This article presents a brief history of the appearance of electron spin in relativistic wave equations. Dirac derived his wave equation in 1928 with the intention to obtain an equation for the "simplest" particle with spin zero. But, as Dirac later announced at the European Conference on Particle Physics (Budapest, 4—9 July 1977), it was a big surprise for him that the equation described the states of a particle with spin 1/2.

Keywords: spin, relativistic wave equations PACS: 01.65.+g, 03.65.−w (all) DOI: 10.3367/UFNe.2019.11.038695 URL: https://ufn.ru/en/articles/2020/7/g/ 000575189200007 2-s2.0-85092533766 2020PhyU...63..721P Citation: Petrov S V "Was Sommerfeld wrong? (To the history of the appearance of spin in relativistic wave equations)" Phys. Usp. 63 721–724 (2020) BibTexBibNote ® (generic)BibNote ® (RIS)Medline RefWorks RT Journal T1 Was Sommerfeld wrong? (To the history of the appearance of spin in relativistic wave equations) A1 Petrov,S.V. PB Physics-Uspekhi PY 2020 FD 10 Jul, 2020 JF Physics-Uspekhi JO Phys. Usp. VO 63 IS 7 SP 721-724 DO 10.3367/UFNe.2019.11.038695 LK https://ufn.ru/en/articles/2020/7/g/ Received: 9th, September 2019, accepted: 11th, November 2019 Оригинал: Петров С В «Ошибался ли Зоммерфельд? (К истории появления спина в релятивистских волновых уравнениях)» УФН 190 777–780 (2020); DOI: 10.3367/UFNr.2019.11.038695