I was suprised to learn (from the wiki page) that the kelvin, mole, and ampere do not have exact numerical definitions yet, though I guess that's expected to ch

I was suprised to learn (from the wiki page) that the kelvin, mole, and ampere do not have exact numerical definitions yet, though I guess that's expected to change in May of this year. And then there's the candela, still basically defined by how luminous whale blubber is when it is burning: > Current (1979): The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 5.4×1014 hertz and that has a radiant intensity in that direction of 1 / 683 watt per steradian. > Note: both old and new definitions are approximately the luminous intensity of a whale blubber candle burning modestly bright, in the late 19th century called a "candlepower" or a "candle".