Ahmad ibn 'Abdallah al-Marwazi,[1][2] known as Habash al-Hasib (Persian: حبش الحاسب, lit. 'Abyssinian calculator',[1][2][3] died c. 869[4]) was a Persian[5][2] astronomer,[6] geographer, and mathematician from Merv in Khorasan, who was the first to describe the trigonometric ratios tangent, and cotangent. Al-Biruni who cited Habash in his work, expanded his astronomical tables.[3]
Habash al-Hasib | |
|---|---|
حبش الحاسب | |
| Born | Ahmad ibn ‘Abdallah al-Marwazi |
| Died | Between 864–874 (aged 100) Possibly in Abbasid Samarra, Abbasid Caliphate |
| Known for | Kepler's equation |
| Children | Abu Ja'far ibn Habash |
| Scientific career | |
| Fields | Astronomy |
Habash al-Hasib flourished in Baghdad, and died a centenarian some time between 864 and 874[2][3][7] possibly in Abbasid Samarra.[4] The title "Habash" (Abbyssian) may refer to dark skin color.[3] He worked under two Abbasid caliphs, al-Ma'mun and al-Mu'tasim.[3]
Habash al-Hasib developed a trigonometric algorithm to solve problems related to parallax, which was later rediscovered by Johannes Kepler in 1609 and it is now known as Kepler's equation.[8][9]
Habash is the father of the astronomer Abu Ja'far ibn Habash.[3]
Work
Habash Hasib made astronomical observations from 825 to 835, and compiled three zijes (astronomical tables): the first were still in the Hindu manner; the second, called the "tested" tables, were the most important; they are likely identical with the "Ma'munic" or "Arabic" tables and may be a collective work of al-Ma'mun's astronomers; the third, called tables of the Shah, were smaller.
Apropos of the solar eclipse of 829, Habash gives us the first instance of a determination of time by an altitude (in this case, of the sun); a method which was generally adopted by Muslim astronomers.
In 830, he seems to have introduced the notion of "shadow", umbra (versa), equivalent to our tangent in trigonometry, and he compiled a table of such shadows which seems to be the earliest of its kind. He also introduced the cotangent, and produced the first tables of for it.[10][11]
The Book of Bodies and Distances
Habash al-Hasib conducted various observations at the Al-Shammisiyyah observatory in Baghdad and estimated a number of geographic and astronomical values. He compiled his results in The Book of Bodies and Distances (Kitāb al-ajrām wa-l-ab 'ād),[7] in which some of his results included the following:[12]
- Earth
- Earth's circumference: 20,160 miles (32,444 km)
- Earth's diameter: 6414.54 miles (10323.201 km)
- Earth radius: 3207.275 miles (5161.609 km)
- Moon
- Moon's diameter: 1886.8 miles (3036.5 km)
- Moon's circumference: 5927.025 miles (9538.622 km)
- Radius of closest distance of Moon: 215,208;9,9 (sexagesimal) miles
- Half-circumference of closest distance of Moon: 676,368;28,45,25,43 (sexagesimal) miles
- Radius of furthest distance of Moon: 205,800;8,45 (sexagesimal) miles
- Diameter of furthest distance of Moon: 411,600.216 miles (662,406.338 km)
- Circumference of furthest distance of Moon: 1,293,600.916 miles (2,081,848.873 km)
- Sun
- Sun's diameter: 35,280;1,30 miles (56,777.6966 km)
- Sun's circumference: 110,880;4,43 miles (178,444.189 km)
- Diameter of orbit of Sun: 7,761,605.5 miles (12,491,093.2 km)
- Circumference of orbit of Sun: 24,392,571.38 miles (39,256,038 km)
- One degree along orbit of Sun: 67,700.05 miles (108,952.67 km)
- One minute along orbit of Sun: 1129.283 miles (1817.405 km)
See also
Notes
References
External links
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