Dörffel, Georg Samuel

(b. Plauen, Vogtland, Germany, 21 October 1643; d. Weida, Germany, 16 August 1688)

astronomy, theology.

Son of Friedrich Dörffel, pastor in Plauen, Georg Dörffel was best known for his representation of the orbit of a comet as a parabola with the sun at the focus. He was married three times and had nine children.

Dörffel studied philosophy, theology, Oriental languages, and mathematics, receiving the degrees of bachelor (Leipzig, 1662), master (Jena, 1663), and bachelor of theology (Leipzig, 1668; dissertation, 1665). He became his father’s substitute in Plauen in 1667 and his successor in 1672. In 1684 he became ecclesiastical superintendent in Weida. He had an excellent astronomical library and good eyesight but observed mostly with an old-fashioned astronomical radius. It consisted of a long arm and a short arm at right angles to each other, with a fixed sight at the end of the long arm and two movable sights at the ends of the transversal. His comet observations with it were accurate to one or two minutes. His home was not favorable for observing because of neighboring buildings.

Dörffel found no observable parallax for the comet of 1672 and measured its angular distance from fixed stars. From measurements made with a quadrant on 27 March, he calculated its latitude and longitude and length and breadth. He depicted its apparent path as circular and noted that it moved in the same direction as the planets. Dörffel published his report while the comet was still visible but growing fainter. He realized that it was soon to be lost in the light of the moon. He considered God responsible for comets. In the last half of the seventeenth century, skepticism existed about astrological predictions. Dörffel, although he accepted the ancient belief that comets were evil omens, said of the comet of 1672 that it signified something new that was not good, but that he would not predict specific events which might follow. His next recorded astronomical activity concerns the comet of 1677.

In 1680 Dörffel shifted his attention from the apparent path to the actual path of comets. He noted Apian’s statement that comets’ tails are directed away from the sun and appreciated Tycho Brahe’s observations of the nova of 1572 and the comet of 1577 as forcing abandonment of the concept of the incorruptibility of the heavens. Although not the first to suggest a parabolic path for a comet, Dörffel was the first to describe the path of the comet of 1680, and possibly other comets, as a parabola with the sun at the focus (Astronomische Betrachtung). Although he had the comet move around the sun while that body moved around the stationary earth, he was not a confirmed anti-Copernican. Using the radius of the earth’s circular orbit around the sun and his observations of the comet’s elongation from the sun, he projected the comet’s path on the ecliptic. Probably the first (25 August) observer of Halley’s comet in 1682, he described it briefly in print and at greater length in correspondence with Gottfried Kirch.

Dörffel’s interests extended to the computation of lunar eclipses, to occultations, to meteors, including computation of their paths, and to mock moons. In 1685 he published his discovery, mentioned in 1682, of a new method to determine the distance of a body from the earth, with observations from only one site, utilizing the earth’s diurnal rotation and expressing the distance in semidiameters of the earth.

Dörffel’s writings, which were in German and anonymous or signed only with initials, were soon superseded by Newton’s Principia. They received little attention until the mid-eighteenth century, when they began to be of historical interest and appealed to German national pride. In 1791 J. H. Schröter named a lunar mountain range after him.

