The kilogram loses weight.

• Position: Science - Brief article

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So how much does a kilogram weigh? For 112 years, a hunk of platinum and iridium (above) kept in an underground vault near Paris has served as the "actual" kilogram--the standard to which all others in the world are compared. Only three people have a key, and the kilogram has been removed from its safe just three times--to be measured against 100 official copies around the world. Recently, though, scientists discovered that the lump of metal had shrunk by 50 micrograms (about the...