Furlong

A furlong is a measure of Distance within Imperial units and U.S. customary units. Although its definition has varied historically, in modern terms it equals 660 feet or 220 yards, and is therefore equal to 201.168 metres. There are ten chains in a furlong and eight furlongs in a Mile. The name "furlong" derives from the Old English words furh (furrow) and lang (long). It originally referred to the length of the furrow in one Acre of a ploughed open field (a medieval communal field which was divided into strips). The system of long furrows arose because turning a team of oxen pulling a heavy plough was difficult. This offset the drainage advantages of short furrows and meant furrows were made as long as possible. For this reason, it was once also called an acre's length.

Distances for thoroughbred horse races in the United Kingdom, Ireland and the United States are given alternately in miles and furlongs ( example), but the unit is otherwise no longer in common use - and even in that discipline its usage is confined mainly to denoting distances of less than one mile. Its official use was abolished in the United Kingdom under the Weights and Measures Act 1985, which also abolished from official use many other traditional units of measurement.

Coincidentally, 5 furlongs is 1005.84 metres (exactly) and is therefore approximately 1 kilometre.

Trivia

• 0.0001663095 Metre per second or roughly one centimetre per Minute (in SI units)
• 0.0005456349 feet per Second (in Imperial units)

• a car travelling at 60 km/h (37 mph) is travelling at a speed of 100,214.7 furlongs per fortnight;
• a Boeing 737 cruising at 420 knots or 216.2 m/s (i.e. typical 0.8 Mach cruise) is travelling at 1,300,013.7 furlongs per fortnight;
• the Speed of light in vacuum is approximately 1.803 logfile.inc.0.1.14 10¹² furlongs per fortnight;
• one furlong per fortnight is 0.166 millimetres per second, which would be barely noticeable to the naked eye.

The city of Chicago's numbering system allots a measure of 800 to each mile. Logically, streets were subsequently laid out 8 to the mile. This means that every block in a typical Chicago neighborhood (in either North/South or East/West direction but rarely both) is precisely one furlong.