a letter authored by the well-known italian nobleman and traveller pietro della valle, dated 1624, is probably the oldest existing persian document in which modern astronomy, in particular the tychonic model, is introduced and discussed in detail. it was written in the reign of the safavid shah abbas i, less than a quarter of century after tycho brahe’s death. in part it was based on what his i...

for the first time in the history of logic, abd al razzaq al-jili (d. 570/1174), in the treatise al-lame fi al-shakl al-rabe, dealt with the modal syllogisms of the fourth figure. previous to him, dinha, the priest, and ibn salah al-hamadani had discussed the non-modal moods of the fourth figure. jili’s treatise deals only with simple modalities and ignores the complex ones. his pupil, fakhr al...

having briefly been reviewed the historical process of changing the formulae for determining the times of islamic prayers, two newly found formulae and a new rule for establishing the times of prayers would be discussed. these matters have been exploited from four texts, still preserved as manuscript: (1) siyyid ¾?y? al-d?n sh?shtar?’s ¼ad b?b dar macrifa al-a½??rl?b, (2) b?r?n?’s ’ist?c?b f? c...

abd al-rah?m?n al-s??f? is a well-known astronomer who has some works in astronomy, mathematics and alchemy. the importance of his s?uwar al-kaw?kib (book about the constellations) caused that researchers don’t practice his other works. four treatises on astrolabe are ascribed to al-s??f?, any one of them is in persian. attribution of the three arabic treatises among these four to him is certai...

all that we know about the life and times of al-sijzī, the 10th century iranian muslim mathematician and astronomer, is limited to the small pieces of information provided by other authors’ accounts and some of his own works. on the basis of al-sijzī’s mathematical works and the extant maunscripts written in his hand, some modern scholars have estimated his date of birth in about 942 ad. numero...