BIBLIOGRAPHY

I. Original Works. De definitione et natura demonstrationis (Dörffel, resp.; Bernhard v. Sanden, praes.) (Leipzig, June 1662); Exercitatio philosophica de quantitate motus gravium (Erhard Weidel, praes.) (Jena, 14 February 1663);... Disputatio philologo-theologica de gloria templi ultimi, ex Hagg. cap. II vers. 6–9, adversus Judaeos asserta... sub praesidio Johannis Adami Scherzeri,... 1666... eruditorum examini publice subjecit.... (Leipzig, n.d.), 2nd ed. in appendix to J. A. Scherzer’s Collegii antisociniani.... 2nd ed. (Leipzig, 1684); Tirocinium accentuationis ad lectionem Biblicam practice accommodatum (Plauen, 1670); Warhafftiger Berićht Von dem Cometen/Welcher im Mertzen dieses 1672. Jahrs erschienen: Dessen Lauff/Art und Beschaffenheit/sampt der Bedeutung/hiermit fürgestellet wird/und in Plauen observire worden. Von M.G.S.D. (1672); Bericht Von dem neulichsten im Mertzen dieses 1672 Jahres erschienenem Cometen/Auss einem zu Plauen gedrucktem Bedencken wiederholet und vermehret (1672); Extract eines Schreibens aus Plauen im Voigtland an einen guten Freund, von dem neuen Cometen. Welcher im April dieses 1677. Jahrs am Himmel erschienen [Plauen, 1677]; Neuer Comet-Stern welcher im November des 1680sten Jahres erschienen, und zu Plauen im Voigtlande dergestalt observiret worden, sampt dessen kurtzer Beschreibung, und darüber habenden Gedanken [Plauen, 1680?]; Astronomische Betrachtung des Grossen Cometen/Welcher im ausgehenden 1680. und angehenden 1681. Jahre höchstverwunderlich und entsetzlich erschienen: Dessen zu Plauen im Voigtlande angestellte tägliche Observationes, Nebenst etlichen sonderbahren Fragen und neuen Denckwürdigkeiten/sonderlich von Verbesserung der Hevelischen Theoriae Cometarum,... (Plauen, 1681); De incertitudine salutis aeternae contra Aloysium Richardum, German title, Der ärgste Seelen-Gifft Des Trostlosen Pabstthums (Jena [?] 1682); Eilfertige Nachricht, von dem itzund am Himmel stehenden neuen Cometen, welcher am 15. Augusti dieses 1682sten Jahres zum erstenmahl, zu Plauen im Voigtlande ist gesehen worden (Plauen, 1682); “Observatio eclipseos lunae totalis, d. XI. Febr. A. 1682... Symmista Plav. in Variscia, instituta, et cum novissimis tabb. Horroccio-Flamstedianis, vix sensibiliter discrepantibus, collata,” in Gottfried Kirch, Annus III. Ephemeridum motuum coelestium ad... M. D. C. LXXXIII (Leipzig, 1683), recto G₁; Neues Mond-Wunder/Wie solches den 24. Jenner dieses angehenden 1684. Jahres/zu Plauen im Voigtlande/gesehen worden: Neben einem kurtzen Bedencken/was hiervon zu halten sey (Plauen, n.d.); “Calculus Eclipseos Lunaris penumbratilis Anno 1684 d. 17/27 Jun. ex Tabbulis Flamstedianis” in Gottfried Kirch, Ephemeridum motuum coelestium Annus IV (Leipzig, 1684), recto D₄; “Methodus nova, phaenomenorum coelestium intervalla a terris facillime determinandi, non variata statione seu loco observationis, neque captis eorundem altitudine vel azimutho,” in Acta eruditorum (1685), pp. 571–580; and Gedächtnisspredigt Herrn Hanns George v. Carlowitz gehalten den 19. des Christmonds 1686.

MS letters from Dörffel to Gottfried Kirch are preserved in the University Library, Leipzig.

II. Secondary Literature. See Angus Armitage, “Master Georg Dörffel and the Rise of Cometary Astronomy,” in Annals of Science, 7 (1951), 303–315; Rudolf Gerlach, in Neue deutsche Biographie, IV (1959), 30–31; Norbert Herz, Geschichte der Bahnbestimmung von Planeten und Kometen, II (Leipzig, 1894), pp. 252–260; Abraham Gotthelf Kästner, “Nachrichten von Georg Samuel Dörfeln...,” in Leipzig Gesellschaft der freyen Künste, Sammlung einiger ausgesuchten Stücke der Gesellschaft, III (Leipzig, 1756), 252–263; Curt Reinhardt, Mag. Georg Samuel Dörffel. Ein Beitrag zur Geschichte der Astronomie im 17. Jahrhundert (Plauen, 1882), a doctoral dissertation presented at Leipzig; and Baron de Zach, Correspondance astronomique, VII (1822), 136–138; VIII (1823), 397–399.

C. Doris Hellman