Ahmad ibn 'Abdallah al-Marwazi, known as Habash al-Hasib (, died 869) was a

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 ...

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 ...

geographer A geographer is a physical scientist, social scientist or humanist whose area of study is geography, the study of Earth's natural environment and human society, including how society and nature interacts. The Greek prefix "geo" means "earth" a ...

, 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 ...

from

Merv Merv (, ', ; ), also known as the Merve Oasis, was a major Iranian peoples, Iranian city in Central Asia, on the historical Silk Road, near today's Mary, Turkmenistan. Human settlements on the site of Merv existed from the 3rd millennium& ...

in Khorasan, who discovered the

trigonometric Trigonometry () is a branch of mathematics concerned with relationships between angles and side lengths of triangles. In particular, the trigonometric functions relate the angles of a right triangle with ratios of its side lengths. The field ...

ratios

tangent In geometry, the tangent line (or simply tangent) to a plane curve at a given point is, intuitively, the straight line that "just touches" the curve at that point. Leibniz defined it as the line through a pair of infinitely close points o ...

, and

cotangent In mathematics, the trigonometric functions (also called circular functions, angle functions or goniometric functions) are real functions which relate an angle of a right-angled triangle to ratios of two side lengths. They are widely used in a ...

Al-Biruni Abu Rayhan Muhammad ibn Ahmad al-Biruni (; ; 973after 1050), known as al-Biruni, was a Khwarazmian Iranian scholar and polymath during the Islamic Golden Age. He has been called variously "Father of Comparative Religion", "Father of modern ...

who cited Habash in his work, expanded his astronomical tables. Habash al-Hasib flourished in

Baghdad Baghdad ( or ; , ) is the capital and List of largest cities of Iraq, largest city of Iraq, located along the Tigris in the central part of the country. With a population exceeding 7 million, it ranks among the List of largest cities in the A ...

, and died a centenarian some time between 864 and 874 possibly in

Abbasid Samarra Samarra is a city in central Iraq, which served as the capital of the Abbasid Caliphate from 836 to 892. Founded by the caliph al-Mu'tasim, Samarra was briefly a major metropolis that stretched dozens of kilometers along the east bank of the Tigr ...

. The title "Habash" (Abbyssian) may refer to dark skin color. He worked under two

Abbasid caliphs The Abbasid caliphs were the holders of the Islamic title of caliph who were members of the Abbasid dynasty, a branch of the Quraysh tribe descended from the uncle of the Islamic prophet Muhammad, Al-Abbas ibn Abd al-Muttalib. The family came ...

al-Ma'mun Abū al-ʿAbbās Abd Allāh ibn Hārūn al-Maʾmūn (; 14 September 786 – 9 August 833), better known by his regnal name al-Ma'mun (), was the seventh Abbasid caliph, who reigned from 813 until his death in 833. His leadership was marked by t ...

and

al-Mu'tasim Abū Isḥāq Muḥammad ibn Hārūn al-Rashīd (; October 796 – 5 January 842), better known by his laqab, regnal name al-Muʿtaṣim biʾllāh (, ), was the eighth Abbasid Caliphate, Abbasid caliph, ruling from 833 until his death in 842. ...

. Habash al-Hasib developed a trigonometric algorithm to solve problems related to

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

, which was later rediscovered by

Johannes Kepler Johannes Kepler (27 December 1571 – 15 November 1630) was a German astronomer, mathematician, astrologer, Natural philosophy, natural philosopher and writer on music. He is a key figure in the 17th-century Scientific Revolution, best know ...

in 1609 and it is now known as

Kepler's equation In orbital mechanics, Kepler's equation relates various geometric properties of the orbit of a body subject to a central force. It was derived by Johannes Kepler in 1609 in Chapter 60 of his ''Astronomia nova'', and in book V of his ''Epitome of ...

