This is a good point. Potential energy is relative to a datum, which is arbitrary. So you could say a box on a table has no potential gravitational energy relat

This is a good point. Potential energy is relative to a datum, which is arbitrary. So you could say a box on a table has no potential gravitational energy relative to the table, but it does have some relative to the floor. But there was no actual change in energy between the two measurements.