One of the best arguments for using the International System (SI) is the alternative: the chaotic collection of confusing, illogical non-SI units we use in the United States, known as customary units (not imperial units). This measurement mess means that we Americans are ignorant of much of the quantitative information we encounter. We can’t use it, relate it to other information, or calculate with it. It’s just a bunch of arbitrary numbers.
We have counted more than 300 non-SI units of the many more that exist. They’re used in various businesses, industries, trades, sports, and scientific fields. We may have some understanding of those we work with—even if we can’t define them—but most of these units are just meaningless names. Sometimes, the same name for several unrelated units! Look at all the units called “ton”. Do you know the difference between a short ton, displacement ton, refrigeration ton, nuclear ton, freight ton, register ton, metric ton, assay ton, or ton of coal equivalent?
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