. Habash is the father of the astronomer

Abu Ja'far ibn Habash Abu Ja'far ibn Habash was a Persian astronomer. He was most likely a son of Habash al-Hasib. Since his father died after 864 AD at the age of 100, it can be concluded that he was active in 3rd century AH (9th century AD). According to Ibn Nadim an ...

Work

Habash Hasib made astronomical observations from 825 to 835, and compiled three ''

zij A ' () is an Islamic astronomical book that tabulates parameters used for astronomical calculations of the positions of the sun, moon, stars, and planets. Etymology The name ''zīj'' is derived from the Middle Persian term ' or ' "cord". Th ...

es'' (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 A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of Earth, totally or partially. Such an alignment occurs approximately every six months, during the eclipse season i ...

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 860, he seems to have introduced the notion of "shadow", umbra (versa), equivalent to our

trigonometry Trigonometry () is a branch of mathematics concerned with relationships between angles and side lengths of triangles. In particular, the trigonometric functions relate the angles of a right triangle with ratios of its side lengths. The fiel ...

, and he compiled a table of such shadows which seems to be the earliest of its kind. He also introduced the

, and produced the first tables of for it.Jacques Sesiano, "Islamic mathematics", p. 157, in

''The Book of Bodies and Distances''

Habash al-Hasib conducted various observations at the Al-Shammisiyyah observatory in

and estimated a number of geographic and astronomical values. He compiled his results in ''The Book of Bodies and Distances'' (), in which some of his results included the following: ;Earth *Earth's

circumference In geometry, the circumference () is the perimeter of a circle or ellipse. The circumference is the arc length of the circle, as if it were opened up and straightened out to a line segment. More generally, the perimeter is the curve length arou ...

: 20,160 miles (32,444 km) *Earth's

diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...

: 6414.54 miles (10323.201 km) *

Earth radius Earth radius (denoted as ''R''🜨 or ''R''E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid (an oblate ellipsoid), the radius ranges from a maximum (equato ...

: 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 Sexagesimal, also known as base 60, is a numeral system with 60 (number), sixty as its radix, base. It originated with the ancient Sumerians in the 3rd millennium BC, was passed down to the ancient Babylonians, and is still used—in a modified fo ...

) miles *Half-circumference of closest distance of Moon: 676,368;28,45,25,43 (sexagesimal) miles *

Radius In classical geometry, a radius (: radii or radiuses) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The radius of a regular polygon is th ...

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 A minute is a unit of time defined as equal to 60 seconds. It is not a unit in the International System of Units (SI), but is accepted for use with SI. The SI symbol for minutes is min (without a dot). The prime symbol is also sometimes used i ...

along orbit of Sun: 1129.283 miles (1817.405 km)

Notes

References

*
PDF version

External links

*
Handbuch der Geschichte : aus den Handschriften der k.k. Hofbibliothek zu Wien, der herzoglichen Bibliothek zu Gotha und der Universitäts-Bibliothek zu Leyden (1850)
', ed.: Ferdinand Wüstenfeld *
An extract from Ibn Kutaiba's 'Adab al-Kâtib; or, The writer's guide (1877)
', ed.: William Oliver Sproull *
Ibn Kutaiba's Adab-al-kâtib. Nach mehreren Handschriften hrsg. von Max Grünert (1900)
', ed.: Max Grünert *
Liber poesis et poetarum (1904)
', ed.:

Michael Jan de Goeje Michael Jan de Goeje (August 13, 1836 – May 17, 1909) was a Dutch orientalist focusing on Arabia and Islam. Early life Michael Jan de Goeje was born in Dronrijp, Friesland. He devoted himself at an early age to the study of oriental lang ...

{{DEFAULTSORT:Habash People from Merv 9th-century Iranian mathematicians Scientists who worked on qibla determination 9th-century Iranian astronomers Year of birth unknown Iranian men centenarians Mathematicians from the Abbasid Caliphate Astronomers from the Abbasid Caliphate

Work

''The Book of Bodies and Distances''

See also

Notes

References

External links