Abu Jafar Muhammad ibn Hasan Khazini (Persian: ابوجعفر
خازن خراسانی; 900–971), also called Al-Khazin, was an Iranian
Muslim astronomer and mathematician from Khorasan. He worked on both
astronomy and number theory.
Al-Khazin was one of
the scientists brought to the court in Ray, Iran by the ruler of the Buyid
dynasty, Adhad ad-Dowleh, who ruled from 949 to 983 AD. In 959/960 Khazini
was required by the Vizier of Ray, who was appointed by ad-Dowleh, to
measure the obliquity of the ecliptic.
One of Al-Khazin's
works Zij al-Safa'ih ("Tables of the disks of the
astrolabe") was described by his successors as the best work in the
field and they make many references to it. The work describes some astronomical
instruments, in particular an astrolabe fitted with plates inscribed
with tables and a commentary on the use of these. A copy of this instrument was
made, but it vanished in Germany at the time of World War II. A
photograph of this copy was taken and examined in D.A. King's New light
on the Zij al-Safa'ih of Abu Ja'far al-Khazin, Centaurus 23 (2) (1979/80),
105-117.
Al-Khazin also wrote a
commentary on Ptolemy's Almagest in which he gives
nineteen propositions relating to statements by Ptolemy. He proposed a
different solar model from Ptolemy's.
Al-Khāzin, usually
known as Abũ Jaʿfar al-Khāzin, was a Sabaean of Persian origin. The Fihrist calls
him al-Khurānāā, meaning from Khurāsān, a province in eastern Iran. He should
not be confused with Aʿbd al-Rahmāan al-Khāzinī (ca. 1100), the probable
author of Kitāb al-āāt alʿajiba al-raādiyya, on obsertvation
instruments, often attributed to al-Khāzin. (E. Wiedemann attributed this work,
inconsistently, to al-Khāzin in the Enzyklopaedie des Islam, II
[Leiden-Leipzig, 1913], pp. 1005-1006, and to al-Khāziniī in Beiträge, 9 [1906],
190. De Slane confounded these two astronomers in his translation of Ibn
Khaldũ’s Prolegomena, I, 111.
Abũ Ja far al-Khāzin,
said to have been attached to the court of the Buwayhid ruler ruler al-Dawla
(932-976) of Rayy, was well known among his contemporaries. In particular
his Zij al-āsafāih (“tables of the Disks [of the astrolabe]”0,
which Ibn al-Qiftī calls the best work in this field, if often cited. it may be
related to manuscript “Liber de sphaera in plano describenda,” in the
Laurentian library in Florence (Pal,-Med. 271).
Al-Bīũnīs Risāla
fi fihrist kutub Muhammad b. Zakariyyā al-Rāzi (“Bibliography”) of
1036 lists several texts (written in cooperation with Abũ Naşr Manşũr ibn
’Irāaq), one of which is Fi tashīh mā waqa’a li Abi Jaʿfar al-Khāzin
min al-shaw fi zäj al-safā ih (“On the Improvement of What Abũ Jaʿfar
Neglected in His Tables of the Disks”). In Tamhid al-mustaqarr
li-tahqīq manā al-mamarr, (“On Transits” ), al-Bīũnī criticizes Abũ
Ja’ al-Khā;zin for not having correctly handled two equations defining the
location of a planet but remarks that the Zī al-safāih is
correct on this matter. Abũ Ma’shar that. unlike manyolthers, he had fully
determined the truth about the planets, which he had included in his Zīj. Abũ
Jafar al-Khāzin regarded this work as a mere compilation. Al-BiũrŪnī compared
Abũ Jaʿfar al-Khāzin very favorably with Abũ Ma’shar, and in his al-āthār
al-bāqiya min al-quũn al-khāliya (“Chronology of Ancient Nations”) he
refers to Zij al safā ih for a good explanation of the
progressive and retrograde motion of the sphere.
