Since the 19th century, scientists have based their definition of the fundamental unit of mass on a physical object — a shining platinum iridium cylinder stored in a locked vault in the bowels of the ...
*Refers to the latest 2 years of stltoday.com stories. Cancel anytime. The U.S. national kilogram, made in 1879 and kept at NIST. Washington Post photo by Salwan Georges Humanity is on the verge of a ...
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