It's a little ironic that the article expressed the value of Planck's constant using an SI Unit with kilograms.
>Based on 16 months' worth of measurements, it calculated Planck's constant to be 6.626069934 x 10−34 kg∙m2/s.
>Based on 16 months' worth of measurements, it calculated Planck's constant to be 6.626069934 x 10−34 kg∙m2/s.
We rearrange the approximation: h = 6.626069934 x 10−34 kg∙m2/s to solve for kg and thus have our definition in terms of h?
I.e., if you know how to measure a second, you could define the meter based on the speed of light by creating light in a vacuum and timing it.
Meanwhile, you can't define a meter or a second in terms of pi, because it has no units. It's just a ratio of the surface area of certain classes of object or shape to thheir dimensions.
Under the new system, Planck's constant would be defined to be exactly 6.626070040e−34 kg.m^2.s^-1, with no error bars, and the prototype would no longer be exactly 1 kg. If we refine our estimate for the physical value of Planck's constant, its numerical value of 6.626070040e−34 kg.m^2.s^-1 would not change, but the numerical value for everything's mass would.
This definition of 1 kg requires we first define 1 m and 1 s, but there are already good definitions for these quantities based on fundamental physical properties (namely, the speed of light and the frequency of the transition between the two hyperfine levels of ground state of the caesium-133 atom).