Al-Battāni: Pioneering Muslim Astronomer Extraordinaire ( Part-1)

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By the time of the Renaissance in Europe, the discoveries of Al-Battani as also his associated deliberations on the same had become an integral part of the vehicle in which the scientific enlightenment of the Western world took root and flourished several centuries after him, writes BIJU ABDUL QADIR, in the first part of this two-part feature on one of the greatest astronomers of all time.

Introduction

Ever heard of a crater on the moon given  the Latinized name, Albategnius?

If that sounds like too much detail from ‘rocket-science’ terrain, perhaps, the hit sci-fi television serial, Star Trek, permanently embedded in recent twentieth century popular imagination, would be much easier to relate to. In the fictional Star Trek universe, the Excelsior-class starship, USS Al-Batani NCC-42995 has the same name yet again, albeit, in an altered form, but similarly mentioned.

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If that’s not enough, those of us who have read the Doctor Who novel, Night of the Humans, know that it features an entire solar system not too differently called Battani 045.

So who, or what, is Albategnius or Al-Batani or Battani – a name which seems to have captured the imagination of 21st century science and science-fiction enthusiasts?

Surprisingly enough to many, these variants of a single name do not belong to an individual, place or object of the twentieth century. Rather, it harks back to a man who lived, worked and died in the ninth-tenth centuries of the solar calendar: the Muslim astronomer and mathematician, Abũ Abdallāh Muhammad b. Jābir al-Battāni, who is, today, globally acknowledged as the greatest astronomer of early Islamic civilization, and perhaps, even of all known civilizations of that time.

The eighth to tenth centuries of Islam marked a period of profound, and unprecedented, intellectual ferment, which saw the rise of not one, but several, Muslim pioneers in the fields of the pure and applied sciences. In the intellectual upsurge thus generated by the Qur’anic revelation some two centuries earlier, the Arab astronomer and mathematician of the tenth century (c. 858-929CE), Abū ʿAbdAllāh Muḥammad ibn Jābir ibn Sinān al-Raqqī al-Ḥarrānī al-Ṣābiʾ al-Battānī was but one among the foremost in this galaxy of science luminaries.

 

Early Life and Education

Little is known about al-Battānī’s early life except for the fact that he was born in Harran – or, to be more precise, in the Battān region of Harrān state, according to one account – near Urfa, in Syria Upper Mesopotamia, which is today situated in Turkey. Going by the year 877CE which al-Battāni himself attached to his earliest astronomical observations, when he was hardly twenty, he is believed to have been born in the 850s and most probably, in the year 858CE.

While the soubriquet, As-Sābi’, which has come attached with his name indicates, at least, an ancestry that was Sabian, the first part of his name – Abũ Abdallāh Muhammad – suggests that he was born into a Muslim family. Interestingly enough, however, the Sabians’ did have a belief system in which the stars played a central role.

Transmitting and cultivating astronomical studies – and legend – that went all the way back to the ancient Mesopotamian culture of centuries past, this religious sect seemed to have had astronomy in their blood: a tradition that was, perhaps, almost second nature to its adherents. To be sure, the area had also been home to other important astronomers and mathematicians, including Thābit b. Qurra, who was some years senior to al-Battāni, and who would have flourished in Harrān while al-Battāni was still a youth.

While some western historians state that al-Battāni belonged to Arab nobility, any suggestions to this effect from Arabic biographers themselves seem far and few in between. Muhammad al-Battāni’s father, Jābir b. Sin’ān al-Battāni, was himself a well-known scientist of his time – indeed, a maker of scientific instruments – who lived and laboured in the north-central city of Raqqah in what was then, by the Euphrates River, the region of al-Shām, or Syria proper of today.

 

At Raqqah: Inventing the Instruments of Astronomy

As a child, the young Muhammad al-Battāni was first taught by his father, whose influence on the development of his intellectual and scientific pursuits may safely be taken for granted. In fact, Muhammad al-Battāni later moved from Harran to Raqqah because of his father’s preoccupation in that town.

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It was at Raqqah that al-Battāni  sought, and received, his higher education and, in later years, established himself as a scientist of world standing. Significantly, and as an interesting aside to his fascinating story, al-Battāni ’s forays into astronomy and mathematics overlapped, by a happy coincidence, the reign of the founder of the great Bayt al-Hikmah (House of Wisdom) tradition – the Abbasid Caliph, Harũn al-Rāshid. With such a favourable ambience of learning and culture, al-Battāni was able to master his preferred sciences and produce contributions in astronomy and geometry unrivalled for centuries thereafter.

One other interesting aspect of al-Battāni’s investigations is that for the entire corpus of his studies and research, he exclusively employed instruments whose design and fabrication were the singular work of his own genius. Not surprisingly, al-Battāni  was soon famous for his expertise in this vocation, with the accuracy of his measurements – for which he eventually became well-known – being directly related to the much higher quality of instruments which he developed by himself .

