The discovery of
