24 ms·
1 nautical mile (~6076 ft) is exactly one minute of arc at the Earth's equator. As a sailor, I wish that all miles were nautical miles because they have a real
by gp 3y ago
1 nautical mile (~6076 ft) is exactly one minute of arc at the Earth's equator.
As a sailor, I wish that all miles were nautical miles because they have a real meaning. What good is 5280 feet?
- delta_p_delta_x 3y agoMost other 'mile's are derivatives of the Roman mile which developed somewhat independently of the English units (foot, yard, inch, barleycorn, etc), ergo the weird conversion factors. The original Roman mile was 5000 Roman feet. In fact, 1 nmi ≡ 1.852 km exactly. Also from the original definition of the metre: 1/60 × 1/90 × 10^7 = 1851.85185185... m. Inter-convertability was a defining trait of SI (or more precisely, its predecessors, MKS and CGS) from the very outset, which is why we have 1 m ≡ 1 s ≡ 1 kg ≡ 1 N ≡ 1 Pa ≡ 1 J ≡ 1 A ≡ 1 C ≡ 1 V ≡ 1 Ω ≡ 1 F ≡ 1 W ≡ 1 Wb ≡ 1 T ≡ 1 H ≡ 1 Hz (I use '≡' loosely here to suggest conversion factors, rather than its usual meaning of equivalence). The only outliers in the SI are the kelvin, the mole, and the candela (and derived units from these). The former two are dealt with straightforwardly with the Boltzmann and Avogadro constants. I have issues with the presence of the candela in the SI.
- skissane 3y ago> Most other 'mile's are derivatives of the Roman mile which developed somewhat independently of the English units (foot, yard, inch, barleycorn, etc), ergo the weird conversion factors. The original Roman mile was 5000 Roman feet. Pre-metric Europe was full of units with weird conversion factors, based on a shared heritage (mixture of Roman and Germanic), but with lots of divergent evolution subsequently. England didn't really stand out; France, Spain, Italy, Germany, etc, were really no different. Then the Continent did away with most of that complexity by adopting metric, and for whatever reason the English dragged their feet on doing that, and their American offshoots even more so. But the fact that people have forgotten that the French/Germans/etc used to have feet/inches/miles/pounds/etc too, [0] albeit with somewhat different definitions, makes people think English units were somehow unique. They never were. The uniqueness is in the slowness in replacing them with metric, not the units themselves. [0] They still have some of these units for certain purposes. In France and Germany, the pound is still used, albeit redefined to be exactly 500 g. Nautical miles are used in maritime and aviation applications; American influence (and to a lesser degree British) led to the adoption of the Anglo-American foot as the unit of altitude in aviation – the foot French pilots use to measure altitudes is the English foot not the old French foot; etc
- delta_p_delta_x 3y ago> American influence (and to a lesser degree British) led to the adoption of the Anglo-American foot as the unit of altitude in aviation There are a few notes I have regarding this. The Airbus consortium initially set up the Airbus A300 cockpit entirely in SI units, but they realised this wouldn't sell well in the US, and they switched to feet and flight levels. Airfield weather data, including pressure and temperature readings in everywhere but the US are given in hectopascals and degrees Celsius. Many post-Warsaw Pact countries (Russia, China, Uzbekistan, Belarus, Ukraine until recently) used to have a completely metric unit setup for their air traffic controls. Both Boeing and Airbus cockpits have settings to output altimeter readings in metres. > Then the Continent did away with most of that complexity by adopting metric, and for whatever reason the English dragged their feet on doing that, and their American offshoots even more so. If there's one export of the US I despise more than anything else, it is making legacy non-SI units relevant again because of its outsize influence in traditional and social media. I live in a country that metricated half a century ago, but I have Gen Z friends who measure their heights in feet and inches, and their gym weights in pounds. What the absolute hell. The SI units are the pinnacle of standardisation and the culmination of a three-hundred-year long effort to make life easier for everyone. I have no idea why the richest country in the world can't metricate properly. Get rid of legacy units, and we save billions in not printing the (XX fl. oz), (XX lbs), or (XX oz) on food packaging alone. It is ironic that a country that did away with colonialism, a whole lot of tea, and embraced the French and their revolution, never embraced the French units, but stuck with the English units.
