Science: Measure for Measure

Three stories underground, surrounded by tons of reinforced concrete, the tiny vault lay undisturbed through nine stormy years. Last week, learned representatives of 18 countries came to the Pavilion de Breteuil outside Paris, solemnly squeezed into the little vault. There, reposing in a glass case, were the objects these delegates to the first postwar convention of the International Bureau of Weights and Measures had come to see: The Kilogram and The Meter, in person—the official standards of weight and measure for the world’s metric system.

The Kilogram is a spool-sized chunk of 90% platinum, 10% iridium, weighing exactly one kilogram (2.2046 Ibs.). The Meter, a rod of the same alloy, is exactly one meter (39.37 in.) long. For nearly 70 years nations have sent their standards to the Pavilion de Breteuil for measuring and checking, but modern science has lessened the importance of The Meter at Paris. Instead of using a meter bar for a check, a scientist in a well-equipped laboratory can now determine the accurate meter in terms of light waves, which give as accurate a measure of distance as direct comparison.