Meter is the standard unit of length used by most countries around the world. But how did they define it?

Hosted by: Hank Green

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Sources:
https://www.nist.gov/sites/default/fi...
http://www.surveyhistory.org/the_stan...
http://physics.nist.gov/cuu/Units/met...
http://www.npl.co.uk/educate-explore/...
https://www.nist.gov/sites/default/fi...
http://www.us-metric.org/origin-of-th...
https://nature.berkeley.edu/classes/e...

Image Sources:
https://commons.wikimedia.org/wiki/Fi...
https://commons.wikimedia.org/wiki/Fi...