Is the Universe Expanding?

For decades afterwards, people were like, well, obviously energy is conserved in the universe. And so therefore the rules of physics must be the same as a function of time. Now we know the universe is expanding and that means that energy is not conserved because space is changing with time. So nuther's theorem is still teaching us things about the nature of the universe. The fact that the universe was symmetric in time - if space was the same size and not expanding then we would have energy conservation. We know why we don't have energy conservation just the same way we know why we do have momentum conservation. All right, well, i think that sort of answeris the main