Al-Marwazi
Overview
Samarra
Sāmarrā is a city in Iraq. It stands on the east bank of the Tigris in the Salah ad-Din Governorate, north of Baghdad and, in 2003, had an estimated population of 348,700....
, Iraq
Iraq
Iraq ; officially the Republic of Iraq is a country in Western Asia spanning most of the northwestern end of the Zagros mountain range, the eastern part of the Syrian Desert and the northern part of the Arabian Desert....
) was an astronomer, geographer, and mathematician from Merv
Merv
Merv , formerly Achaemenid Satrapy of Margiana, and later Alexandria and Antiochia in Margiana , was a major oasis-city in Central Asia, on the historical Silk Road, located near today's Mary in Turkmenistan. Several cities have existed on this site, which is significant for the interchange of...
in Khorasan
Greater Khorasan
Greater Khorasan or Ancient Khorasan is a historical region of Greater Iran mentioned in sources from Sassanid and Islamic eras which "frequently" had a denotation wider than current three provinces of Khorasan in Iran...
.
He flourished in Baghdad
Baghdad
Baghdad is the capital of Iraq, as well as the coterminous Baghdad Governorate. The population of Baghdad in 2011 is approximately 7,216,040...
, and died a centenarian after 869. He worked under the Abbasid
Abbasid
The Abbasid Caliphate or, more simply, the Abbasids , was the third of the Islamic caliphates. It was ruled by the Abbasid dynasty of caliphs, who built their capital in Baghdad after overthrowing the Umayyad caliphate from all but the al-Andalus region....
caliphs al-Ma'mun
Al-Ma'mun
Abū Jaʿfar Abdullāh al-Māʾmūn ibn Harūn was an Abbasid caliph who reigned from 813 until his death in 833...
and al-Mu'tasim
Al-Mu'tasim
Abu Ishaq 'Abbas al-Mu'tasim ibn Harun was an Abbasid caliph . He succeeded his half-brother al-Ma'mun...
.
He made observations from 825 to 835, and compiled three 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
Trigonometry
Trigonometry is a branch of mathematics that studies triangles and the relationships between their sides and the angles between these sides. Trigonometry defines the trigonometric functions, which describe those relationships and have applicability to cyclical phenomena, such as waves...
, and he compiled a table of such shadows which seems to be the earliest of its kind.
Unanswered Questions
