Mile

From Wikipedia, the free encyclopedia

A mile is a unit of length, usually used to measure distance, in a number of different systems, including Imperial units, United States customary units and Norwegian/Swedish mil. Its size can vary from system to system, but in each is between 1 and 10 kilometers. In contemporary English contexts mile refers to either:

• the statute mile of 5,280 feet (about 1,609 m), or 63360 inches
• the international nautical mile of exactly 1,852 m (about 6,076 feet).

There have been several abbreviations for mile, with and without trailing period: mi, ml, m, M. NIST now uses and recommends "mi", but miles per hour are usually shortened to "mph", "m.p.h." or "MPH" instead of "mi/h".

[edit] The original mile

A unit of distance called a mile was first used by the Romans and denoted a distance of 1000 paces (1 pace is 2 steps, 1000 paces being, in Latin, mille passus or mille passuum) or 5000 Roman feet, and corresponded to about 1618 modern yards^[1]. The current definition of a mile as 5280 feet (as opposed to 5000) dates to the 13th century, and was confirmed by statute in the reign of Queen Elizabeth I; the change was needed to accommodate the rod which (as opposed to the mile) was a measure ensconced in legal and commercial documents (see the discussion about furlongs).

[edit] Types of mile

In modern usage, various distances are referred to as miles.

[edit] Statute miles

A statute of the English parliament during the reign of Elizabeth I established the statute mile (abbreviated in meteorology and aviation applications: SM) as eight furlongs or 1,760 yards; that is, 5,280 feet or 63,360 inches. Prior to the statute, the mile in England was commonly considered 5,000 feet, a length not divisible into yards, rods, or furlongs without fractions. There are two slightly different statute miles in current use:

• The international mile is the distance typically meant when the word mile is used without qualification. It is defined to be precisely 1,760 international yards (by definition, 0.9144 m each) and is therefore exactly 1,609.344 metres (1.609344 km). And a kilometer is 0.621371192 miles. It is used in the United States and the United Kingdom as part of the U.S. customary and Imperial systems of units, respectively. The international mile is equivalent to 8 furlongs, 80 chains or 5,280 international feet.
• The U.S. survey mile is based on an inch defined by 1 metre = 39.37 inches exactly. It is equal to 5,280 U.S. survey feet, 6,336/3,937 km or approximately 1,609.347 metres. One international mile is equal to 0.999 998 survey miles. The survey mile is used by the United States Public Land Survey System.

[edit] Nautical miles

On the utility of the nautical mile
Each circle shown is a great circle – the analog of a line in spherical trigonometry – and hence the shortest path connecting two points on the globular surface.

Main article: Nautical mile

The nautical mile was historically defined as 1 minute of arc along a meridian (or in some instances any great circle) of the Earth. Although this distance varies depending on which meridian (or great circle) is used, it works out as approximately 6,076 feet (about 1852 m or 1.15 statute miles).

In the United States, the nautical mile was defined in the nineteenth century as 6,080.2 feet (1,853.249 m), whereas in Britain it was defined as 6,080 feet (1,853.184 m). Other nations had different definitions of the nautical mile, but it is now internationally defined to be exactly 1,852 metres. Current editions of the Collins English Dictionary have separate entries for nautical mile and sea mile. According to the entry the latter is defined as 6000 feet (1828.8 m).

• The nautical mile's pervasive definition and utility relies on its 'close-enough' approximation to an even 1 arc-minute of latitude. The nautical mile is thus used in day-to-day long distance navigation estimates or important close-in restricted water piloting of vessels large or small. In the former case, it greatly simplifies the number of terms in a complex equation; in the latter case, it serves as a good-estimate basis for keeping to a deep water channel and off the rocks and shoals.
• It is still universally used in that respect, although science has refined its base standard into the metric system without materially impacting its utility one way or another.
• It is universally used for aviation, naval and maritime purposes, specifically as it gives a good estimate related to degrees in an integer form without excessive error of approximation.
• An alternative term - sea mile - is still used for the distance travelled in transversing one minute of latitude (or, alternatively, one minute of longitude at the equator).

[edit] Other miles

• The Roman mile, milea passuum, equalled 1000 double paces (passus) of five Roman feet (pes) each. Its length was 5,000 Roman feet, which is almost exactly 1500 m.
• The mil (or Swedish mile, currently used in Norway and Sweden) has been defined as 10 kilometres from 1 January 1889, when a metric system was introduced in Sweden. The pre-metric mil (in earlier times rast, lit. rest, pause) was about 11.3 kilometres in Norway (see Long Mile below) and 10.68854 kilometres in Sweden, representing a suitable distance between rests when walking. In informal and non-precise situations involving longer distances of several kilometres, the mil is, as a rule, used instead of the kilometre. It is also used commonly for measuring vehicle fuel consumption; litres per mil means litres consumed per 10 kilometres [1].
• The Danish mile (Danish mil) was equal to 7,532 metres (or 24,000 danish feet or 12,000 alen).
• The Data mile is used in radar-related subjects and is equal to 6,000 feet (1.8288 kilometres).
• The Dutch mile (the "Hollandic" mile) was nearly the 19th part of a degree (~5.8 kilometres).
• The Dutch mile (or "Netherlandic" mile) was exactly 1 kilometre in the Dutch Metric System 1820-1870.
• The German mile was reckoned to be the 15th part of a degree (and thus about four nautical miles in length or 6.4 kilometres).
• The Irish mile was equal to 2,240 yards (2,048.256 m).
• The Italian mile also called the Roman mile (~1.52 kilometres or 0.944 statute miles) was a thousand paces of 5 Roman feet each (the Roman foot being one fifth of an inch less than the London foot).
• The term Metric mile is used in sports such as athletics and speedskating to denote a distance of 1.5 kilometres. In United States high school competition the term is sometimes used for a race of 1.6 kilometres.
• The Polish mile was nearly equal to the Dutch mile.
• The Scottish mile was equal to 1,976.5 yards (1,807.3116 m).
• The Long mile, traditionally used by the Norwegians, Swedes and Hungarians, was about a German mile and a half or around 11 kilometres.
• The Finnish corresponding unit, virsta, was 1068.8 m. Ten virsta made one peninkulma (literally "hound's hearing", a distance a dog's bark can be heard in still air), 10.688 km. Today peninkulma refers to 10 km in Finnish colloquial usage (compare mil in Norwegian and Swedish usage).
• The swimmer's mile is 1500 meters or 30 laps in a 25 meter pool. This (roughly) converts to 1650 yards in a 25 yard pool (33 laps), the standard distance for intercollegiate competition in the United States.

[edit] See also

• Ancient weights and measures
• Fibonacci sequence application: convert to kilometers
• Four-minute mile
• Imperial units
• League
• Medieval weights and measures
• Square mile
• U.S. customary units

[edit] Reference

'Of Divers Measures', in Laurence Echard, 1741, The Gazetteer's or Newsman's Interpreter, London: Ballard et al. (first published 1703)

[edit] External links

• NIST General Tables of Units of Measurement
• Online conversion
• The Nautical Mile in Freeport, New York