# Muslim Scientists and Thinkers–Muhammad ibn Sinan al- Battani

April 3, 2008 by TMO

**By Syed Aslam**

Muhammad ibn Sinan al- Battani (known in Europe as Albatenius) was born in 853 CE at Battan, a province of Harran, which is now a part of Turkey.

His family had been members of the Sabian sect, a religious sect of star worshippers from Harran. Being worshipers of the stars meant that the Sabians had a strong motivation for the study of astronomy, and they produced many outstanding astronomers and mathematicians.

Al-Battani himself was not a believer in the Sabian religion, he was a good Muslim. He was skilled in making astronomical instruments which he learnt from his father who himself was a well-known scientist. He made remarkably accurate astronomical observations at Raqqah, situated on the bank of river Euphrates, and migrated to Samarra Iraq, where he died in the year 929 CE.

Al-Battani was one of the famous astronomers and a pioneer in geometry, trigonometry, theoretical and practical astronomy. He is famous for his remarkable accurate calculation of the length of the solar year, which he gave as 365 days 5 hours 48 minutes 24 seconds. This value is astonishingly close to the present value and is considered as one of greatest achievement in astronomy for all ages. He also determined many astronomical coefficients with great accuracy. He calculated 54.5” per year for the precession of the equinoxes and obtained the value of 23 degrees 35 minutes for the inclination of the earth’s axis. He found out that the longitude of the sun’s apogee has increased by 16 degrees and 47 minutes since the time of Ptolemy. These numbers which he calculated more than a thousand years ago are still good to this day.

Rather than using geometrical methods, as Ptolemy had done, al-Battani used trigonometric methods which were an important advancement in the field of astronomy. Al-Battani showed that the farthest distance of the Sun from the Earth varies and, as a result, annular eclipses of the Sun are possible as well as total eclipses. He made several emendation to Ptolemy work and recalculated orbits of the moon and other planets – and proposed a new and ingenious method to determine the visibility of the new moon. In 1749, the astronomer Dunthorne used al-Battani’s excellent observation of the lunar and solar eclipses to determine the angular acceleration of the motion of the moon. He used a uniform rate of precession in his tables, choosing not to adopt the theory of trepidation; by contrast, Copernicus held on to this erroneous notion until the sixteenth century.

Al-Battani was the author of many books on astronomy and trigonometry. His most famous book Kitab al Zij which has a set of astronomical treatises, tables and a catalog of 479 stars. This book was translated into Latin in the year 1116 CE as De motu stellarum (On the motion of the star). His work in astronomy influenced European scientists like Kepler, Galileo and Copernicus. In his book De Revolutionibus Coelestium, Copernicus has mentioned the name of al-Battani to express his indebtedness. His book has been translated into almost all of the European languages.

Al-Battani brilliant introduction of the trigonometric ratio in mathematical calculation formed the basis of modern trigonometry. He replaced the use of chords used by the Greeks for the measurement of angles with the Sine of the arc, with clear understanding of its superiority. He developed the concept of the cotangent and furnished their tables in degrees and deduced a number of trigonometric relationships like, tan a = sin a /cos a and solved the equation sinx = a cosx, discovering a new formula. He provided a very ingenuous solution for some problems of spherical trigonometry, using the method of orthographic projection.

In 988 CE, the bookseller Ibn Nadim compiled a list (Fihrist) of authors in which he gave a full account of the Arabic literature which was available in the 10th century. In his list (Fihrist) he describes briefly some of the authors’ work, he writes: Al-Battani one of the famous observers and a leader in geometry, theoretical and practical astronomy, and astrology. He composed a work on astronomy, with tables, containing his own observations of the sun and moon and a more accurate description of their motions than that given in Ptolemy’s “Almagest”. In it moreover, he gives the motions of the five planets, with the improved observations he succeeded in making, as well as other necessary astronomical calculations. Some of his observations mentioned in his book of tables were made in the year 880 and later on in the year 900. Nobody is known in Islam who reached similar perfection in observing the stars and scrutinizing their motions. too:

There is no doubt that al-Battani was one of the greatest astronomer and mathematician of all time. His accurate calculation for lengths solar year, his times for the new moon, his calculation of the inclination of the earth’s axis, his prediction of lunar and solar eclipses, his work on the phenomenon of parallax, and the introduction of trigonometric ratios in mathematics brought the science of astronomy into the space age. The Albategnius carter on the moon was named after him and in the fictional series Star Trek a starship is named the USS Al-Battani.

*Aslamsyed1@yahoo.com*

10-15

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