Arabic/Islamic Astronomy in Intercultural and European Context


11 Jul 2010

Mathematics, Astronomy

George Saliba

George Saliba in this short clip from a longer lecture discusses the mathematics involved in determining the time for the five daily prayers, and in particular, the middle one, ‘asr. 

The definitions for the time for ’asr prayer/salah developed in Mecca based on the length of shadows, he notes, would not work in Damascus (modern-day Syria) around the time of the winter solstice. This required Muslim scholars to adjust the definition so that it would work on all parts of the globe. Muslim scholars had to develop trigonometric concepts (like cotangent) to develop new ideas expanding on prior Greek and Indian ideas in order to fix the times for ritual prayers.  The clip unfortunately ends in the middle of the explanation of the mathematics.

The complete video is available on the Portal here. The lecture was given at the Library of Alexandria, Egypt, on the occasion of the 20th meeting of the International Planetarium Society.  This keynote lecture was delivered on 29 June 2010.


The material on Islam is within the bounds of what Muslims have historically understood as acceptable.

The discussion of the scientific advances needed to determine the times for prayer are accurate.  The historical material in this clip is limited but accurate.

About George Saliba

George Saliba received a Bachelors of Science in mathematics in 1963 and a Masters of Arts in 1965 from the American University of Beirut. He went on to pursue a Masters of Science degree and a doctorate in Islamic Sciences from the University of California, Berkeley. In 1978, Saliba started his teaching career at Columbia University in New York as a professor of Arabic and Islamic Sciences. He has received many awards, most notably the History of Science Prize in 1993 and the History of Astronomy Prize in 1996. Saliba was a Distinguished Senior Scholar at the Kluge Center of the Library of Congress (2005-2006) and at the Carnegie Scholars Program (2009-2010).

Saliba’s studies are described on his website as “the development of scientific ideas from late antiquity till early modern times, with a special focus on the various planetary theories that were developed within the Islamic civilization and the impact of such theories on early European astronomy.” His website provides a link to his most recent research in addition to a listing of his publications. A portion of his public lectures may also be found online at the 1001 Inventions website.

George Saliba does not appear to operate any social media pages as of 2015.  He served as an advisor for the Science and Islam Video Portal project.

Selected Bibliography:

George Saliba.” MESAAS. Columbia, n.d. Accessed 21 May 2015.

George Saliba.” Wikipedia. Wikimedia Foundation, n.d. Accessed 21 May 2015.

Professor George Saliba Lectures | 1001 Inventions.” Professor George Saliba Lectures | 1001 Inventions. 1001 Inventions, n.d. Accessed 21 May 2015.

Saliba, George. “Saliba’s Page.” Saliba’s Page. Columbia, n.d. Accessed 21 May 2015.