I mean, seriously, everyone's freaking out because "THE" kilogram no longer weighs exactly the same as its copies, and flapping their hands about dramatically that they don't know whether the kilogram "ITSELF" has changed in weight, or if the copies have changed.
When I was taking Gen Chem, then Organic, and then teaching these things to others in subsequent years, I came to accept that all numerical amounts in calculations (even in P-Chem) are only relevant to within certain significant figures because our means of interacting with those amounts are fundamentally limited. Limited by both technical possibility and effect on observed outcome. There may be theoretical applications in which we need to define certain constants, certain amounts, to more precise figures and sometimes those theories get tested, but even then the results are always measured in replicate and determined within a given error.
Similarly, how about if we just accept that there's a certain range of weights out to the Nth decimal place that correspond to "a kilogram" and that there is a margin of standard error, represented by its deviation among "THE" kilogram and all its certified copies? Is it really that big of a deal to know the cosmically most precise, TRUE nature of the kilogram for use in practice? Given the following:
- a) it's something we made up
- b) no balance in the world is capable of measuring anything to its exactitude*
- c) no application in which someone would need to weight out some amount of something for use or characterization would likely ever need to be THAT close
- d) even if the application wanted to be that precise, the readout/outcome would likely NOT be precisely enough reproducible, for the very same reasons that make "THE" kilogram so hard to measure in the first place
Can't we just accept that we mortal, biological beings cannot manifest the abstract so pedantically and with such theoretical precision? Can't we just let the kilogram be like Plato's ideal, and be comfortable with our ability to represent it as closely as we are reasonably capable? Do we seriously need to go to such lengths as working for about 12 years to get it measured on a Watt balance*, or relate a material construct of it to a physical, mathematical constant? I love NIST, but this is one enterprise that boggles my mind.
*The Watt balance at NIST is barely even stable enough to do this, and also THEY HAVE A RACCOON PROBLEM! Unless I totally misheard the radio story, raccoons get into their rafters and chew up stuff that falls into some of the rooms in the place that houses the Watt balance. I'm sure they work hard not to let their raccoon problem affect their balance, but it just highlights my point that the world, reality and our interactions with them are heterogenous things, so why can't we accept that maybe so is our ability to actually manifest a theoretical amount?