[delta_p_delta_x]

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.

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]

> 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]

> 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.

[BuyMyBitcoins]

The early US came tragically close to adopting the metric system, and on more than one occasion.

I invite you to watch this amusing and relatively short video by History Maters on the subject: https://youtube.com/watch?v=BtKbq_zAr-A&pp=ygUWaGlzdG9yeSBtY...

As an American I will say this, almost nobody genuinely thinks that our measurement system is superior. I suspect the majority of us know it’s a janky system but it’s so difficult to change.

That being said, I switched over to Kilometers on my iPhone because of Pokémon Go. I’ve actually gotten to the point where I think of walking distance in metric more readily than in fractions of a mile, so metrification is making progress in unexpected and exciting ways!

[db48x]

It’s not ironic, it’s economic. People had other things to worry about during the Revolutionary War, and then afterwards there was an industrial revolution. (The tax on tea might have been the straw that broke the camel’s back, but the protectionist taxes on goods manufactured in the colonies was the real killer.) Once that was in full swing changing the units was impossible.

Every machine in every machine shop was geared towards manufacturing dimensions and tolerances specified in inches, tenths, and hundredths. Changing to metric would have required rebuilding or replacing all of them. England had the same problem. They had the most manufacturing capability in the world, and they weren’t about to spend all that money replacing all of that machinery.

Worse, the SI system isn’t really easier. The SI units were designed to make unit conversions easier, but in practice nobody actually converts units. In the US Customary system (as in the English Imperial system before it), every common activity has it’s own units.

Houses and furniture are measured in feet and inches, and you never ever convert those to miles. Why bother? Miles aren’t useful for measuring cupboards or rocking chairs.

Cooking uses teaspoons, tablespoons and cups, but you never need to convert between spoons and cups let alone cups and gallons or barrels or hogsheads. It is handy to remember that a tablespoon is three teaspoons though, because that can save you some time at the holidays when you have to scale your recipes up to feed all of your relatives.

The SI system is not really any different in practice.

[seszett]

> People had other things to worry about during the Revolutionary War

Well, the metric system was devised in France mostly during the Revolution, with the size of Earth surveyed while at war with most of Europe in order to get a good basis for the length of the meter.

> Cooking uses teaspoons, tablespoons and cups

Or millilitres and grams, which are basically equivalent for liquids, so you only need a kitchen scale to do most cooking as long as it's not an American recipe, and it's extremely easy to scale recipes.

[mr_toad]

> People had other things to worry about during the Revolutionary War

Actually there are plenty of examples of countries adopting metric after a revolution or gaining independence, so perhaps the US didn’t adopt metric in spite of the revolution rather than because of it.

[p_l]

Industrial revolution had nothing to do with it, given that the inch USA uses today is an inch created by a pissed off engineer (gauge block Inventor Carl Johansson) in European company making gauge blocks, who defined an inch to be 25.4 mm @ 20 degrees Celsius in 1912 - created by taking a reasonable metric approximation in between British and American inches.

The popularity of Johansson's blocks is Brits changed their definition of inch in 1930 and USA followed in 1933. Most countries that still used inches started to use "industrial inch" of 25.4mm in 1930s, the rest went metric.

[skissane]

> It’s not ironic, it’s economic.

> and then afterwards there was an industrial revolution.

> Every machine in every machine shop was geared towards manufacturing dimensions and tolerances specified in inches, tenths, and hundredths. Changing to metric would have required rebuilding or replacing all of them.

I don't think this argument makes anywhere near as much sense as you think it does: the part of the US which lags the most in metrication isn't industry, it is in everyday life, K-12 education, and consumer products/services; the US manufacturing industry is significantly ahead of US consumers in the adoption of metric. Entire industries in the US have adopted metric (most notably the US automotive design&manufacturing industry has switched to mostly metric). If the real issue were about industry, you'd expect industry to have the biggest lag, not to be ahead of consumers.

