Unit of length
From Wikipedia, the free encyclopedia
A unit of length is a way of measuring length or distance.
Common units of length in the International System of Units (SI) are:
- meter (or "metre" in British English) and its multiples, such as "centimeter" or "kilometer"
Non-SI units of length include:
- fermi (fm) (= 1 femtometer in SI units)
- angstrom (Å) (= 100 picometers in SI units)
- micron (= 1 micrometer in SI units)
Common Imperial units and U.S. customary units of length include:
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...
...while horse racing keeps alive:
- furlong (~201 m)
Astronomical measure uses:
- astronomical unit (AU) (~149 gigameters)
- light year (ly) (~9.46 petameters)
- parsec (pc) (~30.8 petameters), 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 meters, depending on the country)
- Widths of a human hair (around 80 micrometers)
- A beard-second is a unit created as a teaching concept. It is the distance that a beard grows in a second (about 5 nanometers)
