reply to cowboyro
Re: Weights and measures
said by cowboyro:A kilogram may be a kilogram and a liter may be a liter but the calibration of measurement instruments can drift over time due to temperature, humidity, wear, aging, corrosion, contamination, etc.
No they don't. A kilogram is a kilogram, whether on the Earth at the North Pole or on the bright side of the moon. Same for a meter, same for a liter.
This is why physical quantity measurement equipment needs to be periodically inspected and calibrated.