When was the kilogram first defined by the French National Convention?
The French National Convention defined the kilogram in 1795. They declared that one gram would equal the mass of one cubic centimetre of water at the melting point of ice.
Questions about Kilogram
Short answers, pulled from the story.
What happened to the International Prototype of the Kilogram after 1889?
Scientists stored the original cylinder in a vault near Paris alongside copies distributed to member nations. Measurements showed differences of approximately 50 micrograms since their manufacture late in the 19th century.
On what date did the General Conference on Weights and Measures adopt the new definition of the kilogram?
On the 20th of May 2019, the General Conference on Weights and Measures adopted a new definition. The kilogram no longer depended on a physical object but instead relied on fundamental constants of nature.
Why does the word kilogram include an SI prefix within its name?
The term became unique among SI base units because it includes an SI prefix within its name. Other units add prefixes to the gram rather than the kilogram itself.
How do modern laboratories realize the new definition of mass without using the original prototype?
Laboratories now use devices like the Kibble balance to calibrate secondary standards without needing the original prototype. Any apparatus capable of delineating the kilogram through these constants can serve as a primary standard.