Scientists are meeting this week at Versailles to redefine the kilogram. Sounds weird, doesn’t it? You’d have thought that something as fundamental as the kilogram would have been set in stone, as it were. Well, near enough. For over a century it has been set in metal. Since 1889, the ultimate arbiter of what counts as a kilo has been a small block of platinum-iridium kept in a secure vault in Paris.
It is known as Le Grand K. But the problem with the Grand K is that it takes on very small amounts of pollution, and so gets heavier over time. From Friday – for the vote is little more than a formality – a more accurate definition, based on a stable mathematical formula known as Plank’s Constant, will be established. Stephan Schlamminger, a physicist at the UN National Institute of Standards and Technology has declared this new definition a great triumph.
“The greatest satisfaction for me will be completing that historic arc that started with the French revolution. The idea was to have a measurement system that was for all times and for all people. And its value is woven into the fabric of the universe.”
There is, however, something a little slippery about this way of putting things. Because it repeats a myth about the metric system: that it is a way of measuring things that is read off from the nature of reality itself. This disguises the fact that metric, like other systems of measurement, is rooted in something entirely arbitrary. And more interestingly, that its global success is more a political imposition than a scientific discovery.
Schlamminger is correct that the metric system begins with the French revolution. For at the heart of the French revolution was a desire to wipe away the influence of the church and impose a rational order based, they believed, on the rational discoveries of the Enlightenment. At the same time that the revolutionaries were confiscating the property of the church, banning Christian services and murdering priests and nuns, they were also seeking to redefine how we measured the world thus – so they said – to place measurement on a more rational footing.
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The measurement of time, for example, was to be redefined. Weeks were to be 10 days long. There were to be 10 hours in the day. And each hour was to be 100 decimal minutes. As well as adopting the symmetry of everything being based on ten, this system made the calculation of Christian festivals impossible. Christmas, Easter and Saints Days would all disappear in this new rational system. Calculations of time would no longer be based on religious superstition. And those who continued to use the old system were dismissed as “aristocrats” by the revolutionaries.
Apart from a brief revival for 18 days during the Parish Commune, this way of measuring time lasted 12 years (1793-1805), and collapsed in spectacular failure. But, by contrast, the way the revolutionaries calculated length was a lasting success – indeed, the metre was perhaps the greatest success of the French revolution. Now adopted as the near universal standard of measurement, the metre has become the common language of length and the very skeleton of globalisation. Only the United States, Myanmar and Liberia – and to some extent the United Kingdom – hold out against its complete world domination. Over 95% of the world’s population now use the metric system.
Yet the history of the development of the metre exposes its arbitrary nature. As part of the revolutionary project to root measurement in the nature of reality, the idea was that calculation of distance would be eternal and universal. “For all people at all time”, as the revolutionary mathematician Concorcet explained. The idea was to take the distance between the North-pole and the Equator and divide it by 10,000,000. This would be the metre.
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In 1792, two French scientists, Delambre and Mechain set out to measure the distance between Dunkirk and Barcelona, a distance they would use to calculate the distance between the pole and the equator. As it happens, Mechain got his calculations wrong and Delambre helped him suppress the mistake.
“I have not told the public what it does not need to know” wrote Delambre privately, as he publically deposited Méchain’s calculations in the official records.
“I have suppressed all those details that might diminish its confidence in such an important mission. I have carefully silenced anything which might alter in the least the good reputation of Monsieur Méchain rightly enjoyed for the care he put into all his observations and calculations.”
The fact that they got their sums wrong wasn’t the only problem with the project. The very idea was misconceived as it was based on the presumption that the world is perfectly round, whereas, in fact, it is flatter at the poles and indeed is imperfectly spherical all the way round. But despite all this, a length of platinum rod was agreed upon and declared to be the official metre.
Later this length was redefined, for much the same reason that Le Grand K is being redefined, as the distance travelled by light in a vacuum over the course of 1/299,792,456th of a second. We can define this length with extreme accuracy. But the length itself is no more rooted in the nature of things than the distance between the two apple trees in my garden is rooted in the nature of things.
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So if the metre is an arbitrary distance, why did it garner such near universal support? Of course, most people didn’t know it was arbitrary. And the idea that the metre is a distance that has been supplied by reality is a useful to persuade different cultures to give up their own systems of measurements and adopt a common method of calculating distance. An arbitrary distance, one chosen by one particular culture, would not have commanded such near universal assent. But one that is backed up by the mythology of its rootedness of science and reason was enough to supplant the complex variety of local measurement systems, often traditionally based on parts of the human body – feet and hands etc.
Despite this, the metric system has been imposed on populations rather than chosen by them. The reason it started with the French Revolution is that the revolutionaries imposed their new order by force, under the threat of the guillotine.
So why the need for a common system of measurement? One important consideration, of course, was the development of global trade. A measurement system was required for the facilitation of frictionless trade between different peoples who employed local ways of measuring things. The metre exists as an aid to free markets. To use the language of the day, it’s all about regulatory alignment. How we measure things is a telling pointer of where prevailing power lies. Imperial measurement, for instance, was at least entirely up front about this – it was the system imposed by the British empire on its subjects.
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I prefer it. I don’t like the neatness of metric, with its sense that reality is ordered. I hit a seven iron 150 yards. I like my beer in pints and motorway signs in miles not kilometers. And when measuring distances, feet and inches feels more organic to me than metres and centimeters. A very bourgeoisie list, I accept. And yes, as a cleric, I’d love to overturn any success of the despicable French revolution. But as Protagoras insisted back in the fifth century BC, “Man is the measure of all things”. In other words, lets measure things according to organic human scale, rather than pretend we can find some universal distance that is set into nature. There is no such thing.
Universal measurement isn’t really about science providing an empirically derived answer to that popular philosophical question: how long is a piece of string? It is just that science is a global endeavour and so understandably prefers scientists to employ a common and stable system of measurement.
But it needs to be acknowledged that the story of the history of measurement turns out to be a chapter in the story of globalisation. The prestige of science is used to promote globalisation. The metre and the kilogram are no more ‘true’ than the cubit or the stone. I’d love to return to pre-metric diversity, if only to fight back against that politically dangerous mythology that there is only one way of doing things, and we must all submit to a common standard. That is what the French revolutionaries wanted. And they murdered tens of thousands to bring it about. Scientists like Schlamminger should be less proud about completing their work.