Metric was made necessary when the Americans and the British couldn't agree on the size of a pint.
Change My Mind
If we're going there, let's
really acknowledge the insanity. And this is not intended to poke fun at Americans for still using it, just the sheer level of "dear god why?!", cried out in pain at our mutual ancestors who originated the fucking thing (1).
Firstly, there are some genuinely sensible units in there. Even as a metric-sexual, I have to admit, inches and feet are actually genuinely useful "ish" values, and I do occasionally use multiples of them myself. On the other hand, mathematics is a beutiful and elegant thing, and we just
start there by making it awkward.
Because of course, inches are 1/12th of a foot. Not 1/16th. Sure, 12 is a
really sexy number, gotta love all of those divisors, but that means we need a secondary multiplication table, we can't just stick with powers of 2. And why stop there? Let's have 14 pounds in a stone, but only 8 stone in a hundredweight. On the one hand, yay, power of 2, but on the other hand, that means a
hundredweight is
112lb. Would it not have made more sense to have a stone as 12lb and a hundredweight as 96lb, one might ask? One might not, fuck off with your logic right there.
Going in the other direction, one starts by dividing inches up into fractional powers of 2. Which, great, that looks like a system, and a natural one two, because it's much easier to divide something accurately into 2 than it is into 10. So we have 1/2, 1/4, 1/64 and so on. But, of course, then the industrial revolution came around, and we both needed
much finer measures, and the ability to calculate those finer measures with, at best, a slide-rule. So at some point, you have to start mixing, say, a rod sized in thousands of an inch with a thread sized in 1/64ths of an inch, and
good luck with that (insert pained rage face here)
Meanwhile, inches and feet are great for small scale stuff, but they get to a bit of a pain when you need to know the size of a field, or the distance to market. So we have a progressively larger set of units, all of which are, with the benefit of hindsight, thoroughly silly.
A yard is 3 feet. Not 2, not 8, not 12, not 16.
3. Great,
not even a multiple of 2, never mind a power. Ternary it is! (And while we're on the subject, a
barleycorn was 1/3rd of an inch)
A fathom is 6 feet, and a cable-length is 100 fathoms, ish.
A chain is 22 yards long.
A furlong is 10 chains long (... so we're throwing some decimal in for good measure? Cool.)
And then we come to
miles. Which have no fewer than
22 different definitions on WIkipedia, and while many of those are minor variations defined by different countries, England used no fewer than
4 definitions
simultaneously (The old mile of
about 2100m; the statue mile of 8 furlongs, except
not those furlongs the nautical mile of 60 arcseconds at the equator, defined as such long before there was any kind of general agreement on
the size of the Earth(2), and the roman mile, because of course)
I could go on, and one day I will be annoyed enough to do so, because metrology and its history is
fascinating even if it is infuriating, but just going through some of the basic distances and weights, never mind volumes, we're up to multiples of, count them:
- 2
- 3
- 6
- 8
- 10
- 12
- 14
- 15.5 (did I mention perches?)
- 22
Some of those are degenerate - if you can work with powers of 2, then 8 and 16 kinda come along for free, but still. In a world where we can bang out replicas of known dimensions to high precision and in industrial quantities (so, basically, post 1750
ish), the relationship to natural units such as the width of a finger, or the length of a foot, or the height of a man, became much less important. And the need for precision made the complexity of the system a bit of a liability compared to the elegance of the metric system (3)
---
(1) Yes, I know why it developed this way: much of this originated long before standardisation was needed for anything other than tax purposes, all you had as a reference were natural units such as relations to body parts, and the communications and travel technology of the day amounted to "shouting" and "walking" respectively, so as long as a local area of villages could roughly agree, it was Good Enough.
The thing is, standardisation was important
long before improvements in communications technology moved even as far as the metalled road, and figures in authority - from the king, emperor or pope, all the way down to local landowner - had strong incentives to agree upon known values, either locally or throughout a whole polity, because tax, and rent. Within Britain, commonly defined weights and measures were in place before the writing of the Doomsday book, and while those common measures would not have been as ubiqitously equal as they are today, there was still interest in ensuring that the pound of grain paid in tax in the east was about the same weight as the pound of grain paid in tax in the west.
(2) As annoying as they are today - they get used for measuring
altitude, which is just bonkers - nm are a case of technology preceding knowledge. While the sextant as we would recognise it today only showed up in the early 1700s, meaningful measurements of latitude via the stars was used for navigation in the 1500s.
(3) Pocket calculators post about 1965 have helped reduce the complexity of conversion, and I would be remiss if I did not acknowledge that wonders of the world were built
with, not
in spite of such measurement systems - from the pyramids of antiquity to the wonders of the industrial age. Vast creations like the SS Great Eastern, to the tiniest, finest clockwork.