metre
Sign in to saveThe metre (or meter in US spelling; symbol: m) is the base unit of length in the International System of Units (SI). Since 2019, the metre has been defined as the length of the path travelled by light in vacuum during a time interval of of a second, where the second is defined by a hyperfine transition frequency of caesium.
AI overview
The metre is the standard unit used to measure length or distance in the metric system, and it's used worldwide in science, industry, and everyday life. Since 2019, it has been precisely defined based on how far light travels through a vacuum in a tiny fraction of a second, which ensures consistent and accurate measurements everywhere.
AI-generated from the Wikipedia summary — may contain errors.
Key facts
- Unit.name
- metre
- Unit.image
- Metric standards Rijksmuseum.jpg
- Unit.caption
- Historical replicas of metric standards, including an iron metre
- Unit.standard
- SI
- Unit.units2
- Nautical units
- Unit.inunits2
- ≈
- Unit.quantity
- length
- Unit.symbol
- m
- Unit.units1
- Imperial/US units
via Wikipedia infobox
Article
9 sectionsContents
- Spelling
- Etymology
- History of definition
- SI prefixed forms of metre
- Equivalents in other units
- See also
- Notes
- References
- Cited bibliography
The metre (or meter in US spelling; symbol: m) is the base unit of length in the International System of Units (SI). Since 2019, the metre has been defined as the length of the path travelled by light in vacuum during a time interval of of a second, where the second is defined by a hyperfine transition frequency of caesium.
The metre was originally defined in 1791 by the French National Assembly as one ten-millionth of the distance from the equator to the North Pole along a great circle through Paris, setting as that quarter of the Earth's polar circumference.