- Mountain_Skies 3y agoBase ten is an unfortunate numeric choice and responsible for much of the hesitation to switch to metric. Maybe someday when we have millions of O'Neill Cylinder colonies, one of them will adopt base twelve instead, at which point the main reason against metric would go away.
- skissane 3y ago> Base ten is an unfortunate numeric choice and responsible for much of the hesitation to switch to metric. Maybe someday when we have millions of O'Neill Cylinder colonies, one of them will adopt base twelve instead, at which point the main reason against metric would go away. I've heard this argument many times before, but I don't think it makes much sense. The US customary / British imperial measurements are not consistently based on base 12. Yes, there are 12 inches to a foot; but there are 16 (not 12) ounces in a pound, and 128 (not 12 or 144) US fluid ounces in a US gallon (versus 160 UK fluid ounces in a UK gallon). Fahrenheit has 180 degrees between the freezing and boiling points of water, with water freezing at 32 degrees – none of which has much to do with base 12 either. There is no widely used unit corresponding to 12 feet or a twelfth of a mile. If you really want a system of units based on base 12, the US customary / British imperial system ain't what you are looking for. Also, it ignores the fact that you can metricate while keeping a foot of 12 inches, if you define a new "metric foot" composed of 12 "metric inches". This has been done before – as I mentioned in an earlier comment, many European countries kept the pound when metricating, by defining a new "metric pound" of 500 g. Given the current standard US-UK inch is exactly 25.4 mm, one option would be to have a metric inch of 25 mm (= 2.5 cm), twelve of which would give a metric foot of 300 mm (= 30 cm, versus 30.48 cm exactly for the standard US-UK foot). Sure, having two different foots and inches (old and new) coexisting for a while might cause some confusion; but if the confusion isn't worth it, maybe base 12 isn't really worth it either. And to avoid the confusion, you could always give the new metric units different names ("moots and minches", maybe?)
- earthboundkid 3y agoChina had their own mile. “The journey of a thousand miles begins with a single step” was actually only around 300 English miles long.
- Aerroon 3y agoThe modern Chinese li is defined as exactly 500 meters.
- earthboundkid 3y agoLaozi had some foresight to use meters in 500BCE.
- hashmush 3y agoAnd, similarly, the 斤 (jīn) is defined as 500g.
- labster 3y agoKilogram is also an outlier, as it is the only base unit that comes with a magnitude prefix.
- Aachen 3y agoThe base unit is gram, not sure what you mean
- thomas2718 3y agoThe base unit is indeed the kilogram, see https://www.bipm.org/en/measurement-units/si-base-units https://www.bipm.org/en/measurement-units/si-base-units.
- _dain_ 3y agoI wish those medieval people had defined it as 5040 feet, then it would be divisible by 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 24, 28, 30, 35, 36, 40, 42, 45, 48, 56, 60, 63, 70, 72, 80, 84, 90, 105, 112, 120, 126, 140, 144, 168, 180, 210, 240, 252, 280, 315, 336, 360, 420, 504, 560, 630, 720, 840, 1008, 1260, 1680, and 2520.
- chungy 3y agoConnecting 1 mile to 5280 feet happened many centuries after the medieval period. Such precision wasn't really possible nor desired before the 18th century. To be specific, 5280 feet = 1 mile didn't happen until 1959 and the United States needed higher precision and remove all the fuzziness out of the units. It might be inconvenient on some aspects, but it was also "close enough" to what miles were already established to be.
- _dain_ 3y ago>To be specific, 5280 feet = 1 mile didn't happen until 1959 and the United States needed higher precision and remove all the fuzziness out of the units. It might be inconvenient on some aspects, but it was also "close enough" to what miles were already established to be. uh what? are you sure you're not mixing that up with the international geophysical year or something? the mile has been 1760 yards since before the US even existed. it's called the imperial system because of the british empire. they couldn't have done the great trigonometrical survey of india without an accurate mile.
