I remember from somewhere, about and idea where time is actually a compression wave, like sound. Its movement through causes things to shake and rattle and sometimes things come loose, that all being how change incurs from the passage of time. Also importantly, like sound, it travels at different speeds through different things.
Though the things here aren’t quite as simple as varying densities of matter, rather something else. This is where my memory starts to get really blurry. I don’t remember much beyond that, and doing web searches hasn’t helped any either. Oh well. It was a fun thought, wherever it came from.
Update: I think I found the page that this idea came from. Its this page on theoretical physics, which I think is saying the same sort of thing. (maybe, I have to read it again, its way over my head. I think i get what he is saying, but i duno.)