Al-Khujandi
Encyclopedia
Abu Mahmud Hamid ibn Khidr Khojandi (known as Abu Mahmood Khojandi, Alkhujandi or al-Khujandi, Persian: ابومحمود خجندی, c. 940 - 1000) was a Persian
astronomer
and mathematician
who lived in the late 10th century and helped build an observatory
near the city of Ray
(near today's Tehran
) in Iran
. He was born in Khujand
; a bronze bust of the astronomer is present in a park in modern-day Khujand, now part of Tajikistan
.
The few facts about Khujandi's life that are known come from his surviving writings as well as from comments made by Nassereddin Tusi
. From Tusi's comments it is fairly certain that Khujandi was one of the rulers of the Mongol tribe in the Khudzhand region, and thus must have come from the nobility
.
, Khujandi worked under the patronage of the Buwayhid
Amirs at the observatory near Ray, Iran
, where he is known to have constructed the first huge mural sextant
in 994 AD, intended to determine the Earth's axial tilt
("obliquity of the ecliptic") to high precision.
He determined the axial tilt to be 23°32'19" for the year 994 AD. He noted that measurements by earlier astronomers had found higher values (Indians: 24°; Ptolemy
23° 51') and thus discovered that the axial tilt is not constant but is in fact (currently) decreasing. His measurement of the axial tilt was however about 2 minutes too small, probably due to his heavy instrument settling over the course of the observations.
, he stated a special case of Fermat's last theorem
for n = 3, but his attempted proof of the theorem was incorrect. The spherical law of sines may have also been discovered by Khujandi, but it is uncertain whether he discovered it first, or whether Abu Nasr Mansur
, Abul Wafa or Nasir al-Din al-Tusi
discovered it first.
Persian people
The Persian people are part of the Iranian peoples who speak the modern Persian language and closely akin Iranian dialects and languages. The origin of the ethnic Iranian/Persian peoples are traced to the Ancient Iranian peoples, who were part of the ancient Indo-Iranians and themselves part of...
astronomer
Islamic astronomy
Islamic astronomy or Arabic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age , and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and...
and mathematician
Islamic mathematics
In the history of mathematics, mathematics in medieval Islam, often termed Islamic mathematics or Arabic mathematics, covers the body of mathematics preserved and developed under the Islamic civilization between circa 622 and 1600...
who lived in the late 10th century and helped build an observatory
Observatory
An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geology, oceanography and volcanology are examples of disciplines for which observatories have been constructed...
near the city of Ray
Ray, Iran
Rey or Ray , also known as Rhages and formerly as Arsacia, is the capital of Rey County, Tehran Province, Iran, and is the oldest existing city in the province....
(near today's Tehran
Tehran
Tehran , sometimes spelled Teheran, is the capital of Iran and Tehran Province. With an estimated population of 8,429,807; it is also Iran's largest urban area and city, one of the largest cities in Western Asia, and is the world's 19th largest city.In the 20th century, Tehran was subject to...
) in Iran
Iran
Iran , officially the Islamic Republic of Iran , is a country in Southern and Western Asia. The name "Iran" has been in use natively since the Sassanian era and came into use internationally in 1935, before which the country was known to the Western world as Persia...
. He was born in Khujand
Khujand
Khujand , also transliterated as Khudzhand, , formerly Khodjend or Khodzhent until 1936 and Leninabad until 1991, is the second-largest city of Tajikistan. It is situated on the Syr Darya River at the mouth of the Fergana Valley...
; a bronze bust of the astronomer is present in a park in modern-day Khujand, now part of Tajikistan
Tajikistan
Tajikistan , officially the Republic of Tajikistan , is a mountainous landlocked country in Central Asia. Afghanistan borders it to the south, Uzbekistan to the west, Kyrgyzstan to the north, and China to the east....
.
The few facts about Khujandi's life that are known come from his surviving writings as well as from comments made by Nassereddin Tusi
Nasir al-Din al-Tusi
Khawaja Muḥammad ibn Muḥammad ibn Ḥasan Ṭūsī , better known as Naṣīr al-Dīn al-Ṭūsī , was a Persian polymath and prolific writer: an astronomer, biologist, chemist, mathematician, philosopher, physician, physicist, scientist, theologian and Marja Taqleed...
. From Tusi's comments it is fairly certain that Khujandi was one of the rulers of the Mongol tribe in the Khudzhand region, and thus must have come from the nobility
Nobility
Nobility is a social class which possesses more acknowledged privileges or eminence than members of most other classes in a society, membership therein typically being hereditary. The privileges associated with nobility may constitute substantial advantages over or relative to non-nobles, or may be...
.
Astronomy
In Islamic astronomyIslamic astronomy
Islamic astronomy or Arabic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age , and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and...
, Khujandi worked under the patronage of the Buwayhid
Buwayhid
The Buyid dynasty, also known as the Buyid Empire or the Buyids , also known as Buwaihids, Buyahids, or Buyyids, were a Shī‘ah Persian dynasty that originated from Daylaman in Gilan...
Amirs at the observatory near Ray, Iran
Ray, Iran
Rey or Ray , also known as Rhages and formerly as Arsacia, is the capital of Rey County, Tehran Province, Iran, and is the oldest existing city in the province....
, where he is known to have constructed the first huge mural sextant
Sextant (astronomical)
Sextants for astronomical observations were used primarily for measuring the positions of stars. They are little used today, having been replaced over time by transit telescopes, astrometry techniques, and satellites such as Hipparcos....
in 994 AD, intended to determine the Earth's axial tilt
Axial tilt
In astronomy, axial tilt is the angle between an object's rotational axis, and a line perpendicular to its orbital plane...
("obliquity of the ecliptic") to high precision.
He determined the axial tilt to be 23°32'19" for the year 994 AD. He noted that measurements by earlier astronomers had found higher values (Indians: 24°; Ptolemy
Ptolemy
Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...
23° 51') and thus discovered that the axial tilt is not constant but is in fact (currently) decreasing. His measurement of the axial tilt was however about 2 minutes too small, probably due to his heavy instrument settling over the course of the observations.
Mathematics
In Islamic mathematicsIslamic mathematics
In the history of mathematics, mathematics in medieval Islam, often termed Islamic mathematics or Arabic mathematics, covers the body of mathematics preserved and developed under the Islamic civilization between circa 622 and 1600...
, he stated a special case of Fermat's last theorem
Fermat's Last Theorem
In number theory, Fermat's Last Theorem states that no three positive integers a, b, and c can satisfy the equation an + bn = cn for any integer value of n greater than two....
for n = 3, but his attempted proof of the theorem was incorrect. The spherical law of sines may have also been discovered by Khujandi, but it is uncertain whether he discovered it first, or whether Abu Nasr Mansur
Abu Nasr Mansur
Abu Nasr Mansur ibn Ali ibn Iraq was a Persian Muslim mathematician. He is well known for his work with the spherical sine law....
, Abul Wafa or Nasir al-Din al-Tusi
Nasir al-Din al-Tusi
Khawaja Muḥammad ibn Muḥammad ibn Ḥasan Ṭūsī , better known as Naṣīr al-Dīn al-Ṭūsī , was a Persian polymath and prolific writer: an astronomer, biologist, chemist, mathematician, philosopher, physician, physicist, scientist, theologian and Marja Taqleed...
discovered it first.