Mile

Encyclopedia : M : MI : MIL : Mile

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

the statute mile of 1,760 yards (about 1,609 metres), or
the international nautical mile (exactly 1,852 metres).

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 “m.p.h.” or “MPH” instead of “mi/h”.

Contents

1 The original mile
2 Types of mile

2.1 Statute miles
2.2 Nautical miles

3 History of the International Statute Mile
4 Use of the mile
5 Other miles
6 See also
7 Reference
8 External links

The original mile

A unit of distance called a mile was first used by the Romans and originally denoted a distance of 1,000 (double) steps ("mille passuum" in Latin), which amounted, at approximately 29 inches (0.74 m) per (single) step, to 1,618 yards (1,480 m), or 5,000 Roman feet, per mile.

Types of mile

In modern usage, various distances are referred to as a mile.

Statute miles

A statute of the English parliament during the reign of Elizabeth I established the statute mile 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). 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.

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.

The international nautical mile originated from the geographical mile (one and one-eighth by the original definition) and is now internationally defined to be 1,852 metres; but its pervasive definition and utility is based in the original attempt (definition) to rationalize mathematically (scale) miles–circumference–of–the–earth into a useful integer multiple of length (miles) related to (Spherical trigonometry) the degrees of spherical rotation along a great circle; it works out as approximately 6,076 feet, approximately 1.15 statute miles, or (in demanding fast maneuvering approximations) close-enough to an even 1 arc-minute of latitude to be of great utility.
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.

History of the International Statute Mile

Why 5280 Feet?

With the gradual decline of the Roman Empire the Britons needed a way to join the Roman standard with their own previous standard for measuring land. This was necessary for titles, and tax collection. Prior to Roman occupation the English unit of measure was based on a furlong. A "Furlong" was an agricultural unit of measurement, based upon the distance a horse could pull a plow before it needed a rest. This distance was estimated at 660 feet. So the Britons pondered how to combine 5,000 feet with an equal number of units consisting of 660 feet. Thus came the decision between two formulas:

Formula 1

[\frac = 7.5757 Furlongs]

Formula 2

[\frac = 8 Furlongs]

Formula 1 would reduce the amount of land owned by 280 feet for every mile. This was agreeably not good, neither for the tax collector, nor the land owner. Also, multiplying by 8 was much easier (before pocket calculators were invented) than by 7.5757. Thus a mile was decided to be 5,280 feet.

Use of the mile

See also: Metrication

The processes of metrication have seen the mile lose favour as a unit of measurement in most countries of the world. Currently the mile can only be found on roadsigns in the USA, UK, Liberia and Myanmar. However knots (nautical miles per hour) remain commonly used in international air and sea transport.

The Mile is not a real thing.

Other miles

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 metres).
The Italian mile (~1.5 kilometres) 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.
The Polish mile was nearly equal to the Dutch mile.
The Scottish mile was equal to 1,976.5 yards (1,807.3116 metres).
The Swedish mile (the mil) 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) was about 11.3 km in Norway (see Long Mile below) and 10.68854 km in Sweden, representing a suitable distance between rests when walking. In informal and non-precise situations involving longer distances of several kilometers, the mil is, as a rule, used instead of the kilometre. It is also used commonly for measuring vehicle fuel consumption; litre per mil means litres consumed per 10 km [link].
The Long mile, traditionally used by the Norwegians, Swedes and Hungarians, was about a German mile and a half or around 11 kilometres.

Reference

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

External links

[NIST General Tables of Units of Measurement]

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