Al-Khujandi الخجندي | |
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| Born | 940 |
| Died | 1000 (aged 60) |
| Academic work | |
| Era | Islamic Golden Age (Samanid dynasty era) |
| Main interests | Astronomer,Mathematician |
| Notable works | Encyclopedia of Astronomy & Astrophysics |
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Abu Mahmud Hamid ibn al-Khidr al-Khujandi[1] (known asAbu Mahmood Khujandi,al-khujandi orKhujandi,Persian: ابومحمود خجندی,c. 940 – 1000) was aTransoxanianastronomer andmathematician born inKhujand (now part ofTajikistan) who lived in the late 10th century and helped build anobservatory, near the city ofRay (near today'sTehran), inIran.
Khujandi worked under the patronage of theBuwayhid Amirs at the observatory nearRay, Iran, where he is known to have constructed the first hugemural sextant in 994 AD, intended to determine the Earth'saxial 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 theaxial tilt was however about 2 minutes too small, probably due to his heavy instrument settling over the course of the observations.[2][3]
Khujandi stated a special case ofFermat's Last Theorem for n = 3, but his attempted proof of the theorem was incorrect. Thespherical law of sines may have also been discovered by Khujandi, but it is uncertain whether he discovered it first, or whetherAbu Nasr Mansur,Abul Wafa orNasir al-Din al-Tusi discovered it first.[4][5]
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