- twic 3y ago1959 must be referring to this: https://en.wikipedia.org/wiki/International_yard_and_pound https://en.wikipedia.org/wiki/International_yard_and_pound
- HPsquared 3y agoFor reference, 5280 = 2^5 × 3 × 5 × 11 (8 prime factors, 4 distinct) So 5280 is better if you want to divide by 11, I guess! What a strange thing, how on earth did it end up with a factor of 11 in there... Edit: it's complicated: https://math.ucr.edu/home/baez/inches.html https://math.ucr.edu/home/baez/inches.html
- burlesona 3y agoInterestingly, a mile was originally the less surprising 5000 feet. But in the 1500s the English changed the mile to be 8 furlongs, as that made for much easier math around the agricultural measurements of the time. https://en.m.wikipedia.org/wiki/Furlong https://en.m.wikipedia.org/wiki/Furlong
- opwieurposiu 3y agoA mile is 5280 feet because it is 80 chains (survey chains) long. The chain's length is a byproduct of English land tax laws which were by the acre. The roman mile was 1000 paces, or 5000 feet, which made a bit more sense. https://en.wikipedia.org/wiki/Gunter%27s_chain https://en.wikipedia.org/wiki/Gunter%27s_chain
- CapitalistCartr 3y agoFor those of you marvelling at Romans having a five foot (1.5 m) stride, a Roman pace was two steps, counted from the left foot down to left foot down again.
- dullcrisp 3y agoYou’ve ruined my mental image of the Romans all walking like John Cleese.
- EdwardDiego 3y ago[dead]
- quickthrower2 3y agoLike the marching hammers in Pink Floyd’s The Wall music video
- rootusrootus 3y agoIn my experience many people define pace the same way today. We were taught in Boy Scouts how to pace off a distance measuring 5 feet per pace, or every other footfall.
- romwell 3y agoThat's to account for possibly different (average) left/right steps. Averages out better.
- throwawaylinux 3y agoI'm not a sea dog (or air dog), but even absent electronic calculation and navigation devices of the last half century or so, is there any real advantage to using nm vs any other unit? Other than for the presumably niche case of traveling exactly directly along the equator, that is. nm are great because charts and speeds are in units of nm and kt of course, but what does "real meaning" give you exactly?
- ryandrake 3y agoTo be precise, a nautical mile is always a minute of latitude, everywhere on earth. It is only a minute of longitude at the equator.
- throwawaylinux 3y agoAh, good point. In that case expand the niche cases to traveling due north or south.
- wkat4242 3y agoAnd, at sea level. At altitude this no longer applies either because the circumference at altitude is greater.
- closewith 3y agoWell, it still applies in aviation, as distance and ground speed used in navigation are measured at sea level irrespective of altitude.
- pbmonster 3y ago...by around 0.1%. Which is why nobody is bothering with it, considering how susceptible to wind speed distances and velocities are up there.
- jabl 3y agoIn practice, when navigating by pen and paper, what you do is you measure a distance on the chart with a divider, then you put the divider (with the previously measured distance set) to the north-south scale on the side of the chart to read out the distance in nautical miles. Now, of course, in principle charts could have a separate scale for distances in km, and we could use km for navigation just fine. But, well, I've never seen a nautical chart with such a scale.
- Jedd 3y ago> I wish that all miles were nautical miles because they have a real meaning. Could you define 'real' here please? This feels like one of those 'customary is better because you can't divide 10 by 3 using only integers' claims. You seem to be asserting that once you divide a circle into 360 arcs, then at a a certain distance from the focus, one of those arcs has a certain meaning. I would say that because ~ 2 millennia ago the Greeks pinched the Babylonian's use of 360, and the Babylonians came to that number by perfecting a rough days-in-a-year measurement used for astronomy over the previous 2 millennia, a nautical mile now has a derived / coincidental meaning, more so than a 'real' one. EDIT: And this is before contemplating the complications of living on an oblate spheroid - the NM's length depends on where you are.
