The Arab, Arabic, or Arabian mile (Arabic: الميل, al-mīl) was a historical Arabic unit of length. Its precise length is disputed, lying between 1.8 and 2.0 km. It was used by medieval Arab geographers and astronomers. The predecessor of the modern nautical mile, it extended the Roman mile to fit an astronomical approximation of 1 minute of an arc of latitude measured along a north–south meridian. The distance between two pillars whose latitudes differed by 1 degree in a north–south direction was measured using sighting pegs along a flat desert plane.
There were 4000 cubits in an Arabic mile. If al-Farghani used the legal cubit as his unit of measurement, then an Arabic mile was 1995 meters long. If he used al-Ma'mun's surveying cubit, it was 1925 meters long or 1.04 modern nautical miles.
Al-Ma'mun's arc measurementEdit
Around 830 AD, Caliph Al-Ma'mun commissioned a group of Muslim astronomers and Muslim geographers to perform an arc measurement from Tadmur (Palmyra) to Raqqa, in modern Syria. They found the cities to be separated by one degree of latitude and the corresponding meridian arc distance to be 66⅔ miles and thus calculated the Earth's circumference to be 24,000 miles.
Another estimate given by his astronomers was 56⅔ Arabic miles (111.8 km per degree), which corresponds to a circumference of 40,248 km, very close to the current values of 111.3 km per degree and 40,068 km circumference, respectively.
- Edward S. Kennedy, Mathematical Geography, pp=187–8, in (Rashed & Morelon 1996, pp. 185–201)
- See: p. 608 (note 11) in: Cytryn-Silverman, Katia (2007). "The Fifth Mīl from Jerusalem: Another Umayyad Milestone from Southern Bilād Al-shām". Bulletin of the School of Oriental and African Studies, University of London. 70 (3): 603–610. doi:10.1017/S0041977X07000857. JSTOR 40378940. S2CID 162314029.
- Gharā'ib al-funūn wa-mulah al-`uyūn (The Book of Curiosities of the Sciences and Marvels for the Eyes), 2.1 "On the mensuration of the Earth and its division into seven climes, as related by Ptolemy and others," (ff. 22b-23a)
- Gharā'ib al-funūn wa-mulah al-+uyūn , 2.1" On the mensuration of the Earth and its division into seven Climes, es related by Ptolemy and others, "(ff. 22b-23)