Keywords: meter, standards, metrology
In my post Metrology is not about the weather. Part I – How to weigh a potato, I mentioned that international standards used to be based on physical artifacts. I just came across this short article, The Last Original Standard Metre by Atlas Obscura. The cover picture is of one of the original such artifacts. (Picture credited to BridgetZoe [Atlas Obscura User].) I didn’t know that, “To define the meter, French astronomers Delambre and Méchain measured 10 millionths of the distance from the North Pole to the Equator through a Paris meridian.”
The nautical mile has a similar definition. It was historically defined as one minute (1/60 of a degree) of latitude along any line of longitude. If you don’t know, meridians (lines running from pole to pole) connect points with the same longitude.