May 20, 2019
There's a Brand-New Kilogram, And It's Based on Quantum Physics
The kilogram isn't a thing anymore. Instead, it's an abstract idea about light and energy. As of today (May 20), physicists have replaced the old kilogram — a 130-year-old, platinum-iridium cylinder weighing 2.2 pounds (1 kilogram) sitting in a room in France —— with an abstract, unchanging measurement based on...