The new definition of the kg

Question

The new definition of the kg

In: Physics

Answer 1

It was redefined so that it doesn’t depend on a physical object.

Until this year a kilogram was defined by the weight of the [International prototype kilogram](https://en.wikipedia.org/wiki/International_prototype_kilogram). Multiple copies of it were made for reference. The problem was that the mass between the original and the copies deviated over time, and there was no way to tell if it was the mass of the original or the copies that was changing.

So the kilogram and four other base SI units [were redefined](https://en.wikipedia.org/wiki/2019_redefinition_of_the_SI_base_units) mathematically by setting exact numerical values based on several constants: Planck constant, elementary charge, Boltzmann constant, and Avogadro constant.