• rbos@lemmy.ca
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    3 days ago

    This hurts my brain. Why do we care about all the weird fractions? +/- 0.1 is just another way of saying 1/10. You can still do that if you want without having to do fraction math in random denominators.

    • ryathal@sh.itjust.works
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      3 days ago

      The fraction allows you to communicate length and tolerance in a single number. A decimal implies precision to the last number, a measure with a fraction can show 1/8 as more granular than 1/16. 1/8 of a cm is less precise than a mm, but if you wrote 1.125 cm, you are now implying sub mm level precision.

      This matters because the level needed in building generally doesn’t line up to 1/10 measurements. For example if you had a brick wall and a row had 1 cm height differences between bricks in a row it would be extremely obvious and look terrible. A 1mm height difference would be impossible to notice, but is also overkill to get that level. Ideal is about 5/8 cm or 6.35 mm difference over 3 meters of wall. The fractional measure often ends up easier to work with in practice.

      • rbos@lemmy.ca
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        2 days ago

        “The fraction allows you to communicate length and tolerance in a single number”

        I don’t see how that isn’t true of decimals, too. 0.1 indicates a precision of 1 digit, 0.12 indicates a precision of 2, 0.120 indicates a precision of three.

        • ryathal@sh.itjust.works
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          2 days ago

          Exactly like my example above. 1/8 implies +or- 1/16. While .125 implies +or- .0005, but it was only measured to +or- .0625, which is 2 orders of magnitude different.

          • rbos@lemmy.ca
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            2 days ago

            In any context where it’s important, you’d note it with +/-. Not really a problem.

            I guess there’s nothing wrong with saying 1/8th metre, 1/8th centimetre, 15/16th metre either. Just as some people might use 0.356 inches.

            • chiliedogg@lemmy.world
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              2 days ago

              I’d be a big fan of fractional metric.

              Although if we really wanted to go crazy (this will never happen), we’d ditch base-10. It’s a stupid base that we only use because of our fingers. Base 12 is superior and is actually the strongest defense of feet and inches (though yards can fuck right off). It has 6 divisors whereas 10 only has 4.

              Base 60 is also cool (divisible by 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, and 60), but that would also be significantly more difficult to teach children - it takes them long enough to learn the order of 26 letters.

              And being a geographer, I adore 360 because it’s fucking awesome to work with, and you don’t get a better composite until 2520, which is just too much to deal with.

              • rbos@lemmy.ca
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                1 day ago

                yeah, a duodecimal metric system would have been better. Still, it’s more important to have a standard system than it is for it to be ideal. It’s the strongest argument for US customary system within the USA, as well - but that argument breaks down when you widen the scope to the world.

                In the 18th century context, and its dozens of competing measurement systems, something like the metric system was sorely needed just for standardization. We’re just lucky that it was something more or less sensible. Had the US customary system won out, I think we’d be objectively worse off.

                So it could have been better, but it could also have been MUCH much much worse.