Measuring gravity for the layman

The company Kern Precision Scales is trying to prove that gravity varies (not “weight,” which is measured for practical use according to a standard) by shipping a scale and a gnome of known mass over the world. Scientists set up the scale and report the weight the scale reads for the gnome. However, there is no way to know that the differences are due to gravity and not to shipping vibration or other causes. Once again, there is no experiment to prove changes in gravity. This one could work, if they had proved that the scale always weighs the gnome the same exact reading at the factory, even after having been shipped over the world. This is apparently nothing but a marketing publicity stunt.