The Story of the Kilogram: The Last Artifact
Until 2019, the kilogram was defined by a physical metal cylinder in a vault. Here is how we finally digitized mass.
For 130 years, 'Le Grand K', a platinum-iridium cylinder in Paris, was the definition of 1 kilogram. If it lost an atom, the entire universe's definition of mass changed effectively.
The Problem with Physical Artifacts
Measurements showed that Le Grand K and its copies were drifting apart in mass by roughly 50 micrograms. This was unacceptable for modern high-precision physics.
The Kibble Balance
In 2019, scientists voted to redefine the kilogram using the Planck constant, a fundamental constant of quantum mechanics. Now, mass is defined by the electromagnetic force required to counteract gravity, measured by a Kibble Balance.
Contributing writer at MetricConv, covering measurement science, unit history, and practical conversion guides.