France – and the majority of the rest of the world – is marking 150 years since the Metre Convention first united them in a shared language of measurement, laying the foundations for international scientific cooperation.

Issued on: 25/05/2025 - 17:15

Modified: 25/05/2025 - 17:20

There aren't many 136-year-old metal cylinders tucked away in Paris basements that can claim global fame.

Yet "Prototype 35" – a shimmering iridium-platinum artefact – quietly changed the course of modern life.