| From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, pp. 1157-1159 |
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Courtesy of 
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Ulugh Beg: Muḥammad Ṭaraghāy ibn Shāhrukh ibn Tīmūr
Benno van Dalen
Died near Samarqand,
(Uzbekistan), 27 October 1449
Ulugh
Beg (Turkish for “great prince”) was governor of Transoxiana and Turkestan
and, during the last 2 years of his life, Timurid Sultan. However, he is mostly
remembered as a patron of mathematics and astronomy. In Samarqand, he founded
a school and the famous astronomical observatory, where the most extensive
observations of planets and fixed stars at any Islamic observatory were made.
Ulugh Beg is associated with a Persian astronomical handbook (zīj)
that stands out for the accuracy with which its tables were computed.
Ulugh
Beg was the first‐born son of Shāhrukh (youngest son of the infamous
conqueror Tīmūr or Tamerlane) and his first wife Gawharshād.
He was raised at the court of his grandfather and, at the age of 10, was married
to his cousin Agha Bīkī, whose mother was a direct descendent of
Chingiz Khan. Thus Ulugh Beg could use the epithet Gūrgān, “royal
son‐in‐law,” which had originally been used for Chingiz's son‐in‐law.
In
the years after Tīmūr's death in 1405, Ulugh Beg became governor
of Turkestan and Transoxiana, the most important cities of which were the
cultural centers Samarqand and Bukhara. Although not completely divorced from
affairs of state, he is better known for his interest in religion, architecture,
arts, and sciences, which were fostered by the Mongols as well as by the Timurids.
Ulugh Beg is said to have spoken Arabic, Persian, Turkish, Mongolian, and
some Chinese. He had a thorough knowledge of Arabic syntax and also wrote
poetry. Although he honored Turkic–Mongolian customs, he also knew the Quran
by heart, including commentaries and citations. Ulugh Beg was also a passionate
hunter.
By 1411, Ulugh Beg had developed a lively interest in mathematics and
astronomy, which may have been aroused by a visit in his childhood to the
remnants of the Marāgha Observatory that had been directed by Ṭūsī. In 1417, he founded
in Samarqand a madrasa (religious school or college) that can still
be seen on the Registan Square. At this institution, unlike other madrasas,
mathematics and astronomy were among the most important subjects taught. The
most prominent teacher was Qāḍīzāde al‐Rūmī,
who was joined somewhat later by Kāshī.
Two
extant letters by Kāshī to his father in Kāshān make clear
that Ulugh Beg was personally involved in the appointment of scholars and
that he was frequently present, and actively participated, in seminars, where
he displayed a good knowledge of mathematical and astronomical topics. Kāshī
relates how Ulugh Beg performed complicated astronomical calculations while
riding on horseback. Anecdotes from other sources show that Ulugh Beg, like
many other Muslim rulers, believed in astrology and fortune‐telling.
He appears as a person who very much respected the scholars he appointed,
and whose main objective was to reach scientific truth.
In 1420, Ulugh Beg founded his famous astronomical observatory on a
rocky hill outside the city of Samarqand. Its circular main building, beautifully
decorated with glazed tiles and marble plates, had a diameter of about 46
m and three stories reaching a height of approximately 30 m above ground level.
The north–south axis of the main building was occupied by a huge sextant with
a radius of 40 m (called Fakhrī sextant after that of Khujandī).
On the scale of this instrument, which partially lay in an underground slit
with a width of half a meter, 70 cm corresponded to 1° of arc, so that the
solar position could be read off with a precision of 5". On the flat roof of the main building various smaller instruments
could be placed, such as an armillary sphere, a parallactic ruler, and a triquetrum.
Among other instruments known to have been used in Samarqand are astrolabes,
quadrants, and sine and versed sine instruments.
Although Ulugh Beg was the director of the Samarqand Observatory, Kāshī
was in charge of observations until his death in 1429, after which he was
succeeded by Qāḍīzāde, who died after
1440. The observational program was completed by Qūshjī,
who had studied in Kirmān (southeastern Iran) before returning to Samarqand.
The results of the observations made under Ulugh Beg include the measurement
of the obliquity of the ecliptic as 23° 30'17" (the actual value at the time was 23° 30'48") and that of the latitude of Samarqand as 39° 37'33"
N. (modern value: 39° 40'). Furthermore, most of
the planetary eccentricities and epicyclic radii were newly determined, and
the longitudes and latitudes of the more than 1,000 stars in Ptolemy's
star catalogue were verified and corrected. Precession was found to amount
to 51.4" per year (corresponding
to 1° in little more than 70 years; the actual value is 50.2" per year).
The
observatory of Ulugh Beg stayed in operation for little more than 30 years.
It was finally destroyed in the 16th century and completely covered by earth
in the course of time. In 1908, archaeologist V. L. Vyatkin recovered the
underground part of the Fakhrī sextant, consisting of two parallel walls
faced with marble and the section of the scale between 80° and 57° of solar
altitude. Ulugh Beg's observatory exerted a large influence on the huge masonry
instruments built by Jai
Singh in five Indian cities (most importantly Jaipur and Delhi) in
the 18th century, more than 100 years after the invention of the telescope.
The
main work with which Ulugh Beg is associated is an astronomical handbook with
tables in Persian, variously called Zīj‐i Ulugh Beg, Zīj‐i
Jadīd‐i Sulṭānī, or Zīj‐i
Gūrgānī. In the introduction, Ulugh Beg acknowledges the
collaboration of Qāḍīzāde, Kāshī, and Qūshjī,
who were undoubtedly responsible for the underlying observations as well as
the computation of the tables. The Zīj is in many respects a standard
Ptolemaic work without any adjustments to the planetary models. It consists
of four chapters dealing with chronology, trigonometry and spherical astronomy,
planetary positions, and astrology, respectively. The instructions for the
use of the tables, which were edited and translated into French by L. Sédillot
in the middle of the 19th century, are clear but very brief and do not even
include examples of the various calculations.
Thus, the most significant part of Ulugh Beg's Zīj lies
in the observations and computations underlying the tables. Most impressively,
the sine table, covering 18 pages in the manuscript copies, displays the sine
to five sexagesimal places (corresponding to nine decimals) for every arc
minute from 0° to 87° and to six sexagesimal places (11 decimals) between
87° and 90°. All independently calculated values for multiples of 5' are correct to the precision
given, whereas the intermediate values, calculated by means of quadratic interpolation,
contain incidental errors of at most two units. Also most of the planetary
tables in the Zīj were calculated to a higher precision than before.
New types of tables were added that simplified the calculation of planetary
positions. Ulugh Beg's star catalog for the year 1437 represents the only
large‐scale observations of star coordinates made in the Islamic realm
in the medieval period. (Most other catalogs simply adjusted Ptolemy's ecliptic
coordinates for precession or were limited to a relatively small number of
stars.)
Ulugh
Beg's Zīj was highly influential and continued to be used in the
Islamic world until the 19th century. It was soon translated into Arabic by
Yaḥyā ibn ʿAlī al‐Rifāʿī
and into Turkish by ʿAbd al‐Raḥmān
ʿUthmān. Reworkings
for various localities were made in Persian, Arabic, and Hebrew by scholars
such as ʿImād al‐Dīn ibn Jamāl al‐Bukhārī
(Bukhara), Ibn Abī al‐Fatḥ
al‐Ṣūfī (Cairo), Mullā Chānd
ibn Bahāʾ al‐Dīn and Farīd al‐Dīn al‐Dihlawī
(both Delhi), and Sanjaq Dār and Husayn Qusʿa (Tunis). Commentaries
to the Zīj were written by Qūshjī, Mīram
Chelebī, Bīrjandī,
and many others. Hundreds of manuscript copies of the Persian original of
Ulugh Beg's Zīj are extant in libraries all over the world. Already
in 17th‐century England, various parts of the Zīj were published
in edition and/or translation.
Little
is known about other works of Ulugh Beg. A marginal note by him in the India
Office manuscript of Kāshī's Khāqānī Zīj
presents a clever improvement of a spherical astronomical calculation. A Risāla
fī istikhrāj jayb daraja wāḥida (Treatise on the extraction of the sine of 1°) has
been attributed to Ulugh Beg on the basis of a citation in Bīrjandī,
although most manuscripts of this work mention Qāḍīzāde as the author.
Aligarh Muslim University Library lists a treatise Risāla‐yi
Ulugh Beg that is yet to be inspected. Finally, an astrolabe now preserved
in Copenhagen and made in 1426/1427 by Muḥammad
ibn Jaʿfar al‐Kirmānī, who is known
to have worked at the observatory in Samarqand, was originally dedicated to
Ulugh Beg.
In 1447,
Ulugh Beg succeeded his father Shāhrukh as sultan of the Timurid empire.
However, he was killed on the order of his son ʿAbd
al‐Laṭīf.
An investigation of Tīmūr's mausoleum by Soviet scholars in the
1940s showed that Ulugh Beg was buried as a martyr in accordance with Sharīʿa (Islamic
law), i. e., fully clothed in a sarcophagus.
Selected References
Bagheri, Mohammad (1997). “A Newly Found Letter of Al‐Kāshī
on Scientific Life in Samarkand.” Historia Mathematica 24: 241–256.
Barthold, V. V. (1958). Four Studies on the History of Central
Asia. Vol. 2, Ulugh‐Beg. Leiden: E. J. Brill.
Kary‐Niiazov, T. N. (1950). Astronomicheskaya shkola
Ulugbeka (The astronomical school of Ulugh Beg) (in Russian). Moscow:
Akademia Nauk SSSR. (Second enlarged edition in Kary‐Niiazov, Izbrannye
trudy [Collected works]. Vol. 6. Tashkent: FAN, 1967.)
——— (1976). “Ulugh
Beg.” In Dictionary of Scientific Biography, edited by Charles Coulston
Gillispie. Vol. 13, pp. 535–537. New York: Charles Scribner's Sons.
Kennedy, E. S. (1956).
“A Survey of Islamic Astronomical Tables.” Transactions of the American
Philosophical Society, n.s., 46, pt. 2: 121–177, esp. 125–126 and 166–167.
(Reprint, Philadelphia: American Philosophical Society, 1989.)
——— (1960). “A Letter
of Jamshīd al‐Kāshī to His Father: Scientific Research
and Personalities at a Fifteenth Century Court.” Orientalia 29: 191–213.
(Reprinted in E. S. Kennedy, et al., Studies in the Islamic Exact Sciences,
edited by David A. King and Mary Helen Kennedy. Beirut: American University
of Beirut, 1983, pp. 722–744.)
——— (1998). “Ulugh
Beg as Scientist.” Chapter 10 in Astronomy and Astrology in the Medieval
Islamic World. Aldershot: Ashgate. (Describes the marginal note by Ulugh
Beg in a manuscript of Kāshī's Zīj.)
Knobel, Edward Ball (1917). Ulugh Beg's Catalogue of Stars:
Revised from All Persian Manuscripts Existing in Great Britain, with a Vocabulary
of Persian and Arabic Words. Washington: Carnegie Institution of Washington.
Krisciunas, Kevin (1992). “The Legacy of Ulugh Beg.” In Central
Asian Monuments, edited by H. P. Paksoy, pp. 95–103. Istanbul: Isis. (Includes
a bibliography of all publications of parts of the Zīj of Ulugh
Beg.)
——— (1993). “A More Complete Analysis of the Errors in Ulugh
Beg's Star Catalogue.” Journal for the History of Astronomy 24: 269–280.
Kunitzsch,
Paul (1998). “The Astronomer al‐Ṣūfī as a Source for
Uluġ Beg's Star Catalogue.” In
La science dans le monde iranien ā l'époque islamique, edited
by Ž. Vesel, H. Beikbaghban, and B. Thierry de Crussol des Epesse, pp. 41–47.
Tehran:
Institut français de recherche en Iran.
Manz, Beatrice F. (2000). “Ulugh Beg.” In Encyclopaedia of
Islam. 2nd ed. Vol. 10, pp. 812–814. Leiden: E. J. Brill.
Rosenfeld, B. A. and Jan P. Hogendijk (2002/2003). “A Mathematical
Treatise Written in the Samarqand Observatory of Ulugh Beg.” Zeitschrift
für Geschichte der Arabisch‐Islamischen Wissenschaften 15: 25–65.
Sayılı, Aydın (1960). The Observatory in Islam.
Ankara: Turkish Historical Society, esp. pp. 260–289.
———(1960). Ghiyâth
al‐Dîn al Kâshî's Letter on Ulugh Beg and the Scientific Activity in
Samarqand. Ankara: Turkish Historical Society.
Schoy,
Carl (1927). Die trigonometrischen Lehren des persischen Astronomen Abū
ʾl‐Rayḥān Muḥammed ibn Aḥmed al‐Bīrūnī
dargestellt nach al‐Qānūn al‐Masʿūdī.
Hanover: Lafaire. (Reprinted in Schoy, Beiträge zur arabisch‐islamischen
Mathematik und Astronomie, edited by Fuat Sezgin, Vol. 2, pp. 629–746.
Frankfurt am Main: Institute for the History of Arabic‐Islamic Science,
1988.) (Includes an edition of parts of Ulugh Beg's sine and tangent tables.)
Sédillot,
Louis P. E. Amélie (1847). Prolégomènes des tables astronomiques d'Oloug‐Beg.
Publiés avec notes et variantes et précédés d'une introduction. Paris:
Firmin Didot.
———
(1853). Prolégomènes des tables astronomiques d'Oloug‐Beg. Traduction
et commentaire. Paris: Firmin Didot.
Shevchenko, Mikhail Yu (1990). “An Analysis of Errors in the Star Catalogues of Ptolemy and Ulugh Beg.” Journal for the History of Astronomy 21: 187–201.