Because there's 90 degrees in a right angle. And 3600 seconds in an hour. We're not completely decimalised.
Traditionally nautical miles and knots where used because it made calculations easy. It makes sense to use a unit of length that is directly related to latitude and longitude. The nautical mile is one minute of latitude.
These days with calculators we could use attoparsecs per month but most folk are too lazy to do the conversion.
Because its universal maritime language. Much the same as the collision regulations span all corners of the globe, so mariners universally know them. Regardless of where they are from. So it remains with knots/nautical miles.
It makes sense when you consider that shipping is global, to keep everyone on the same page.
Just googled the original definition of the metre. Which is 1/10,000,000 of the distance pole to equator.
en.wikipedia.org/wiki/Metre#Speed_of_light_definition.
So if there were 100 degrees in a right angle and 10,000 seconds in an hour, a knot would be a couple of even factors of 10, one way or the other, of a kph. Yes we should push for further metrification.
but with the poles moving all over Canada towards Siberia we'd have different speeds each week! 
Select to expand quoteJethrow said..
but with the poles moving all over Canada towards Siberia we'd have different speeds each week!
Is that why the wind feels stronger on some days 
Global warming comes into it too. Rock expands as temperature rises, and so does the water in the ocean. If a knot is defined by geophysical measurement it will gradually get longer.
I briefly worked in America where they used Decimal feet, work that one out.....
What is 11.5 feet is that 11foot 6 inches or 11foot 5 inches....??
1 inch can make a big difference as my wife keeps saying.
Select to expand quoteMr Milk said..
Global warming comes into it too. Rock expands as temperature rises, and so does the water in the ocean. If a knot is defined by geophysical measurement it will gradually get longer.
If that was the case, so would the KM.
The current definition of the metre dates from 1983, and it fixes the metre in terms of the second and the speed of light. In practice, the metre is realised by measuring the frequency or vacuum wavelength of specific types of lasers."The metre is the length of the path travelled by light in a vacuum during a time interval of 1/299 792 458 of a second."
There only three primitive countries that have not converted to the metric system; Myanmar, Liberia and the United States.
Select to expand quotetbwonder said..
Traditionally nautical miles and knots where used because it made calculations easy. It makes sense to use a unit of length that is directly related to latitude and longitude. The nautical mile is one minute of latitude.
These days with calculators we could use attoparsecs per month but most folk are too lazy to do the conversion.
...but Andrew, what if we were to travel in a longitudinal direction? Would it not make sense to mandate a conversion to the measurement from knots? I say we go back to the traditional metric of furlongs per payday!
All of the above and it makes no sense to be calculating angles of latitude when the world is flat!
It makes sense to use nautical miles if you are navigating on a ship or in an aeroplane. The unit is not an Imperial unit like we used to use or that the USA still uses. That system uses a Statute Mile. Lines of Longitude originate from True North not magnetic north. The Earth's magnetic field keeps changing but the position of the North and South Poles don't. Using nautical miles is really easy with maps because everything is done in degrees.
Select to expand quoteGuru4 said..
All of the above and it makes no sense to be calculating angles of latitude when the world is flat!
If it is flat then how do all the people keep it balanced. All those people to the north of us must cause the earth to tilt downwards away from us.
Select to expand quoteremery said..
There only three primitive countries that have not converted to the metric system; Myanmar, Liberia and the United States.
As a Liberian, I resent being grouped with that lot.
(Actually, not Liberian nor related to any librarians and haven't been to a library in years.)
Select to expand quoteremery said..
There only three primitive countries that have not converted to the metric system; Myanmar, Liberia and the United States.
The medical field and car manufacturers are metric in the US. My understanding is the US military also uses metric. In science, metric is also used. So "only" regular people are resisting the change.
Select to expand quotesegler said..
...and the UK.
As a reluctant englishman, i have to partially agree with you. We appear to use both systems, the imperial, as the name suggests is to appease the pompous tossers that sadly remain in power, and the metric by those who look towards the rest of the world for help and guidance. It is however handy to have tape measures which record both, for those who both surf and windsurf, as surfboards appear to have escaped the metric system (except for volume????) but windsurfing has fully embraced modernity. I do, actually use the nearest figure on a tape measure for ease, ie something could measure 1m 2" or another 2'1cm. Perhaps that is why we are rubbish at making boards.
Select to expand quoteWillyWind said..remery said..
There only three primitive countries that have not converted to the metric system; Myanmar, Liberia and the United States.
The medical field and car manufacturers are metric in the US. My understanding is the US military also uses metric. In science, metric is also used. So "only" regular people are resisting the change.
It is all about manufacturing. The cost of converting would be enormous so they have kept it as it is. No big deal. I was a kid when we went from Imperial to Metric so I had to learn both systems. Not too difficult if you don't overcomplicate things by trying to convert. I worked in aviation where we used both systems depending upon where it was made. Best of both worlds!
I think the biggest change in my thinking came when speedo's in cars changed to Metric. After that, thinking in metric became more normal. All the USA have to do is change their speedo's......
Volvo, being made in Sweden, continued to use imperial in their cars until the late 70s. I had a 1974 Volvo 245 wagon that was easy to work on with my American tools and imperial nuts and bolts.
But yes, the issue is tooling, and the USA ain't no dinky little installed base of imperial-based hardware going back 150 years. Think of all those screw and bolt threads and pipe threads. It is happening in the USA, albeit slowly. Everything new in the USA is metric now. Vehicle speedos show both, but road signs and plumbing are still stubbornly imperial.
My toolbox at home is heavier than it needs to be because i have to keep both sets. Is it 17mm or 5/8" ?
Select to expand quotejontyh said..
windsurfing has fully embraced modernity
Except for one well known foil and board company that mixes the two like a teen mixing drinks. Foil mast is in inches, foil wing area in cm2. Board length in feet/inches, volume in l. Why?
And then wingdings came along and continued the misery. I'm looking for a 95 l board maybe 5' 6" to go with my 5m2 wing. Really?
fwiw, American car speedos have had km/hr for ages. Probably not 1 in 20 or even 50 could tell you what the speed limit is in km/hr is though. And, like Segler, my wrench drawer is divided into the Hatfield and McCoy sides.
en.wikipedia.org/wiki/Hatfield%E2%80%93McCoy_feud
Its all about reality and living in the real world.
You engineers would love to have a universal measuring system.
Guess what? Real world means you have to adjust and adapt!
I suggest real world is - metric easier.
10mm plus 19mm is way easier than 3/8" plus 3/4"
I do like having both sets though. you can use imperial drill bit for a hole to accept a metric bolt so it has a smidge of wiggle
I agree "easier", but POV, tradition, bias,human nature, and we all come from didderent backgrounds.
Hey LeeD,
Is the word Didderent, the imperial version of Different.......
Its about 1/8 of an inch apart on the keyboard.
