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by FoeNyx
2178 days ago
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> I know imperial was invented by the British, but it's largely just the US left using it According to wikipedia, the US do not use the "Imperial System" but the "United States customary units" and they are not exactly equivalent, although they both derive from the "English units ".¹ Also, from the article: "The international foot is exactly 0.3048 of a meter". And it seems the international yard and pound are defined using the SI units as the reference.² (Edit: So by transitivity they also are defined using caesium-133 atom's radiation, light speed in vacuum and Planck constant.) ¹ https://en.wikipedia.org/wiki/Comparison_of_the_imperial_and... ² https://en.wikipedia.org/wiki/International_yard_and_pound |
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Then in 1959 the major non-metric countries (I want to say US, UK, SA, AU and NZ?) unified their units under the "International Yards and Pounds". This metrified the definitions of various non-metric units.
So for all the units with an "international" version, "US customary" and "imperial" are now the same thing (though the pre-international versions might still be used in some contexts e.g. US surveyor units are, in fact, pre-international US customary units), and there are units which were not unified, most notably units of volume which remain different in the US and in imperial dominions.