Test and measurement is based on agreement. Le Grand K was merely a block of metal that nineteenth century scientists agreed weighed a kilogram. The length of a metre is as it is because scientists agreed it should be one 10-millionth of the distance from the North Pole to the equator.
Similar universal agreements form the basis of every measurement, calculation and interrogation we perform. Every sample and communication, every unit of anything we monitor, relies on agreement.
But agreement is nothing without trust, which is why, when the International General Conference on Weights and Measures met in Versailles, France, to redefine the kilogram, they agreed on a measurement based on unchanging scientific principles. These principles are more trustworthy than the original hunk of metal, which could be damaged, or simply absorb atoms from the atmosphere, changing its weight.
We have to trust the process of calibration, which is why the original definition of each unit of measurement is so important. Then, once our instruments are calibrated, whether to a kilogram, meter or another measurable unit, we have to trust them too.
Read the full article in the January 2020 issue of DPA.