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.
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.
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