| From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, p. 568 |
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Ibn al‐Samḥ: Abū
al‐Qāsim Aṣbagh ibn Muḥammad ibn al‐Samḥ
al‐Gharnāṭī
Mònica Rius
Died Granada, al‐Andalus,
(Spain), 29 May 1035
Ibn
al‐Samḥ, known
also as al‐Muhandis (the geometer), was a noted mathematician and astronomer
in Andalusia and an important member of the school of Maslama
al‐Majrīṭī
centered in Cordova. Because of political unrest, Ibn al‐Samḥ
fled to Granada where he lived out the rest of his life. There he worked in
the service of the local chief, the Berber Ḥabbūs
ibn Māksan (reigned: 1019–1038), whose Jewish Minister, Samuel ben Nagrella,
was also interested in mathematics and astronomy.
Ibn
al‐Samḥ worked
in the fields of astronomy, mathematics, and, possibly, medicine. The 14th‐century
historian Ibn al‐Khaṭīb states that Ibn al‐Samḥ wrote an essay on history, but there is no other evidence
for this assertion. Ibn al‐Nāshī, one of Ibn al‐Samḥ's
most important disciples, gives a list of nine books written by his teacher.
In astronomy, Ibn al‐Samḥ, like his teacher Maslama al‐Majrīṭī,
composed a zīj (an astronomical handbook with tables) based on
Khwārizmī's Sindhind,
which had been composed in 9th‐century Baghdad. Ibn al‐Samḥ
also composed a treatise on the construction of the astrolabe and another
on its use (Kitāb al‐ʿAmal bi‐ʾl‐asṭurlāb). Although Ibn
al‐Ṣaffār's treatise on the astrolabe
gained more popularity, this long book (129 chapters on the use of the instrument)
is the most complete tract written in the Iberian Peninsula during the Middle
Ages. The text is especially interesting because it deals with questions not
usually analyzed in works of this kind, such as the visibility of the Moon
and its latitude and longitude. His Kitāb al‐ʿAmal is also important because
in it he quotes an unknown work by Ḥabash
al‐Ḥāsib, clear evidence that
this eastern astronomer was known in Andalusia at the end of the 10th century.
The text also shows that the school of Maslama knew and used the works of
Battānī. The Kitāb
al‐ʿAmal was the source of a treatise
on the use of the spherical astrolabe composed at the court of Alfonso
X. Since the king's astronomers did not have an Arabic text on the
spherical astrolabe from which to make the Castilian translation, they took
Ibn al‐Samḥ's treatise and made an adaptation of it. His treatise on
the construction of the equatorium – an instrument originally conceived in
Andalusia and later developed in Latin Europe – is another of Ibn al‐Samḥ's
major contributions to astronomy. Indeed, this treatise is the first known
work dealing with this instrument and was followed by works written by Zarqāli
and Abū al‐Ṣalt of Denia. The instrument
described by Ibn al‐Samḥ
is a hybrid astrolabe/equatorium, and his treatise is preserved in the Alfonsine
translation included in the Libros del Saber de Astronomia. Ibn al‐Samḥ
gives the numerical parameters necessary for the construction of the instrument
and uses Battānī's values for the longitudes of the apogees of the
planets, Khwārizmī‐Maslama's values for the ascending nodes
of the planets, and the eccentricities and radii of the epicycles of the planets
from the Almagest. The equatorium has eight plates (one for the Sun,
six for the deferents of the Moon and the five planets, and one for the planetary
epicycles) carefully explained and placed within the mater of an astrolabe.
This instrument helps to determine the longitude of a planet and saves astronomers
a great deal of time, especially considering that one of their main aims in
the Middle Ages was to cast a horoscope. The historian Ibn Khaldūn mentions
that Ibn al‐Samḥ wrote an abstract of the Almagest.
Ibn
al‐Samḥ is well
known for his many compositions in mathematics. His range of subject matter
includes calculation, numbers, commercial arithmetic, theory of proportions,
arithmetical operations, and the solution of quadratic and cubic equations.
His work in geometry includes a commentary on the book of Euclid, and a general
treatise that includes an important study of straight, curved, and broken
lines. The latter is partially extant in a Hebrew translation.
Selected References
Comes,
Mercè (1991). Ecuatorios andalusíes:
Ibn al‐Samḥ, al‐Zarqālluh
y Abū‐l‐Ṣalt. Barcelona,
pp. 27–78.
Millás Vallicrosa,
José María (1943–1950). Estudios sobre Azarquiel. Madrid–Granada.
——— (1955).
“Los primeros tratados de astrolabio en la España árabe.” Revista del Instituto
Egipcio de Estudios Islámicos 3: 55–76, esp. 35–49. (Reprinted in Nuevos
estudios sobre historia de la ciencia española. Barcelona,
1960, pp. 61–78.)
Pingree, David
(1971). “Ibn al‐Samḥ.” In Encyclopaedia of Islam. 2nd
ed. Vol. 3, pp. 928–929. Leiden: E. J. Brill.
Rashed, Roshdi
(1995). Les mathématiques infinitésimales du IXeau XIesiècle,
Vol. 1, pp. 885–973. Fondateurs et commentateurs: Banū Mūsā,
Ibn Qurra, Ibn Sinān, al‐Khāzin, al‐Qūhī,
Ibn al‐Samḥ, Ibn Hūd. London.
Rosenfeld, B. A.
and Ekmeleddin Ihsanoğlu
(2003).
Mathematicians, Astronomers, and Other Scholars of Islamic Civilization
and Their Works (7th – 19th c.). Istanbul: IRCICA, pp. 120–121.
Ṣāʿid
al‐Andalusī (1912). Kitāb Ṭabaqāt
al‐umam, edited by P. Louis Cheikho. Beirut: Imprimerie
Catholique, pp. 69–70. French translation with notes by Régis Blachère as
Livre des catégories des nations. Paris: Larose, 1935,
pp. 130–131.
Samsó, Julio
(1992). Las ciencias de los antiguos en al‐Andalus. Madrid:
Mapfre.
Sezgin, Fuat (1978). Geschichte des arabischen
Schrifttums. Vol. 6, Astronomie, p. 249. Leiden: E. J. Brill.
Viladrich,
Mercè (1986). “El Kitāb al‐ʿamal bi‐l‐asturlāb” (Llibre de l'ús de l'astrolabi)
d'Ibn al‐Samḥ. Estudi i traducció. Barcelona.