Using French Revolutionary units doesn’t really matter in STEM, either: one can conduct science just as well in any units one wishes. One unit of measure is not more scientific than another. For example, degrees Kelvin and Rankine measure the same thing with different units. If anything, the Rankine degrees are more precise!
Anyway, the French system isn't what people mean by "metric" in this context, they mean the SI system of units, and so in practice it's not so much that it wouldn't matter which you choose as that you don't have any option except SI.
If you wanted an independent system of units you'd need to do a lot of expensive metrication, and in practice Americans are too cheap for that, so the US "customary" units are just aliases for so-and-so-much amount of some SI unit, they aren't actually independent at all.
The reason people focus on metric is that for everyday people that's the part which jumps out as more intuitive. All these nice powers of 10, very tidy.
For T&E it really matters see NASA's Mars Climate Orbiter and the need for heroics in the Gimli glider.
You need to keep to the same unit.
> You need to keep to the same unit.
Completely agreed. You’ll get similar issues if you have one set of parts using m/s and others using km/hr.
And you’ll avoid those issues with any standard, whether it’s m/s, knots or mph. The important thing is to have a standard.
It's not just obstinance, switching everything to metric in the US would likely cost billions (if not trillions) of dollars. And other countries that have made the switch have often ended up with weird Frankensystems of measurement, like the UK where they mix metric and imperial all the time (plus the weird UK-specific measurements they have like "stone", which is based on the pound).
Anything to do with STEM is metric.
Milk is also allowed to be sold in pints, traditionally glass bottle re-usable milk bottles were one pint.
It is also usual (but not legal) to sell a pint or a half of various soft drinks, in theory you should be sold these in some other way, I always say "large" or "small" but in practice ordinary people say "pint" and after all the staff will probably more or less fill a pint glass so, whatever.
Spirits (e.g. gin) are measured in either 25ml or 35ml shots. An establishment can choose either, post which one they picked and use that consistently. Why two seemingly unrelated sizes? Well, historically there were two different non-metric sizes permitted in law, and when the government legislated to make these SI units there were lobbyists demanding they allow this to continue despite the opportunity to rationalize.
As in the US, containers you purchase in a store are labelled, but here the labels must prominently show SI volume units and EU-style value metrics are required on shelf markings, so e.g. 10p per 100ml of Coke is a good price, maybe the Pepsi is on a deal for 9.5p per 100ml, the store's terrible own brand is 5p per 100ml. This EU strategy prevents people screwing with sizes to make you think you're getting a better deal, that cheaper bottle may look like a good idea but hey, it's 18p per 100ml, ah, it's slimmer in the middle which makes it actually much smaller than it looks.
https://en.wikipedia.org/wiki/Metrication_in_the_United_Stat...
One does have to wonder what it is about Anglo countries specifically that makes it so difficult for them, though. Well, Canada at least has the excuse of being next door to US, with the resulting economic effects. For UK I'm pretty sure it's just about not being like "the Continent" at this point.
A huge percentage of those countries didn't have established industrial bases, infrastructure, etc. And also no educated general populace that needed reeducating. And often those countries were effectively forced into adopting metric through colonization and/or invasion.
People get very worked up about it too. People got very worked up about a government proposal to allow people to put imperial units on food in larger type than metric (at the moment it has to be metric larger - or at least the same size).
Everything in engineering and science has been entirely metric since the 80s.
OTOH on road sings, US at least seems to be using miles alone consistently, so you end up with labels like "1 3/4 miles" every now and then, which I find to be difficult to parse quickly.
I tend to think in metres at that scale but a yard is near enough.
Some of those "Metric martyr" types, the kind of people who think anything which changed after they were 35 is an abomination, but somehow anything which changed ten years before they were born has never been any other way, will vandalize legal stuff which uses (in their opinion) the wrong units. So if you put a (legal and reasonable) 1.5km distance sign on a cycle route, but some car driver who thinks sane units are fascism sees it, they might smash it to pieces which is annoying.
There has been a very gradual lean towards sanity, after all my mother was taught decimal currency because it was forthcoming when she was at school, her parents had used a non-decimal currency system. When I was a teenager I still had coins which, though they were treated as their modern decimal value, if you read their faces had a non-decimal value printed on them, because it's too expensive to replace the currency when you switch.
