Yes, it’s from a book called “Uncle John’s Bathroom Reader” and that book was resting on a closed toilet seat in a nation that only kind of uses the metric system in certain situations… however, you’d be surprised how much you can learn after a single visit to any local fast-food joint!
The metric prefix system is a fantastic invention, akin to the arabic number system. Honestly it’s surprising no one came up with it sooner… but (and I’m sure I’ll catch some flak for this) the metre is an awkward length - it’s too big for human scale measurements. The decimetre is not as bad but still not very good, and it’s also not commonly used. The centimetre has the opposite problem - it’s too small for the human scale but too big for precision work.
Don’t get me wrong, the horrible conversions between imperial units make the system unusable for me, but the unit lengths themselves are scaled to humans because they weren’t initially defined arbitrarily by some committee (why should the distance from the pole to the equator be used as the baseline for a measurement used by humans?). I think the inch and foot are great lengths to use on a daily basis, they feel quite natural.
What annoys me the most is that we could have had the best of both, since the foot and inch are only a factor of 12 apart, so we could have had a metre measuring about one foot and a decimetre measuring about an inch.
All measurements are arbitrary. This feels like that Fahrenheit debate where “60 feels natural for room temperature” as if anyone has any idea what number a room should be. A meter is just a chunk of distance about this size (holds hands apart). There’s nothing a foot can add to a measurement that a meter can’t. You’ll need fractions and smaller or bigger units in all real world cases anyway, so having easy conversions is much more useful than a “natural” base unit.
Perhaps in a perfectly rational world, but humans are silly creatures. The human brain evolved to deal with small numbers. Distinguishing one vs two lions is important, but distinguishing 14 vs 15 lions is not, so our brain immediately recognises numbers up to about six and has to rely on conscious counting for anything larger. If I told you that “This dog is two ducks tall” you’d have a pretty good idea of how big the dog is, but if I said it was “20 mice tall” you might have trouble visualising, or worse “450 ants tall” at which point I would have no idea. Our brains don’t innately have the ability to accurately conceptualise large numbers, which is why the metric prefix system works so well - it keeps numbers relatively small. I think the same logic applies to decimals and fractions. Simple fractions like halves through to perhaps fifths can be visually conceptualised at a glance, but beyond that it requires calculation.
What that means to me is that ideally your measurement unit should be big enough to be able to measure most things you deal with on a daily basis using no more than say 10 units (arbitrary, I could be persuaded down to 6 or up to 20), and still measuring most things without going smaller than about 0.2 units. As an example, consider human height (after all, what could be more a more human measurement?). The average person is between 1.5 and 1.9m tall, which is not a great start since we’re riding close to the 0.2 ‘lower resolution’ just describing the whole range. You could use centimetres but then you’re looking at 150 or 190 which is much too large to visualise nicely. Decimetres is better but not great. Feet is a pretty good fit for this, since that’d be about 4.9 to 6.2 ft. We haven’t violated either the max or minimum requirements and we still have a decent resolution within the range too.
I agree, but my whole point is that we didn’t have to choose!
Well that would be because you use them on a daily basis. I find meters and centimeters perfectly natural too, and would be hard pressed to think of a situation where the scale of inches and feet would be strictly better.
Nice try! I live in a metric country and use exclusively metric units.
How do you know how it feels to use imperial if you exclusively use metric? And daily!
Because I have had to work with American companies as part of my job for the past couple years. For the entirety of my personal life and the rest of my professional life I use metric. I’ll grant you I should have said ‘almost exclusively’ in my previous comment, but I think that’s just splitting hairs.
For both philosophical and scientific reasons, they wanted a definition that could be recreated any where in the world, certainly not the thumb or foot of any one man. With the “distance from pole to equator” definition, you just need to measure a long north-south axis (say a few hundreds km), and knowledge about the figure of the Earth helps you scale that to the full definition. You can do that anywhere on Earth.
Another considered definition was the length of a pendulum whose half period is 1s, but even at the time the effect of local gravity was deemed to be too much
That’s not the point I’m trying to make. You can derive a length from any number of physical constants to make it reproducible, but considering the divisor of exactly ten million suggests the metric committee were far more interested in making something ‘clean’ than something human-friendly. They could have basically done what they do with the modern redefinitions of the metre - the distance travelled by light in 1/299792458 ths of a second. Obviously they chose that number to keep the definition in line with the original, but they could have done that with the original definition to make the metre basically any length they wanted, but they didn’t.