10 Remarkable Achievements of Muslim Astronomers

In 8^th century Baghdad, a miraculous movement began that resulted in  step changes in many areas of  knowledge. This pre-renaissance progress, termed as the “Translation Movement”   thrusted fowards one particular science leaps and bound. That subject of science was Astronomy.

Led by the caliph Al Mamoon, the translation movement breathed new life in the work of Hipparchus and Ptolemy.  As natural philosophy sought refuge from Europe to Arabia, the work that was almost buried picked up, revived and developed further  by many Muslim Astronomers. For the next 600 years, the world saw the emergence of great polymaths like Beruni, Khwarizmi, Ummar Khayyam and remarkable astronomers like Battani and Ulugh Beg.

Astronomy has always been called mother of all sciences.  In its pursuit mankind has been inspired and at the same time humbled. However, this science historically had been intertwined with astrology. One of the earliest and biggest contributions of Muslim astronomers was to decouple the two.

Muslims have always taken a special interest in astronomy. This is mainly to fulfill religious obligations. The customary rituals like daily prayers are based on the position of the sun. The Islamic calender (Religious days and months) on the other hand is  based on the phases of the moon.

In Islamic faith, the five daily prayers have to be offered in the direction of Kaaba (Mecca).  With the expansion of Islamic empire, measures had to be devised to ensure religious requirements are met. Therefore it was in the interest of state to back indiviuals and institutes that worked to find solutions. Territories were mapped, star charts were created and instruments such as Equatrium, quadrant and astrolabe were invented.

One of the verses of the Quran says:

“And it is He who ordained the stars for you that you may be guided thereby in the darkness of the land and the sea.” <Qur’an-An’am-97>

(This verse clearly ordains muslims to use stars for navigating and for finding directions )

There was also the need to understand over 40 verses in the Quran that contain astronomical information in addition to verses on speed of light and time travel.

One of the verses in the Quran is as follows:

“…He created the sun, the moon, and the stars (all) governed by laws under His commandment.” <Qur’an-A’raf 7:54>

The verse explicitly mentions that the movement of celestial objects is based on a defined pattern which in turn encouraged many Muslims to map the stars and track their movement. Two of the biggest observatories of their time that are still present today were made by Muslims (Samarkand Observatory and Istanbul Observatory).

Ulugh Beg  (1393-1449) a famous Timurid ruler and astronomer determined the length of the sidereal year as  365^d 5^h 49^m 15^s, which has an error of +25 seconds compared to the values that are used today. This indeed was a remarkable feat given the difference in technology available then and now. In light of his contributions to astronomy, a crater on the moon was named after him.

The precedence for Ulugh Beg was set 500 years earlier by another famous Muslim astronomer  Al Battani. Al –Battani or Albatenious (858-959) calculated the length of sidereal year to be 365^d 5^h 48^m 24^s. This calculation was used in Europe for the next 600 years. He was also one of the first person to calculate the tilt of the earth. The value he worked out was 23° 35′. Today through much superior technology, it is known that the tilt of the earth varies between 22.1 and 24.5 degrees because of an axial wobble. Its current value is 23.44 and is decreasing.

After Al-Battani the torch was picked up by Abu Rehan Al-Beruni (973-1048), who calculated the radius of the earth to be 6,339.6 kilometres. It is interesting to note that there still exists a false notion that attributes bravery to Christopher Columbus for discovering America at a time when earth was considered to be flat. Not much is mentioned about the fact that not only it was known that the earth was round 500 years before Columbus’s journey but that the earth’s radius had also been calculated. Al Beruni’s calculated radius is only out by 1% when compared to the radius of the earth as we know today (6378 km).

Al Beruni, without any optical aid was able to theorize that the appearance of Milky Way was because of the presence of numerous stars.  It was 500 years later, after the invention of telescope that it was possible to verify his claims.

Summary of Achievements of Muslim Astronomers

It is difficult to list all the achiement made by numerous muslim astronomers across the globe. From the  Ibn al Haytham (Alhazen) work on optics to Taqi ad-Din ibn Maruf’s observatory in Istanbul, the contribution is not only remarkable but almost unfathomable. Therefore only a 10 point summary of the achievements of Muslim Astronomers is mentioned below:

1. Distinguishing Natural Philosophy from Astronomy
2. Differentiating between Astrology and Astronomy
3. Translation of ancient Greek, Persian and Sanskrit Text
4. Respect and thirst for Knowledge from all corners of the globe
5. Amalgamation of existing Knowledge
6. Development and several measurement devices and Astrolabes
7. Construction of the first observatories
8. Establishing Heliocentricity
9. Establishing Spherical Geometry and improvement of mathematical astronomy
10. Establishing methods for estimation of Moon sighting

Astronomy not only has inspired Muslims to scientific greatness but has also featured in their art , poetry and literature. For example:

Up from Earth’s Center through the Seventh Gate
I rose, and on the Throne of Saturn sate,
And many a Knot unravel’d by the Road;
But not the Master-knot of Human Fate.

(Ummar Khayyam, trans Edward Fitzgerald)

Ummar Khayyam (1048-1131) was a famous persian polymath after whom a lunar crater was named in 1970 and an asteroid (3095) in 1980.