I think the real reason is actually cultural. Almost every country which successfully metricated, did so with some degree of government coercion – "you are going to start using metric now, and we aren't giving you a choice about it". The US cultural emphasis on individual freedom led it to refuse to go down that path, insisting that metrication be voluntary only – which is a large part of why, decades later, so little progress has been made. Similarly, the UK's insistence on retaining miles for road distances is due to cultural and political reasons, not any practical concern – Australia successfully converted all its road distance and speed limit signs to kilometres, despite having much longer roads than the UK does

Also, for all that US insistence on "freedom", it actually engages in anti-metric governmental coercion – consider the Fair Packaging and Labelling Act (FPLA), a federal law which makes metric-only packaging illegal for many categories of consumer goods.

> The SI units were designed to make unit conversions easier, but in practice nobody actually converts units

I can remember doing lots of unit conversions in science and maths classes in high school. If I'd gone on to study physical science or engineering at university, I'm sure I would have done plenty more. From an educational viewpoint, I think it is easier to teach students how to do science with SI units if they have already been taught basic metric units at the primary/elementary level, and are used to using them in everyday life. Whereas, students in the US start out with less familiarity with basic metric units, which makes learning to use SI units in science class more work for them

And every time I visit the US I find myself constantly trying to remember stuff like "what is an ounce, again?" "what's 60 degrees Fahrenheit in Celsius?". If the US finally finished adopting the metric system, it would eliminate the need for many unit conversions which are now required by international visitors, immigrants/emigrants to/from the US, journalists, businesses engaged in product localisation, etc

> Cooking uses teaspoons, tablespoons and cups, but you never need to convert between spoons and cups

Some countries (Australia I know is one, there are probably others) have defined metric cups, teaspoons and tablespoons. So this isn't really the argument against the metric system that you think it is

[pmontra]

I just checked and one of my tablespoons is 4 of my teaspoons, but none of them is imperial :-)

On the other side, 1 liter of water is 1000 grams so if I need 100 cc I can put water in a glass and weight it.

[Mountain_Skies]

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.

[skissane]

> 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?)

[p_l]

A lot of traditional units are based on random reference points that were an issue from antiquity - consider how pretty much every market town kept their own measure references even if they used same terminology.

That said, Fahrenheit use of brine solution for 0 and his wife's armpit for 100 remains among most WTF for me.

[skissane]

> A lot of traditional units are based on random reference points that were an issue from antiquity - consider how pretty much every market town kept their own measure references even if they used same terminology.

A lot of that was because keeping the definition of units consistent across time and space was very hard in ancient and mediaeval times, even the first few centuries of the modern period. Units were defined in terms of physical artefacts (as long as this metal rod, as heavy as this particular stone), which tended over the centuries to be lost or stolen, or slowly decay. Issues such as expansion and contraction of metals at different temperatures were also not widely understood, and accurate/reproducible thermometers didn't exist until the 18th century. As we improved our knowledge of natural science, we became more and more aware of these issues – but the initial solution was often just to make the whole country adopt the standard of the national capital, and empires were made to adopt the standard of the imperial capital (the British don't call their traditional units "Imperial" for nothing)

[mitthrowaway2]

When it comes to precision machining, even Americans seem to prefer to use "thous" (1/1,000") and "tenths" (1/10,000"). Isn't it strange that the preferred measurements aren't fractional: 1/1,728" and 1/20,736"? Why do you think that is?

What would a machine shop say if you called out a dimension as (5,081/20,736")?

I think they'd stare at it for a while, chuckle at your sense of humor, and then punch it into a calculator to work it out in decimals.

[mr_toad]

Or base 16 if the machine overlords have their way.

[saalweachter]

The biggest argument against base 10 is that one day our descendants will have to explain to aliens, "because the monkeys that built us had ten fingers".

Positively mortifying.

[pmontra]

And those aliens would shrug "the slugs that built us had no fingers at all, that's why we're using binary, not because of electronics."

[userbinator]

English dragged their feet on doing that

Pun intended? ;-)

It's also worth noting that English and American units also differ slightly --- one of the more common examples being that the US gallon is not the same as the Imperial gallon.

[pwagland]

Footer to your footer. At least in the Netherlands, ounce is still used as well, it's defined to 100g.