- nmilo 3y agoEach of those arcs do have a meaning, they're called 'degrees' and any human being whose not being obtuse for the sake of argument would tell you that they're 'real'. The point of calling nautical miles 'real' is that you can do easy mental math with them to express a distance in terms of latitude and longitude.
- wnoise 3y agoWell, latitude, or longitude at the equator.
- Jedd 3y agoI think you may have missed my point. The actual length of a nautical mile only makes sense because we have this weird way of measuring earth (based on how we measure circles). NM's were obviously defined using that weird numbering system - 360 degrees in a circle, 60 minutes in a degree, 60 seconds in a minute - so it shouldn't be a surprise that they 'feel real' within that system. Given a quarter of the circumference of earth is ~ 10,000km, it seems ripe for using base-10 and metric units ... but for the fact, obviously, that these arc-based-at-6-thousand-km-from-the-centre measurements are highly variable and not hugely useful. > The point of calling nautical miles 'real' is that you can do easy mental math with them to express a distance in terms of latitude and longitude. And that's not true either. At best it works for latitude -- even a small way from the equator you'll suffer the effects of longitudinal meridians converging. But at that point, why not just do your mental math in minutes rather than (yet another) mile variant?
- soligern 3y agoWhat good is a mile to begin with. Just use kms and then we have a nice round figure. Being from the US and as someone that does a lot of woodworking, I’m very used to inches but I can’t do anything beyond basic calculations in inches and always have to pull out a very specific carpenters calculator. It’s not trivial to add up 2’13/32” + 5’11/16”, there’s too much carrying over and doubling to equalize the denominators to do easily in your head. That’s just addition, dividing is a whole other beast.
- paulddraper 3y agoIDK if 2.40625 + 5.6875 is any easier :) Inches using base 2 for the fractions is useful.
- spiderice 3y agoYeah, I don’t think woodworking is the best example for arguing that metric is better than imperial. In fact, it’s one of the few disciplines where the imperial system as a decent argument for superiority.
- kozak 3y agoMetric woodworking just uses integer millimeters for everything.
- ggm 3y agoWoodworking measurement has two forms: lumber, which is notional, pre drying, shrinkage and rough handling, and cut, which is required to be beautiful. Sometimes, it isn't about feet and inches as much as "the same"
- bialpio 3y agoPlumbing is another example where imperial works and is even used in Europe. It doesn't matter that a pipe is 3", it may as well be called "type B", since all you care about is if it's big enough for the purpose (you look that up in building code) and if the parts match together. The moment you need to perform calculations is when imperial becomes a total PITA to use.
- mcpackieh 3y agoWhat good is converting miles into feet anyway? I've never found a reason to perform that conversion, or reverse. A mile is just an arbitrary unit of distance that doesn't need to be related to any other. Even in sports, swimmers may casually call a 1650 yard swim 'a mile' but if you do the conversion it isn't. That doesn't matter to anybody though. To be perfectly honest, I never remember how many feet are in a mile and the only times I've looked it up have been to calculate some meaningless trivia like how many tape measures it would take to stretch across the country, or some useless nonsense like that. Even then I usually just approximate 3 feet to a meter and 1.6 km to a mile, close enough.
- Timon3 3y agoThe most simple example is adding or subtracting distances. You might say you don't need that, but I'd wager most people need to at some point.
- mcpackieh 3y agoAdding miles to miles or feet to feet make sense, but when do you add feet to miles?
- Timon3 3y agoCan you really imagine no scenario when this might happen? Like "A to B is one mile, B to C is 200 feet, how long is A to B to C"? You've never come across anything like this in your whole life?
- nojvek 3y agoAgreed. When I learnt about nautical miles and knots (nm/h) which is both used by aviation and sailors, I feel we should be using nautical miles for all travel distance. Miles really don’t have much meaning. If someone goes at 60 nautical miles per hour (111.112 km/h), for 360 hours (15 days), they cover the circumference of the planet around the equator. I.e go around the planet.