Astronomer Abu Ishaq Ibrahim al-Zarqali
The famous mathematician, astronomer and maker of astronomical instruments, Abu Ishaq Ibrahim ibn Yahya al-Naqqah al-Zarqali (1029–1100) – in Latin he was called Arzachel, which means “engraver” – was born and worked in the city of Toledo in Andalusia (Spain) and then moved to Cordoba.
The works of this talented scientist had a great influence on a whole generation of Islamic astronomers in Andalusia and after his works were translated into other languages, for European specialists as well. The safeya (an improved astrolabe), which al-Zarqali invented, was extremely popular and was actively used by sailors all over the world until the 16th century. Safeya is also known as the “Zarqali board”. The crater Arzachel on the Moon is named after the great merits of the Islamic inventor.
The future Arab scientist al-Zarqali was born in a village near Toledo, at that time the capital of the recently created Muslim emirate. Having learned blacksmithing, he became a skilled metal engraver and created astronomical instruments at the request of celestial cartographers and then became a famous astronomer himself. He also distinguished himself in geometry, which he loved.
Abu Ishaq Ibrahim al-Zarqali also showed talent in teaching. His great experience and knowledge made him the leading astronomer of his time. The inventions of the Islamic scientist led the city of Toledo to become the intellectual centre of Andalusia.
Al-Zarqali created several works on astronomical instruments. Among them is the “Book of Actions with the Zij Tympanum” (zij is an astronomical table). It explains in detail the astrolabe “zarkala”, from which the scientist got his nickname. The astrolabe “zarkala” gained great popularity in Europe under the name Saphеa Arzachelis.
The Arab mathematician al-Zarqali was the first to build an equatorial astronomical computing device. It was used to determine the location of the Sun, Moon and other celestial objects without calculations (using a geometric model).
The great astronomer and mathematician also made amendments to the general geographical studies of Ptolemy and al-Khwarizmi, namely, he refined Ptolemy’s estimate of the width of the Mediterranean Sea from 62 degrees to the correct value of 42 degrees.
In the 16th century, Copernicus used al-Zarqali’s model of the Sun’s motion in his work “On the Revolutions of the Celestial Spheres”.
Al-Zarqali took an active part in the creation of the famous Toledo Tables, adapting earlier astronomical information from al-Khwarizmi and al-Battani to establish the coordinates of Toledo.
The almanac of Zij al-Zarqali was translated into Latin in the 12th century by Gerard of Cremona (1114–1187), a famous mathematician, philosopher, astrologer, physician and one of the greatest translators of the Middle Ages. Al-Zarqali’s works contributed to the flourishing of mathematical astronomy in Christian Europe and were later included in the Toledo Tables in the 12th–13th centuries.
Al-Zarqali’s almanac contained tables that allowed one to identify the first days of the Roman, Coptic and Persian lunar months. Other tables showed the positions of the planets in a given period and also facilitated the determination of lunar and solar eclipses.
The almanac compiled by the Muslim astronomer contained data on the position of celestial bodies and did not require additional calculations. It is very important that he claimed to establish longitude using the planetary cycles of each planet.
The greatest Islamic scholar al-Zarqali devoted his entire life to astronomy in order to help his fellow citizens accurately determine the time of namaz and know the direction to Mecca (qibla). Grateful descendants still respectfully preserve the memory of him.
