Noel M. Swerdlow, 1941–2021

We regret to inform our readers of the passing of our friend and colleague, Noel M. Swerdlow, who was long a member of the JHA Advisory Board and who was one of the most accomplished historians of astronomy of his generation. Noel was born and raised in the Los Angeles area, attended UCLA, then went on to Yale for graduate work. Before settling on a professional direction, Noel had hesitated between music and history of science. Noel’s doctoral dissertation at Yale, directed by Bernard Goldstein, was titled Ptolemy’s Theory of the Distances and Sizes of the Planets: A Study of the Scientific Foundations of Medieval Cosmology (1968). Although this was never published in its entirety, parts of it later appeared in articles; moreover, the dissertation is well known and has been highly influential among historians of astronomy. In the acknowledgments, Noel of course thanks Goldstein, who worked closely with him through the entire project, but also Asger Aeboe, Derek J. De Solla Price (who suggested the topic in the first place), as well as Gerald Toomer—a notable set of mentors. Noel joined the History Department of the University of Chicago in 1968, but, in a rather unusual arrangement, moved to the Department of Astronomy and Astrophysics in 1982. He was an active member of his new department, attending the weekly astrophysics colloquium, for example. He had particularly warm relations with Subrahmanyan Chandrasekhar, whom he thanked “for recognizing and encouraging historical work as a serious part of the study of astronomy and astrophysics.”1 After his 2010 retirement at Chicago, Noel and his wife Nadia relocated to southern California, where Noel was a visiting professor at the California Institute of Technology. Noel was an extraordinarily helpful colleague, generous with his time and energy, but he was famous for having little patience for nonsense. JE recalls a meeting in which Noel had the misfortune to be seated at a dinner table directly below the dais, from which the after-dinner speaker held forth with a highly conjectural story about the origin of the constellations. Noel could be seen writhing in agony at each new unsupported guess. In his dissertation on Ptolemaic planetary distances, Swerdlow wrote: