| From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, pp. 627-628 |
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Khayyām: Ghiyāth
al‐Dīn Abū
al‐Fatḥ
ʿUmar ibn Ibrāhīm al‐Khayyāmī
al‐Nīshāpūrī
Behnaz Hashemipour
Alternate
name
Omar Khayyām
Born Nīshāpūr,
Khurāsān, (Iran), 18 May 1048
Died Nīshāpūr
Khurāsān, (Iran), circa 1123
Better
known in the West as ʿUmar Khayyām,
Khayyām was one of the most prominent scholars of medieval times, with
remarkable contributions in the fields of mathematics and astronomy. His worldwide
fame today mainly comes from a number of quatrains attributed to him that
have tended to overshadow his brilliant scientific achievements. Besides his
ingenious achievements in mathematics, Khayyām is said to have supervised
or actively taken part in the formulation and compilation of a solar calendar
that potentially surpasses all calendar systems ever composed in precision
and exactness – a legacy alive today in his native Iran. Khayyām's contributions
to astronomy should be viewed within the context of his efforts to compile
this calendar.
Nīshāpūr
was known for its great learning centers and its prominent scholars. Khayyām
studied the sciences of the day in his native town and is said to have mastered
all branches of knowledge in early youth. Khayyām soon rose to prominence
in Khurāsān, the political center of the powerful Saljūq dynasty
that ruled over a vast empire extending from the borders of China to the Mediterranean.
As the leading scientist, philosopher, and astronomer of his day, he enjoyed
the support and patronage of the Saljūq court.
With the ascent of Jalāl al‐Dīn Malik Shāh to
the throne, in 1072, Isfahān was chosen as the new capital of the Saljūq
dynasty. Consequently, a group of prominent scientists and scholars from Khurāsān,
among them Khayyām and al‐Muẓaffar
al‐Isfizārī, were summoned to the court in the new
capital to embark on two grand projects: the construction of an observatory
and the compilation of a new calendar to replace the existing calendars. In
addition to other deficiencies, these calendars had proved inefficient in
monetary and administrative matters related to time‐reckoning. No details
have survived regarding the observatory and its site, except for brief notes
saying that huge sums of money were spent on it and that it was very well
equipped. However, one finds references made by Naṣīr
al‐Dīn al‐Ṭūsī, Quṭb al‐Dīn al‐Shīrāzī,
and others to a Zīj‐i Khayyām or Zīj‐i
Malikshāhī (Astronomical handbooks of Khayyām or Malikshāh)
that could possibly be one major outcome of the observatory.
By
1079, a solar calendar was developed that was named the “Jalālī”
or “Malikī” calendar, thus carrying the name of the monarch who was the
project's patron. The most remarkable feature of the new calendar was the
correspondence of the beginning of the year (Nowrūz or new day)
and the beginning of Aries, i. e., where the Sun passing from the Southern
Celestial Hemisphere to the Northern appears to cross the Celestial Equator,
marking the beginning of spring or the vernal equinox. The Jalālī
year was a true solar year that followed the astronomical seasons. The length
of this year was the mean interval between two vernal equinoxes. Recent studies
have underscored the advantage of the Jalālī calendar by demonstrating
the superiority of the vernal equinox as a calendar regulator, arguing that
the vernal equinox year length is much more consistent than other natural
regulating points.
The
second important feature of this calendar was the introduction for the first
time of leap years using the rule of quinquennium (5‐year periods for
leap years). After a normal period of 7 quadrennia (4‐year periods for
leap years – in exceptional cases 6 or 8), there comes a quinquennia in which
the extra day is added to the 5th and not the 4th year as usual. This produces
patterns of 33‐, 29‐ and 37‐year cycles for 7, 6, and 8
quadrennia, respectively. As modern calculations have shown, this introduction
of 5‐year leap‐days into the calendar has the potential, provided
that a correct pattern is employed, of rendering the calendar quite accurate
over relatively long time spans – indeed, more accurate than the modern Gregorian
calendar. There is, however, a wide variety of opinions on the pattern (the
number of times 29 or 37 cycles are combined with 33‐year cycles) of
leap years originally built into the Jalālī calendar, thus leaving
its actual accuracy an open question to be investigated.
Khayyām's
major role in the court of Malik‐Shāh, as well as the historical
testimony of prominent astronomers such as Ṭūsī, Shīrāzī,
and Nīsābūrī, all
associating the name of ʿUmar Khayyām with the Jalālī calendar, leaves little
doubt of his leading role in the compilation of the Jalālī calendar.
His prominence as a major astronomer of his time is also borne out by his
critical notes on Ibn al‐Haytham's
Maqāla fī ḥarakat al‐iltifāf (Treatise on the winding motion). This work, which
is discussed by Shīrāzī, demonstrates the fact that Khayyām
had been engaged in quite complicated and difficult aspects of theoretical
astronomy that involved the development of new models to replace the unwieldy
latitude models of Ptolemy.
