In a thought experiment, imagine I have a 1 light year long cylinder of matter that extends radially up from the surface of the Earth held in my hand. Just below my hand on a table is a spring scale with high capacity. If I set the cylinder on the spring scale, will it register the entire weight of the cylinder almost immediately, or will it take a year for the weight to be fully transmitted to the scale? I emphasize that I set the cylinder DOWN on the scale because I do not want to "pick it up" and then "put it down" which might simply serve to compress and decompress they cylinder locally.
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In order to measure weight on a scale, the scale must have reached dynamic equilibrium (the gauge needle reach a rest state). You cannot ignore the process of putting the object on the scale. Regardless of how gentle you are, the process will generate a normal force on the object to stop it from free fall. You can imagine the soundwaves moving up and down until equilibrium is reached. So it will certainly take a few up and down propagating waves that eventually settle into rest, taking many many years, even if the soundwaves propagated at the speed of light (which is not the case, they generally propagate way slower).
Alternatively, you could just push the balance down with the same force the cylinder would do, and also hold the cylinder right above also at complete rest, then unlock both so that they experience only a minimal perturbation and effectively remain in equilibrium. In such a case the balance will register the weight "immediately", but not because it is testing the wight of the object, but because it was already being released from such state and will remain unperturbed.
Wolphram jonny
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