[beerandt]

Knots and nautical miles are interesting because the nautical mile was originally based on latitude: one minute (1/60 degree) of latitude was 1 nautical mile.

So an airplane traveling due north at 120 knots would cover 2 degrees of latitude per hour.

Most of the US Customary and British Imperial units actually have similar logical definitions or derivations, but they aren't regularly taught anymore.

[taeric]

Right. My point was more that in industries where there is some advantage to keeping a non SI unit, they are want to do so without major external pressure.

So, knots persist because lat lon persists. Home cooks persist with imperial in some places because nobody cares to reprint all recipes and measuring devices. Astrological units because at that scale... Nothing scales. And computers, because binary won. (Curious to consider if ternary had been the winner...)

I confess I am actually personally moved by some of the intuitive arguments for older measurements. Usually very physical based and very in tune with numbers actually used in an industry. It is odd to think of a sixteenth inch wrench, but it is just the natural result of dividing by two, four times, after all. (That is, you have a measuring rod, put a midpoint on there. Four times. Now, do the same for millimeters?). (granted, in the age of computers, any measurement is much easier to do at the machining level.)

[beerandt]

16ths and even 32nds are common wrench increments.

>Usually very physical based

Land records in the US are all feet, acres, furlongs, arpents, sections, and townships.

That's not changing.

And they all divide easily from townships of 36-square miles to 10-acre quarter-quarter-quarter-sections to 66x660ft-acres.

66 ft is a gunter's (surveyors) chain = 100 links

10 chains = 660ft = 1 furlong = 1/8 mile

It's a brilliantly thought out system, but most people promoting SI won't take the time to see the benefits.

Personally, I find it much easier to make blunders with SI, because a decimal shift one place over isn't always an obvious mistake.

[taeric]

Sounds like you and I would be in violent agreement. :D