Once upon a time we lived in a society that was not only completely analog but infinitely simpler. A time when it seemed the physical world could be understood and described, perhaps even tamed, purely through the application of rational thought. Contemporaries dubbed that era the Age of Enlightenment and looked forward to the wonders that this brave new world would bring. This week, one of the last icons of that heady time was dethroned and retired to a museum in Paris.
I am speaking, of course, about the kilogram, the last of the seven International System of Units measures to be represented by a physical object rather than an “invariant constant of nature.” But where did it come from? And why, after two hundred twenty years, has it been replaced?