A Phylogenetic Study of the Concept of Celestial Orb


  • Mohammad Mahdi Sadrforati University of Tehran
  • Amir-Mohammad Gamini




Celestial orb, conceptual change, conceptual components, Islamic astronomy, hardness of orbs


This paper presents a phylogenetic study of the concept of orb from its rise to its abandonment. While a heavy load of literature is dedicated to the introduction and abandonment of the concept, there are few systematic studies on the semantic components of this concept in the Islamic tradition of astronomy. We will investigate conceptual articulation among Arab astronomers by distinguishing the astronomical and philosophical understandings of the concept. While the former mainly focuses on the empirical evidence, the latter emphasizes causal and physical role of the concept’s referent. Such a distinction enables us to characterize some key conceptual components of the concept of orb. Among other components articulated by the Arab astronomers, the hardness of orbs, led Tycho Brahe and his fellow astronomers to abandon the concept.




Avicenna. 2000. Kitāb al-Najāt [Persian]. Ed. Mohammad Taghi Daneshpajooh. Tehran: The University of Tehran.

Avicenna. 1984. Kitāb al-Shifā’ [Arabic], vol. 2. Qom: Marashi Najafi Publications.

al-Bīrūnī, A. R. 1954. Al-Qānūn al-Masʿūdī. Hyderabad: Osmania.

Brigandt, I. 2006. A Theory of Conceptual Advance: Explaining Conceptual Change in Evolutionary, Molecular, and Evolutionary Developmental Biology. Doctoral Dissertation. Pittsburgh: University of Pittsburgh.

Brigandt, I. 2010. The Epistemic Goal of a Concept: Accounting for the Rationality of Semantic Change and Variation. Synthese 177: 19–40.

Britton, J. & Walker, C. B. F. 1996. Astronomy and Astrology in Mesopotamia. In C. B. F. Walker (ed.), Astronomy Before the Telescope, p. 42-67. New York: St. Martin’s Press.

Duhem, P. 1954 [1913]. Le Systeme du monde. 2nd ed. Paris: Hermann.

Furley, D. 1987. The Greek Cosmologists (The Greek Cosmologists). Cambridge: Cambridge University Press. doi:10.1017/CBO9780511552540.

Gamini, A. & Sadrforati, M. 2022. The principle of simplicity for Quṭb al-Dīn Shīrāzī. Studies in History and Philosophy of Science 91: 60-65.

Graham, D. W. 2010. The texts of early Greek philosophy: The complete fragments and selected testimonies of the major Presocratics (Part I). Cambridge: Cambridge University Press.

Gardner, M. 1983. Realism and Instrumentalism in Pre-Newtonian Astronomy. In J. Earman (ed.), Testing Scientific Theories, p.201-165. Minnesota Studies in the Philosophy of Science. Minneapolis: University of Minnesota Press.

Granada, M. A. 2006. Did Tycho Eliminate the Celestial Spheres before 1586?. Journal for the History of Astronomy 37(2): 125-145.

Gingerich, O. 1973. Kepler. In C. C. Gillespie (ed.), Dictionary of Scientific Biography, vol. 7, p.289-312. New York: Scribners.

Grant, E. 1987. Celestial Orbs in the Latin Middle Ages. Isis 78(2): 153-173.

Grant, E. 1994. Planets, Stars, and Orbs. Cambridge: Cambridge University Press.

Guthrie, W. K. C. (ed.). 1939. Aristotle’s On the Heavens. Cambridge, MA: Harvard University Press.

Hartner, W. 1955. The Mercury Horoscope of Marcantonio Micbiel of Venice: A Study in the History of Renaissance Astrology and Astronomy. Vistas in Astronomy 1: 84-138.

Hartner, W. 1964. Medieval Views on Cosmic Dimensions and Ptolemy’s Kitāb al-Manshūrāt. In Mélanges Alexandre Koyré: publiés à l'occasion de son soixantedixième anniversaire, p.254-282. Paris: Hermann.

Heath, T. 1991. Greek Astronomy. New York: Dover.

Hullmeine, P. 2019. Al-Bīrūnī and Avicenna on the Existence of Void and the Plurality of Worlds. Oriens 47: 114-144.

Ibn al-Haytham. 1971. Al-Shukūk ʿalā Baṭlamīyūs [Doubts Concerning Ptolemy]. Ed. A. Sabra & N. Shehaby. Cairo: The National Library Press.

Ibn al-Haytham. 1990. Ibn al-Haytham’s On the Configuration of the World. Ed. T. Langermann. New York: Garland.

