Would that (the longer tube) take into effect the diminishing force of gravity on each additional mile?
No. From the description I quoted:
For this measurement, the definition of weight is the force of gravity at the earth's surface applying to the entire length of the material, not diminishing with height.
No. From the description I quoted:
For this measurement, the definition of weight is the force of gravity at the earth's surface applying to the entire length of the material, not diminishing with height.