The Metre (Meter, m) is the base unit of length in the International System (SI) of Units that is the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second. mm (Millimetre) is equal to one-thousandth (1/1000, 10^-3) of a metre (m). cm (Centimetre) is equal to one-hundredth (1/100, 10^-2) of a metre (m). km (Kilo) equals to one thousand (1,000, 10^3) of a metre (m).
Reference Definition by NIST: The definition of Metre origins go back to at least the 18th century. At that time, there were two competing approaches to the definition of a standard unit of length. The 1889 definition of the meter, based upon the artifact international prototype of platinum-iridium, was replaced by the CGPM in 1960 using a definition based upon a wavelength of krypton-86 radiation. This definition was adopted in order to reduce the uncertainty with which the meter may be realized. In turn, to further reduce the uncertainty, in 1983 the CGPM replaced this latter definition by the following definition: A Meter is a unit of length, the meter is the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second.
Related Definitions in the Project: The Property and Unit