[wnoise]

That's over three times too big though.

[kergonath]

in the end, who cares? It’s just a name on a unit. There is no law of nature that puts a limit on its value. There always have been many definitions for an ounce (one of the reason for going metric in the first place); this one is just a bit on the large side.

[earthboundkid]

And everyone measures TVs in inches, somewhat bizarrely.

[skissane]

Are they actually designed and manufactured in inches, or only marketed in inches?

Almost everyone called 90 mm floppy disks "3.5 inch", despite the fact the formal standard which defined their dimensions was metric. I believe the same was true of the "5.25 inch" disks which preceded them. (I think the original 8-inch floppy disks were non-metric though???)

[delta_p_delta_x]

Strictly speaking, this is also a consumer-oriented thing, using the diagonal. The diagonal is also misleading, because it gives no information about the dimensions and aspect ratio of a given panel. Consider a 15.6" 16:9 display, versus a (now increasingly more common) 16" 16:10 display.

Panel manufacturers are all based in Asia, and measure only the edges in millimetres, as they should. Even xrandr outputs EDID data in millimetres.

[pmontra]

CRTs were 4:3 and tiny, they could fit basically everywhere. The diagonal was more than enough for consumers. Computer monitors started to have different ratios but they were not as widespread as today, even in a world of laptops and mobile devices.

The last time I had to buy a TV set I was more interested in the width of the appliance (screen plus bezel) than in its diagonal because I had to fit it into a set space. I went to a shop with a tape ruler.

[pmontra]

Gas and water pipes are often in inches too (Italy) probably because it's an old and critical infrastructure and nobody wants to risk mistakes by trying to fit a 1 inch pipe with a 25 mm one, or 1 1/4" with a 32 mm. Close but not close enough.

However I guess that even American engines are measured in liters or cc, cubic centimeters.

[skissane]

> Gas and water pipes are often in inches too (Italy)

English inches (now 25.4 mm) or Italian inches? (“once”/“oncia”-varied in definition between different parts of Italy, but was always at least a fraction more or less than the English one)

[pmontra]

English inches.

I'm not sure I ever heard the Italian word oncia as a unit of length. I thought it was a translation of the imperial unit of weight, ounce. However all is possible in the world of the old semi forgotten traditional units.

[skissane]

My Italian begins and ends with ciao. I’m just going by what Wikipedia says on the topic:

https://en.m.wikipedia.org/wiki/Italian_units_of_measurement

[bmicraft]

We do measure TVs in Zoll here in German speaking countries, which has been redefined to exactly 1 in.

[wkat4242]

In the Netherlands we also colloquially use the 'ons' (ounce) which is defined though as 100g.

[0xFEE1DEAD]

In Germany we've got 'Unze' (ounce) which is defined as ~30g which we only use when talking about precious metals.

What we do use is 'Pfund' (pounds lbs) which is defined as 500g.

I am amazed the nations of the world actually came to an agreement about what to use as base units and I can't even fathom what shit show it must've been before that.

I live a 30min drive away from the Netherlands and your ounce is already 230% more then my ounce.

[e12e]

But "hecto" (gram) is not used as a synonym?

[wkat4242]

No it's not, at least not in the Netherlands.

[c4mpute]

In Germany the short "hecto" stands for "hectoliter", when ordering larger amounts of beer.

[azepoi]

This is commonly used in Italy modified in the form "etto"

[earthboundkid]

China had their own mile. “The journey of a thousand miles begins with a single step” was actually only around 300 English miles long.

[Aerroon]

The modern Chinese li is defined as exactly 500 meters.

[earthboundkid]

Laozi had some foresight to use meters in 500BCE.

[hashmush]

And, similarly, the 斤 (jīn) is defined as 500g.

[labster]

Kilogram is also an outlier, as it is the only base unit that comes with a magnitude prefix.

[Aachen]

The base unit is gram, not sure what you mean

[thomas2718]

The base unit is indeed the kilogram, see https://www.bipm.org/en/measurement-units/si-base-units.