When I was a child I would buy a quarter pound of sweets. At the turn of the century I'd ask for, and receive, 100 grams or 200 grams as I felt, but most customers would use pounds (although legally they'd be served in grams). These days everybody else would likely also ask in grams. So it's changing, it's just very slow.
What's clumsy about 30cm though? If you are working at scales where this level of precision is needed, you can just use cm throughout, and the beauty of metric is that even someone who has never had to do that before will know immediately how much it is because conversion to meters (or millimeters, or whatever the primary unit is in their usual applications) is so easy.
Similarly, I've heard similar sentiments expressed about lack of pound equivalent in metric. But in practice we just say "500 grams" etc (and for bonus points you get 400 grams, 300 grams etc).
Miles and yards are both used as units of distance, so conversion is obviously relevant. The only reason why "yards in a mile" doesn't come up all the time is because Americans work around it by subconsciously (?) avoiding any such cases where the conversion is non-trivial. E.g. a road sign in Europe might say "400 m", whereas in US a similar one will be "1/4 miles".
And "evolved from hundreds years of usage" generally means a lack of internal consistency, because most units originated a long time ago as a way to measure something very specific - in many cases, something completely irrelevant to most people using those units today. Nor did those units remain consistent through history - just look at how many definitions ounce has in US in different contexts, all of them historical! Or regular vs nautical vs survey mile. Even just cleaning up that mess would be a massive improvement.
This is where we disagree. It would be a small improvement at best. Most of what you're pointing out are the awkward corner cases that just don't come up or, like you said, we already have other solutions for. Outside of some specialties, pretty much no one needs to know how many cups are in a gallon or yards in a mile or what a nautical mile is. I don't know those things, and I somehow get by OK.
These are conversions I know off the top of my head, I didn't need to look them up. Which is the point the GP was making: it's not hard to memorize the handful of conversions you will encounter in everyday life. Most people living here did it as children and have never had to think about it since. That's why there's no actual gain for us to switch to metric units. On the other hand there would be quite a bit of pain as everyone had to adjust to estimating things in kilos vs pounds, grams vs cups (in recipes), and so on. So for the typical American, it is actually a net negative for the country to switch to the metric system. It isn't just stubbornness.
This is not true and that's trivially verifiable.
No calculator, no references, no Google:
How many inches are in 5 and three-quarter miles?
How much does 5 & 3/4 gallons of water weigh?
The point is that it is easy to interconvert units in the metric system: they're all interrelated and all of them can be expressed in terms of other units.
A litre is the volume of a cube that is 10x10x10cm. A cubic cm of water weighs a gram. Therefore, 10 cubic cm of water weighs 1kg. In other words, a kilo is the weight of a litre of water.
It takes 1 calorie of energy to heat 1g of water by 1ºC. So to heat a litre by one degree takes 1000 calories, or 1 kilocalorie. To boil it, you need to raise its temperature to 100 degrees, because that's the boiling point of water. From room temperature of say 20º that means
100-20 = 80 80 x 1000 = 80,000 80 kcal
This is useful. You can work out how much energy you need, using a pencil and paper.
This makes it easy to convert. Units that are easier to convert are more useful.
Whereas, as Josh Bazell put it:
« Whereas in the American system, the answer to ‘How much energy does it take to boil a room-temperature gallon of water?’ is ‘Go fuck yourself,’ because you can’t directly relate any of those quantities. »
That's stupid. They can easily be related, but the people who devised this batshit set of scaled random numbers a few centuries ago didn't think of it.
It's not "what you're used to is better".
It's "one system is easier to work with than the other, and lets you do things the other system does not permit you to do."
Metric is objectively, demonstrably better than imperial.
And the common response of "oh but my system is what people feel" is also total bullshit, because that is 100% what you're used to.
A warmish day is feels like 20º to me. A hot day feels like 30º. A burning can't think straight day is 40º. Below freezing is below zero: it's simple and intuitive.
Except they didn't actually, see my points about the UK (similar points apply to Canada).
And sure, of course metric isn't necessary. You can also write all software in COBOL and PL/I. But over the long term, the convenience of having a self-consistent system based on a few simple principles rather than historical precedent adds up.
Americans are just very obstinate about those things. It's like the Windows of metrology - backwards compatibility trumps everything else, even when you have utterly bonkers things like ounces vs fluid ounces.