We’re 10 days late for SI’s anniversary. Let’s call that a small margin on 50 years – although this little bit of science news is all about being precise.

It was on October 11 1960 that the General Conference on Weights and Measures had their 11^th official meeting, in which they decided to unilaterally adopt the metric system and name it the International System of Units, with its fancy French-reversed abbreviation SI. In 1960 six base units were recommended: the meter, kilogram, second, ampere, kelvin and candela, the unit for luminous intensity. In 1971 the mol was added, the chemical weight unit.

Did you know why a meter is a meter long – apart from being that comfortable distance between any persons left and right hand?

It is exactly one 10,000,000^th part of the distance between the North Pole and the Equator – which since defining the meter of course proved to be just a tad different. That’s a good thing, because the Earth isn’t such a perfectly shaped sphere either. So we can state with some confidence that our planet’s circumference is around 40 million meter long.

This means within some 15 years, according to the most recent of UN world population prospects (2008, newsletter pdf) we’d be sharing one meter with 200 fellow-Earthlings. Humans however are not yet included as an official SI unit – so it’s not quite established science to correspond these measurements.

© Rolf Schuttenhelm | www.bitsofscience.org