c. 825

Early Islamic Astronomy

Habash al-Hāsīb (c. 770–870), Muhammad ibn Mūsā al-Khwārizmī (c. 780–c. 850), Muhammad ibn Jābir al-Harrānī al-Battānī (c. 858–929), Abū ar-Rayhān al-Bīrūnī (973–1048)

Much of the modern language and methodology of astronomy and mathematics can be directly traced back to a several-centuries-long burst of genius and creativity in the arts and sciences in medieval Islam. Scientific development stagnated in Europe during this period, and so it was primarily the Persian and Arab world that became the heir to the Greco-Roman legacy of astronomy and mathematics.

Among the many early Islamic astronomers and mathematicians who made important new contributions were al-Khwārizmī, who founded modern algebra (al-jabr, or “completion” in Arabic) and developed new methods for calculating the positions of the Sun, Moon, and planets; al-Hāsīb, who calculated the best estimates yet made for the diameter and distance of the Moon and the diameter of the sun, and compiled his observations in The Book of Bodies and Distances; al-Battānī, who refined results from Ptolemy’s Almagest and developed new methods of timing the first appearance of the Moon’s crescent; and al-Bīrūnī, who invented new astronomical instruments and observing methods, and who (along with a number of other Persian and Arabic astronomers) hypothesized that a Sun-centered model of the solar system could fit the available observational data as well as the widely accepted Earth-centered model. Indeed, the work of these and other medieval Islamic astronomers went on to influence Renaissance Western astronomers such as Brahe, Kepler, Copernicus, and Galileo, and the eventual overthrow of Ptolemaic geocentrism in favor of a heliocentric cosmology.

In addition, almost all the noted astronomers and mathematicians of early Islam were working as part of teams in what were essentially the world’s first research groups—part of the world’s first system of state-run observatories and research institutes. This kind of collaborative environment enabled Islamic scientists to achieve significant advances in astronomy and other fields, and it is the basis for the way most science is done today.

SEE ALSO Greek Geocentrism (c. 400 BCE), Sun-Centered Cosmos (c. 280 BCE), Ptolemy’s Almagest (c. 150), Andromeda Sighted (964), Experimental Astrophysics (c. 1000), Copernicus’s De Revolutionibus (1543), Brahe’s “Nova Stella” (1572), Galileo’s Starry Messenger (1610), Three Laws of Planetary Motion (1619).

Illustration and text (in Persian) by al-Bīrūnī of different phases of the Moon, from his astrological treatise Kitāb al-tafhīm.