Flourished (Iraq), 12th
century
Died Marāgha,
(Iran), 1174/1175
Samawʾal
was an eminent mathematician, physician, and astronomer, who composed some
85 treatises, all in Arabic. He was from a cultivated Jewish family that
was originally from the Maghrib or, according to some sources, from al‐Andalus.
His father migrated to Baghdad and settled there. The young Samawʾal
studied Hebrew, mathematics, and medicine. He traveled in the Muslim east,
eventually settling in Marāgha in northwestern Iran, which was then
a major city. He spent the rest of his life there as a physician in service
of Jahān Pahlawān (died: 1186) of a semi‐independent minor
dynasty, the Atābakān. There he converted to Islam and wrote a
book against Judaism, which became very controversial.
His
main astronomical work is Kashf ʿawār al‐munajjimīn
wa‐ghalaṭihim fī akthar al‐aʿmāl wa‐ʾl‐aḥkām (Exposure of the deficiencies
of the astronomers and their errors in most of [their] operations and judgments),
written in 1165/1166. This treatise is divided into 25 (chapters) bābs,
each consisting of several (sections) faṣls, in which he indicates
the errors that he has found in the astronomical works of Greek scientists,
such as Euclid, Archimedes,
and Apollonius,
of Islamic scientists such as Ibrāhīm
ibn Sinān, Abū Jaʿfar
al‐Khāzin, Bīrūnī,
Abū Maʿshar,
Ḥabash, Ṣūfī, and Ibn
al‐Haytham, and of Indian scientists such as Brahmagupta.
The titles of the chapters are as follows:
| (l) |
The reason for composing this book; |
| (2) |
On finding altitudes by astrolabe; |
| (3) |
On finding altitudes by shadow; |
| (4) |
On sines; |
| (5) |
On observations; |
| (6) |
On calendars; |
| (7) |
On interpolation; |
| (8) |
On finding hour‐angles from equal hours; |
| (9) |
On equation of time; |
| (10) |
On daily hours; |
| (11) |
On ascensions; |
| (12) |
On projection of rays; |
| (13) |
On latitudes of planets; |
| (14) |
On aphesis; |
| (15) |
On true horizons; |
| (16) |
On finding heights of mountains and other high objects; |
| (17) |
On positions of fixed stars; |
| (18) |
On the nature of planets; |
| (19) |
On animodars; |
| (20) |
On elections (of proper times); |
| (21) |
On oblique ascensions; |
| (22) |
On the times of conjunctions, syzygies, and transfers; |
| (23) |
On properties of inscribed polygons and their effects
on the sublunar world; |
| (24) |
On syzygies of epicycles; and |
| (25) |
Types of indications. |
In
the last chapters (20–25), Samawʾal uses a type of philosophical argument
based upon his previous chapters to explain his view regarding the effects
of stars on terrestrial events. He concludes that because the stars are
innumerable and the relations and effects among them are virtually incalculable,
an astrologer would need to take into consideration 6,817 variables for
each person, therefore making it impossible to predict the future in any
meaningful way.
Samawʾal
was perhaps best known for his work in mathematics, especially algebra and
arithmetic. He also wrote on medicine.
Berggren, J. L. (1986). Episodes in the Mathematics of Medieval
Islam. New York: Springer Verlag, pp. 112–118.
