Abu Sa'id Ahmed ibn Mohammed ibn Abd al-Jalil al-Sijzi was an Iranian Muslim astronomer, mathematician, and astrologer. He is notable for his correspondence with al-Biruni and for proposing that the Earth rotates around its axis in the 10th century.
A page from Al Sijzi's geometrical treatise
Model of the solar system and earth movement ("planetarium") according to al-Sijzi
Astronomy in the medieval Islamic world
Medieval Islamic astronomy comprises the astronomical developments made in the Islamic world, particularly during the Islamic Golden Age, and mostly written in the Arabic language. These developments mostly took place in the Middle East, Central Asia, Al-Andalus, and North Africa, and later in the Far East and India. It closely parallels the genesis of other Islamic sciences in its assimilation of foreign material and the amalgamation of the disparate elements of that material to create a science with Islamic characteristics. These included Greek, Sassanid, and Indian works in particular, which were translated and built upon.
18th century Persian brass astrolabe at the Whipple Museum of the History of Science in Cambridge, England. The astrolabe consists of a disk engraved with the positions of the celestial bodies.
The Tusi-couple is a mathematical device invented by Nasir al-Din al-Tusi in which a small circle rotates inside a larger circle twice the diameter of the smaller circle. Rotations of the circles cause a point on the circumference of the smaller circle to oscillate back and forth in linear motion along a diameter of the larger circle.
An illustration from al-Biruni's astronomical works that explains the different phases of the moon, with respect to the position of the sun.
Ibn al-Shatir's model for the appearances of Mercury, showing the multiplication of epicycles using the Tusi-couple, thus eliminating the Ptolemaic eccentrics and equant.