 

Al-Battāni’s ingenious improvisation of the armillary-sphere astronomical model was a major advance for the field of astronomy. Put up not unlike a modern globe, it held out rings representing the movements of celestial bodies and, quite globe-like, the hollow sphere rotated on a central axis. The rotational motion was not confined to the sphere alone, for the individual rings could also be put into similar motion. Lastly, the sphere, as a whole, was circumscribed by a larger ring the total circumference of which was sectioned into degrees.

To be sure, al-Battāni was not the first inventor of the armillary sphere, but his celestial sphere – the astrolabe – was far more precise and accurate than all earlier models. In effect, it was modeling of this innovative kind that aided al-Battāni in making several critical astronomical calculations with regard to the sun-earth relationship.

Using the astrolabe and other instruments like the gnomon, horizontal and vertical sundials, parallactic rulers and a mural quadrant with an alidade, al-Battāni gave the eventual recommendation that sizes above a meter were ideal for securing accurate results in observations made. It was in Antioch, Syria, that al-Battāni made observations both for a solar as well as a lunar eclipse which occurred in the same year. (Benno van Dalen, 2007)

Al-Battāni had labored away at Raqqah for many years, but by the beginning of the ninth century, he was again on the move and was soon settling himself down at Samarra, where he would ultimately work till nearly the end of his eventful life.

 

Harbinger of the Copernican Revolution

If al-Battāni’s remarkable career of 40-odd years was to be known only for one outstanding achievement, it would suffice, perhaps, to prove him among the greatest scientists of his time. That single feat was, by far, his accurate determination of the length of the solar year as being 365 days, 5 hours, 46 minutes and 24 seconds. This was short of the actual modern estimate by just 2 minutes, 22 seconds – clearly, the most accurate measurement of this duration till that time in history.

Of course, as things turned out, this was not to be the only significant contribution of this pioneering astronomer. In hindsight, the accuracy of al-Battāni’s measurements proved, on occasion, to be higher than even those of the celebrated Nicolaus Copernicus who came several centuries later. Researchers have opined that this greater accuracy has been due, in the main, to al-Battāni’s closer proximity to the southern latitude: a geographical position that was probably more favourable for such observations. In addition, it has also been suggested that al-Battāni did not have to make adjustments in his calculations for certain types of atmospheric refraction that become more pronounced at locations closer to the poles. Even accepting the probability suggested here, it was no casual happenstance that al-Battāni was centuries ahead of his time.

It was al-Battāni who observed, with great accuracy, that the distance between sun and earth keeps varying, rather than remaining the same as was earlier supposed. Drawing on this important observation, he was then able to correctly infer that annular eclipses of the sun – wherein the moon interposes itself exactly between earth and sun, leaving behind a bright ring around its edge – would occur occasionally, when the sun was farthest from the earth.

Another assumption that was taken apart by al-Battāni’s keen observations was the idea that the earth’s equatorial plane (or the plane formed by an imaginary slice through the earth’s equator) matches with the plane formed by the earth-sun orbit. In fact, al-Battāni’s calculations showed that the angle between these two planes – called the obliquity, or inclination, of the ecliptic – read out as 23 degrees and 35 minutes, which is amazingly close to the actual figure of 23 degrees, 27 minutes, and 8.26 seconds.

Nor were al-Battāni’s discoveries limited to these highly precise calculations. The precession of the equinoxes (which he deduced as 54.5″ per year, or 1° in 66 years), the changes in the time of the annual equinox as calculated with reference to the positions of the heavenly bodies, the length of the seasons and the true and mean orbit of the sun – all were discoveries which he realized in the due course of his studies at Raqqah.

By the time of the Renaissance in Europe, these discoveries and the associated deliberations of al-Battāni had become an integral part of the vehicle in which the scientific enlightenment of the West took root and flourished several centuries after him.

To be sure, al-Battānī’s work is, today, seen as pivotal in the progress of science and astronomy. Tellingly indicative of the reverence with which al-Battāni was held some 500 years after his passing, is the fact that Copernicus quoted him in his De Revolutionibus Orbium Coelestium – the book that set in motion the Copernican Revolution. The sixteenth century Danish astronomer, Tycho Brahe (1572-1601CE) and the Italian astronomer-cum-Jesuit priest, Giovanni Riccioli (1598-1671CE) among other European scientists, too, have frequently quoted al-Battānī in their works. Even the greats of Western science, like Johannes Kepler and Galileo Galilee, showed not just a passing interest in al-Battāni’s observations. Indeed, just how fundamental a shift was ushered in through al-Battāni’s work can be made out by the easily verifiable fact that his data continues to be used in geophysics well into the 21st century.

The first to explore the Azimuth and Nadir and their exact points in the sky, al-Battāni was cited, not unjustly, by the Italian orientalist, Carlo Alfonso Nallino (1872-1938CE), as having made so many observations for the phenomena of lunar and solar eclipses that Richard Dunthorne (c.1749CE), the English astronomer, relied heavily on these very observations to specify moon acceleration in its movement through one century. To Lalande (1732-1807CE), the French astronomer, al-Battāni was among the foremost guides for astronomers all over the world. (Zarkaly, 2002, p. 68)

(To be continued)