4 ms·
>This answers the "how", but not the "where Potential energy is a property of a system rather than an actual physical thing. It's not energy an object has, it'
by Rury 6y ago
>This answers the "how", but not the "where
Potential energy is a property of a system rather than an actual physical thing. It's not energy an object has, it's energy an object potentially has relatively speaking. And it's relative to whatever you use as your reference point in your system.
>Since energy itself has mass
Energy doesn't have mass. It is equivalent to mass.
- kwk1 6y agoThis 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.
- cygx 6y agoExcepting the confusion between the relationship of mass and energy which you cleared up, that was a totally legit question: Energy gravitates, so we do in fact need to know where all (non-gravitational) energy - including contributions we label 'potential' - is located if we want to determine the metric. The answer to the question of 'where' is the underlying (non-gravitational) physical field (and in particular the electromagnetic field, which is long-range, whereas the nuclear fields normally get folded into mass terms). The case of gravitational potential energy is a bit more subtle: It's excluded from the stress-energy-momentum source term of the Einstein equations, and there's no expression for a gravitational stress tensor (though there are pseudo-tensorial approaches).