In light of What is “International Service of Weights and Measures”?, I did a bit of searching for our policy on questions about units and measurement (metrology)... but I don't think we really have one. So how should we handle these sorts of questions?
On one hand, units and measurement are topics of relevance to all sorts of science and engineering, not just physics. But on the other hand, they often seem to be associated with physics, as the "most basic" of the physical sciences. Do we allow them or not?
Other examples include: