Abu Sa’id Ahmed ibn Mohammed ibn Abd al-Jalil al-Sijzi;
(c. 945 – c. 1020, also known as al-Sinjari and al-Sijazi; Persian: ابوسعید سجزی; Al-Sijzi is short for “Al-Sijistani”) 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.