A weighty issue: scientists redefine the kilogram after 129 years
The kilogram will no longer be measured against an actual weight, after scientists voted to start using an electromagnetic current. Since 1889, a kilogram has been defined by a single lump of platinum-iridium which is housed inside three glass bell jars at the headquarters of the But the master copy, known as ‘Le Grand K’, has been picking up microparticles of dust, or losing mass in cleaning, causing consternation for scientists using it to measure ever more accurate weights. Now, after a week-long meeting at the Palace of Versailles ...
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