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Abu Sa'id Ahmed ibn Mohammed ibn Abd al-Jalil al-Sijzi (c. 945 - c. 1020, also known as al-Sinjari and al-Sijazi; ; Al-Sijzi is short for " Al-Sijistani") was an
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* {{DEFAULTSORT:Sijzi Medieval Iranian astrologers 10th-century Iranian mathematicians 11th-century Iranian mathematicians 940s births 1020 deaths Year of birth uncertain 10th-century Iranian astronomers Scholars under the Buyid dynasty 10th-century inventors 11th-century Iranian astronomers Astronomers of the medieval Islamic world
Abu Sa'id Ahmed ibn Mohammed ibn Abd al-Jalil al-Sijzi (c. 945 - c. 1020, also known as al-Sinjari and al-Sijazi; ; Al-Sijzi is short for " Al-Sijistani") was an Iranian
Iranian () may refer to:
* Something of, from, or related to Iran
** Iranian diaspora, Iranians living outside Iran
** Iranian architecture, architecture of Iran and parts of the rest of West Asia
** Iranian cuisine, cooking traditions and practic ...
Muslim astronomer, 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 ...
, and astrologer
Astrology is a range of Divination, divinatory practices, recognized as pseudoscientific since the 18th century, that propose that information about human affairs and terrestrial events may be discerned by studying the apparent positions ...
. He is notable for his correspondence with 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 ...
and for proposing that the Earth rotates around its axis in the 10th century.
He dedicated work to 'Adud al-Daula, who was probably his patron, and to the prince of Balkh
Balkh is a town in the Balkh Province of Afghanistan. It is located approximately to the northwest of the provincial capital city Mazar-i-Sharif and approximately to the south of the Amu Darya and the Afghanistan–Uzbekistan border. In 2021 ...
. He also worked in Shiraz
Shiraz (; ) is the List of largest cities of Iran, fifth-most-populous city of Iran and the capital of Fars province, which has been historically known as Pars (Sasanian province), Pars () and Persis. As of the 2016 national census, the popu ...
making astronomical observations from 969 to 970.
Mathematics
Al-Sijzi studied intersections of conic sections and circles. He replaced the old kinematicaltrisection of an angle
Angle trisection is a classical problem of straightedge and compass construction of ancient Greek mathematics. It concerns construction of an angle equal to one third of a given arbitrary angle, using only two tools: an unmarked straightedge and ...
by a purely geometric solution (intersection of a circle and an equilateral hyperbola.)
Earth's rotation
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 ...
tells us that Al-Sijzi invented an astrolabe
An astrolabe (; ; ) is an astronomy, astronomical list of astronomical instruments, instrument dating to ancient times. It serves as a star chart and Model#Physical model, physical model of the visible celestial sphere, half-dome of the sky. It ...
, called "al-zūraqī", whose design was based on the idea that the Earth rotates:
Al-Biruni also referred to Al-Sijzi as a prominent astronomer who defended the theory that the Earth rotates in ''al-Qānūn al-Masʿūdī''."ʾaḥad al-mubrazīn fī ʿilm al-hayʾa"
The fact that some people did believe that the Earth is moving on its own axis is further confirmed by a reference from the 13th century which states:"According to the geometers r engineers(''muhandisīn''), the earth is in constant circular motion, and what appears to be the motion of the heavens is actually due to the motion of the earth and not the stars."
References
Sources
* * Suter, Heinrich: Die Mathematiker und Astronomen der Araber und ihre Werke (80–81, 224, 1900).Further reading
*External links
*PDF version
* {{DEFAULTSORT:Sijzi Medieval Iranian astrologers 10th-century Iranian mathematicians 11th-century Iranian mathematicians 940s births 1020 deaths Year of birth uncertain 10th-century Iranian astronomers Scholars under the Buyid dynasty 10th-century inventors 11th-century Iranian astronomers Astronomers of the medieval Islamic world