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A mile is any of several units of distance, or, in physics terminology, of length. Today, one mile is mainly equal to about 1609 metres on land and 1852 metres at sea and in the air, but see below for the details.
Current definitions
The meanings of mile that are commonly used today are: - The statute mile, or more specifically
- The international mile is the one typically meant when the word mile is used without qualification. It is defined to be precisely 1,609.344 m or 5280 international feet. It is used in the United States and the United Kingdom as part of the Imperial system of units. The international mile is equivalent to 8 furlongs, or 80 chains, or 1760 international yards.
- The U.S. survey mile is precisely equal to 6336/3937 kilometres or 5280 U.S. survey feet, approximately 1609.347 metres. One international mile is precisely equal to 0.999 998 survey miles. The survey mile is used by the United States Public Land Survey System.
- The international nautical mile is defined to be exactly 1852 metres. It is used universally for aviation, naval and maritime purposes and originated from the geographical mile.
- In Norway and Sweden, a distance of 10 kilometres is most commonly referred to as a mile, see mil.
History Throughout history many units of length named mile have been used, with widely differing definitions, originating with the Roman mile of approximately 1479 metres. A Roman mile consisted of 1000 "double steps", or two strides by a Roman soldier, each such double stride being called a passus having a length of approximately 2.4 feet. The word mile itself has been derived from the words mille passus (plural milia passuum), a thousand paces. Along the roads built by the Romans throughout Europe, it was common to erect a stone every mile to announce the distance to Rome, the so-called milestones. The noun milliarium (plural milliaria), designating a milestone, was also used as a figurative alternative for mile.
In navigation, the geographical mile was commonly used, defined as 1 minute of arc along the Earth's equator, approximately equal to 1855 metres.
The name statute mile goes back to Queen Elizabeth I of England who redefined the mile from 5000 feet to 8 furlongs (5280 feet) by statute in 1593.
When the international mile became legal in mid-1959, the survey mile was retained for measurements derived from U.S. cadastral surveys.
In Denmark and most of Germany the mile in the 19th century was an approximately 7.5 km geographical mile (determined by 4 minutes of arc) specified by Ole Rømer. In parts of Germany there also existed an exact 7.5 km metric mile variant, but it mostly went out of use at the beginning of the 20th century. The Ole Rømer mile was for a long time used as a sea mile in Scandinavia, but was in the middle of the 20th century replaced by the international nautical mile. The international nautical mile is still often referred to by traditionalist Scandinavians as a quarter mile. In Norway and Sweden, a mile in daily speech refers to a traditional unit that is still very commonly used, but now defined as 10 kilometres, see mil.
In Ireland the Irish mile of 2240 yards (about 2048.3 m) was used legally until 1826, and by some reports survives still on road signage in parts of the country.
See also
External links - NIST General Tables of Units of Measurement (http://ts.nist.gov/ts/htdocs/230/235/appxc/appxc.htm)
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