How and Why Scientists Redefined the Kilogram

Illustrations from the Scientific American archive break down this “massive” development

The One Kilogram Reference Unit.

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This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American


Last Friday brought big news to the world of physics: at a meeting in France, scientists from 57 countries voted to replace the famous object known as Le Grand K with a new system of defining the kilogram. This change was a long time coming, and as the physics community has prepared for it over the years, Scientific American has been there to cover the topic. The following graphic from the archives shows how scientists went about redefining the kilogram.

Credit: Jen Christiansen

And the graphic below, from 2017, below puts the redefinition in context of a larger planned overhaul of the International System of Units.


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Credit: Nigel Holmes

Amanda Montañez is senior graphics editor and been at Scientific American since 2015. She produces and art directs information graphics for the Scientific American website and print magazine. Montañez has a bachelor's degree in studio art from Smith College and a master's in biomedical communications from the University of Toronto. Before starting in journalism, she worked as a freelance medical illustrator. Follow her on Bluesky @unamandita.bsky.social

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