The kilogram just got a revamp. A unit of time might be next
The unit of mass is now defined by a fundamental constant of nature, not a hunk of metal
![metal kilogram](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2019/05/051719_ec_kilogram_feat.jpg?fit=860%2C460&ssl=1)
HAS-BEEN For 130 years, this metal cylinder was the definition of a kilogram. Now, it's just another hunk of metal, as scientists have instituted a new definition based on a quantity known as the Planck constant.
BIPM