View source for Company:Abu-Mahmud Khojandi

{{Short description|10th-century Persian astronomer and mathematician}}
'''Abu Mahmud Hamid ibn al-Khidr al-Khujandi'''<ref>{{MacTutor|id=Al-Khujandi|title=Abu Mahmud Hamid ibn al-Khidr Al-Khujandi}}</ref> (known as '''Abu Mahmood Khujandi''', '''al-khujandi''' or '''Khujandi''', Persian: ابومحمود خجندی, {{Circa|940}} - 1000) was a Muslim Transoxanian astronomer and mathematician born in Khujand (now part of Tajikistan) who lived in the late 10th century and helped build an [[Astronomy:Observatory|observatory]], near the city of Ray (near today's [[Place:Tehran|Tehran]]), in [[Religion:Iran|Iran]].

==Astronomy==
{{See|Sextant (astronomy)#Mural sextants}}
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 [[Astronomy:Sextant (astronomical)|mural sextant]] in 994 AD, intended to determine the Earth's [[Astronomy:Axial tilt|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°; [[Biography:Ptolemy|Ptolemy]] 23° 51') and thus discovered that the axial tilt is not constant but is in fact (currently) decreasing. His measurement of the [[Astronomy:Axial tilt|axial tilt]] was however about 2 minutes too small, probably due to his heavy instrument settling over the course of the observations.<ref>[http://www.encyclopedia.com/doc/1G2-2830902295.html Al-Khujandī, Abū Maḥmūd Ḥāmid Ibn Al-Khiḍr], ''Complete Dictionary of Scientific Biography'', 2008</ref><ref>{{MacTutor|id=Al-Khujandi|title=Abu Mahmud Hamid ibn al-Khidr Al-Khujandi}}</ref>

==Mathematics==
Khujandi stated a special case of [[Fermat's Last Theorem]] for n = 3, but his attempted proof of the theorem was incorrect. The [[Law of sines#Spherical case|spherical law of sines]] may have also been discovered by Khujandi, but it is uncertain whether he discovered it first, or whether [[Biography:Abu Nasr Mansur|Abu Nasr Mansur]], Abul Wafa or [[Biography:Nasir al-Din al-Tusi|Nasir al-Din al-Tusi]] discovered it first.<ref>''Also the 'sine law' (of geometry and trigonometry, applicable to spherical trigonometry) is attributed, among others, to khujandi. (The three others are Abul Wafa Bozjani, Nasiruddin Tusi and Abu Nasr Mansur).'' Razvi,  Syed Abbas Hasan (1991) ''A history of science, technology, and culture in Central Asia, Volume 1'' University of Peshawar, Peshawar, Pakistan, page 358, {{OCLC|26317600}}</ref><ref>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, {{OCLC|66527483}}</ref>

== Notes ==
{{reflist}}

== References ==
* {{MacTutor|id=Al-Khujandi|title=Abu Mahmud Hamid ibn al-Khidr Al-Khujandi}}

==External links==
*{{cite encyclopedia|editor=Thomas Hockey|last=Brummelen|first=Glen Van|title=Khujandī: Abū Maḥmūd Ḥāmid ibn al‐Khiḍr al‐Khujandī|encyclopedia=The Biographical Encyclopedia of Astronomers|publisher=Springer|year=2007|location=New York|pages =630–1|url=http://islamsci.mcgill.ca/RASI/BEA/Khujandi_BEA.htm|isbn=978-0-387-31022-0|display-editors=etal |ref=none}} ([http://islamsci.mcgill.ca/RASI/BEA/Khujandi_BEA.pdf PDF version])
* {{cite encyclopedia|last=Tekeli|first=Sevim|title=Al-Khujandī, Abū Maḥmūd Ḥāmid Ibn Al-Khiḍr| url=http://www.encyclopedia.com/doc/1G2-2830902295.html|encyclopedia =Complete Dictionary of Scientific Biography|publisher=Encyclopedia|orig-year=1970-80|year=2008 |ref=none}}
* [http://www.levity.com/alchemy/islam16.html History of Islamic Science]

{{Islamic astronomy}}
{{Islamic mathematics}}

{{DEFAULTSORT:Khujandi}}
[[Category:Scientific instrument makers]]

{{Sourceattribution|Abu-Mahmud Khojandi|1}}