Astrolabe – the first personal computer

From the Greek astron “star” and lambanein “to take,”  the astrolabe is an ancient astronomical instrument used for observing planetary movements. Astrolabes are amongst the most sophisticated scientific instruments ever made.

Medieval Arab astrolabe. Image: History of Computers and Computing

Invented by the Greeks in about the second or third century BC, the astrolabe was further advanced by the Arabs in the eighth to eleventh centuries CE. The translation of Ptolemy’s Almagest in the court of Caliph al-Ma’mun in Baghdad in the ninth century, astronomers working in the region adopted and advanced the knowledge of the Greek, Persian, and Indian traditions.

A famous female scientist and astrolabe designer Mariam “Al-Astrolabiya” Al-Ijliya, lived in tenth-century in Aleppo, Syria. Having learned the art from her father who worked for  a prominent astrolabe maker in Baghdad, she became renowned for her unique designs and was employed by the ruler of the city of Aleppo. The main-belt asteroid 7060 Al-‘Ijliya, discovered by Henry E. Holt at Palomar Observatory in 1990, is named after Mariam.

There were two main types: the mariner’s astrolabe used for navigation – to determine the altitudes of the sun and starts; the planispheric astrolabe, the most common instrument, was used for astrological purposes. Initially consisting of six parts including the latitude plate which was made for specific latitudes, Ibrahim al-Zarqali (d. 1087), known as Azarchel in the West, introduced a universal plate capable of calculations at any latitude, thereby rendering the astrolabe usable in any part of the world – it did not need electricity, batteries or WiFi. The compact versatile nature of the astrolabe made it the most treasured instrument for astronomers.

The astrolabe was introduced to Europe through North Africa and the Iberian Peninsula (al-Andalus) as early as the eleventh century although its use was not widespread until the thirteenth century, with peak usage in the fifteenth and sixteenth centuries. In al-Andalus of the fourteenth century, Muslim scientists worked together with Christian and Jewish counterparts to translate and transmit scientific knowledge at the famous Toledo translation centre.

Planispheric astrolabe
Planispheric astrolabe, from the Iberian peninsula, 1300s. Aga Khan Museum. The inscriptions on the astrolabe bear the names of constellations in both Arabic and Latin, with additional inscriptions in Arabic. Later, Hebrew was added to one of the plates.

Latin names were engraved alongside the Arabic words on the astrolabes; it seems likely that the use of Arabic star names in Europe was influenced by the importing of these instruments.

The use of the astrolabe declined in the late seventeenth century with the invention of the pendulum clock and the telescope.

Planispheric Astrolabe, Aga Khan Museum (accessed May 2017)
Hamza Khalid, Mariam Al-Astrulabi (accessed May 2017)
The International Astronomical Union Minor Planet Center (accessed May 2017)
Robert A. Agler, Measuring the Heavens: Astronomical Instruments before the Telescope, The Smithsonian Astrophysical Observatory (accessed May 2017)

Compiled by Nimira Dewji

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