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The World's Roundest Object (and Why it Exists)


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The world's roundest object helps solve the longest running problem in measurement -- how to define the kilogram. A kilogram isn't what it used to be. Literally. The name, weight, and definition of a kilogram has been changing constantly since its invention, and the Avogadro Project looks to change that. 

The "kilogram of the archives" had diverged from its original measurement by as much as 50 micrograms by 1990. What is an equivalent of this measurement?

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