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Mathematical Treasure: Sphaera Mundi of Abraham bar Hiyya

Frank J. Swetz (Pennsylvania State University)

Abraham bar Hiyya (ca.1065 - ca.1136) was a member of a Jewish community in Spain. Born in Barcelona, he was a rabbi, a mathematician, an astronomer, and a philosopher. He was known by several other names, including Savasorda, Abraham Judaeus, and, as he was identified in the following work, Abraham Hispano, or Abraham the Spaniard. The author of several works in mathematics and astronomy, his most famous was Sphaera mundi. The 1546 edition featured here was published in both Hebrew and Latin, together with two other works. The first was the arithmetic text, Arithmetica secundum omnes species, by a Rabbi Elija Orientali, also given in Hebrew and Latin. The third work, Quos Libros osuualdus ..., is in Spanish. The title page for Sphaera mundi is shown below.

The text begins with a “preface”:

The frontispiece on the opposite page depicts an astronomical globe of the period.

Sample pages discuss the relative position of the sun and resulting shadows and the phenomena of night and day as influenced by the earth’s position in respect to the sun.

Although further information about the author of the Arithmetic, Rabii Elija Orientali [the Oriental], is lacking, his book is said to have influenced Leonardo of Pisa in his writing of Liber Abaci in 1202. Here is an image of the introduction to the Arithmetic:

A sample page from the Arithmetic discusses use of the cubic numbers in working in a sexagesimal number system.

The images above are presented courtesy of the History of Science Collections, University of Oklahoma Libraries.

Index to Mathematical Treasures

Frank J. Swetz (Pennsylvania State University), "Mathematical Treasure: Sphaera Mundi of Abraham bar Hiyya," Convergence (May 2019)