A ‘Voyage of Discovery’ into the origins of the metric system

A recent programme in the ‘Voyages of Discovery’ series on BBC4 described the meridian expedition to the Andes between 1735 and 1744. During the programme, the presenter suggested that the metric system owes its origins to the Enlightenment, and partly to this expedition. [article contributed by Derek Pollard]

The fourth programme in BBC4’s series ‘Voyages of Discovery’, broadcast on 14 December 2006, was highlighted in ‘Radio Times’ as follows:

‘Eloquent explorer Paul Rose retraces the 1735 journey of the delicate and bewigged French academics who set out to discover the true shape of the world’.

Previous programmes in the series had dealt with Magellan, Cook and Nansen. Clearly, this one would be different.

The story began with the Enlightenment and with Newton, who had predicted that the earth is not a perfect sphere, but is flattened at the poles. The Head of the Royal Observatory in France thought otherwise – that it is elongated. The difference is not academic as it has effects for mapping on land and sea. The French Government decided to try to resolve the question by carrying out three meridian surveys, one of which would cross the equator. This latter was the subject of the BBC4 programme.

Until recently, surveying over long distances involved setting up a chain of stations on high points, then measuring both the angles in the triangles so formed and the length of base lines established at each end of the chain. The Andes were the obvious choice for the survey, and the expedition set off in 1735 for Peru, now Ecuador. The programme outlined many of the problems encountered by the expedition, which took nine years to complete its task, not the three envisaged. The final results confirmed Newton’s prediction. One of the members of the expedition, C de la Condamine, became a respected figure in eighteenth century scientific circles.

The presenter, Paul Rose, made two suggestions during the programme that are relevant to our subject. Firstly, he said that when the expedition passed through the high Andes, they noticed that each region, town and village had its own variation of the colonial measures. And secondly, they realised that, if a universal measure was needed, then the distance from pole to equator, which their work would help to define, might be its basis.

We know now that this distance is not an ideal standard for length. It varies from place to place and with time. And perhaps Paul Rose overstated the importance of the 1735 expedition. But he brought part of the story of the search for an improved and universal system of measures to a wider audience, and he reminded us that the origins of the metric system predate the French Revolution by many decades.

BBC4 programmes have a habit of appearing subsequently on BBC2, so viewers limited to terrestrial channels may yet have an opportunity to see it and comment.

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