TODAY is World Metrology Day. That’s metrology, not meteorology. It celebrates the signing of the Metre Convention on May 20, 1875 which established the metre as a standard unit of measurement. 1.

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Since the 19th century, science and industry have honored a holy of holies: a bar of platinum-iridium alloy, triple-locked in a subbasement at Sèvres on the outskirts of Paris. Near the ends of the ...