Re:Someday aliens will land and all will be fine until we ex...
by fanf2 on Monday September 26, 2022 @07:58AM
(#32981999)
The metric system was based on the existing unit of time and the dimensions of the earth. The metre was originally defined as 1/40,000,000 of the circumference of the earth (through the poles and Paris). From the metre they derived units of weight and volume.
There was some debate at the time about using a pendulum with a 1s period to define the metre, but it was known to be less accurately reproducible than the geodetic version.
Their aim was to define a system that could in principle be recreated from scratch anywhere on Earth without necessarily relying on access to the physical prototypes. In practice the relative imprecision of the original measurements compared to the later demands of science and engineering meant that the prototypes became the definition.
Itβs interesting to compare with the British Imperial units reform in the 1820s. Part of that act specifies how to recreate the prototypes from physical properties of the units. When the Palace of Westminster burned down in the 1830s the ancient prototypes were destroyed. But the replacements were recreated from copies, not from the specification in the act. And not much later, the official definition was based on the metric system because the metric standards were manufactured to much greater quality.
There was some debate at the time about using a pendulum with a 1s period to define the metre, but it was known to be less accurately reproducible than the geodetic version.
Their aim was to define a system that could in principle be recreated from scratch anywhere on Earth without necessarily relying on access to the physical prototypes. In practice the relative imprecision of the original measurements compared to the later demands of science and engineering meant that the prototypes became the definition.
Itβs interesting to compare with the British Imperial units reform in the 1820s. Part of that act specifies how to recreate the prototypes from physical properties of the units. When the Palace of Westminster burned down in the 1830s the ancient prototypes were destroyed. But the replacements were recreated from copies, not from the specification in the act. And not much later, the official definition was based on the metric system because the metric standards were manufactured to much greater quality.