Kilogram/Talk

All terms of science, including units of measure, use operational definitions, that is, definitions based on actually performable experiments and observable results. The kilogram is intended to represent the mass of one liter of water (where liter is defined in terms of meter, and meter is defined in terms of the measurable speed of light), but that's a theoretical thing--it's not possible with today's technology (nor was it in the past) to conduct any specific experiment with water to produce this value. The kilogram has always been officially defined in terms of the artifact in Paris (the meter once was as well, but now we have new experiments). There is a movement among some scientists now to redefine it in terms of a new experiment in which measurable electrical potentials move a specific mass, but this is still in the works. --LDC