| From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, p. 574 |
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Ibrāhīm ibn
Sinān ibn Thābit ibn Qurra
Glen Van Brummelen
Born Baghdad, (Iraq),
908/909
Died Baghdad, (Iraq),
946
Ibrāhīm
ibn Sinān was a creative scientist who, despite his short life, made
numerous important contributions to both mathematics and astronomy. He was
born to an illustrious scientific family. As his name suggests his grandfather
was the renowned Thābit ibn Qurra;
his father Sinān ibn Thābit was also an important mathematician
and physician. Ibn Sinān was productive from an early age; according
to his autobiography, he began his research at 15 and had written his first
work (on shadow instruments) by 16 or 17. We have his own word that he intended
to return to Baghdad to make observations to test his astronomical theories.
He did return, but it is unknown whether he made his observations. Ibn Sinān
died suffering from a swollen liver.
Ibn
Sinān's mathematical works contain a number of powerful and novel investigations.
These include a treatise on how to draw conic sections, useful for the construction
of sundials; an elegant and original proof of the theorem that the area of
a parabolic segment is 4/3 the inscribed triangle (Archimedes'
work on the parabola was not available to the Arabs); a work on tangent circles;
and one of the most important Islamic studies on the meaning and use of the
ancient Greek technique of analysis and synthesis.
Ibn
Sinān composed several astronomical works. On the Motions of the Sun
presents his approach to the apparent motion of the Sun, including the question
of the motion of the solar apogee. He includes a critical analysis of Ptolemy
and his Arabic predecessors but apologizes for not being able to test his
own theory, hoping for someone to make the relevant observations in future.
In this work he also takes a stand against Aristotle's
authority, especially with respect to meteorological optics, accusing Aristotle's
supporters of adopting his positions without question. Ibn Sinān evidently
wrote on the trepidation of the equinoxes, a theory that he combined with
a variable obliquity of the ecliptic. Though this work has not survived, later
writers ascribe such a theory to him and there are hints of it in his work
On the Motions of the Sun. Ibn Sinān's theory explaining an apparent
variation in the obliquity of the ecliptic did not impress Bīrūnī
sufficiently to change his position that the obliquity is constant. Another
treatise by Ibn Sinān, The Determination of the Anomalies of Saturn,
Mars, and Jupiter, contains a critique of Ptolemy's models of the motions
of the planets.
Like
his grandfather, Ibn Sinān wrote a book on shadow instruments (such as
sundials and gnomons). It contains discussions of sundials erected on plane
surfaces, errors in the application of sundials, how one might use a sundial
as a replacement for the astrolabe, and how to draw time lines on various
surfaces.
A short
tract, On the Astrolabe, must have been written late in life, since
it is not included in Ibn Sinān's own summary of his works. In it he
proves the fundamental theorem of stereographic projection required to construct
an astrolabe, namely that circles on the sphere (other than those that pass
through the pole) are mapped to circles in the plane.
Selected References
Ali, Jamil (trans.) (1967). The Determination of the Coordinates
of Cities: Al‐Bīrūnī's Taḥdīd al‐Amākin.
Beirut: American University of Beirut.
Ibrāhīm ibn Sinān (1983). The Works of Ibrahīm
ibn Sinān (in Arabic), edited by A. S. Saidan. Kuwait.
———
(1999). Die Schrift des Ibrāhīm b. Sinān b. Ṯābit
über die Schatteninstrumente. Translated and annotated
by Paul Luckey, edited by Jan P. Hogendijk. Frankfurt am Main: Institute for
the History of Arabic‐Islamic Science.
Kennedy, E. S. (1973).
A Commentary Upon Bīrūnī's Kitāb Taḥdīd
al‐Amākin. Beirut: American University of Beirut.
——— (1976). The
Exhaustive Treatise on Shadows by Abū al‐Rayḥān Muhammad
b. Ahmad al‐Bīrūnī. Translation and commentary. 2
Vols. Aleppo: Institute for the History of Arabic Science.
Ragep, F. J. (1993).
Nasīr al‐Dīn al‐Ṭūsī's Memoir
on Astronomy (al‐Tadhkira fī ʿilm
al‐hayʾa). 2 Vols. New York:
Springer‐Verlag, Vol. 2, pp. 400–408.
Rashed, Roshdi (1997). “Ibrāhīm ibn Sinān.” In
Encyclopaedia of the History of Science, Technology, and Medicine in Non‐Western
Cultures, edited by Helaine Selin, pp. 441–442. Dordrecht: Kluwer, Academic
Publishers.
Rashed,
Roshdi and Hélène Bellosta (2000). Ibrāhīm ibn Sinān: Logique et géométrie
au Xesiècle. Leiden:
E. J. Brill.
Sezgin, Fuat. Geschichte des arabischen Schrifttums. Vol. 5, Mathematik (1974): 292–295; Vol. 6, Astronomie (1978): 193–195; Vol. 7, Astrologie – Meterologie und Verwandtes (1979): 274–275. Leiden: E. J. Brill.