Redefining the Kilogram


The chief of quantum measurement at the National Institute of Standards and Technology, which oversees weights and measures in the United States, Jon Pratt and his colleagues gained gained interest in revolutionizing the Kilogram.


“I think it’s cool, but I don’t understand why we needed to redefine it,” junior Carson Lane said.


The problem with the current Kilogram? It’s losing weight, although ever so slightly.


“I don’t think it would make much of a difference,” Lane said.


Although there is only a slight change in measurement, however objects that depend on the exact number of Kilograms, like the efficiency of diesel engines which depend on the mass of the soot they enter.


“It’s not obvious that it’s a big deal, but it’s a big deal,” Jon Pratt said in an interview with the Washington Post.


Planck’s constant is a value from quantum mechanics describes the behavior of particles and waves on the atomic scale. However, measuring this is a long process they use a tool called a Kibble balance where an electrical current is sent through a coiled wire, generating a magnetic field that creates the upward force needed to balance the scale. Scientists can figure out the strength of that field by pulling on the coil. If you know the voltage, the current and the velocity at which the coil was pulled, you can calculate the Planck constant with extreme precision.


“It’s a difficult thing to measure,” Pratt said.


The process took 16 months to measure, but the conclusion was that Planck’s constant is 6.626069934 x 10−34 kg∙m2/s, 0.0000013 percent of the correct number.


“There’s a lot that rides on these sorts of things that people take for granted,” Pratt said.


In 2018, at the next General Conference on Weights and Measures, the scientific community will draft a resolution to redefine kilogram based on this constant.