On Mon, Apr 25, 2022 at 8:08 AM Bruce Kellett <bhkellet...@gmail.com> wrote:

*> You appear to be assuming that one measures energy against some
> reference energy. So that if both your reference and the thing you are
> measuring change by the same factor, you do not see any difference.*

Yes, there must always be some sort of an energy standard if you're going
to make any sort of energy measurement. That's why utility workers can
safely grab a half million volt power line with both hands provided they
make sure they're not grounded and are at the same voltage potential as the
powerline, their right and left hands are at the same voltage potential so
no current flows between them through their bodies, so the worker feels
nothing and is perfectly safe, but if he were to touch a ground wire he'd
be instantly fried. The same thing would happen if somebody in a high
energy universe touched a wire that led to a lower energy universe, but
fortunately for the inhabitants of both universes there is no way for that
to happen.

* > That is true enough, but we do not always measure energy by comparison
> with some reference energy. Sometimes we use other laws of physics. For
> example, most of the energy in our immediate environment is mass energy,
> coming from the relation E = mc^2. So we can consider mass as a surrogate
> for energy. Mass can routinely be measured by weighing, assuming that the
> gravitational constant does not change.*

The only reason we think the gravitational constant does not change is
because when we measure the potential gravitational energy in something
today against a standard calibration energy we find that we get the same
number of energy units that we got yesterday when we measured the potential
gravitational energy it was in against a standard calibration energy. But
if the gravitational potential energy dropped by 90% and the calibration
energy also dropped by 90% then we'd notice no difference and get the same
number of units of energy both yesterday and today.

*> But that standard measure may not simply be another energy or mass. It
> could be the force on a charge in an electric field,*

Electrical potential energy and gravitational potential energy are *both*
energy, and if you want to measure either one you're going to need an
energy calibration standard to do it. And the same is true for nuclear
potential energy.

> * > or the measure on a spring balance in the gravitational field.*

It doesn't matter what you use, you're going to need an energy calibration
standard because there's just no way to measure the absolute energy of
anything, you can only measure the relative energy.

John K Clark    See what's on my new list at  Extropolis

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