Worth the Weight: The kilogram is finally being redefined

In a basement vault near Paris, under a series of nested bell jars, sits a one kilogram platinum-iridium cylinder. Even as it wears away or collects dust particles, it is still exactly one kilogram. That’s because it is the kilogram: “Le Grand K.” For more than 100 years, it has been the international standard for the unit of mass, even though its mass has changed … Continue reading Worth the Weight: The kilogram is finally being redefined