Jones, A. 1991. The adaptation of Babylonian methods in Greek numerical astronomy. Isis 82: 441-453.

Kahn, C. H. 1960. Anaximander and the Origins of Greek Cosmology. Indianapolis: Hackett Publishing Company.

Knorr, W. 1990. Plato and Eudoxus on the Planetary Motions. Journal for the History of Astronomy 21(4): 313-329.

Lennox, J. G. 2001. History and philosophy of science: A phylogenetic approach. História, Ciências, Saúde-Manguinhos 8: 655-669.

Lennox, J. G. 2013. Concepts, Context and the Advance of Science. In A. Gotthelf & J.G. Lennox (eds.), Concepts and their Role in Knowledge: Reflections on Objectivist epistemology, p.112-133. Pittsburgh: University of Pittsburgh Press.

Lerner, M-P. 1996. Le Monde des Spheres: 1. Genèse et triomphe d’une représentation cosmique. Paris: Les Belles Lettres.

Lloyd, G. E. R. 1978. Saving the Appearances. Classical Quarterly 28: 202-22.

Love, A. C. 2003. Evolutionary Morphology, Innovation, and the Synthesis of Evolutionary and Developmental Biology. Biology and Philosophy 18: 309-345.

Love, A. C. 2005. Explaining Evolutionary Innovation and Novelty: A Historical and Philosophical Study of Biological Concepts. Dissertation. Pittsburgh: University of Pittsburgh.

Murschel, A. 1995. The Structure and Function of Ptolemy’s Physical Hypotheses of Planetary Motion. Journal for the History of Astronomy 26(1): 33-61.

Nasr, S. H. 2010. Majmūʿat al-Asʾalat wa-l-Ajwiba [Arabic]. Paris: Dar Byblion.

Neugebauer, O. 1954. Babylonian Planetary Theory. Proceedings of the American Philosophical Society 98(1): 60-89.

Neugebauer, O. 1967. Problems and Methods in Babylonian Mathematical Astronomy: Henry Norris Russell Lecture. The Astronomical Journal 72(8): 964-972.

Pedersen, O. & Jones, A. 2011. A survey of the Almagest. New York: Springer.

Ragep, J. 1990. Duhem, the Arabs, and the History of Cosmology. Synthese 83: 201-214.

Ragep, J. 1993. Nasir al-Din al-Tūsi”s Memoir on Astronomy (Al-Tadkira ficilm al-Haya), vol.2 New York: Springer.

Ragep, J. 1996. Al-Battānī, Cosmology and the Early History of Trepidation in Islam. In J. Casulleras & J. Samsó, From Baghdad to Barcelona, p.267-298. Barcelona: Instituto Millás Vallicrosa de Historia de la Ciencia Árabe.

Rashed, R. 2014. Ibn al-Haytham, New Spherical Geometry and Astronomy: A History of Arabic sciences and mathematics, vol. 4. London and New York: Routledge, Taylor and Francis.

Richard, M. 2019. Meanings as Species. Oxford: Oxford University Press.

Rosen, E. 1985. The dissolution of the Celestial Spheres. Journal for the history of ideas, xlvi: 13-31.

Sabra, A. 1998. Configuring the Universe: Aporetic, Problem Solving, and Kinematic Modeling as Themes of Arabic Astronomy. Perspectives on Science 6(3): 288-330.

Sadrforati, M. M. 2019. Conceptual Change: Rationality, Progress and Communication. Doctoral Dissertation. Melbourne: The University of Melbourne.

Swerdlow, N. 1976. Pseudoxia Copernicana: or, Enquiries into Very Many Received Tenents and Commonly Presumed Truths, Mostly Concerning Spheres. Archives Internationales d’Histoire des Sciences 26: 108-158.

al-Shīrāzī, Q. [manuscript]. Ikhtīyārāt Muẓaffarī [Preferences for Muẓaffar]. The Library of Iranian Congress (majlis), No. 11954.

Toomer, G. J. 1984. Ptolemy’s Almagest. London: Duckworth.

Weber, M. 2014. Reference, Truth, and Biological Kinds. In: J. Dutant; D. Fassio; A. Meylan (eds.), Liber Amicorum Pascal Engel, p.422-448. Genf: University of Geneva.

Wolfson, H. A. 1962. The Problem of the Souls of the Spheres from the Byzantine Commentaries on Aristotle through the Arabs and St. Thomas to Kepler. Dumbarton Oaks Papers 16: 65-93.

Zainaldin, J. 2017. The Philosophical Justification for the Equant in Ptolemy’s Almagest. Phronesis 62(4): 417-442.