Originally Posted by JimJast

Finally I have understood the problem. You have mixed physical law with physical system. While the first might be preserved in expanding universe physical system might change so that its energy isn't conserved (in other words the words "translation through time" don't mean the same thing for both). E.g. two charges separated by a certain distance in expanding universe are a second later separated by a greater distance. So depending on the sign of the charges their energy either grows or becomes smaller, or in other words, energy changes. It is not conserved. Since their physical system can't be translated through time in expanding universe, while all physical physical laws (even the conservation of energy) can. That's why the energy can be conserved in expanding universe in separated islands and so that law of conservation of energy can, but energy can't be conserved globally. It is kind of ironic but it is just how it is. It can be conserved globally in a static universe though, since the example with two charges don't work there since their system is translated through time but only in a static (or stationary) universe.

I hope you learned something and later I'll try to explain you more physics since it must be frustrating not to understand basic ideas like "translated through time". But don't worry just imagine my problems while changing from a sculptor to a relativist. But I'm already there and still remember my old problems so I may help you a lot. Just cheer up