A Theory of Electrons and Protons. Paul Dirac.

A Theory of Electrons and Protons

"Physics has produced other far-fetched predictions that have subsequently been confirmed by experiment. But Dirac's prediction of anti-matter stands alone in being motivated solely by faith in pure theory, without any hint from data, and yet revealing a deep and universal property of nature." -Kurt Gottfried

"Dirac divided the initial wave equation into two simpler ones, each providing solutions independently. It now appeared that one of the solution systems required the existence of positive electrons having the same mass and charge as the known negative electrons. This initially posed considerable difficulty for Dirac's theory, since positively charged particles were known only in the form of the heavy atom nucleus. This difficulty which at first opposed the theory has now become a brilliant confirmation of its validity. For later on, positive electrons, the positrons, whose existence was stipulated in Dirac's theoretical investigation, have been found by experiment." -Nobel Prize Presentation Speech

FIRST EDITION IN ORIGINAL WRAPPERS of Dirac's electron "hole" theory; the foundation for his prediction of anti-matter.

One troubling consequence of the famous Dirac relativistic wave equation was that it implied that electrons should exist in states of negative as well as positive energy. Therefore a Dirac electron with initially positive energy should fall indefinitely by spontaneous emission towards states of lower and lower energy. To avoid this Dirac postulated in “A Theory of Electrons and Protons” that the states of negative energy were normally filled up according to the exclusion principle. Holes in this “sea” would behave like positively-charged particles. Dirac initially believed that these holes could be identified with protons, but Hermann Weyl and others showed that they should have the same mass as the electron. The following year, in the introduction to another paper (on a different topic), Dirac conceded and called these holes ‘anti-electrons’. The existence of this particle was demonstrated experimentally by Carl Anderson in 1932; he called it the ‘positron’.

Dirac shared the 1933 Noble Prize in Physics with Schrodinger for "for the discovery of new productive forms of atomic theory". Particle Physics: One Hundred Years of Discoveries: “Introduction of the negative energy electron sea with holes treated as positive electrons”.

IN: Proceedings of the Royal Society, A126, Vol. 126, pp.360-65. London: The Royal Society, 1930. Octavo, original wrappers; custom box. Toning to wrappers, otherwise fine. Scarce in original wrappers.

Price: $2,900 .

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