Great idea, Tom. Film in front of Parliament. It's imposing. It's relevant to the story.
It'll look great. It is covered in scaffolding. When you buy a tape measure,
that tape measure had to be checked and calibrated with equipment
at the tape measure factory. And that manufacturing equipment
had to be calibrated by other calibration equipment
at its factory. And that equipment had to be calibrated,
and so on, and so on, and so on, until at some point,
that chain has to stop, there has to be an organisation
whose job it is to say: "you don't need to calibrate any
more. Here is the truth." These days, that job's done at the
National Physical Laboratory in the UK, or the National Institute of
Standards and Technology in the US. I've actually been lucky enough
to visit both of those in the past, so I'll put links to those
videos at the end of this one. The international standard
for length is the meter, and it's based on unchanging
physical constants: a meter is defined as how far
light travels in a vacuum in a certain fraction of a second. Is that all in frame? I've got no idea.
I can't see my screen. But anyway, ever since the mid-20th century, the international agreement has been that
an inch is exactly 25.4 millimetres. Which means yes, the US and imperial
systems of measurement, inches, feet, yards, miles:
they're all based on metric now. But before all those
modern standards were set, those systems of measurement
were based on prototypes. Not 'prototypes' as in
'early test versions', but as in physical artifacts
which were, by definition, the length they said they were. "The metre" was the distance
between two marks on a platinum-iridium bar stored in Paris. If those marks somehow changed, then the definition of the
metre changed with them. Before we went metric, Britain
had physical standards for the old imperial units, too,
dating back centuries. There are references to various
standards all through history, but as far as I could tell, the first prototype that could reasonably
be called a British national standard was a brass rod that was created in 1760. That standard was eventually
set in law: in 1825, the yard, so three feet, 36 inches, was defined as being the distance between
the marks on that one object, stored with the Clerk of the
House of Commons, in Parliament. Nine years after that law was passed...
Parliament burned down. They were trying to burn old records
that were on wooden "tally-sticks", and the fire got out of control. That famous Parliament building,
the one that's behind the scaffolding, it isn't some ancient castle: heck, the US Capitol Building is
older than what's behind there. Only a few parts from medieval
times are still standing: the rest was built during Queen
Victoria's reign, after the fire. Anyway, all the standards
for imperial units were also destroyed in that fire. The ‘standard Yard’
had been partly melted. Which meant Britain didn't have
any legal standard of measurement. But that was fine! Because
the law also had a provision for what to do in that case:
you make a new Standard Yard, defined by the length of a pendulum that
takes a certain amount of time to swing. Great idea. More than a century early, they were defining the measurements by
physical constants! Just one problem: those definitions were wrong.
Or as the law later put it, "by the Researches of scientific Men
Doubts were thrown on the Accuracy". Those Scientific Men were
the Standards Commission, headed by Astronomer and
Mathematician Sir George Airy. That commission was in charge of
re-establishing the lost units, and their final report made it clear: the government had put a
dodgy experiment into law. It wasn't accurate enough. So instead, the standard was reconstructed
based on all the copies and other versions that had
been made over all the years, all the objects, not like tape measures,
or anything like that, but the things that were one step
down that chain of calibration. So by 1855, a new physical yard had
been constructed, made of bronze, and the law was changed
to define the idea of a "yard" as the distance between
two gold studs on that new bar. There were a few other suggestions
in the commission's report: they strongly argued for the
decimalisation of units and currency, which wasn't successful for a century. But they also said that there should be
a public version of the standards in every large town: not because they'd be
perfectly accurate, but because it would make it
really really obvious if a shopkeeper with a dodgy tape
measure was trying to cheat you. Those standards still exist
in a few places. In London, you can find them in Trafalgar Square,
in the Guildhall, and by the gate of
the Royal Observatory. So if you have bought lunch from, let's say,
a certain shop and want to check if your "footlong sandwich" really
is a foot long, you can do that. And I did. So: was the new yard the same
distance as the old one? Well, it would be difficult to
mess it up too much, there were a lot of copies
of the original to work from. But every time you make an
analogue copy of something, you do lose a little bit of precision. Before the 1834 fire, the yard was the
length of one particular block of metal; after 1855, it was the length of
another block. In between: well, you could take a pretty accurate guess, but that chain of calibration,
that source of truth, was broken. For twenty-one years: no-one knew how long a yard,
a foot, or an inch actually was.
Tom holding up a Subway sandwich up to the imperial yard plaque was a lot more satisfying than I thought it would be.
If you wanna see what 12 inches looks like....
unzips
It’s six of these.
Loving Tom's work these days. Just little tidbits of information I wouldn't have ever thought of otherwise.
If you follow the link to his COVID safety precautions he says he lives in a 2m x 5m apartment. What absurd measurements for an apartment!
The imperial system is now based of metric.
Just watched an episode on the making of medieval castles. Interestingly, every building site would have their own set of measurements that they would use. It was based on someone’s real thumb or real foot. They’d mark it out so everyone on the site could see it, and also in case the person died before construction (a real possibility given major buildings like churches and castles could take decades to finish).
From the thumbnail I can't tell if this guy is 19 or 59.
Now what sitcom an I remembering where a guy gets a hold of the official inch and shows it off and then smashes it and tries to fix it? Then he's worried about having ruined the official inch, but then they come back and are like you actually made it more precise.
My inch is bigger than your inch.