An anonymous manuscript
in Berlin (Staats-bibliothek, Ahlwardt Cat. No. 5857) contains two short
chapters on astronomical instruments from a work by Abũ Jafar al-Khāzin,
probably the Zij al-safā ih. The MS Or. 168 (4) in Leiden by
Abũ’l-Jũd quotes Abũ Jaʿfar al-Khāzin’s remark in Zij al-safā ih that he would
be able to compute the chord of an angle of one degree if angle trisection were
possible.
In Kitāb fi isi’ā,
dedaling with constructions of astrolabes, al-Biũnī cites Abũ Ja‘far al-Khāin’s
work “Design of the Horizon of the Ascensions for the Signs of the
Zodiac.” And in his Chronology he describes two methods for
finding the Signum Muharrami (the day of the week on which
al-Muharram, the first month of the Muslim year, begins) described by Abũ
Jaʿfar al-Khāzin in al-Madkhal al-kabīr fīilm al-nujũm (“Great
Introduction to Astronomy”). Neither work is extant.
Also treated in
al-Bīũnī’s Chronology is Abũ Jaʿfar al-Kh˜zin’s figure,
different from the eccentric sphere and epicycle, in which the sun’s distance
from the earth is always the same, independent of the rotation. This treatment
gives two isothermal regions, one northern and one southern. Ibn Khaldũn gives
a precise exposition of Abũ Jaʿfar al-Khāzin’s division of the earth into eight
climatic girdles.
Al-Kharaqī (d.
1138/1139), in al-Muntahā, mentions Abũ Jaʿfar al-Khāzin and Ibn
al-Haytham as having the right understanding of the movement of the
spheres. This theory was perhaps described in Abũ Jaʿfar al-Khāzin’s Sirr
al-’ālamin (not extant).
In Tahdī
nihāyāt al-amākin. . ., al-Bīũni criticizes the verbosity of Abũ Ja‘far
al-Khāzin’s commentary on the Almagest and objects to Ibrāhīm
ibn Sānān and Abũ Jafar al-Khāzin’s theory of the variation of
the obliquity of the ecliptic; al-Bīũnī himself considered it to be
constant. The obliquity was measured by al Harawi and Abũ Jafar al-Khāzin at
Rayy (near modern Teheran) in 959/960, on the order of Abu’l Faḍl ibn al-’Amid,
the vizier of Rukn al-Dawla. The determination of this quantity by “al-Khāzin
and his collaborators using a ring about 4 meters” is recorded by al-Nasawi.
Abũ Jaʿfar al-Khāzin
was, according to Ibn al Qifţi, an expert in arithmetic, geometry, and tasyīr (astrological
computastions based on planetary trajectoris). According to al-Khayyāmi, he
used conic sections to give the first solution of the cubic equation by which
al-Māhānī represented Archimedes’ problem of dividing a sphere by a plane into
two parts whose volumes are in a given ratio (Sphere and Cylinder II,
4) and also gave a defective proof of Euclid’s fifth postulate.
Abũ Jaʿfar al-Khāzin
wrote a commentary on Book X of the Elements, a work on numerical
problems (not extant), and another (also not extant) on spherical
trigonometry, Maţālib juziyya mail almuyũl al-juz iyya wa ‘l-maţāli’
fi’l0kura al-mustaqima From the latter, al-Ţũsī, in Kitāb šakl
al-qaţţā (“On the Transversal Figure”), quotes a proof of the sine
theorem for right spherical triangles. Al-Tũsī also added another proof of
Hero’s formula to the Verba filiorum of the Banuũ Mũsũ
(in Majmũ al-rasaāil, II [Hyderabad, 1940]), attributing it to
one al-Khāzin. This proof, closer to that of Hero than the proof by the Banũ
Mũsã, and in which the same figure and letters are used as in Hero’s Dioptra,
is not found in the Latin editions of the Verbafiliorum.
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