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Arabic mile

The Arab, Arabic, or Arabian mile (Arabic: الميل, al-mīl) was a historical Arabic unit of length. Its precise length is disputed, lying between 1,800 metres (5,900 ft) and 2,000 metres (6,600 ft). 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 4,000 cubits in an Arabic mile. If al-Farghani used the legal cubit as his unit of measurement, then an Arabic mile was 1,995 meters long. If he used al-Ma'mun's surveying cubit, it was 1,925 meters long or 1.04 nautical miles (1.93 km)[1]

During the Umayyad period (661–750), the "Umayyad mile" was roughly equivalent to 2,285 metres (7,497 ft), or a little more than 2 kilometres (6,600 ft), or about 2 biblical miles, for every Umayyad mile.[2]

Al-Ma'mun's arc measurement

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 Arabic miles and thus calculated the Earth's circumference to be 24,000 miles (39,000 km).[3] Using this measurement, knowing that earth's circumference is 40,007.683 km makes the Arabic mile little more than 1,666.994 metres. With Firuzabadi in his famous dictionary saying that a mile equals 3000 old dhira (ie cubit) this makes the dhira about 0.5556647 metres which is consistent with the tradition that kaaba height's is 27 dhira and its current height of 15 metres.

Another estimate given by his astronomers was 56⅔ Arabic miles (111.8 kilometres (69.5 mi) per degree), which corresponds to a circumference of 40,248 kilometres (25,009 mi), very close to the current values of 111.3 kilometres (69.2 mi) per degree and 40,068 kilometres (24,897 mi) circumference, respectively.[1][4]

See also

Notes

  1. ^ a b Edward S. Kennedy, Mathematical Geography, pp=187–8, in (Rashed & Morelon 1996, pp. 185–201)
  2. ^ 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.
  3. ^ 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)[1]
  4. ^ 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)[2]

Bibliography

Quelle: https://en.wikipedia.org/wiki/Al-Ma%27mun%27s_arc_measurement