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 <https://groups.google.com/g/extropolis> 87u -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/CAJPayv0Ogt72vrAr-Pa1E-apNvHSrrXfeg_Gk51oeiU00f_moQ%40mail.gmail.com.
