The furlong–firkin–fortnight (FFF) system is a humorous system of units based on unusual or impractical measurements. The length unit of the system is the

furlong A furlong is a measure of distance in imperial units and United States customary units equal to one-eighth of a mile, equivalent to any of 660 foot (unit), feet, 220 yards, 40 rod (unit), rods, 10 chain (unit), chains, or a ...

, the mass unit is the mass of a firkin of water, and the time unit is the

fortnight A fortnight is a unit of time equal to 14 days (two weeks). The word derives from the Old English term , meaning "" (or "fourteen days", since the Anglo-Saxons counted by nights). Astronomy and tides In astronomy, a ''lunar fortnight'' is hal ...

. Like the SI or metre–kilogram–second systems, there are derived units for

velocity Velocity is a measurement of speed in a certain direction of motion. It is a fundamental concept in kinematics, the branch of classical mechanics that describes the motion of physical objects. Velocity is a vector (geometry), vector Physical q ...

volume Volume is a measure of regions in three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch) ...

mass Mass is an Intrinsic and extrinsic properties, intrinsic property of a physical body, body. It was traditionally believed to be related to the physical quantity, quantity of matter in a body, until the discovery of the atom and particle physi ...

and

weight In science and engineering, the weight of an object is a quantity associated with the gravitational force exerted on the object by other objects in its environment, although there is some variation and debate as to the exact definition. Some sta ...

, etc. It is sometimes referred to as the FFFF system where the fourth 'F' is degrees

Fahrenheit The Fahrenheit scale () is a scale of temperature, temperature scale based on one proposed in 1724 by the German-Polish physicist Daniel Gabriel Fahrenheit (1686–1736). It uses the degree Fahrenheit (symbol: °F) as the unit. Several accou ...

for temperature. While the FFF system is not used in practice, it has been used as an example in discussions of the relative merits of different systems of units. Some of the FFF units, notably the microfortnight, have been used jokingly in computer science. Besides having the meaning "any obscure unit", the derived unit ''furlongs per fortnight'' has also served frequently in classroom examples of

unit conversion Conversion of units is the conversion of the unit of measurement in which a quantity is expressed, typically through a multiplicative conversion factor that changes the unit without changing the quantity. This is also often loosely taken to incl ...

and dimensional analysis.

Base units and definitions

Multiples and derived units

Microfortnight and other decimal prefixes

One microfortnight is equal to 1.2096

second The second (symbol: s) is a unit of time derived from the division of the day first into 24 hours, then to 60 minutes, and finally to 60 seconds each (24 × 60 × 60 = 86400). The current and formal definition in the International System of U ...

s. This has become a joke in computer science because in the VMS

operating system An operating system (OS) is system software that manages computer hardware and software resources, and provides common daemon (computing), services for computer programs. Time-sharing operating systems scheduler (computing), schedule tasks for ...

, the TIMEPROMPTWAIT variable, which holds the time the system will wait for an operator to set the correct date and time at boot if it realizes that the current value is invalid, is set in microfortnights. This is because the computer uses a loop instead of the internal clock, which has not been activated yet to run the timer. The documentation notes that " e time unit of micro-fortnights is approximated as seconds in the implementation". The ''

Jargon File The Jargon File is a glossary and usage dictionary of slang used by computer programmers. The original Jargon File was a collection of terms from technical cultures such as the MIT Computer Science and Artificial Intelligence Laboratory, MIT AI Lab ...

'' reports that the millifortnight (about 20 minutes) and nanofortnight have been occasionally used.

Furlong per fortnight

One furlong per fortnight is a speed that would be barely noticeable to the naked eye. It

converts Conversion or convert may refer to: Arts, entertainment, and media * ''The Convert'', a 2023 film produced by Jump Film & Television and Brouhaha Entertainment * "Conversion" (''Doctor Who'' audio), an episode of the audio drama ''Cyberman'' * ...

to: * 1.663 m/s, (i.e. 0.1663 mm/s), * roughly 1 cm/ min (to within 1 part in 400), * 5.987 km/h, * roughly in/min, * 3.720 mph, * the speed of the tip of a inch minute hand.

Speed of light

The

speed of light The speed of light in vacuum, commonly denoted , is a universal physical constant exactly equal to ). It is exact because, by international agreement, a metre is defined as the length of the path travelled by light in vacuum during a time i ...

is furlongs per fortnight (1.8026 terafurlongs per fortnight). By

mass–energy equivalence In physics, mass–energy equivalence is the relationship between mass and energy in a system's rest frame. The two differ only by a multiplicative constant and the units of measurement. The principle is described by the physicist Albert Einstei ...

, 1 firkin is equal to (≈ , or ).

Others

In the FFF system,

heat transfer coefficient In thermodynamics, the heat transfer coefficient or film coefficient, or film effectiveness, is the Proportional (mathematics), proportionality constant between the heat flux and the thermodynamic driving force for the Heat transfer, flow of heat ...

s are conventionally reported as BTU per foot-fathom per degree

per fortnight.

Thermal conductivity The thermal conductivity of a material is a measure of its ability to heat conduction, conduct heat. It is commonly denoted by k, \lambda, or \kappa and is measured in W·m−1·K−1. Heat transfer occurs at a lower rate in materials of low ...

has units of BTU per fortnight per furlong per degree Fahrenheit. Like the more common furlong per fortnight, a firkin per fortnight can refer to "any obscure unit".

Footnotes

References

{{systems of measurement Systems of units Tech humour