> it's also a little silly to have a prefixed base unit I somewhat agree with that - I had the exact same conversation with my kids very recently. Re. physica

> it's also a little silly to have a prefixed base unit I somewhat agree with that - I had the exact same conversation with my kids very recently. Re. physical object: well, whatever physical reference artefact is used, to all intents and purposes the physical stuff is water, with the basically sensible equivalence 1L = 1kg = 1000cc. As you point out, it's not perfect because of the somewhat arbitrary scales (kg, cc), and it gets worse when you bring temperature into it (I believe it's supposed to be measured at 4 degrees C, but I'm not totally sure of that). You're right in that it is not perfect, but at least it is a fair attempt at coherence.