About Opentopia

Opentopia Directory Encyclopedia Tools

Unit of length

Encyclopedia : U : UN : UNI : Unit of length

A unit of length is a way of measuring length or distance.

Common units of length in the International System of Units (SI) are:

metre (or "meter" in US English) and its multiples, such as "centimetre" or "kilometre"

Non-SI units of length include:

fermi (fm) (= 1 femtometre in SI units)
angstrom (Å) (= 100 picometres in SI units)
micron (= 1 micrometre in SI units)

Common Imperial units and U.S. customary units of length include:

inch (25.4 mm)
foot (0.3048 m)
yard (0.9144 m)
(terrestrial) mile (1609.344 m)

In addition, the following are used by mariners...

fathom (for depth) (1.8288 m)
nautical mile (1852 m)

...and surveyors in the United States continue to use...

chain (~20.1m)
rod (also called pole or perch) (~5 m)

...while horse racing keeps alive:

furlong (~201 m)

Astronomical measure uses:

astronomical unit (AU) (~149 gigametres)
light year (ly) (~9.46 petametres)
parsec (pc) (~30.8 petametres), including kiloparsec (kpc) and megaparsec (Mpc)

Physics also uses:

Archaic units of distance are described in the article on Ancient weights and measures. They include:

cana
cubit
league
li (China)
pace (the "double pace" of about 5 feet used in Ancient Rome)
verst (Russia)

In everyday conversation, and in informal literature, it is common to see lengths measured in units of objects of which everyone knows the approximate width. Common examples are:

Football field (generally around 110 metres, depending on the country)
Widths of a human hair (around 80 micrometres).

See also

From Wikipedia, the Free Encyclopedia. Original article here. Support Wikipedia by contributing or donating.
All text is available under the terms of the GNU Free Documentation License See Wikipedia Copyrights for details.