Al-Birjandi

al-Birjandi
A work of al-Birjandi's, Sharh al-Tadhkirah, a manuscript copy, beginning of the 17th century
Native name	ʿAbd al‐ʿAlī ibn Muḥammad ibn Ḥusayn al‐Birjandī
Died	1525-1526
Academic background
Influences	Naṣīr al‐Dīn al‐Ṭūsī, al-Kashi
Academic work
Era	Islamic Golden Age

Abd Ali ibn Muhammad ibn Husayn Birjandi (Persian: عبدعلی محمد بن حسین بیرجندی‎‎) (died 1528) was a prominent 16th-century Persian astronomer, mathematician and physicist who lived in Birjand.

In discussing the structure of the cosmos, al-Birjandi continued Ali al-Qushji's debate on the Earth's rotation. In his analysis of what might occur if the Earth were moving, he develops a hypothesis similar to Galileo Galilei's notion of "circular inertia", which he described in the following observational test (as a response to one of Qutb al-Din al-Shirazi's arguments):

"The small or large rock will fall to the Earth along the path of a line that is perpendicular to the plane (sath) of the horizon; this is witnessed by experience (tajriba). And this perpendicular is away from the tangent point of the Earth’s sphere and the plane of the perceived (hissi) horizon. This point moves with the motion of the Earth and thus there will be no difference in place of fall of the two rocks."

Al-Birjandi wrote some more than 13 books and treatises, including:

He also wrote on theology.