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, the mass unit is the mass of a firkin of water, and the time unit is the fortnight. Like the SI or metre-kilogram-second system, there are derived units for velocity etc.
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", furlongs per fortnight have also served frequently in classroom examples of unit conversion and dimensional analysis.
Base units and definitions
|Unit||Abbreviation||Dimension||SI unit||Imperial unit|
|furlong||fur||length||201.168 m||220 yards|
|firkin||fir||mass||40.8233133 kg||90 lb|
|fortnight||ftn||time||1,209,600 s||14 days|
Notable multiples and derived units
One microfortnight is equal to 1.2096 seconds. This has become a joke in computer science because in the VMS operating system, 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 bogus, 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. In a further twist, the documentation notes that "[t]he time unit of micro-fortnights is approximated as seconds in the implementation." Millifortnights (about 20 minutes) and nanofortnights (1.2096 milliseconds) have also been used occasionally in computer science, usually in an attempt to be deliberately over-complex and obscure.
One furlong per fortnight, a speed which would be barely noticeable to the naked eye, converts to: 1.663×10−4 metre per second, roughly one centimetre per minute (to within 1 part in 400), 5.987×10−4 km/h, roughly three eighths of an inch per minute, or 3.720×10−4 mph. The expression has also been used figuratively[by whom?] to mean at glacial speed (the pace or rate of progress is experienced as excruciatingly slow), as it is a realistic speed of some glaciers, about 14 m/day. Another notable constant based on those units is the speed of light, known as "Strapp's Constant" (Jock "Strapp" Marshall), which is 1.8026×1012 furlongs/fortnight.
Notes and references
- Stan Kelly-Bootle, "As Big as a Barn?", ACM Queue, March 2007, pp. 62–64.
- John D. Neff, "Imbedding the Metric", The Two-Year College Mathematics Journal, Vol. 14, No. 3 (Jun., 1983), pp. 197–202.
- For example, in Jack G. Ganssle, The art of designing embedded systems, 2nd ed., Newnes, 2008, ISBN 0-7506-8644-8, p. 50.
- Giambattista, Alan; Richardson, Betty McCarthy & Richardson, Robert C. (2004). College Physics. Boston: McGraw Hill. p. 20. ISBN 0-07-052407-6.
- Stephan, Elizabeth A.; Park, William J.; Sill, Benjamin L.; Bowman, David R. & Ohland, Matthew W. (2010). Thinking Like an Engineer: An Active Learning Approach. Prentice Hall. p. 259. ISBN 0-13-606442-6.
- The firkin of the FFF System is defined as the mass of an imperial firkin (9 imp gal) of water. The imperial gallon was originally defined as the volume of 10 lb of distilled water (weighed according to specific conditions). From this definition a density of 10 lb/imp gal is derived, giving the firkin of water a mass of 90 lb.
- Robert Slade, Dictionary of information security, Syngress, 2006, ISBN 1-59749-115-2, p. 122.
- "microfortnight". Retrieved 2007-07-06.
- "HP OpenVMS System Management Utilities Reference Manual". Retrieved 2008-11-26.
- Indeed, if the inch were defined as 2.5454... cm rather than 2.54 cm exactly, it would be 1 cm/min. "FAQ for newsgroup UK.rec.sheds, version 2&3/7th" (TXT). 2000. Retrieved 2006-03-10.
- Paul Connally – 1992 – Derived after several discussions with Jock Marshall concerning his endeavors with fabricating parts for the Cassini deep space project
- Page-Jones, Meilir & Constantine, Larry L. (2000). Fundamentals of object-oriented design in UML. Addison–Wesley. p. 235. ISBN 0-201-69946-X.