Abu Mahmud Hamid ibn al-Khidr al-Khujandi (known as Abu Mahmood Khujandi, al-khujandi or Khujandi,

Persian Persian may refer to: * People and things from Iran, historically called ''Persia'' in the English language ** Persians, the majority ethnic group in Iran, not to be conflated with the Iranic peoples ** Persian language, an Iranian language of the ...

: ابومحمود خجندی, – 1000) was a Transoxanian

astronomer An astronomer is a scientist in the field of astronomy who focuses on a specific question or field outside the scope of Earth. Astronomers observe astronomical objects, such as stars, planets, natural satellite, moons, comets and galaxy, galax ...

and

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...

born in

Khujand Khujand, sometimes spelled Khodjent and formerly known as Leninabad from 1936 to 1991, is the second-largest city of Tajikistan and the capital of Tajikistan's northernmost Sughd province. Khujand is one of the oldest cities in Central Asia, d ...

(now part of

Tajikistan Tajikistan, officially the Republic of Tajikistan, is a landlocked country in Central Asia. Dushanbe is the capital city, capital and most populous city. Tajikistan borders Afghanistan to the Afghanistan–Tajikistan border, south, Uzbekistan to ...

) who lived in the late 10th century and helped build an

observatory An observatory is a location used for observing terrestrial, marine, or celestial events. Astronomy, climatology/meteorology, geophysics, oceanography and volcanology are examples of disciplines for which observatories have been constructed. Th ...

, near the city of Ray (near today's

Tehran Tehran (; , ''Tehrân'') is the capital and largest city of Iran. It is the capital of Tehran province, and the administrative center for Tehran County and its Central District (Tehran County), Central District. With a population of around 9. ...

), in

Iran Iran, officially the Islamic Republic of Iran (IRI) and also known as Persia, is a country in West Asia. It borders Iraq to the west, Turkey, Azerbaijan, and Armenia to the northwest, the Caspian Sea to the north, Turkmenistan to the nort ...

Astronomy

Khujandi worked under the patronage of the

Buwayhid The Buyid dynasty or Buyid Empire was a Zaydi and later Twelver Shi'a dynasty of Daylamite origin. Founded by Imad al-Dawla, they mainly ruled over central and southern Iran and Iraq from 934 to 1062. Coupled with the rise of other Iranian dyna ...

Amirs at the observatory near

Ray, Iran Shahre Ray, Shahr-e Ray, Shahre Rey, or Shahr-e Rey (, ) or simply Ray or Rey (), is the capital of Ray County, Iran, Rey County in Tehran Province, Iran. Formerly a distinct city, it has now been absorbed into the metropolitan area of Greater T ...

, where he is known to have constructed the first huge mural sextant in 994 AD, intended to determine the Earth's

axial tilt In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, which is the line perpendicular to its orbital plane; equivalently, it is the angle between its equatorial plane and orbita ...

("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 Claudius Ptolemy (; , ; ; – 160s/170s AD) was a Greco-Roman mathematician, astronomer, astrologer, geographer, and music theorist who wrote about a dozen scientific treatises, three of which were important to later Byzantine science, Byzant ...

23° 51') and thus discovered that the axial tilt is not constant but is in fact (currently) decreasing. His measurement of the

was however about 2 minutes too small, probably due to his heavy instrument settling over the course of the observations.

Mathematics

Khujandi stated a special case of

Fermat's Last Theorem In number theory, Fermat's Last Theorem (sometimes called Fermat's conjecture, especially in older texts) states that no three positive number, positive integers , , and satisfy the equation for any integer value of greater than . The cases ...

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 Abū Naṣr Manṣūr ibn ʿAlī ibn ʿIrāq al-Jaʿdī (; c. 960 – 1036) was a Persian Muslim mathematician and astronomer. He is well known for his work with the spherical sine law.Bijli suggests that three mathematicians are in contention ...

, Abul Wafa or

Nasir al-Din al-Tusi Muḥammad ibn Muḥammad ibn al-Ḥasan al-Ṭūsī (1201 – 1274), also known as Naṣīr al-Dīn al-Ṭūsī (; ) or simply as (al-)Tusi, was a Persians, Persian polymath, architect, Early Islamic philosophy, philosopher, Islamic medicine, phy ...

discovered it first.Bijli suggests that three mathematicians are in contention for the honor, khujandi, Abdul-Wafa and Mansur, leaving out Nasiruddin Tusi. Bijli, Shah Muhammad and Delli, Idarah-i Adabiyāt-i (2004) ''Early Muslims and their contribution to science: ninth to fourteenth century'' Idarah-i Adabiyat-i Delli, Delhi, India, page 44,

Notes

References

External links

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{{DEFAULTSORT:Khujandi 940s births 1000 deaths 10th-century Iranian astronomers Astronomers of the medieval Islamic world Inventors of the medieval Islamic world Scientific instrument makers Scholars under the Buyid dynasty 10th-century inventors 10th-century Iranian mathematicians