Researchers Will Consider a New World Kilogram Standard

In a laboratory vault outside Paris is a small cylinder of platinum–iridium alloy that serves as the standard for all mass measurements worldwide. By an 1889 international accord, the mass of this metal cylinder defines the kilogram.

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The reference cylinder’s mass has drifted slightly through the years—not enough to throw off your bathroom scale, but enough to bother measurement scientists.

Researchers plan to discuss relating the kilogram to Planck’s constant.