Metre explained to kids

The metre is the base unit of length in the International System of Units (SI). The SI unit of length is the metre. The metre was originally defined in 1793 as one ten-millionth of the distance from the equator to the North Pole. In 1799, it was redefined as the distance between two marks on a platinum rod that was kept at the temperature of melting ice. The new definition was declared to be exact by the International Prototype of the Meter (IPM) in 1889. The metre is currently defined as the length of the path travelled by light in a vacuum in 1/299,792,458 of a second. This definition was adopted in 1983 by the 18th General Conference on Weights and Measures (CGPM). The metre is used in all sorts of measurements, from the size of an atom to the size of the universe. It is also used to measure the speed of light and the duration of a second.