Right, I get that, and if anything I feel less dumb now that I've asked it publicly and people seem to think that it's a non-dumb question, but when talking abo

Right, I get that, and if anything I feel less dumb now that I've asked it publicly and people seem to think that it's a non-dumb question, but when talking about fundamental constants I understand there is a practical nature to it all, but just as we have a nano-meter and a light-year I figured we'd have the same for mass. Why do I need both kg and u as fundamental constants? I believe the comments here have answered it. It isn't something weird, like quantum gravity or some such. If I understand everyone correctly it's just a practical decision we made at some point because we didn't want mass to be in u and that's that. I feel better about it now.