Khayyām's
work in astronomy has been overshadowed by his outstanding achievements in
mathematics, in which his genius and originality are best manifested. His
contributions to the subject may well be considered some of the greatest during
the entire Middle Ages. In particular, his treatise entitled Risāla
fī al‐barāhīn ʿalā masāʾil
al‐jabr wa‐ʾl‐muqābala (Treatise on the proofs
of the problems of al‐jabr and al‐muqābala)
is one of the most important algebraic treatises of the Middle Ages. He also
dealt with the so-called parallel postulate and arrived at new propositions
that were important steps in the development of non‐Euclidean geometries.
His work in the theory of numbers was also significant, eventually leading
to the modern notion of real positive numbers that included irrational numbers.
Khayyām
also wrote short treatises in other fields such as mechanics, hydrostatics,
the theory of music, and meteorology. Through his work in ornamental geometry,
he contributed to the construction of the north dome of the Great Mosque of
Isfahān. He may have also served as a court physician.
Though
little remains of his work in philosophy, Khayyām was a follower of Ibn
Sīnā and much respected by his contemporaries for his work
in this field. In a later work, he concludes that ultimate truth can be grasped
only through mystical intuition. This perhaps gives some inkling of how to
read his famous poetry, not all of which has been accepted as authentic by
modern scholarship.
Khayyām
seems to have spent the most fruitful scientific years of his life in Isfahān.
But with the assassination of Malikshāh in 1092, he returned to Khurāsān,
spending the rest of his life in Marw and Nīshāpūr. His death
brought to an end a brilliant chapter in Iranian intellectual history.
Selected References
Abdollahy, Reza (1990). “Calendar: Islamic Period.” In Encyclopaedia
Iranica, edited by Ehsan Yarshater. Vol. 4, pp. 668–674. London: Routledge
and Kegan Paul.
Al‐Bayhaqī,
ʿAlī
ibn Zaid (1935). Tatimmat ṣiwān al‐ḥikma, edited by M. Shafīʿ. Lahore: University of Panjab.
Angourāni, Fāteme and Zahrā. Angourāni (eds.)
(2002). Bibliography of ʿOmar
Khayyām (in Persian). Tehran: Society for the Appreciation of Cultural
Works and Dignitaries.
Borkowski, Kazimierz M. (1996). “The Persian Calendar for 3000
Years.” Earth, Moon, and Planets 74: 223–230.
Djebbar,
Ahmed (Spring 2000). “ʿOmar
Khayyām et les activités mathématiques en pays d'Islam aux XI–XII siècles.”
Farhang 12, no. 29–32: 1–31. (Commemoration of Khayyām.)
Hashemipour, Behnaz (Winter 2002). “Guftārī dar bār‐i‐yi
kullīyāt‐i wujūd (Khayyām's Treatise on The Universals
of Existence [Edited with an Analytical Introduction])” (in Persian). Farhang
14, no. 39– 40: 29–87.
Meeus, Jean (2002). “The Gregorian Calendar and the Tropical
Year.” More Mathematical Astronomy Morsels. Richmond, Virginia: Willmann‐Bell
Inc., pp. 357–366.
Nasr, Seyyed Hossein (Winter 2002). “The Poet‐Scientist
Khayyām as Philosopher.” Farhang 14, no. 39– 40: 25–47.
Netz, Reviel (Winter 2002). “ʿOmar Khayyām
and Archimedes.” Farhang 14, no. 39– 40: 221–259.
Niẓāmī‐i
ʿArūḍī‐i
Samarqandī (1957). Chāhār Maqāla (Four Discourses).
Tehran: Zawwār Pub. Originally edited with introduction, notes and index
by Mohammad Qazvīnī. Revised with a new introduction, additional
notes and complete index by Moḥammad Moʿīn.
Rashed, Roshdi and Bijan Vahabzabeh (2000). Omar Khayyām
the Mathematician. Persian Heritage Series, no. 40. New York: Bibliotheca
Persica Press.
Rosenfeld, Boris A.
(2000). “ʿUmar
Khayyām.” In Encyclopaedia of Islam. 2nd ed. Vol. 10, pp.
827–834. Leiden: E. J. Brill.
Steel, Duncan (April
2002). “The Proper Length of the Calendar Year.” Astronomy and Geophysics
43, no. 2: 9.
Struik,
D. J. (1958). “Omar Khayyam, Mathematician.” Mathematics
Teacher 51: 280–285.
Vitrac,
Bernard (Spring 2000). “ʿOmar
Khayyām et Eutocius: Les antécédents grecs du troisième chapitre du commentaire
sur certaines prémisses problématiques du Livre d'Euclide.” Farhang
12, no. 29– 32: 51–105.
———
(Winter 2002). “ʿOmar
Khayyām et l'anthypérèse: Études du deuxième livre de son commentaire.”
Farhang 14, no. 39– 40: 137–192.
Youschkevitch,
A. and B. A. Rosenfeld (1973). “Al‐Khayyāmī.”
In Dictionary of Scientific Biography, edited by Charles Coulston Gillispie.
Vol. 7, pp. 323–334. New York: Charles Scribner's Sons.