Al-Sijzi


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.
He dedicated work to 'Adud al-Daula, who was probably his patron, and to the prince of Balkh. He also worked in Shiraz making astronomical observations from 969 to 970.

Mathematics

Al-Sijzi studied intersections of conic sections and circles. He replaced the old kinematical trisection of an angle by a purely geometric solution

Earth's rotation

tells us that Al-Sijzi invented an astrolabe, 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.
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 , 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."