The Arab, Arabic, or Arabian mile ( ar, الميل, ''al-mīl'') was a historical Arabic unit of

length Length is a measure of distance. In the International System of Quantities, length is a quantity with dimension distance. In most systems of measurement a base unit for length is chosen, from which all other units are derived. In the Inte ...

. Its precise length is disputed, lying between 1.8 and 2.0 km. It was used by medieval Arab geographers and

astronomers An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, planets, moons, comets and galaxies – in either obser ...

. The predecessor of the modern

nautical mile A nautical mile is a unit of length used in air, marine, and space navigation, and for the definition of territorial waters. Historically, it was defined as the meridian arc length corresponding to one minute ( of a degree) of latitude. Today t ...

, it extended the

Roman mile The mile, sometimes the international mile or statute mile to distinguish it from other miles, is a British imperial unit and United States customary unit of distance; both are based on the older English unit of length equal to 5,280 Engli ...

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

cubit The cubit is an ancient unit of length based on the distance from the elbow to the tip of the middle finger. It was primarily associated with the Sumerians, Egyptians, and Israelites. The term ''cubit'' is found in the Bible regarding ...

s in an Arabic mile. If

al-Farghani Abū al-ʿAbbās Aḥmad ibn Muḥammad ibn Kathīr al-Farghānī ( ar, أبو العبّاس أحمد بن محمد بن كثير الفرغاني 798/800/805–870), also known as Alfraganus in the West, was an astronomer in the Abbasid court ...

used the legal cubit as his unit of measurement, then an Arabic mile was 1995 meters long. If he used

al-Ma'mun Abu al-Abbas Abdallah ibn Harun al-Rashid ( ar, أبو العباس عبد الله بن هارون الرشيد, Abū al-ʿAbbās ʿAbd Allāh ibn Hārūn ar-Rashīd; 14 September 786 – 9 August 833), better known by his regnal name Al-Ma'm ...

's surveying cubit, it was 1925 meters long or 1.04 modern nautical miles. During the Umayyad period (661–750), the "Umayyad mile" was roughly equivalent to , or a little more than two

kilometers The kilometre ( SI symbol: km; or ), spelt kilometer in American English, is a unit of length in the International System of Units (SI), equal to one thousand metres ( kilo- being the SI prefix for ). It is now the measurement unit used for ...

, or about 2

biblical mile Biblical mile () is a unit of distance on land, or linear measure, principally used by Jews during the Herodian dynasty to ascertain distances between cities and to mark the Sabbath limit, equivalent to about ⅔ of an English statute mile, or w ...

s, for every Umayyad mile.

Al-Ma'mun's arc measurement

Around 830 AD, Caliph

Al-Ma'mun Abu al-Abbas Abdallah ibn Harun al-Rashid ( ar, أبو العباس عبد الله بن هارون الرشيد, Abū al-ʿAbbās ʿAbd Allāh ibn Hārūn ar-Rashīd; 14 September 786 – 9 August 833), better known by his regnal name Al-Ma'm ...

commissioned a group of Muslim astronomers and Muslim geographers to perform an

arc measurement Arc measurement, sometimes degree measurement (german: Gradmessung), is the astrogeodetic technique of determining of the radius of Earth – more specifically, the local Earth radius of curvature of the figure of the Earth – by relating the l ...

from Tadmur (

Palmyra Palmyra (; Palmyrene: () ''Tadmor''; ar, تَدْمُر ''Tadmur'') is an ancient city in present-day Homs Governorate, Syria. Archaeological finds date back to the Neolithic period, and documents first mention the city in the early seco ...

) to

Raqqa Raqqa ( ar, ٱلرَّقَّة, ar-Raqqah, also and ) (Kurdish: Reqa/ ڕەقە) is a city in Syria on the northeast bank of the Euphrates River, about east of Aleppo. It is located east of the Tabqa Dam, Syria's largest dam. The Hellenistic, Rom ...

, in modern Syria. They found the cities to be separated by one degree of

latitude In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north po ...

and the corresponding

meridian arc In geodesy and navigation, a meridian arc is the curve between two points on the Earth's surface having the same longitude. The term may refer either to a segment of the meridian, or to its length. The purpose of measuring meridian arcs is to ...

distance to be 66⅔ miles and thus calculated the

Earth's circumference Earth's circumference is the distance around Earth. Measured around the Equator, it is . Measured around the poles, the circumference is . Measurement of Earth's circumference has been important to navigation since ancient times. The first kn ...

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 '' 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

/ref>

Notes

Bibliography

*Paul Lunde. “Al-Faraghani and the Short Degree.” The Middle East and the Age of Discovery Aramco World Magazine Exhibition Issue, 43:3. pp. 15–17. * {{DEFAULTSORT:Arab Mile Obsolete units of measurement Geography in the medieval Islamic world Units of length

Al-Ma'mun's arc measurement

See also

Notes

Bibliography