Scientists are redefining the kilogram.
For years, the kilogram has been defined by the specific mass of a lump of platinum-iridium contained in a vault in France. But scientists are now looking to replace it with an electric current called the Planck constant.
Modern measurements of mass are traced to the lump of platinum-iridium, making it the standard for weighing all objects. But the metal can be altered by dirt or dust, making it an unreliable source.
The Planck constant, however, will weigh the same mass without being subject to changes. It is measured by a device called a Kibble balance, which measures the electromagnetic force and outputs the force as weight.
“We need to be able to measure at different scales because it’s again in the present system you have to relate small masses to large masses by subdivision and that’s very difficult,” Dr. Ian Robinson of the National Physical Laboratory explained. “The uncertainties build up very, very quickly. And one of the things that this technique allows us to do is to actually measure mass directly at whatever scale we like and that’s a big step forward.”