The Metric System Encodes 18th Century Lab Equipment
owl writes:
https://markatwood.substack.com/p/the-metric-system-encodes-18th-century
Part one of this series argued that traditional units are good for daily life: human-scaled, body-derived, requiring no equipment. The metric system, I said, is for science.
I was being generous.
The metric system isn't a rational system derived from nature. It's a fossil record of what a late-18th-century laboratory could measure. Every "fundamental" SI unit encodes the instrumentation limits of the Enlightenment, wrapped in a story about universality and reason.
We covered this in part one [see below for link], but it bears repeating. The meter was defined as one ten-millionth of the distance from the North Pole to the equator along a meridian passing through Paris. This required a years-long surveying expedition that produced a measurement nobody else could verify.
The competing proposal was the seconds pendulum: a pendulum whose half-period is exactly one second, whose length anyone with a clock and a string could reproduce. They rejected it. The meridian definition was grander, more French, and completely impractical.
The original survey was wrong. The meter we use today isn't one ten-millionth of anything. It's defined as the distance light travels in 1/299,792,458 of a second, a number chosen specifically to match the historical platinum bar as closely as possible. The "rational" definition is a retrofitted rationalization of a measurement error from 1799. [...]
Note, the "part 1" referenced above is here: In Defense of Traditional Units.
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