Yes, the metre used to be defined as; “1/10 mill.-part of the distance from the North Pole to Equator, along the meridian of Paris”.
I.e. 1/2 of earth’s diameter as measured “from pole to pole”. (At the poles the diameter is Zero)
Another interesting fact is that the Nautical Mile has also changed definition over time:
Luckily the US eventually followed the rest of the world on this one.
Maybe there are still hope that the same will happen again before more expensive mistakes are done??
Connecting to the circumference of the earth was obviously a bad move. Blame the French Academy of Sciences. Having a tradesman design the system would have been better.
The meter should have been made equal to a fathom. (roughly the span of between fingertips with the arms fully outstretched.
Than we wouldn’t be having this diameter / circumference confusion and the meter would be less abstract. It also would make the cm about 0.7 inch which would be more useful.
That ties the meter into feet (6 feet = 1 meter). Define 4 cubits as exactly equal to one meter (6 feet or 1 fathom) and that ties into Vitruvius’ system.
Vitruvius, the architect, says in his architectural work that the measurements of man are in nature distributed in this manner, that is 4 fingers make a palm, 4 palms make a foot, 6 palms make a cubit, 4 cubits make a man, 4 cubits make a footstep, 24 palms make a man and these measures are in his buildings
The purpose of the metric system was to get away from the size of the feet, arms or whatever other parts of the body of long dead English Kings.
The standard meter was not “abstract”, but physical present in the form of an iridium rod kept at constant temperature in Paris:
The foot is now defined by it’s exact length. in cm.:
Just to make it more confusing. other Imperial and US Customary units are not the same either:
As recently as WW1 (Which admittedly was over 100 yrs ago now! But I’m 81 and it seems like just awhile ago!) wood was considered such an essential structural material for airplanes and ships that the War Dept. (ancestor of DOD) sent soldiers into the wood of WA & OR to ensure that Sitka Spruce & Douglas Fir production kept up with war demands! There was actually a Sitka Spruce Commission established but it’s one of the rare govt. agencies that has disappeared without a trace! But here’s an interesting short article about the extent to which the US Govt. went to keep the structural wood supply flowing: Army Spruce Production Division
As you’ll read, it was actually in part a labor unrest response because the “Wobblies” (WOW) and the AFL were fomenting a lot of labor activism agains the admittedly really bad working conditions in the woods of those days. But as you can see from the pictures, the Army guys really got into it with over 200 camps in the woods and spruce splitting contests (that one on the Seaside, OR beach is about 8 miles from the Columbia River entrance).
Thus the affection of the US Navy for use of “yards” in estimating ranges for gunnery: 1 nm = 2000 yds (+26.7 if you’re counting!). One assumes that’s perhaps since most American boys are comfortable with eyeballing 100 yds from their sandlot football days. Don’t know if that works so well outside the US since soccer pitches (here at least) typically vary according to age & level of players from 60-70 yds. up to over 120 yds…
The length was arbitrarily decided and could have been anything we wanted. It was originally defined as one ten-millionth of the distance from the equator to the North Pole along a great circle, which is fairly abstract.
The first official meter bar wasn’t invented until years later and has been changed multiple times since then as the meter has been redefined.
For me as SI guy, acre-inch and acre-foot, miles per gallon are interesting concepts. And small AWG’s correspond to the large sections. Also never got used to sheet metal gauges.
To add insult to injury, there are often different definitions for a given unit name, many tons (from masses to refrigeration power) and there are also several “miles”.
As a side note, the Indian digit grouping is interesting too.
I even always wondered how it mentally works to sort imperial wrench sizes.
And when performing even basic engineering computations nothing is coherent when it comes to units of measurement.
I grew up in the SI world, excepted for people’s heights I need to convert mentally. If woman is 5’11" I visualize the height without the need for a unit conversion but I’ve no clue about something like 5 19/128" nor 521 °F.
At a engineering class many years ago I referred to something as being so many centimetres long.
I was admonished by the instructor to use the correct SI unit and centimetres were only used by dressmakers.
Even below absolute zero temperature, which corresponds to −273.15 °C on the Celsius temperature scale and to −459.67 °F on the Fahrenheit temperature scale.
Source: Absolute zero | Definition & Facts | Britannica
The first standard meter was a bar of iron, which was prone to elongation / contraction depending on the temperature. Copies were placed around in Paris for people to calibrate their own measuring stick against.
In 1875, the Treaty of the Meter, signed by 17 countries including the U.S., established the General Conference on Weights and Measures (Conférence Général des Poids et Mésures , CGPM)
A new Standard meter bar was created from platinum-iridium alloy.
The original was kept in a temperature controlled cabinet in Paris, but 30 replica meter bars were given to member countries.
