On the Metre Definition?

The metre or meter is the base unit of length in the International System of Units. The SI unit symbol is m. 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.

How is the metre defined?

Since 1983, the metre has been internationally defined as the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second. ... By using a light source of known and stable wavelength, lengths up to 100 metres can be directly measured, with accuracies up to 1 part in a few million.

Where did meter come from?

The French originated the meter in the 1790s as one/ten-millionth of the distance from the equator to the north pole along a meridian through Paris. It is realistically represented by the distance between two marks on an iron bar kept in Paris.