> On Wed, Mar 16, 2016 at 9:15 PM, Vibrator ! <mrvibrat...@gmail.com> wrote: >> But the PE of the system in question is 1 kg * 1 G * 1 meter, not the full >> distance from heaven to hell. >> >
I wrote: > Measure PE relative to the place where the force of gravity is zero > inside the Earth. That place has an objective existence even if it is > impossible for a body to fall there in practice. Well I guess there could be more than one place with zero gravity so that wouldn't eliminate the arbitrariness of mass from gravitational PE. What one could do is to acknowledge is that the conversion of energy into mass doesn't happen by accident. Imagine a hill separating two valleys A and B where B is twice as deep as A. I find a log in valley A and roll it up to the top of the hill where it could roll either way. It has now acquired mass from being rolled out of valley A. If a gust of wind causes the log to roll into valley B it loses the added mass half way down the hill. Harry
