Contributions of Muslim Astronomers and Geographers

Muslims needed astronomy and geography in daily life: to find the direction of the Qibla, the times of prayer and the start of Islamic months. This practical need, together with books translated from Greek, Persian and Indian scholars, led to great observatories and new maps from the 8th to the 15th century. Today, many star names, such as Aldebaran, Altair, Deneb and Rigel, still come from Arabic.

1. Al-Fazari (died c. 800 CE)

Worked in: Baghdad

• Translated an Indian astronomy book into Arabic, with help from a scholar who came to Baghdad with a delegation from Sindh (about 771 CE). The tables he made were called Zij al-Sindhind.
• Is said to be the first in the Muslim world to build an astrolabe, an instrument for measuring the height of stars and the Sun.

2. Al-Khwarizmi (c. 780–850 CE)

Worked in: the House of Wisdom, Baghdad

• Better known as the father of algebra, he also wrote Kitab Surat al-Ard (The Image of the Earth, about 833 CE).
• Listed the latitude and longitude of about 2,400 places, correcting the Greek maps of Ptolemy.

3. Al-Farghani (Alfraganus) (c. 800–870 CE)

Worked in: Baghdad and Cairo

• Wrote Elements of Astronomy, a clear, simple summary of astronomy that was translated into Latin and used in Europe for centuries.
• Supervised the building of the Nilometer in Cairo (861 CE), a structure that measured the level of the Nile's yearly flood.

4. Al-Battani (Albategnius) (c. 858–929 CE)

Worked in: Raqqa, Syria

• Measured the length of the year as 365 days, 5 hours, 46 minutes and 24 seconds, very close to the true value.
• Measured the tilt of the Earth's axis as 23° 35′. This tilt is what causes the seasons.
• Copernicus later quoted his measurements.

5. Abd al-Rahman al-Sufi (Azophi) (903–986 CE)

Worked in: Isfahan and Shiraz, Iran

• Wrote The Book of Fixed Stars (964 CE), describing the stars of 48 constellations with their brightness and drawings.
• Gave the first known written description of the Andromeda Galaxy, which he called a "small cloud". It is one of the farthest objects you can see without a telescope.

6. Al-Biruni (973–1048 CE)

Born in: Khwarazm (Uzbekistan) · Worked in: Ghazni, and travelled in the subcontinent

• Measured the radius of the Earth from a hill near Nandana Fort, Jhelum district (Pakistan). His answer, about 6,340 km, is close to the modern 6,371 km.
• In Kitab al-Hind, he wrote that the plain of the Indus and Ganges was once a sea that had been filled in by sediment carried by rivers, an early idea in geology.
• Discussed whether the Earth spins on its axis, and wrote about latitudes, longitudes and how to find the Qibla.

7. Al-Idrisi (1100–1165 CE)

Born in: Ceuta (Morocco) · Worked in: Sicily

• Made the Tabula Rogeriana (1154 CE) for King Roger II of Sicily, one of the most accurate world maps of the Middle Ages.
• His book described the countries, rivers, cities and trade routes on the map. Like many maps of that time, it had south at the top.

8. Nasir al-Din al-Tusi (1201–1274 CE)

Worked in: Maragha, Iran

• Built the Maragha observatory (1259 CE), with a large library and a team of astronomers.
• His Tusi couple gave a better model of how the planets move, and later astronomers used it.

9. Ibn Battuta (1304–c. 1369 CE)

Born in: Tangier, Morocco

• Travelled for about 30 years, roughly 117,000 km, across North Africa, the Middle East, Central Asia, India, China and Spain.
• In 1333 CE he crossed the Indus and visited Sindh and Multan. His book Al-Rihla (The Journey) is a valuable record of the places and people of his time.

10. Ulugh Beg (1394–1449 CE)

Ruled and worked in: Samarkand, Uzbekistan

• Built a great observatory in Samarkand in the 1420s, with a giant curved instrument for measuring the Sun's position.
• His Zij-i Sultani gave the positions of about 1,000 stars, the best star catalogue since ancient Greece.

Summary table