Scientists from more than 60 countries agreed to change the definition of the kilogram during a conference on Friday in Versailles, France.
The history: The kilogram was originally defined as being equivalent to the mass of a liter of water. Since 1889 scientists have based its definition on a physical object: a platinum alloy cylinder known informally as “Le Grand K” which was kept in a safe in Paris. An obvious drawback was that if the cylinder changed, so did the entire global system of measurement. When it was measured in 1980s, it weighed several micrograms less than it was supposed to, forcing manufacturers who made products based on the standards to reissue their weights.
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